Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    Description of the phosphorus sorption and desorption processes in lowland peaty clay soils
    Schoumans, O.F. - \ 2013
    Soil Science 178 (2013)6. - ISSN 0038-075X - p. 291 - 300.
    semiarid altered wetland - acid soils - phosphate adsorption - agricultural land - organic-matter - flooded soils - iron-oxides - sandy soil - aluminum - release
    To determine phosphorus (P) losses from agricultural land to surface water, information is needed about the behavior of P in soils. In this study, the sorption and desorption characteristics of lowland peaty clay soils are described based on experimental laboratory studies. The maximum P sorption capacity is comparable to that of acid sandy soils if based on the amount of oxalate-extractable aluminum and iron. A fraction of the maximum amount of sorbed P is bound reversibly (Q), which can be measured with an iron-impregnated paper. The fraction of the maximum reversibly sorbed P depends on the amount of oxalate-extractable aluminum and iron. In the topsoil, the maximum of the fraction of reversibly bound P (Qm) is about one third of maximum P sorption capacity; and in the subsoil, about two thirds. All sorption and desorption parameters are related to soil characteristics of peat samples.
    Sulfaat in veenweiden: gebiedsvreemd of gebiedseigen?
    Hendriks, R.F.A. ; Twisk, J.W.R. ; Gerven, L. van; Harmsen, J. - \ 2013
    H2O : tijdschrift voor watervoorziening en afvalwaterbehandeling 2013 (2013)mei. - ISSN 0166-8439 - p. 1 - 8.
    waterbodems - geochemie - veenweiden - bodemchemie - zure gronden - waterbeheer - krimpenerwaard - water bottoms - geochemistry - peat grasslands - soil chemistry - acid soils - water management - krimpenerwaard
    Sulfaat is een belangrijke stof in sloten in veenweidegebieden. Het wordt in de zuurstofloze waterbodem door micro-organismen omgezet in sulfide, dat zich bindt aan ijzer. Daardoor komt fosfaat vrij, wat slecht is voor de ecologische kwaliteit van het slootwater. De gedachte was altijd dat de inlaat van gebiedsvreemd water in de polders de grootste bron van sulfaat is. De laatste jaren is duidelijk geworden dat het sulfaat vooral afkomstig is uit de veenweidebodem zelf. In de Krimpenerwaard gaat het om 75%. Het inlaatwater blijkt de sulfaatconcentraties in de gemiddelde veensloot zelfs omlaag te brengen!
    Evaluation of an approach for the characterization of reactive and available pools of twenty potentially toxic elements in soils: Part I – The role of key soil properties in the variation of contaminants’ reactivity
    Rodrigues, S.M. ; Henriques, B. ; Ferreira da Silva, E. ; Pereira, M.E. ; Duarte, A.C. ; Romkens, P.F.A.M. - \ 2010
    Chemosphere 81 (2010)11. - ISSN 0045-6535 - p. 1549 - 1559.
    iberian pyrite belt - heavy-metals - acid soils - organic-matter - trace-elements - mercury - extraction - sediments - desorption - speciation
    Harmful effects of potentially toxic elements (PTE’s) in soils relate to their geochemically reactive fraction. To assess the degree of the reactivity, specific extractions or models are needed. Here we applied a 0.43 M HNO3 chemical extraction to assess reactive pools of a broad range of PTE’s in 136 contaminated and non-contaminated soils. Furthermore we derived Freundlich-type models based on commonly available soil properties (pH, organic carbon and clay) as well as extended models that used other properties such as amorphous Al and Fe oxides and evaluated their possible use in risk assessment. The approach allowed to predict the reactivity of As, Hg, Co, U, Ba, Se, Sb, Mo, Li, Be (r2: 0.55–0.90) elements not previously included in such studies, as well as that of Cd, Zn, Cu, Pb, Ni and Cr (r2: 0.73–0.90). The inclusion of pH, organic carbon and clay improved the performance of all models except for Be and Mo, although the role of clay is not completely clear and requires further investigation. The ability of amorphous metal oxides to affect the reactivity of As, Hg, Cu, Ni, Cr, Sb, Mo and Li was expressed by the models in agreement with known geochemical processes leading to the retention of PTE’s by the solid matrix. Hence, such approach can be a useful tool to account for regional differences in soil properties during the identification of risk areas and constitute a significantly more powerful tool than the analysis of total pools of PTE’s in soils.
    Multiple benefits of manure: the key to maintenance of soil fertility and restoration of depleted sandy soils on African smallholder farms
    Zingore, S. ; Delve, R.J. ; Nyamangara, J. ; Giller, K.E. - \ 2008
    Nutrient Cycling in Agroecosystems 80 (2008)3. - ISSN 1385-1314 - p. 267 - 282.
    organic-matter - cattle manure - resource-allocation - crop production - western kenya - acid soils - management - zimbabwe - tropics - variability
    Manure is a key nutrient resource on smallholder farms in the tropics, especially on poorly buffered sandy soils, due to its multiple benefits for soil fertility. Farmers preferentially apply manure to fields closest to homesteads (homefields), which are more fertile than fields further away (outfields). A three-year experiment was established on homefields and outfields on sandy and clayey soils to assess the effects of mineral nitrogen (N) fertilizer application in combination with manure or mineral phosphorus (P) on maize yields and soil chemical properties. Significant maize responses to application of N and manure were observed on all fields except the depleted sandy outfield. Large amounts of manure (17 t ha¿1 year¿1) were required to significantly increase soil organic carbon (SOC), pH, available P, and base saturation, and restore productivity of the depleted sandy outfield. Sole N as ammonium nitrate (100 kg N ha¿1) or in combination with single superphosphate led to acidification of the sandy soils, with a decrease of up to 0.8 pH units after three seasons. In a greenhouse experiment, N and calcium (Ca) were identified as deficient in the sandy homefield, while N, P, Ca, and zinc (Zn) were deficient or low on the sandy outfield. The deficiencies of Ca and Zn were alleviated by the addition of manure. This study highlights the essential role of manure in sustaining and replenishing soil fertility on smallholder farms through its multiple effects, although it should be used in combination with N mineral fertilizers due to its low capacity to supply N.
    Aluminium fractionation of European volcanic soils by selective dissolution techniques
    Garcia-Rodeja, E. ; Novoa, J.C. ; Pontevedra, X. ; Martinez-Cortizas, A. ; Buurman, P. - \ 2004
    Catena 56 (2004). - ISSN 0341-8162 - p. 155 - 183.
    organic-matter - acid soils - humus complexes - extractable aluminum - northeastern japan - variable charge - release rates - forest soil - solubility - horizons
    Several selective dissolution methods were used to differentiate Al forms in 12 soils formed from volcanic materials (64 andic, vitric and organic horizons) in Iceland, Azores (Portugal), Tenerife (Spain) and Italy. The soils differ in many properties because of differences in parent materials, climatic conditions, soil age and history of land use. 'Inorganic' fractions of Al were characterized using pyrophosphate (Al-p), acid oxalate (Al-o) and cold NaOH (Al-n) extractions. The difference in Al-o-Al-p, and Si extracted using acid oxalate, shows important differences among soils from different sources: allophane is richer in alumina in the Andosols from Azores and Tenerife than in those from Iceland and Italy. Cold NaOH generally extracted the same quantity of Al as acid oxalate, but in the soils from Tenerife Al-n exceeds Al-o, indicating the presence of gibbsite or poorly ordered halloysite. To characterize the Al bonded to the organic matter fraction, extractions with pyrophosphate, CuCl2 and LaCl3 were used. Except in one soil from Tenerife (N10), CuCl2 extracted less Al than pyrophosphate. In organic-rich mineral horizons, Al-LA, Al-Cu and Al-p increase with organic carbon content. Using unbuffered KCl and LaCl3, the amount of Al extracted increased with decreasing soil pH, but there was no similar relationship with unbuffered CuCl2. The general sequence of efficiency of the extractants was Al-p>Al-Cu>Al(La)greater than or equal toAl(K) in organic matter-rich horizons. Al-Cu constituted 30% of Al-p in all soils, indicating that CuCl2 extracts a very specific Al fraction. Al-p and Al-Cu are positively related to organic C. Al-p/Al-o, and Al-p-Al-Cu in andic horizons also increase with organic C. Phosphate retention and pH in NaF were related to Al-o and Al-n. The soils of Iceland have larger P retention than the others, and vitric horizons from Tenerife have higher pH in NaF and smaller Al pools than the other soils. For many horizons, there is a strong relationship between Al-Cu and components that determine soil CEC (organic matter and allophane), suggesting a possible action of CuCl2 on noncrystalline alummosilicates. This should be taken into account if CuCl2 is used to estimate Al in humus complexes. (C) 2003 Elsevier B.V. All rights reserved.
    Iron and sulphate as possible key factors in the restoration ecology of rich fens in discharge areas
    Kemmers, R.H. ; Delft, S.P.J. van; Jansen, P.C. - \ 2003
    Wetlands Ecology and Management 11 (2003)6. - ISSN 0923-4861 - p. 367 - 381.
    bodemchemie - veengronden - bodemwaterbeweging - calcium - zure gronden - soil chemistry - calcium - acid soils - peat soils - soil water movement
    Seven reference areas in the Netherlandswere selected to trial restoration measuresin acidified rich fens in discharge areas.In about half of the projects the measuresthat aimed to restore the high base statusof the topsoil failed. The aim of thepresent study was to identify the keyfactors and processes in base regulation ofrich fen systems, in order to underpinfuture restoration. We sampled soil andinterstitial water from distinct soilhorizons and analysed it for variablesinvolved in geohydrochemical processes. Wemonitored interstitial water chemistry andredox potentials to calibrate and validatea chemical speciation model, that we usedfor the interpretation of our observations.It appeared that soil pH, Ca2+saturation and iron contents weresignificantly lower at sites whererestoration efforts had failed. At the sametime, soils of these sites were verystratified instead of homogenous. Onlysoils with high iron contents recovered ahigh Ca2+ saturation. All sites werecharacterised by considerable downwardwater fluxes through the soil. Chemicalspeciation modelling was a useful tool forthe interpretation of processes underlyingour observations and helped elucidate thefactors and processes that control therecharge of the CEC by base cations. The modelling results suggested that the mainprocess in proton neutralisation ofsuccessful sites is the production ofinternal alkalinity by reduction of ironoxides. Additional redox capacity can besupplied by the ample presence ofsulphates. From our results we hypothesisethat the CEC will only be rechargedsuccessfully with base cations in thepresence of sufficient redox capacity ofthe soil. It seems that redox processesfacilitate the ionic exchange of protonsfor Ca2+ ions. Sites where restorationefforts failed changed from discharge areasto recharge areas, which caused irondepletion by leaching. We conclude thatproper understanding of the pedological andgeohydrochemical processes that control thebase status of soils is a prerequisite forsuccessful nature restoration. The role ofsoil processes cannot be ignored as itseems that the production of internalalkalinity upon reduction exceeds theexternal supply of alkalinity bygroundwater flow.
    Release rates of Al from inorganic and organic compounds in a sandy podzol, during laboratory experiments
    Salm, C. van der; Westerveld, J.W. ; Verstraten, J.M. - \ 2000
    Geoderma 96 (2000)3. - ISSN 0016-7061 - p. 173 - 198.
    bodemoplossing - bodem - aluminium - zure gronden - adsorptie - soil solution - soil - aluminium - acid soils - adsorption
    Research with respect to release rates of Al and Al concentrations in the soil solution has led to two contrasting hypotheses, stressing either the importance of kinetically constrained dissolution reactions or the role of complexation of Al to soil organic matter. The existence of two contrasting hypotheses is partly due to the fact that the interpretation of existing results is hampered by the lack of specificity of the extractants used to quantify the organic and inorganic pools of Al and by the fact that simultaneous measurements on the release of Al and the change in Al pools are missing. This study was conducted to obtain more information on the release rates of Al from various amorphous pools and to evaluate the validity of the above hypotheses. To overcome the above-mentioned shortcomings both release rates of Al and changes in the various,Al pools were measured during the experiment. Experiments were conducted for Ap, Bs and C horizons from a sandy podzol. Results indicated that Al was released from both the inorganic Al pool (oxalate minus pyrophosphate extractable Al) and the strongly bound organic Al pool (pyrophosphate minus CuCl2 extractable Al) according to a first-order reaction. The decline in the weakly bound organic Al pool (CuCl2 extractable minus adsorbed Al) could be described by a rapid dissolution of part of the pool, combined with an equilibrium reaction describing the complexation of Al to organic sites. Rate constants were highest for the non-complexed part of the weakly bound organic Al pool, intermediate for the inorganic Al pool and lowest for the strongly bound organic Al pool. Large differences exist in rate constants of the organic pools between the three horizons. Differences between the rate constants of the inorganic Al pool for the three horizons were not significant.
    Biological nitrogen fixation of soybean in acid soils of Sumatra, Indonesia
    Waluyo, S.H. - \ 2000
    Agricultural University. Promotor(en): W.M. de Vos; L. 't Mannetje; L.T. An. - S.l. : S.n. - ISBN 9789058082954 - 151
    glycine max - sojabonen - bodembiologie - stikstoffixatie - stikstofbindende bacteriën - rhizobium - bradyrhizobium - inoculatie - entstof - biochemische technieken - dna-fingerprinting - stamverschillen - stammen (biologisch) - zaadbehandeling - omhullen - zure gronden - bodemaciditeit - bekalking - sumatra - indonesië - glycine max - soyabeans - soil biology - nitrogen fixation - nitrogen fixing bacteria - rhizobium - bradyrhizobium - inoculation - inoculum - biochemical techniques - dna fingerprinting - strain differences - strains - seed treatment - pelleting - acid soils - soil acidity - liming - sumatra - indonesia

    The aim of this study is to improve soybean cultivation in transmigration areas, especially in Sitiung, West Sumatra. However, these soils are very acid, and have a high P-fixing capacity. To reduce the amounts of fertilisers, normally 5 - 7 ton lime ha -1 and 100 kg P as TSP, seed, pelleted with lime (60 kg ha -1 ) and TSP (10 kg ha -1 ), was introduced. In this way only 2 ton lime ha -1 are required.

    Soybean can fix nitrogen (BNF) in symbiosis with ( Brady ) Rhizobium bacteria. However, these acid soils in general, have low numbers of ( Brady ) Rhizobium . By inoculating the soils with ( Brady ) Rhizobium , BNF of soybean, and yield, were considerably improved.

    A study was made of the indigenous ( Brady ) Rhizobium population in view of the following:

      Although at the beginning the numbers may be low, by repeated soybean cultivation, the numbers will increase, and they may interfere with inoculation of effective ( Brady ) Rhizobium strains.These indigenous ( Brady ) Rhizobium are adapted to local stress conditions, and they may be useful for the improvement of strains, to be used as inoculants.

    Using molecular techniques, indigenous strains derived from soil samples from old soybean areas (Java) and from new soybean areas (Sumatra) were classified in more detail. Most likely B. japonicum is the dominant strain in Java while in Sumatra B. elkanii is more present. A Sinorhizobium fredii -like strain was isolated from one soil sample from Java.

    Water management for rice cultivation on acid sulphate soils in the Plain of Reeds, Vietnam
    Husson, O. ; Hanhart, K. ; Mai Thanh Phung, ; Bouma, J. - \ 2000
    Agricultural Water Management 46 (2000). - ISSN 0378-3774 - p. 91 - 109.
    rijst - zure gronden - waterbeheer - vietnam - kattekleigronden - rice - acid sulfate soils - acid soils - water management - vietnam
    Quantification and simulation of errors in categorical data for uncertainty analysis of soil acidification modelling
    Finke, P.A. ; Wladis, D. ; Kros, J. ; Pebesma, E.J. ; Reinds, G.J. - \ 1999
    Geoderma 93 (1999). - ISSN 0016-7061 - p. 177 - 194.
    zure gronden - zure regen - cartografie - ruimtelijke variatie - schaalverandering - landen van de europese unie - acid soils - acid rain - mapping - spatial variation - scaling - european union countries
    Uncertainty assessment in modelling soil acidification at the European scale: a case study
    Kros, J. ; Pebesma, E.J. ; Reinds, G.J. ; Finke, P.A. - \ 1999
    Journal of Environmental Quality 28 (1999)2. - ISSN 0047-2425 - p. 366 - 377.
    zure gronden - zure regen - modellen - nederland - acid soils - acid rain - models - netherlands
    Modelling impacts of atmospheric deposition, nutrient cycling and soil weathering on the sustainability of nine forest ecosystems
    Salm, C. van der; Vries, W. de; Olsson, M. ; Raulund-Rasmussen, K. - \ 1999
    Water Air and Soil Pollution 109 (1999). - ISSN 0049-6979 - p. 101 - 135.
    bosbouw - zure depositie - bodemchemie - zure gronden - voedingsstoffen - modellen - zweden - denemarken - nederland - forestry - acid deposition - soil chemistry - acid soils - nutrients - models - sweden - denmark - netherlands
    Biological management for productive and sustainable cropping systems on acid upland soil in the humid tropics : final report of a project funded under the European Communities STD3 programme 1994 - 1997; contract TS3* - CT94-0261
    Whitmore, A.P. ; Cadish, G. ; Hairiah, K. - \ 1998
    Wageningen : AB-DLO (Nota / Research Institute for Agrobiology and Soil Fertility (AB-DLO) 89) - 78
    teeltsystemen - middelgebergte - hooggelegen gronden - zure gronden - humide tropen - cropping systems - upland areas - upland soils - acid soils - humid tropics
    Evaluation of water management strategies for sustainable land use of acid sulphate soils in coastal low lands in the tropics
    Bosch, H. van den; Phi, H.L. ; Michaelsen, J. - \ 1998
    Wageningen : DLO-Staring Centrum (Report / DLO-Staring Centrum 157) - 177
    zure gronden - kattekleigronden - bodemwater - drainage - tropen - indonesië - vietnam - acid soils - acid sulfate soils - soil water - drainage - tropics - indonesia - vietnam
    The use of upscaling procedures in the application of soil acidification models at different spatial scales
    Vries, W. de; Kros, J. ; Salm, C. van der; Groenenberg, J.E. ; Reinds, G.J. - \ 1998
    Nutrient Cycling in Agroecosystems 50 (1998)1-3. - ISSN 1385-1314 - p. 223 - 236.
    zure gronden - kattekleigronden - neerslag - chemische eigenschappen - zuurgraad - zure regen - modellen - onderzoek - geostatistiek - acid soils - acid sulfate soils - precipitation - chemical properties - acidity - acid rain - models - research - geostatistics
    Different soil acidification models have been developed for use on different scales, i.e., NUCSAM for the local scale, RESAM for the regional (national) scale and SMART for the continental scale. This paper focuses on the uncertainties associated with scale transfer by a simpler model description by (i) temporal aggregation of process descriptions, (ii) neglection of processes associated with vertical aggregation of soil layers and (iii) the use of less detailed formulations of processes (process aggregation) and by spatial aggregation of input data. Results obtained for simulations in acid (sandy) soils indicate that (i) temporal aggregation and process aggregation have a limited impact on the long-term (decades) annual response of soil solution chemistry to atmospheric deposition, (ii) vertical aggregation mainly affects predictions of solutes which show a strong concentration gradient with depth and (iii) spatial aggregation hardly affects the average output for a given forest/soil combination. However, ignoring the variability in input parameters, largely affects the frequency distribution of model outputs in a region. Results imply that model simplification is an adequate step in the upscaling of modelling results from a local to a regional scale.
    SMASS - a simulation model of physical and chemical processes in acid sulphate soils; Version 2.1
    Bosch, H. van den; Bronswijk, J.J.B. ; Groenenberg, J.E. ; Ritsema, C.J. - \ 1998
    Wageningen : DLO Winand Staring Centre (Technical document / DLO Winand Staring Centre 21) - 161
    zure gronden - kattekleigronden - fysicochemische eigenschappen - bodemeigenschappen - bodemchemie - infiltratie - hydraulisch geleidingsvermogen - kwel - modellen - onderzoek - chemische processen - acid soils - acid sulfate soils - physicochemical properties - soil properties - soil chemistry - infiltration - hydraulic conductivity - seepage - models - research - chemical processes
    The Simulation Model for Acid Sulphate Soils (SMASS) has been developed to predict the effects of water management strategies on acidification and de-acidification in areas with acid sulphate soils. It has submodels for solute transport, chemistry, oxygen transport and pyrite oxidation. The model must be used together with the water transport model SWACROP. It combines physical and chemical processes. The output includes the acidity and chemical quality of soil and groundwater, and the occurrence of toxic compounds. This user's manual presents an outline of input and output files, guidelines for installation on a VAX-VMS computer, and the description of an application.
    Tillage and water management for riceland productivity in acid sulfate soils of the Mekong delta, Vietnam.
    Minh, L.Q. ; Tuong, T.P. ; Mensvoort, M.E.F. van; Bouma, J. - \ 1997
    Soil & Tillage Research 42 (1997). - ISSN 0167-1987 - p. 1 - 14.
    zure gronden - kattekleigronden - bodem - uitspoelen - acid soils - acid sulfate soils - soil - leaching
    Acid sulfate soils are characterized by low pH and high concentrations of aluminum, sulfate, iron and hydrogen sulfide. Removal of at least part of these substances is a prerequisite for land use, at least in severely acid soils. In this study, the effectiveness of harrowing and flushing with surface water for the removal of toxic substances from the topsoil of acid sulfate soils (ASS) with different toxicity levels was investigated. During the flood recession period, at three experimental sites ranging from slightly, to moderately to strongly acid, two flushing treatments (once or three times, denoted as F1 and F3, respectively) combined with two harrowing treatments (also once or three times, denoted as H1 and H3, respectively) were applied. Soils were classified as very fine Typic Sulfaquepts. At all three sites, when F1 was practiced, H3 did not have a significantly lower soluble aluminum concentration compared with H1. In slightly ASS, the differences between H1 and H3 and between F1 and F3 were not significant. Under moderately acid conditions, the soluble aluminum concentration after H3 was not significantly different from after H1, but it was significantly lower after F3 compared with F1. In severe ASS, H3 combined with F3 gave a significantly lower soluble aluminum concentration compared with F3H1. In addition to soluble Al, Al at the exchange complex was also investigated. The combinations of flushing and harrowing did not significantly change Al at the exchange complex. The F3H3 treatment resulted in a significantly greater rice yield compared with other treatments (F3H1, F1H3 and F1H1). In order to minimize the contamination of surface water, the flood recession period is the optimal time for flushing aluminum out of ASS.
    Contamination of surface water as affected by land use in acid sulfate soils in the Mekong River Delta, Vietnam.
    Minh, L.Q. ; Tuong, T.P. ; Mensvoort, M.E.F. van; Bouma, J. - \ 1997
    Agriculture, Ecosystems and Environment 61 (1997). - ISSN 0167-8809 - p. 19 - 27.
    zure gronden - kattekleigronden - bodem - uitspoelen - aluminium - rivieren - waterlopen - kanalen - water - oppervlaktewater - waterverontreiniging - waterkwaliteit - Vietnam - acid soils - acid sulfate soils - soil - leaching - aluminium - rivers - streams - canals - water - surface water - water pollution - water quality - Vietnam
    Bypass flow and its role in leaching of raised beds under different land use types on an acid sulphate soil.
    Minh, L.Q. ; Tuong, T.P. ; Booltink, H.W.G. ; Mensvoort, M.E.F. van; Bouma, J. - \ 1997
    Agricultural Water Management 32 (1997). - ISSN 0378-3774 - p. 131 - 145.
    infiltratie - hydraulisch geleidingsvermogen - kwel - zure gronden - kattekleigronden - infiltration - hydraulic conductivity - seepage - acid soils - acid sulfate soils
    A better understanding of leaching processes in raised beds is useful in assessing management options for acid sulphate soils. Field and laboratory studies were carried out to quantify the effects of soil physical properties and bypass flow on leaching processes of new, 1-year-old and 2-year-old raised beds for yam and pineapple cultivation in a Typic Sulfaquept in Tien Giang, Vietnam. The methylene blue staining technique was used to characterize the water-conducting pores in terms of number, stained area, and total pore perimeter at 10 cm depth intervals of six 1 x 1 m subplots. Undisturbed 20 cm x 25 cm soil cores taken from the raised beds were subjected to three 30 mm h-1 rains. Volume, aluminum and sulphate concentration of the outflows were monitored. Consolidation with time decreased the area and perimeter of water-conducting pores in 2-year-old pineapple beds to about a third, and bypass flow rate to about 80% of those in newly constructed beds. Consolidation did not affect macropore network geometry in yam beds because they were subjected to annual tillage and yam tubers were uprooted regularly. Al3 and SO4/2- concentrations in the outflows of the newly constructed and 1-year-old raised beds were higher in pineapple, while those in 2-year raised beds were higher in yam
    Surface water management under varying drainage conditions for rice on an acid sulphate soil in the Mekong Delta, Vietnam.
    Hanhart, K. ; Ni, D. van; Bakker, N. ; Bil, F. ; Postma, I. ; Mensvoort, M.E.F. van - \ 1997
    Agricultural Water Management 33 (1997). - ISSN 0378-3774 - p. 99 - 116.
    verbetering - zure gronden - kattekleigronden - drainage - sloten - vietnam - improvement - acid soils - acid sulfate soils - drainage - ditches - vietnam
    Validation and application of soil acidification models at local, national and European scale; a compilation of articles on the models NuCSAM, ReSAM and SMART
    Kros, J. ; Groenenberg, J.E. ; Salm, C. van der; Vries, W. de; Reinds, G.J. - \ 1996
    Wageningen : DLO Winand Staring Centre - 158
    zure gronden - kattekleigronden - bosbouw - neerslag - zure regen - zure depositie - chemische eigenschappen - zuurgraad - modellen - onderzoek - acid soils - acid sulfate soils - forestry - precipitation - acid rain - acid deposition - chemical properties - acidity - models - research
    An overview is given of three dynamic soil acidification models for application on different spatial scales. NUCSAM, the model for the local scale, was validated on data from two intensively monitored research sites. Results of annual average soil solution concentrations and fluxes calculated with the validated NUCSAM model agreed well with those of the national-scale model RESAM and to a lesser extent with those of the European-scale model SMART. Various deposition scenarios for SOx, NOx and NHx on soils were evaluated with the three acidification models.
    Spatial variability of soil actual and potential acidity in the mangrove agroecosystem of West Africa.
    Sylla, M. ; Stein, A. ; Mensvoort, M.E.F. van; Breemen, N. van - \ 1996
    Soil Science Society of America Journal 60 (1996). - ISSN 0361-5995 - p. 219 - 229.
    zure gronden - kattekleigronden - dalen - west-afrika - geostatistiek - agro-ecosystemen - acid soils - acid sulfate soils - valleys - west africa - geostatistics - agroecosystems
    Soil knowledge for farmers, farmer knowledge for soil scientists : the case of acid sulphate soils in the Mekong delta, Viet Nam
    Mensvoort, M.E.F. van - \ 1996
    Agricultural University. Promotor(en): J. Bouma, co-promotor(en): V.T. Xuan. - S.l. : Van Mensvoort - ISBN 9789054855552 - 135
    zure gronden - kattekleigronden - landevaluatie - grondvermogen - bodemgeschiktheid - vietnam - acid soils - acid sulfate soils - land evaluation - land capability - soil suitability - vietnam

    Half the Mekong delta in Vietnam, i.e. around 2 million hectares, suffers soil related problems due to acid sulphate soils. These soils generate sulphuric acid due to the oxidation of pyrite after aeration. Pyrite is most easily formed in tidal swamps. Human interference through land drainage is the most important way in which the acidification takes place. The processes of pyrite formation, of acidification and of the solution chemistry of these soils have been well explained (e.g. van Breemen 1976, Dent 1986). The translation of this knowledge into practical recommendations for farmers is still problematic.

    The Can Tho University (CU), the only institution for higher education in the delta, saw it as its duty to assist the farming community on these soils and come up with practical recommendations for improved agricultural use. From 1980 - 1992 a project of co-operation between CU and the Wageningen Agricultural University, particularly the Soil Science Department, where specialised knowledge on the processes of formation and the chemistry of these soils was present, was carried out. Objectives of the project were (1) to train CU staff in acid sulphate soils formation and survey; (2) to carry out research for improved management of these soils and (3) to equip CU with the necessary facilities for such a research and training programme.

    The aims of this thesis are:

    1 . to review the recent literature on acid sulphate soils in order to screen themethodological developments for survey and identification, for chemical and physical support in field and laboratory, for simulation and mathematical modelling of the soil processes, for management and land use and for acid sulphate land evaluation;
    2. to screen the recent literature, particularly the information supplied by the world's leading specialists in acid sulphate soils in the form of the proceedings of the three most recent conferences on this subject, for its practical applicability by other groups involved with acid sulphate soils: farmers and local experts;
    3. to describe the way the project VH 10, a project of co-operation between the Universities of Can Tho (CU), Mekong delta, Vietnam, and Wageningen Agricultural University (WAU) carded out research for improved management of acid sulphate
    soils between 1980 and 1992 with particular emphasis on the balanced exchange of knowledge between the three groups of people involved: farmers, local experts and specialists;
    4. to describe the way the VH 10 project operated in view of the emphasis it placed onfarmer-expert-specialists knowledge exchange, its strong outreach component towards the farming community and its special ways of operation;
    5. to give some examples of studies which combine farmers, local expert and specialists knowledge to evaluate the acid sulphate land in the Mekong delta.

    The review of the recent literature (chapter II of this thesis) shows how difficult the diagnosis of acid sulphate land is. Some indications can be expected from the vegetation or the drainage patterns. Coastal wetlands, inland marshes and swamps and mine spoils are the land forms where potential acid sulphate soils occur. Surface water usually gives a first warning of acidification having taken place by an oily skin at the surface (iron) or suspicious water clarity (acidity and aluminium). Identification of acidified soils is usually easy through the appearance of pale-yellow jarosite mottles, but is much more difficult in potential acid sulphate soils (pyrite is invisible) or in acidified soils without jarosite. Field tests such as oxidation by hydrogen peroxide for potential acidity, or the azide-soap and the red lead paint for sulphide may help in identification. Moist incubation for prolonged periods is recommended to make sure. Soil survey is difficult because of land inaccessibility, high spatial variability of the diagnostic characteristics and the need for specialised laboratory assistance to identify acid sulphate components. The dynamic modelling of acid sulphate soils received much attention in recent years and resulted in sophisticated models encompassing the processes but inevitably requiring many detailed data for model application. Regardless of all research efforts many management decisions have still to be taken after the problems have already become manifest. Local farmers have, particularly in Southeast Asia, succeeded in adapting to the situation and they have developed interesting management systems for cultivation of rice, shrimp and fish, yams, pineapples, sugar cane and fruit trees.

    The proceedings of the three last conferences dedicated to acid sulphate soils show that most knowledge is communicated specialists to specialists; that some attention is paid to generating knowledge suited for the needs of the local experts such as soil survey methodologies and for the needs of the farmers and the extension workers such as fertiliser recommendations, on-farm water management strategies and crop choice. Only in a few cases, however, the indigenous knowledge of the farmers has been used to its full potential. It is particularly in the Mekong delta that the local farmers' knowledge has played a dominating role in acid sulphate soils research for practical application.

    The VH 10 project of CU and WAU profited from the strong embedding of CU, in particular its Faculties of Agriculture and of Water Management and Rural Engineering, in the rural society of the Mekong delta. The network of contacts with provincial and district agricultural services, with state farms and with private farmers could be used for gathering local farmer knowledge, for experimentation in line with farmers experience, for extrapolation of the findings to other locations in the delta and for knowledge dissemination through workshops and TV programmes.

    The research set-up of the project changed from a top-down technology driven approach in the early and mid-eighties to a system of a balanced knowledge exchange between farmers, local experts and soil/water specialists in the late eighties and early nineties. This approach generated much more successful recommendations for farmers than the top-down approach.

    The project had a number of deviating organisational aspects which might be interesting for application elsewhere: (1) no permanent foreign staff present in Vietnam; (2) large share of the responsibility for the execution of the project left with the Vietnamese counterparts; (3) long term continuity of the project with the same staff (twelve-and-a-half years); (4) mutual interest in project objectives by both partners; (5) applying the principle of learning from each other.

    The project profited from the political change of economic liberalisation in Vietnam in the second half of the eighties since recommendations for improved use of acid sulphate soils, emphasising small-scale development, could much better applied by small farmers than by large scale state farms.

    Two evaluation studies of the acid sulphate land in the Mekong delta (chapter V) showed that fresh water availability is the most important constraint to farming. Moderately and slightly acid land, characterised by a sulphuric horizon deeper than 50 cm, of which large tracts are present in the Mekong delta, can become suited for rice and tolerant upland crops such as yam, cassava or sweet potato when fresh water is available. However, severely acid land will only become marginally suited and should therefore not be given priority for development. Well constructed raised beds can improve the land and makes moderately acid land highly suited for pineapple and sugar cane, provided the coastal salt intrusion in the dry season is short (less than 3 months) and the annual Mekong river flood does not exceed a depth of about 60 cm. Both evaluation studies describe in detail farmers' practices of an unexpected wide variety of land use types and thereby emphasise the main focal point of this thesis which is the major input of farmer's expertise in developing innovative management schemes for these problem soils.

    Integrated soil and water management in acid sulphate soils : balancing agricultural production and environmental requirements in the Mekong Delta, Viet Nam
    Le, Q.M. - \ 1996
    Agricultural University. Promotor(en): J. Bouma, co-promotor(en): T.P. Tuong. - S.l. : Le Quang Minh - ISBN 9789054855569 - 134
    zure gronden - kattekleigronden - grondwaterspiegel - bodem - uitspoelen - aluminium - acid soils - acid sulfate soils - water table - soil - leaching - aluminium

    The objectives of this study in the Mekong delta, Vietnam, were: (1) to obtain a better understanding of the effects of soil physical properties and flow types on solute transport in ASS emphasing aluminum; (2) to quantify environmental hazards resulting from amelioration activities in acid sulphate soils (ASS); and (3) to identify measures which can increase agricultural production and reduce negative environmental side effects.

    This study was conducted on ASS in the Mekong delta, Vietnam and consisted of 5 experiments starting in the dry season and ending at the end of the flood season. All experiments were carried out under field conditions. Transport of soluble aluminum was investigated for different types of water flow, which are typical for each season such as capillary rise, bypass flow and runoff.

    During the dry season, soluble aluminum was accumulated in topsoil layers by capillary rise. Effects of land management methods on accumulation of aluminum was the main focus in this period: Plowing (P1) and mulching (Ml), compared with non-plowing (P0) and non-mulching (M0). Experiments were conducted in lysimeters, and under field conditions. In both experiments, topsoils were treated with P1M1, P1M0, P0M1, and P0M0. Three levels of ground water (GWL: 30, 60, and 90 cm below the ground surface) were maintained in the undisturbed soil columns in the lysimeters. Aluminum accumulation increased with increased evaporation. Under field conditions, where ground water levels were monitored but not controlled, mulching treatments gave a significantly lower aluminum accumulation as compared with the non-mulching treatments, whereas plowing did not result in a significant decrease of this accumulation. Rainfall during the first 3 weeks of the rainy season caused the ground water to rise rapidly while its aluminum concentration increased. This increased the soluble aluminum concentrations in the topsoils and eliminated the leaching effects of earlier land management practices.

    During the rainy season, the study was focused on aluminum transport with bypass flow and runoff in and on raised beds, which are constructed by soil materials excavated from adjacent lateral ditches with the objective to avoid flooding and to enhance leaching of soil. This is a very common technique to grow upland crops in ASS. Therefore, a better understanding of leaching processes in raised beds is needed to properly assess management options for ASS. Three types of raised beds, which are commonly constructed in the Mekong delta, were studied. In the low raised beds only topsoil material was used to construct the bed. In the high type both top soil and the jarosite layer were used. In the "traditional" raised beds, pyritic material was also found on top of the beds. The amount of runoff increased with cumulative rainfall due to a decrease of infiltration rates and saturated hydraulic conductivities. Due to surface crusting, traditional beds gave the highest runoff amounts among the three types. Concentrations of aluminum in bypass flow were consistently higher than in runoff In low and high beds, amounts of aluminum in bypass flow were also higher than in runoff, whereas in traditional bed-types it was slightly lower. However, the negative impacts on the surrounding surface water was not significantly different for the three types of beds. Therefore, the low bed type is the most desirable from an agricultural production point of view, because less effort is needed in construction.

    Pore system distribution can play a very important role in determining water flows in and on the raised beds and as a consequence, on the effectiveness of leaching toxic substances. Thus, field and laboratory studies were carried out to quantify the effects of soil physical properties and bypass flow on leaching processes of new, 1-year old and 2-year old raised beds for yam and pineapple cultivation. Water-conducting pores were characterized using Methylene Blue. Number, area, and perimeter of water- conducting pores at 10-cm depth intervals of six 1 x 1m subplots were investigated. Undisturbed 20 cm x 25 cm soil cores were subjected to three 30 mm h -1rains in 30 minutes. Volume, aluminum and sulphate concentration of outflows were monitored. Due to consolidation, the area and perimeter of water-conducting pores in 2-year old pineapple beds had decreased to about one third, and bypass flow rates to about 80% of those in newly constructed beds. Consolidation, however, did not affect macropore network geometry in yam beds because they were subjected to annual tillage and yam tubers were uprooted regularly. Al and SO42-concentrations in the outflows of newly constructed and 1-year old raised beds were higher in pineapple, while those in 2-year raised beds were higher in yam.

    A side effect of leaching of ASS may be the pollution of surrounding waters. In order to obtain a proper assessment of this problem, the concentration and the amount of aluminum in water leaching from ASS during cultivation of rice, pineapple and yam were investigated. The fields have been reclaimed for 2 months, 1 and 2 years, respectively. Pineapple and yam were cultivated on raised beds. Values of pH in drainage water ranged from 2.9 to 3.9 and aluminum concentration from 3 to 13 mmol(+) l -1. Mean monthly aluminum concentrations in the water discharged from pineapple and yam raised beds was about 3 times higher than from rice fields. Monthly total amount of aluminum released by the raised beds could be as high as 16,690 mol ha -1, and was 3 to 5 times higher than that from rice fields. Consolidation and crust formation in pineapple beds reduced the concentration and amount of aluminum released as the beds grew older. In June, leaching from ASS was most hazardous to the environment due to a combination of highest total aluminum released to the canal network and a relatively low river discharge.

    At the flood recession period, the effectiveness of flood water (in combination with harrowing) in flushing out toxic substances from the top soil of ASS was investigated. Three experimental sites with slight, moderate and strong acidity were selected. Treatments were the number of harrowings (one: H1 and three times: H3) and the number of flushings (one: F1 and three times: F3).Three times harrowing in combination with three times flushing was the most effective in leaching acid in the most acid soils. When flushing once, the number of harrowings had no effect. The quantity of aluminum adsorbed on the soil exchange complex was not affected by different harrowing and flushing treatments. F3H3 also gave a significantly higher rice yield as compared with other treatments. The flood recession period is the most appropriate moment for flushing topsoils for rice cultivation, which has a high water requirement.

    Developing management packages for acid sulphate soils based on farmer and expert knowledge : field study in the Mekong Delta, Viet Nam
    Quang Tri, Le - \ 1996
    Agricultural University. Promotor(en): J. Bouma; V.T. Xuan. - S.l. : Le Quang Tri - ISBN 9789054855583 - 200
    zure gronden - kattekleigronden - landevaluatie - grondvermogen - bodemgeschiktheid - ruimtelijke ordening - landgebruik - zonering - expertsystemen - vietnam - kunstmatige intelligentie - acid soils - acid sulfate soils - land evaluation - land capability - soil suitability - physical planning - land use - zoning - expert systems - vietnam - artificial intelligence

    Effective interaction of farmers' expertise and expert knowledge has been a special point of attention for this study. The objectives of the study were to describe the process of interaction between farmers and experts in improving the use of acid sulphate soils and to point out difficulties encountered. Actual conditions for four major areas were described including variabilities. Four representative areas: Tan Thanh, Tri Ton, Phung Hiep, and Hong Dan in the Mekong Delta, Viet Nam were selected for this study. Physical conditions were defined in terms of soil properties, as reflected by soil classification, and hydrological conditions were defined by climate data including flooding. Methods for land improvement in different areas were first defined by describing and analyzing measures taken by farmers, and by next developing schemes for improvement, using expert knowledge. These schemes were expressed by decision trees as a part of expert systems. But many questions were left and a series of experiments was designed and executed to answer those questions that could not be answered by experts.

    Four study areas were selected. Tan Thanh and Tri Ton (in the Plain of Reeds and Long Xuyen Quadrangle, respectively) have acid sulphate soils with sulphuric horizons within 50 cm from the soil surface, and deep flooding (>100cm) during the rainy season. The Phung Hiep area with moderately acid sulphate soils is not deeply flooded and is located in the fresh water area of Ca Mau peninsula. The Hong Dan area contains mainly moderately and strongly acid sulphate soils with salt water intrusion during the dry season. The main agricultural problems in these study areas, where most farmers are poor, arise from the fact that most modem practices or new cropping patterns are applied incompletely and at unequal levels. Also unfavourable soil acidity coincides with high flooding depth or salt water intrusion, poor infrastructure for irrigation and drainage and shortage of capital for farm production. Furthermore, price fluctuations of farm products are very high, which makes economic production very difficult.

    A study at farmers' level shows that the history of fanners' land use, including their soil-water-crop management practices clearly indicates changes of land use over time and the important role of expert knowledge in initiating these changes. Developments also illustrate the positive effects of the creative interaction between fanners and experts in developing innovative management systems. Ten, four, sixteen and eleven actual land use types, including land and water practices, were described for the Tan Thanh, Tri Ton, Phung Hiep, and Hong Dan areas, respectively. Water-soil-crop management practices such as construction of canals and infrastructure for irrigation, construction of high raised beds for cultivation of upland crops, and construction of a ditch system for the prawn/shrimp-rice system were essential parts of these land use systems.

    Studies by experts paid more attention to the cultivation of crops, mainly rice, and the associated water management practices. Sixteen promising land use types were defined for a land suitability classification study based on present land use systems of four study areas. Double cropping of modem rice varieties is present in all study areas. Eight land qualities were identified for a farm-level land evaluation. Land quality "(potential) soil acidity" is important for all land use types selected. Land qualities: "flood hazard", "drought hazard", "salt water intrusion", and "fresh water availability" are important for double cropping of modem rice varieties. Land qualities: "potential for daily tidal flooding and drainage" are critical for raising of prawn/shrimp. For land evaluation at farm level, decision trees were developed and used as an decision support system. Decision trees were made for each promising land use type. Using decision trees as a decision support system for land evaluation study at the farm level was shown to be helpful to identify optimal management decisions. Conditions for improvement of suitability were identified and visualized in those decision trees, in terms of improved soil and water practices based on farmers' expertise and expert knowledge.

    While developing these schemes, it became clear that many unanswered questions on land use requirements and water management practices were encountered. These were formulated and field experiments were carried out to answer the questions. Some conclusions were drawn from these experiments: (1) For yam cultivation in acid sulphate soil areas with a deep flood in the wet season, application of a mulch layer on top of the raised bed resulted in a 46% higher yield as compared with urimulched plots; (2) the use of fresh water in an irrigation frequency of 20 days, when available during the dry period of the cropping season, increased yields of yam by 31%. (3) Rolled-carpet raised beds gave higher yields as compared with mixed-raised beds. (4) A relatively high yield of yarn can be obtained by application of N 120 -P 60 -K 60 as is already being practised by farmers in the area or N 80 -P 160 -K 100 . Higher fertilizer applications give no better yields. Staking yam vines is of limited importance and does not increase yarn production. A planting density of 40 cm. x 50 cm is proposed for yam cultivation. (5) For pineapple cultivation in areas with dry season salinity, supplementary irrigation in the early dry season had no effect on pineapple yield. (6) Production was higher on high raised beds as compared with traditional lowraised beds because excess water in the rainy season. Old raised beds gave significantly higher yields as compared with younger raised beds because of lower acidity due to longer leaching by rain. (7) A yield increase of pineapple of about 20% can be obtained by a combination of high P and K fertilization ( 10N-7g P 2 O 5 -10K 2 O/plant). And (8) application of the zero-tillage technique was profitable as it shortened the duration of double cropping of Winter-Spring modem rice followed by Summer-Autumn rice in areas with long duration flooding. These accumulated results provided quantitative data to characterize land qualities and land use requirements relating to fresh water availability, soil acidity, and flooding hazard . Also data for agronomic practices were obtained by experiments to be used for formulating optimal management packages.

    Under different physical conditions, optimal management packages on acid sulphate soils were finally formulated for the four study areas in. These optimal management packages were based on the farmers' practice, expert knowledge, results of land evaluation study at farm level and accumulated results obtained by field experiments. There are many options including various cultural, soil and water management practices for the different physical conditions encountered. Double modem rice cropping, and growing yam, pineapple, and sugarcane, are suitable in areas where fresh water is available during the dry season. In areas with salt water intrusion during the dry season, land use types incorporating shrimp are more profitable. Melaleuca spp. is most suitable for remote and unfavourable areas for crop growth as a means for reforestation in order to protect natural environments. These results provides a good start to obtain description of realistic and acceptable systems. In the future, these description can also be used to identify areas of additional research by measurement or by simulation modelling.

    Scenario studies on soil acidification at different spatial scales
    Vries, W. de; Kros, J. ; Groenenberg, J.E. ; Reinds, G.J. ; Salm, C. van der; Posch, M. - \ 1995
    In: Scenario studies for the rural environment : selected and edited proceedings of the symposium scenario studies for the rural environment, Wageningen, The Netherlands, 12 - 15 September 1994 / Schoute, J.T.H., Finke, P.A., Veeneklaas, F.R., - p. 169 - 188.
    zure gronden - kattekleigronden - neerslag - chemische eigenschappen - zuurgraad - zure regen - modellen - onderzoek - acid soils - acid sulfate soils - precipitation - chemical properties - acidity - acid rain - models - research
    Three dynamic soil acidification models have been developed for application on local, national and continental (European) scales, namely NUCSAM, RESAM and SMART. This paper gives an overview of results of various model validation and scenario studies for the effects of SOx, NOx and NHx deposition on soils. Furthermore, the various strong and weak points of the models are evaluated in terms of uncertainties in model predictions, the use of the models in acidification abatement policies, and the limitations and possibilities of using the models in other scenario studies, such as changes in land use, hydrology and heavy-metal deposition.
    Effects of acid deposition on Dutch forest ecosystems
    Vries, W. de; Leeters, E.E.J.M. ; Hendriks, C.M.A. - \ 1995
    Water Air and Soil Pollution 85 (1995)3. - ISSN 0049-6979 - p. 1063 - 1068.
    zure gronden - kattekleigronden - bodem - stikstof - bosschade - zure regen - nederland - acid soils - acid sulfate soils - soil - nitrogen - forest damage - acid rain - netherlands
    Effects of elevated sulphur and nitrogen deposition on the solution chemistry of Dutch forest soils are mainly manifested by increased aluminium concentrations, associated with increased concentrations of sulphate and nitrate. Critical aluminium/base cation ratios are often exceeded below 20 cm soil depth. Besides, elevated nitrogen deposition during the last decades has affected the forest nutrient status and caused large changes in vegetation. About half of the Dutch forests have absolute shortage of phosphorus and relative magnesium deficiences compared with foliar nitrogen contents. There is no evidence of a relationship between soil acidification and nutrient imbalances on the one hand and forest vitality on the other.
    Evaluation of water management strategies for acid sulphate soils using a simulation model: a case study in Indonesia
    Bronswijk, J.J.B. ; Groenenberg, J.E. ; Ritsema, C.J. ; Wijk, A.L.M. van; Nugroho, K. - \ 1995
    Agricultural Water Management 27 (1995)2. - ISSN 0378-3774 - p. 125 - 142.
    zure gronden - kattekleigronden - drainage - sloten - indonesië - modellen - onderzoek - acid soils - acid sulfate soils - drainage - ditches - indonesia - models - research
    Reclamation and drainage of potential acid sulphate soils results in acidification and release of toxic elements, hampering their use for agriculture. Ecologically valuable habitats located downstream of reclamation areas may be disrupted. Proper water management is essential to a sustainable reclamation of these soils. The Simulation Model for Acid Sulphate Soils (SMASS) has been developed to predict the effects of water management on soil and water quality. A case-study in the Barambai area in Indonesia, for which six water management strategies were evaluated, illustrates how SMASS can be applied to make a scientifically based evaluation of water management strategies.
    Uncertainties in long-term predictions of forest soil acidification due to neglecting seasonal variability
    Kros, J. ; Groenenberg, J.E. ; Vries, W. de; Salm, C. van der - \ 1995
    Water Air and Soil Pollution 79 (1995)1/4. - ISSN 0049-6979 - p. 353 - 375.
    bosschade - zure regen - zure gronden - kattekleigronden - neerslag - chemische eigenschappen - zuurgraad - modellen - onderzoek - forest damage - acid rain - acid soils - acid sulfate soils - precipitation - chemical properties - acidity - models - research
    Soil and soil solution response simulated with a site-scale soil acidification model (NUCSAM) was compared with results obtained by a regional soil acidification model (RESAM). Uncertainties due to neglecting seasonal variability in long-term predictions were investigated by comparing long-term RESAM and NUCSAM simulations. Although both the seasonal and the interannual variations in soil solution parameters were large, the trend in soil solution parameters of RESAM and NUCSAM corresponded quite well. Generally, it appeared that the uncertainty due to time resolution in long-term predictions was relatively small.
    Modelling the response of terrestrial ecosystems to acidification and desiccation scenarios
    Kros, J. ; Reinds, G.J. ; Vries, W. de; Latour, J.B. ; Bollen, M. - \ 1995
    Water Air and Soil Pollution 85 (1995)3. - ISSN 0049-6979 - p. 1101 - 1106.
    zure gronden - kattekleigronden - plantengemeenschappen - vegetatie - onderzoek - modellen - acid soils - acid sulfate soils - plant communities - vegetation - research - models
    In order to evaluate the effects of eutrophication, acidification and drought on site factors, the SMART2 model has been developed. For the Netherlands, combinations of acidification and seepage scenarios were evaluated with SMART2. The results are focused on pH, nitrogen availability and base saturation. Results showed that deposition reductions lead to a relatively fast improvement of the site factors, increase in pH and base saturation and decrease in nitrogen availability, whereas a reduction in groundwater abstractions by 25% has little or no effect on pH and nitrogen availability.
    Application of soil acidification models with different degrees of process description (SMART, RESAM and NUCSAM) on an intensively monitored spruce site
    Salm, C. van der; Kros, J. ; Groenenberg, J.E. ; Vries, W. de; Reinds, G.J. - \ 1995
    In: Solute modelling in catchment systems / Trudgill, S.T., - p. 327 - 346.
    zure gronden - kattekleigronden - bosbouw - neerslag - zure regen - zure depositie - chemische eigenschappen - zuurgraad - modellen - onderzoek - acid soils - acid sulfate soils - forestry - precipitation - acid rain - acid deposition - chemical properties - acidity - models - research
    A one-layer (SMART) and a multi-layer (RESAM) soil acidification model with temporal resolutions of one year and a multi-layer model with a resolution of one day (NUCSAM) were applied to an intensively monitored spruce site in Solling, Germany. The major aim was to study the influence of model simplifications and reduction of temporal and vertical resolutions on the simulation of soil solution concentrations. Results showed that all the models were able to simulate most of the concentrations reasonably during the examined period (1973-1989). However, the one-layer model, SMART, had difficulties in simulating strong changes in soil solution concentrations owing to a lower retardation in the soil system.
    Modelling phosphate sorption kinetics in acid soils.
    Freese, D. ; Riemsdijk, W.H. van; Zee, S.E.A.T.M. van der - \ 1995
    European Journal of Soil Science 46 (1995). - ISSN 1351-0754 - p. 239 - 245.
    bodem - fosfor - absorptie - adsorptie - zure gronden - kattekleigronden - modellen - onderzoek - soil - phosphorus - absorption - adsorption - acid soils - acid sulfate soils - models - research
    A world perspective on acid sulphate soils.
    Dent, D.L. ; Pons, L.J. - \ 1995
    Geoderma 67 (1995). - ISSN 0016-7061 - p. 263 - 276.
    zure gronden - kattekleigronden - statistiek - wereld - acid soils - acid sulfate soils - statistics - world
    SMASS : a simulation model of physical and chemical processes in acid sulphate soils : version 2.0
    Bronswijk, J.J.B. ; Bosch, H. van den; Nugroho, K. - \ 1994
    Wageningen : DLO Winand Staring Centre (Technical document / DLO Winand Staring Centre 21) - 161
    zure gronden - kattekleigronden - fysicochemische eigenschappen - bodemeigenschappen - bodemchemie - infiltratie - hydraulisch geleidingsvermogen - kwel - modellen - onderzoek - acid soils - acid sulfate soils - physicochemical properties - soil properties - soil chemistry - infiltration - hydraulic conductivity - seepage - models - research
    Soil salinity and acidity : spatial variabil[it]y and effects on rice production in West Africa's mangrove zone
    Sylla, M. - \ 1994
    Agricultural University. Promotor(en): N. van Breemen, co-promotor(en): L.O. Fresco. - S.l. : Sylla - ISBN 9789054852865 - 175
    zure gronden - kattekleigronden - bodem - natrium - verbetering - verzilting - rijst - oryza sativa - landevaluatie - grondvermogen - bodemgeschiktheid - west-afrika - geostatistiek - acid soils - acid sulfate soils - soil - sodium - improvement - salinization - rice - oryza sativa - land evaluation - land capability - soil suitability - west africa - geostatistics

    In the mangrove environment of West Africa, high spatial and temporal variability of soil constraints (salinity and acidity) to rice production is a problem for the transfer and adoption of new agronomic techniques, for land use planning, and for soil and water management. Recently, several National and International Agricultural Centers have initiated research programs to characterize environments where their newly developed technologies have to be applied. However, the mangrove agro- ecosystems in West Africa have not been characterized in a detailed way. Most of the soils in this environment are potential or actual saline acid sulfate soils. The spatial and temporal variability of soil salinity and acidity in these coastal lowlands results from complex interactions between climate, coastal morphology, river hydrology, vegetation, landform and tidal flooding. Diagnosing the occurrence of both potential and actual acid sulfate soils is the first step in land use planning for such areas. But to cope with the intricacies of these soils, understanding the processes of soil salinization and acidification at different scales should be formalized to properly characterize mangrove environments.

    The main objectives of this thesis were: 1) to give a comprehensive characterization framework for the West African mangrove environments with emphasis on the possibilities of and constraints for rice cultivation; 2) to determine the various causal factors for soil salinization and acidification; 3) to test whether temporal variability of soil chemistry is sufficient to provide a time window of minimum stress during the rice growing period; 4) to relate the response of rice to improved agronomic practices in specific environments and to provide a means to characterize specific rice growing locations, and 5) to test rice varietal responses to saline and acid sods under different agronomic practices and to relate yields and yield components to the nutrient contents in leaves, in order to diagnose physiological disorders.

    First, a multi-scale approach was developed involving a range from Macro to Micro level based on the pre-conditions of acid sulfate soil formation. The main factors for classification are climate and coastal morphology at Macro scale; hydrology, physiography and vegetation complexes at Meso level; and topography (catena), vegetation species, tidal flooding and sedimentation rate at Micro level. Information from previous process-based studies on acid sulfate soil formation and data from secondary sources were used. Different environments were then distinguished and their characteristics were summarized by ecological zone. Constraints to rice production and potentials for agricultural development were matched with environmental conservation issues.

    To determine the significance of the causal factors developed in the multiple scale approach, 12 sites were selected along 4 river basins in West Africa, vz. from north to south the Gambia, the Casamance (Senegal), the Geba (Guinea Bissau) and the Great Scarcies (Sierra Leone). Along each river basin 3 sites were selected based on distance from the river mouth. Within a site a strip of land perpendicular to the river was selected for intensive grid sampling (40 by 20 m). Soil samples were taken at each grid node during the dry season of 1991. The relation between causal factors and soil salinization and acidification was determined at Macro and Meso levels by nested ANOVA and yielded a classification of the study area in main ecoregions and sub-environments within watershed. At a detailed scale, geostatistics were applied and zones within catena were defined in terms of their main soil characteristics. A nested statistical approach and geostatistics were used complementarily to disentangle the complexity of the causes of soil salinization and acidification.

    Temporal variability was studied by monitoring soil solution chemistry at each main landscape unit within the catena. Since the production of rice critically depends on the lowering of salinity and acidity by natural flooding during rainy season, time windows during which soil limitations are minimal were defined and matched with rice varietal duration.

    The response of rice to different improvement techniques were tested by means of a network of trials in the 1991 and 1992 rainy seasons. The residual effects of lime and phosphate rock (applied in 1991) during 1992 was also evaluated. Lime dressing (2 t ha -1) was found effective whenever dissolved Ca and Mg in the soil were low, and had a clear residual effect in the year after application. Application of phosphate rock did not seem to be effective in general. For iron toxicity, the molar fraction of Fe and (Ca + Mg) in soil solution and in flag leaves were found to be more relevant for diagnosing physiological disorders than the absolute Fe content in the soil solution and in rice flag leaves at panicle initiation.

    In the 1993 rainy season, rice varietal behavior under different improvement techniques within the main soil limitations in the mangrove environment was tested. Differences in yield and yield components and element contents in flag leaves at panicle initiation were observed between varieties in saline and less saline acid soils. Multiple correlation between rice yields, yield components, element contents in flag leaves at panicle initiation was found to be an effective diagnostic tool for assessing physiological disorders.

    The approach used in this study provides a logical framework to describe mangrove environments. The multiple-scale can assist in identifying the information required to cater for the needs of various decision-makers and land use planners. It also provides a key to develop technology packages for intensified and sustainable use. It can be used for the extrapolation of site-specific information to geographically different areas, with similar characteristics.

    Time trends & mechanism of soil acidification
    Wesselink, L.G. - \ 1994
    Agricultural University. Promotor(en): N. van Breemen; J.J.M. van Grinsven. - S.l. : Wesselink - ISBN 9789054852896 - 129
    zure gronden - kattekleigronden - bosbouw - verzuring - bodem ph - bodemaciditeit - neerslag - chemische eigenschappen - zuurgraad - zure regen - acid soils - acid sulfate soils - forestry - acidification - soil ph - soil acidity - precipitation - chemical properties - acidity - acid rain

    The effects of acid atmospheric deposition on forest ecosystems have been studied intensively in the past two decades. Measurements of element budgets in forested ecosystems throughout the world have shown that acid deposition may deplete stores of exchangeable base cations in the soil, decrease the soil pH, increase rates of mineral weathering, and release potentially toxic Al into the soil solution. In summary, acid atmospheric deposition can strongly alter the chemical environment for living organisms.

    In this thesis the mechanisms that may control those phenomena are studied, with emphasis on soil chemical processes. Central in this study are long and comprehensive data sets from continuous measurements (monitoring) of element fluxes in forest ecosystems, specifically from the Solling experimental forest in Germany.

    Base Cations

    Using over 20 years of data on deposition and soil chemistry at Solling, chapter 2 discusses how long-term changes in atmospheric deposition of acid anions and base cations affect dissolved and exchangeable pools of base cations in the soil, through the process of cation exchange. Positive effects of declining SO 4 deposition in the 1980s, which potentially reduces leaching of base cations from the soil, were partially offset by (i) continued high concentrations of dissolved SO 4 in the soil and (ii) declining deposition of the base cations Ca and Mg. The latter appears to result from stricter controls on particle emissions from fuel combustion and industrial processes. Recent studies indicate that declining deposition of base cations is observed in other regions of Europe and North America as well. This is a matter of concern as forests may be sensitive to changes in base cation deposition which is, together with mineral weathering, the most important source of nutrients to forests on acidified soils.

    In chapter 3 we quantified rates of mineral weathering at Solling, as a source of nutrients and acid neutralization. Estimates of field weathering rates were obtained from, (i) long-term input- output mass balances, correcting for changes in stores of exchangeable base cations in the soil, and (ii) elemental analysis of the soil profile. At Solling, rates of supply of Ca, K and Na by weathering are much lower than by atmospheric deposition; for Mg the contributions are of similar magnitude. This emphasizes (i) the relevance of atmospheric deposition of base cations as a nutrient source to the Solling forests, and (ii) the concern with respect to its present decline. To investigate mechanisms of mineral weathering of Mg and K, a series of laboratory weathering experiments with soils from Solling were conducted.

    These focused on weathering of illite, the dominant mineral source of K and Mg. A major problem in quantifying rates of mineral weathering is the large discrepancy in rates obtained in laboratory studies and field estimates, with laboratory rates being generally one to three orders higher. In the laboratory, effects of pH, temperature, and soil solution composition on illite weathering were studied. Corrected for the effects of these factors, Mg and K release rates from illite measured in the laboratory were comparable (K) or a factor 2 to 4 higher (Mg) than rates inferred from field methods. It is concluded that field estimates of weathering rates, from elemental analysis of the soil profile or input-output flux balances, remain necessary to obtain reliable estimates of base cation weathering rates.

    Anions

    In a simplified way, anions in the soil solution can be regarded as carriers of base and acid cations, through charge balance constraints. Understanding the processes that determine dissolved concentrations of these components in the soil is therefore of prior importance. In chapter 4 we discussed the processes that govern the mobility of dissolved Cl, SO 4 and NO 3 in the Solling spruce soil over a period of 18 years. For this purpose a simulation model describing soil hydrology and a number of biogeochemical processes was introduced. Using throughfall water and concentrations as input to the model, concentrations of Cl in soil solutions were successfully simulated, a requirement to further study components that interact chemically or biologically with the soil.

    Sorption of SO 4 is of significance in the soils at Solling due to comparatively high contents of Al and Fe oxides. By contrast, in the mineralogically poor sandy soils in the Netherlands SO 4 often behaves chemically nearly conservative. The steep increase in dissolved SO 4 in the Solling spruce soil during the mid-1970s was modelled adequately using adsorption parameters reported in literature, and was explained by a steep adsorption isotherm and a state of near saturation of SO 4 sorption sites in the early 1970s, at the start of the monitoring program. Rates of desorption of SO 4 in the 1980s in response to declining SO 4 deposition, described by the same model, were less than those measured in the field. In the absence of evidence for alternative controls on dissolved SO 4 , like jurbanite (AlOHSO 4 dissolution, the mechanism of SO 4 desorption remains unclear.

    The model increased our understanding of the processes that control repeated 3-year cycles of high and low concentrations of N0 3 in deeper layers (90 cm) of the Solling spruce soil. Recently, there is increasing interest in N-dynamics in forest ecosystems, as N-saturation has been hypothesized as an additional cause of forest decline. In the Solling spruce soil, concentrations of N0 3 water leaving the soil profile increased when the N-flux into the mineral soil, from deposition and net mineralization, exceeded the N uptake capacity of the forest at a threshold value of around 4 kmol ha -1yr -1. At present, total deposition of N on the spruce forest amounts to 3.3 kmol ha -1yr -1and is close to this threshold value. This points to the critical role of N mineralization processes in the litter layer, where large stores of N have accumulated over the past 25 years. The annual release of N from the spruce litter layer was positively correlated with rainfall. This was apparent from large N releases from litter in relatively wet years which subsequently increased NO 3 concentrations at the 90 cm depth.

    Aluminum

    The main acid neutralizing process in acid forest soils under high acid loads is the release of AI to the soil solution. Soil acidification models generally describe the solubility of reactive soil Al by equilibrium or kinetic dissolution of Al-trihydroxide (Al(OH) 3 ), In chapters 5 and 6, we scrutinized the evidence for this reaction mechanism from extensive sets of field data, but found little support for the gibbsite model. By contrast, evidence points to AI binding to soil organic matter as a control of dissolved Al, even when organic matter contents are low. In chapter 6 a new, mechanistic, and yet simple model was presented that explained much of the spread in Al-solubility, as observed in 29 different soil layers from 18 forest soils. The model describes Al-solubility as a function of the degree to which humus binding sites are saturated with Al. It involves only two soil specific parameters, the organic C content of the soil and an estimate of the pool of organically bound soil Al, and may therefore be easily incorporated in current soil acidification models.

    The soils studied in this thesis generally receive high loads of acid deposition, and acidity is largely neutralized by release of Al in the upper 20 cm of the mineral soil. It has been suggested that in surface layers of these soils depletion of reactive soil Al may result within decades. The depletion hypothesis was put to test by measuring pools of organically bound soil Al in old (around 1980) and new (around 1993) samples from research sites at Hackfort and Gerritsfles in the Netherlands, and Solling in Germany. Indeed, significant decreases with time were found. Independently measured depletion of organically bound soil Al and declining Al solubility, as observed previously from 6 years of field monitoring at Hackfort in the 1980s, proved to be consistent with the humus-Al model presented in this thesis. Rates of depletion of organically bound soil Al at Hackfort, the Netherlands, during a period of about 13 years were lower than expected from long-term monitoring of Al solute fluxes. This suggests that pools other than organically bound Al, i.e. silicates and inorganic Al hydroxides, may contribute to Al mobilization as well. Literature indicates that release of Al from these pools may be kinetically constrained. The current discussion on whether Al activities in solutions of acid forest soils are controlled by kinetically constrained (time dependent) dissolution of inorganic Al hydroxides or by equilibrium binding to soil organic matter is, in my view, clarified when the kinetic and the equilibrium process are regarded as sequential; kinetic release supplying Al to the organic exchanger, which equilibrates with the soil solution.

    GENERAL CONCLUSIONS

    1. In the recent past, deposition of SO 4 , Ca and Mg on the German Solling forests has declined significantly as a result of reduced industrial emissions.
    2. Results from Solling indicate that soil de-acidification, i.e. an increase in the pool of exchangeable base cations, as a result of declining SO 4 deposition may be offset by i) continuous release of sorbed SO 4 from the soil and ii) declining deposition of base
    cations.
    3. Weathering rates of Ca, K and Na at Solling, Germany, are much lower than their supply by atmospheric deposition; for Mg the contributions of deposition and weathering are of similar magnitude.
    4. Illite is the main mineral source of Mg and K at Solling. Although coming from the same mineral source, the two cations are released by different mechanisms. Magnesium release is controlled by chemical kinetic processes and its release is highly
    pH dependent (R≈(H +) 0.8), whereas K is released from interlayers by diffusion, a process that showed independent of pH.
    6. A six-fold increase of dissolved SO 4 in the Solling spruce soil (90 cm) in the mid 1970s, and continuously high concentrations thereafter, is explained by 'peaking' SO 4 deposition loads in the mid-1970s that entered a mineral soil where the SO 4 sorption capacity was nearly saturated.
    6. Repeated 3-year cycles of high and low concentrations of NO 3 in deeper layers (90 cm) of the Solling spruce soil are related to excess release of N from the litter layer in comparatively wet years.
    7. Strong changes in pH and less strong changes in pAl (-log{Al 3+}) in response to varying acid anion concentrations, generally observed in acid forest soils, and the measured increased of CEC with time in the surface soil of the Solling spruce sites, support the hypothesis of Al solubility control by complexation to soil organic matter.
    8. Data from 29 soil layers of 18 forest soils, covering a range in soil pH, Al activities, and reactive soil Al pools indicate that Al solubility control by complexation to soil organic matter is a general phenomenon, even when organic C contents are low.
    9. Much of the variation in Al solubility observed in 29 different soil layers of 18 forest soils is explained by the organically bound Al: soil C ratio.
    10. In surface soils where stores of organically bound Al are low and release rates high depletion of reactive, organically bound, soil Al is significant on a time scale of 12 to 14 years only.
    11. Independently measured declines in (i) Al solubility in surface soils at Hackfort the Netherlands, from 6 years of monitoring of soil water chemistry and (ii) pools of organically bound soil Al, are consistent with the Al-humus equilibrium model
    proposed in this thesis.
    12. In acid forest soils where dissolved Al activities are controlled by equilibrium complexation to soil organic matter, kinetically constrained release of Al from inorganic Al pools may well contribute to acid neutralization.

    Effects of flooding on pH of rice-producing, acid sulfate soils in Indonesia.
    Konsten, C.J.M. ; Breemen, N. van; Suping, S. ; Bagus Aribawa, I. ; Groenenberg, J.E. - \ 1994
    Soil Science Society of America Journal 58 (1994). - ISSN 0361-5995 - p. 871 - 883.
    rijst - oryza sativa - zure gronden - kattekleigronden - landevaluatie - grondvermogen - bodemgeschiktheid - veldcapaciteit - waterverzadiging - indonesië - rice - oryza sativa - acid soils - acid sulfate soils - land evaluation - land capability - soil suitability - field capacity - waterlogging - indonesia
    Seasonal and spatial variation of heavy metal solubilities in a fallow, acidic loamy sand loam
    Castilho, P. del; Blaauw, D. ; Salomons, W. - \ 1993
    In: Integrated soil and sediment research : a basis for proper protection : selected proceedings of the first European conference on integrated research for soil and sediment protection and remediation (EUROSOL), held in Maastricht, 6 - 12 September 1992 / Eijsackers, H.J.P., Hamers, T., Kluwer (Soil & environment vol. 1) - p. 255 - 256.
    bodemoplossing - bodem - zware metalen - zure gronden - kattekleigronden - soil solution - soil - heavy metals - acid soils - acid sulfate soils
    Time series analysis of changes in the soil solution: evidence for approach to nitrogen saturation in Dutch forest soils.
    Stein, A. ; Breemen, N. van - \ 1993
    Agriculture, Ecosystems and Environment 47 (1993). - ISSN 0167-8809 - p. 147 - 158.
    zure gronden - kattekleigronden - neerslag - chemische eigenschappen - zuurgraad - zure regen - statistiek - waarschijnlijkheidsanalyse - wiskunde - acid soils - acid sulfate soils - precipitation - chemical properties - acidity - acid rain - statistics - probability analysis - mathematics
    Sulfidic materials in the Western Mekong Delta, Vietnam.
    Brinkman, R. ; Nguyen Bao Ve, ; Tran Kim Tinh, ; Phuoc Hau, Do; Mensvoort, M.E.F. van - \ 1993
    Catena 20 (1993). - ISSN 0341-8162 - p. 317 - 331.
    zure gronden - kattekleigronden - vietnam - acid soils - acid sulfate soils - vietnam
    Selected Papers of the Ho Chi Minh City Symposium on Acid sulphate soils. Vietnam, March 1992
    Dent, D.L. ; Mensvoort, M.E.F. van - \ 1993
    Wageningen : ILRI (ILRI Publication 53) - 425
    zure gronden - kattekleigronden - wereld - acid soils - acid sulfate soils - world
    Analysis of aluminium sensitivity in sorghum (Sorghum bicolor (L.) Moench) genotypes
    Tan, K. - \ 1993
    Agricultural University. Promotor(en): G.R. Findenegg; W.G. Keltjens. - S.l. : Tan - ISBN 9789054850946 - 155
    oogstschade - bodemverontreiniging - bodemgiftigheid - bodemzoutgehalte - Sorghum bicolor - toxische stoffen - chemie - indicatorplanten - toxinen - planten - bodem - aluminium - oogsttoename - oogstverliezen - opbrengsten - zure gronden - kattekleigronden - chemische factoren - crop damage - soil pollution - soil toxicity - soil salinity - Sorghum bicolor - toxic substances - chemistry - indicator plants - toxins - plants - soil - aluminium - yield increases - yield losses - yields - acid soils - acid sulfate soils - chemical factors

    Twelve genotypes of sorghum ( Sorghum bicolor (L.) Moench) differing in Al sensitivity were grown in an acid soil (with additions of lime or MgSO 4 ) and in nutrient solutions (with or without Al at constant pH) for periods between 14 and 35 days. The objective was the identification of the factors controlling dry matter yield of sorghum under different growth conditions. In both media Al was the major constraint, restricting growth in two independent ways: (1) by inducing Mg deficiency and (2) via damaging the roots ( i.e. by giving them a stubby and discolorated appearance and by reducing their specific root length, m g -1dry root). The sensitivities of the genotypes against Al-induced Mg deficiency and Al-induced root damage were not correlated. At moderate acidity (pH around 4.8), Mg deficiency dominantly limited growth whilst at a higher acidity (pH ~4.2) root damage overruled Mg deficiency in its negative effect on growth. At pH 4.8, addition of Mg improved growth by reducing the degree of Mg deficiency. At pH 4.2, Mg improved growth mainly by preventing the roots from Al- induced damage.

    Several external factors modified the AI sensitivity of the genotypes by strengthening or weakening the negative effects of Al on Mg nutrition and root development. At pH 4.2, Ca and NH 4 both counteracted AI-induced root damage but aggravated Al-induced Mg deficiency. The contrary was true for NO 3 . When the concentration of soluble Al was kept approximately constant at 15 μM, both Al-induced root damage and Mg deficiency were aggravated by acidity in the range pH 3.9-4.8. Aluminium toxicity in sorghum grown in nutrient solution was independent of P deficiency, although an increased P supply partly eliminated Al phytotoxicity.

    The results stress the importance of both Al and Mg ions and their interactions in determining growth response of sorghum and other cereals to acid soils.

    The transformation of potential into actual acid sulphate soils studied in column experiments
    Ritsema, C.J. ; Groenenberg, J.E. ; Bisdom, E.B.A. - \ 1992
    Geoderma 55 (1992)3/4. - ISSN 0016-7061 - p. 259 - 271.
    zure gronden - kattekleigronden - acid soils - acid sulfate soils
    The transformation of potential into actual acid sulphate soils was studied in a 450 day column experiment to determine the rate and extent of pyrite oxidation and accompanying buffering processes. One potential acid sulphate soil was derived from the lower section of a Typic Sulfaquept (Soil Survey Staff, 1987) or Thionic Fluvisol (FAO, 1988) near the village of Nieuwkoop, the Netherlands, and the other from beneath the acidified upper part of a Typic Sulfaquent (Soil Survey Staff, 1987) or Thionic Fluvisol (FAO, 1988) of the Pulau Petak region in South Kalimantan, Indonesia.

    Drainage of both the potential acid sulphate soils caused a strong acceleration in pyrite oxidation, i.e. approximately 10 g FeS2 per kg soil in the Dutch soil and more than 20 g in the Indonesian soil. In both columns, iron, released by the oxidation of pyrite, is immobilized instantaneously due to the precipitation of jarosite and/or iron hydroxides.

    The presence of carbonates prevented acidification of the soil solution upon pyrite oxidation in the Dutch soil, whereas severe acidification of the soil solution occurred in the Indonesian soil. The cationic composition of the adsorption complex is seriously affected in layers where pyrite oxidation occurred; main exchange reactions are Al3+ against Ca2+ and Mg2+ for the drained Dutch and drained Indonesian soils, respectively.

    The experimentally obtained actual acid sulphate soils show a high similarity with the actual acid sulphate soils found in the regions under consideration.
    Research on acid sulphate soils in the humid tropics : proposal phase 2
    Anonymous, - \ 1992
    Wageningen : LAWOO (Research on acid sulphate soils in the humid tropics )
    zure gronden - kattekleigronden - verbetering - bodem - niet-metallische elementen - onderzoek - zwavel - tropen - acid soils - acid sulfate soils - improvement - soil - nonmetallic elements - research - sulfur - tropics
    Improvement of acid sulphate soils by leaching with salt or brackish water.
    Mensvoort, M.E.F. van; Duong van Ni, ; Schans, J. van der - \ 1991
    In: Rice production on acid soils of the tropics / Deturck, P., Ponnamperuma, F.N., - p. 219 - 224.
    verbetering - zure gronden - kattekleigronden - bodem - uitspoelen - improvement - acid soils - acid sulfate soils - soil - leaching
    Proton sinks in soil controlling soil acidification.
    Bruggenwert, M.G.M. ; Hiemstra, T. ; Bolt, G.H. - \ 1991
    In: Soil acidity / Ulrich, B., Sumner, M.E., - p. 8 - 27.
    zure gronden - kattekleigronden - bodem - bodemkunde - ionenuitwisseling - acid soils - acid sulfate soils - soil - soil science - ion exchange
    Calculated rates of soil acidification of intensively used grassland in the Netherlands
    Oenema, O. - \ 1990
    Fertilizer research 26 (1990)1-3. - ISSN 0167-1731 - p. 217 - 228.
    graslanden - zure gronden - kattekleigronden - bodem - uitspoelen - nitraten - grasslands - acid soils - acid sulfate soils - soil - leaching - nitrates
    The major processes involved in acidification of soils under intensively managed grassland are the transformation and subsequent leaching of applied nitrogen (N), assimilation of excess cations in herbage and acidic atmospheric deposition. Carbonates from fertilizers and excess cations in purchased concentrates are the most important proton (H ) neutralizing agents applied to grassland. In this study, the effects of grazing, cutting and N application on the net proton loading from each of the main processes were calculated, using a simple model. On mown swards, simulated excess cation uptake by the sward released 4.5–9.3 kmolc H ha–1 yr–1. The total proton loading on mown grassland decreased from about 8.0 to 5.3 kmolc ha–1 yr–1 when fertilizer N input as CAN-27 increased from 0 to about 400 kg ha–1 yr–1. Contributions from atmospheric deposition ranged from 2.2 kmolc ha–1 yr–1 when herbage yield exceeded 10 Mg ha–1 yr–1 to 3.0 kmolc ha–1 yr–1 when herbage production was only 5.5 Mg ha–1 yr–1. On grazed swards, transformation of organically bound N from urine and dung to nitrate (NO 3 - ) and the subsequent leaching of excess NO 3 - was the main source of protons. Application of 400 kg N ha–1 yr–1 to grazed swards increased the proton loading from transformed N from 3.9 to 16.9 kmolc ha–1 yr–1. The total proton loading on grazed swards exceeded that of mown swards when the input of fertilizer N exceeded 150 kg ha–1 yr–1. Underestimation of the amount of N immobilized in the soil biomass and lost by denitrification may have resulted in a slight overestimation of the amount of N lost by leaching and thereby also the simulated total proton loading.
    Inhibition of nodulation of lucerne (Medicago sativa L.) by calcium depletion in an acid soil.
    Pijnenborg, J.W.M. ; Lie, T.A. ; Zehnder, A.J.B. - \ 1990
    Plant and Soil 127 (1990). - ISSN 0032-079X - p. 31 - 39.
    medicago - bodem - calcium - zure gronden - kattekleigronden - stikstofbindende bacteriën - symbiose - rhizobium - medicago - soil - calcium - acid soils - acid sulfate soils - nitrogen fixing bacteria - symbiosis - rhizobium
    Biological nitrogen fixation by lucerne (Medicago sativa L.) in acid soils
    Pijnenborg, J. - \ 1990
    Agricultural University. Promotor(en): A.J.B. Zehnder; T.A. Lie. - S.l. : Pijnenborg - 112
    medicago - assimilatie - stikstof - zure gronden - kattekleigronden - medicago - assimilation - nitrogen - acid soils - acid sulfate soils

    Growth of lucerne( Medicago sativa L.) is poor in soils with values of pH-H2O below 6. This is often due to nitrogen deficiency, resulting from a hampered performance of the symbiosis withRhizobium meliloti. This thesis deals with the factors affecting biological nitrogen fixation by lucerne in acid soils.

    In a field experiment, lucerne seeds were either inoculated withR.meliloti only,or inoculated and pelleted with lime, before sowing in a sandy soil of pH 5.2. Lime-pelleting significantly improved the establishment of the seedlings. This was caused by earlier nodulation, as evidenced by the formation of crown nodules,i.e.the nodules on the upper 10 mm of the seedling taproot. The number of seedlings carrying crown nodules tripled from 18% to 56%, 26 days after sowing as a result of lime-pelleting. The dry matter yield and nitrogen fixation of the plants at later stages showed a close correlation with crown nodulation.

    To minimize the problems inherent to field experiments,e.g.costs and labour, besides pots, rhizotrons (small root boxes made of plastic petri dishes) were developed to study the symbiosis under controlable conditions in the laboratory (Chapter 2). Comparative trials showed that crown nodulation in pots was practically similar to that in the field. In rhizotrons, the early root development and nodule formation could continuously be observed. moreover, lime- pelleting resulted in a greater increase of crown nodulation (5% to 90%) during a shorter incubation period (14 days).

    R.melilotibacteria are notorious for their acid sensitivity. As a consequence the increased crown nodulation by lime-pelleting might be the result of a better proliferation of these bacteria, thus resulting in a higher chance of root infection. To verify this hypothesis, the effect of lime-pelleting on the survival of inoculated R.meliloti around the seed was recorded during a period of 12 days following sowing. In the initial 12 hours a strong increase in rhizobial numbers coincided with the germination of the seed. Little differences in multiplication were measured in the presence or absence of a lime-pellet. To obtain optimal nodulation in this soil, however, lime-pelleting was a prerequisite and at least 10 5cells ofR.meliloti per seed were required. In the absence of lime, only a few plants nodulated, even when the number of rhizobia was increased to 10 7per seed (Chapter 3).

    The nodulation effect of lime-pelleting could not be explained by a better rhizobial multiplication. The benefit of CaC0 3 can be due to either neutralization of soil acidity and/or to the input of calcium.Tostudy the pH changes in the rhizosphere while leaving the spatial arrangement of the soil intact, the following method was deviced: The soil was covered with a thin layer of agar containing the pH indicator bromocresol purple. To prevent the contamination of agar with soil particles, a nylon gauze was used to keep the soil separated from the agar. Quantitative pH measurements were done by inserting a micro-electrode into the agar after 3 hours of contact with the soil. The validity of the data obtained by this method was investigated by comparing the results with those obtained using standard procedures for pH measurement in a soil-water suspension (Chapter 4).

    Using the agar-contact method, it was shown that the benefit of lime on the nodulation of lucerne was largely (80%) due to neutralization of acidity, and to a lesser extent (20%) to the supply of calcium. For nodulation, soil-pH measured around lime-pelleted seeds, should at least be 5.8. Untreated roots were also able to induce a pH-increase of 0.6 units at 6 days after sowing (d.a.s.) or later, but only very few plants nodulated. These results, obtained with soil-grown plants, confirm earlier findings with hydroponically grown plants, that nodulation is sensitive for acidity only during the early phase of the process (0 to 3 d.a.s.) (Chapter 5).

    The soil already contained 1.2 meq of calcium per 100 g. Hence, the contribution of calcium in the lime effect was rather small. When the native calcium was removed with a specific calcium chelator (EGTA). crown nodulation could further be reduced to 12%. However, an additional complication was the acidification that accompanied the chelation of soilcalcium, with soil-pH dropping from 6.1 to 5.2. This problem could be overcome by applying small agar blocks containing the chelator. This technique allowed local application and temporal treatment of the root with EGTA. It was shown that the nodulation could be inhibited by calcium depletion only during the first day (Chapter 6). Obviously, the early phase of the nodulation of lucerne in acid soil is transiently susceptible to low calcium availability, similar to the transient sensitivity to low pH.

    Lange-termijn effecten van verschillende depositiescenario's op representatieve bosbodems in Nederland
    Vries, W. de; Kros, J. - \ 1989
    Wageningen : Staring Centrum (Rapport / Staring Centrum 30) - 89
    bosbouw - verzuring - bodem pH - bodemaciditeit - bodem - metaalelementen - zure gronden - kattekleigronden - neerslag - zure regen - zure depositie - aluminium - modellen - onderzoek - chemische eigenschappen - zuurgraad - Nederland - computersimulatie - simulatie - simulatiemodellen - forestry - acidification - soil pH - soil acidity - soil - metallic elements - acid soils - acid sulfate soils - precipitation - acid rain - acid deposition - aluminium - models - research - chemical properties - acidity - Netherlands - computer simulation - simulation - simulation models
    Om inzicht te krijgen in het lange-termijn effect van verschillende depositiescenario's op bosbodems zijn simulaties uitgevoerd gedurende een periode van 100 jaar met het regionale bodemverzuringsmodel RESAM, dat in het kader van het Nationaal Programma Zure Regen is ontwikkeld
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