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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.

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    On the biology and evolution of fungi from soda soils
    Grum-Grzhimaylo, A. - \ 2015
    Wageningen University. Promotor(en): Bas Zwaan, co-promotor(en): Fons Debets. - Wageningen : Wageningen University - ISBN 9789462574281 - 232
    bodemschimmels - zoute gronden - diversiteit - bodembiologie - evolutie - soil fungi - saline soils - diversity - soil biology - evolution

    Summary to the thesis “On the biology and evolution of fungi from soda soils”

    Alexey Grum-Grzhimaylo

    The presented thesis addresses aspects of biology and evolution of fungi that were recovered from saline soda soils. The work highlights the fact that saline soda soils are populated by a large diversity of fungi capable of withstanding high salts content and high pH. Some of these fungi have been shown to require exceptionally high pH and salts to grow optimally and therefore are called alkaliphiles.

    Introductory CHAPTER 1 provides examples of seemingly inhabitable environments and some of its most prominent tenants, with the emphasis on soda lakes ecosystem and alkaliphilic organisms. Aspects of physiology and major adaptive strategies to high pH and salts found in bacteria are portrayed. To our knowledge, there are no studies devoted to the fungi inhabiting saline soda lakes making this work a starting point towards further explorations in the field.

    In CHAPTER 2, I show that fungi are actually present in saline soils and focus closely on the fungus that dominated across all our soda soils samples. This fungus displayed a rare obligate alkaliphilic phenotype – it was capable of growing at pH 11.4 on agar plates, with the optimum of around 9–10 and no ability to grow at pH 5.2. Using a combination of morphological and phylogenetic approaches, I describe it as a new name Sodiomyces alkalinus (previously known as Heleococcum alkalinum). We looked at the morphological details of its life cycle and tested for the capacity of utilizing various carbon sources. Given its unique extreme physiology, dominance across the soil samples, and partly for historical reasons, S. alkalinus has become our model organism that found considerable attention across this thesis.

    Inspired by the fact that saline soda soils harbour new fungi, I moved on to the investigation of another set of isolates we obtained from soda soils, which belong to the Emericellopsis group (Hypocreales). CHAPTER 3 presents an investigation of the Emericellopsis isolates that showed a much broader pH preference tagging them as facultative alkaliphiles. Here again, combined morphological, phylogenetic, and physiological data allowed us to set this group apart from the rest and described it as a new species – Emericellopsis alkalina. This species is genetically unrelated to S. alkalinus, which provides evidence for the alkaliphilic trait to be polyphyletic, i.e. arisen several times throughout evolutionary history. I showed E. alkalina to be genetically closer to marine-bourne isolates than typical terrestrial species. Such a result provides evidence for the origin of alkaliphilic trait in this group from the marine-bourne fungi, as sea and soda soils environmental factors coincide.

    CHAPTER 4 is devoted to a systematic study of our whole collection of fungi recovered from saline soda soils across the world. I investigate over a hundred isolates morphologically, phylogenetically, and test them for growth pH preference. These data confirms the notion that alkaliphily is polyphyletic and has emerged in several lineages of the fungal phylogenetic tree. Detailed morphological descriptions and phylogenetic reconstructions gave me confidence in describing several more new species. A prominent finding is the discovery of two additional Sodiomyces species that also show the obligate alkaliphilic adaptation. Systematic approaches let me to link certain morphological characters of the species to the alkaliphilic phenotype they possess. Although a substantial part of fungi from soda soils indeed displayed alkaliphilic capabilities, we detected typical neutrophilic species that presumably are transient or reside in a dormant state as spores or survival structures.

    The next chapters of the thesis are focused on S. alkalinus, chosen as a model organism for studying alkaliphily that we sequenced in collaboration with Joint Genome Institute (Walnut Creek, USA). CHAPTER 5 looks into the aspects of the hydrolytic capabilities of S. alkalinus. The genome and transcriptome provide immense body of data that gave insight on the enzyme sets encoded in the genome involved in the degradation of carbohydrate compounds (so-called CAZymes). Such in silico analysis was backed-up by the enzyme bioassays carried out at various pH and substrates. In S. alkalinus, I found cellulolytic and hemicellulolytic enzymes that act at high pH, as opposed to neutrophilic A. oryzae enzymes that were active mostly at pH 6. Another prominent finding was the detection of strong proteolytic enzymes acting optimally at pH 8. Based on the genome data and bioassays patterns, I speculate on the ecological role of S. alkalinus in soda soils.

    CHAPTER 6 addresses the aspects of the PacC transcription factor, a key player in mediating the gene expression under different ambient pH. I sought to find differences in the primary structure of PacC or detecting the multicopiness of the pacC gene, given its function under extreme alkaline conditions. It turned out that the primary structure of the PacC was the same as in other fungi and the pacC gene is presented in a single copy in S. alkalinus genome. However, I noted a shifted expression and proteolytic activation pattern of PacC if compared to neutrophilic fungi. This results provides evidence for the re-tuned pH-sensors on the plasma membrane, however we could not convincingly detect signs of positive selection affecting the PalH sensors that would change its threshold to trigger the downstream molecular cascade.

    CHAPTER 7 gives insights into a quite unexpected finding – the presence of viruses in several of the S. alkalinus isolates. I show their effective vertical but not horizontal transmission. Possession of dsRNA as genetic material, icosahedral shapes, and symptomless phenotypes are common characters for a mycovirus. The virus I studied in S. alkalinus exhibits these exact same features. Curiously, no other alkaliphiles from our collection nor known sister species harboured mycoviruses, making this the first instance of mycoviruses detected in an alkaliphilic filamentous fungus.

    CHAPTER 8 focuses on another peculiar finding – a bacterial gene in the genome of S. alkalinus. Presumably introduced by a horizontal gene transfer event, this gene encodes for a DD-peptidase homologue commonly found in bacteria, but only in very few eukaryotes. I found only three fungi that possess this gene; two are alkaliphilic – S. alkalinus and its sister species Acremonium alcalophilum. This suggests the importance of this gene for alkaliphily in those species. The DD-peptidase gene appears to be functional and its peak expression was observed at pH 8. Comparative analysis showed this fungal DD-peptidase to be closely related to the homologues derived from halophilic and alkaliphilic bacteria, rather than from neutrophilic ones. I speculate on the putative function of this unusual gene, including the role in the build-up of exo-cellular matrix or defense against dense communities of prokaryotes in soda soils.

    The discussion in CHAPTER 9 contemplates on the results obtained throughout the thesis and provides future perspectives on the topic.

    Modelling of soil salinity and halophyte crop production
    Vermue, E. ; Metselaar, K. ; Zee, S.E.A.T.M. van der - \ 2013
    Environmental and Experimental Botany 92 (2013). - ISSN 0098-8472 - p. 186 - 196.
    gewasproductie - bodemfactoren - zoute gronden - halofyten - bodemwater - verzilting - modellen - crop production - edaphic factors - saline soils - halophytes - soil water - salinization - models - salt tolerance - root water - growth - plants - irrigation - stress - extraction - simulation - wheat - transpiration
    In crop modelling the soil, plant and atmosphere system is regarded as a continuum with regard to root water uptake and transpiration. Crop production, often assumed to be linearly related with transpiration, depends on several factors, including water and nutrient availability and salinity. The effect of crop production factors on crop production is frequently incorporated in crop models using empirical reduction functions, which summarize very complex processes. Crop modelling has mainly focused on conventional crops and specific plant types such as halophytes have received limited attention. Crop modelling of halophytes can be approached as a hierarchy of production situations, starting at the situation with most optimal conditions and progressively introducing limiting factors. We analyze crop production situations in terms of water- and salt limited production and in terms of combined stresses. We show that experimental data as such may not be the bottleneck, but that data need to be adequately processed, to provide the basis for a first analysis. Halophytic crops offer a production perspective in saline areas, but in other areas long-term use of low quality irrigation water for halophyte production can result in serious soil quality problems. An overview is given of potential problems concerning the use of (saline) irrigation water, leading to the conclusion that soil quality changes due to poor quality water should be considered in determining the areas selected for halophyte growing.
    Plant growth under high salinity
    Blom, M. ; Brandenburg, W.A. - \ 2011
    Egypte : Wageningen UR, Plant Research International
    zoutwaterlandbouw - zoute gronden - zout water - agrarische bedrijfsvoering - veldgewassen - prestatie-onderzoek - duurzame landbouw - teeltsystemen - teelthandleidingen - saline agriculture - saline soils - saline water - farm management - field crops - performance testing - sustainable agriculture - cropping systems - cultivation manuals
    Plants most suitable for growing under high saline or even seawater conditions are the ones naturally living under high saline circumstances. A series of tolerant or moderate salt tolerant plants are experimentally tested and described in literature. For many species of this group a threshold value has also been described.
    Zilte landbouw Texel : een voorbeeld transitieproject 2006-2010 : eindrapport
    Vos, A. de; Rozema, J. ; Rijsselberghe, M. van; Duin, W.E. van; Brandenburg, W.A. - \ 2010
    Amsterdam [etc.] : Vrije Universiteit [etc.] - 86
    gewassen - zoute gronden - landbouw - crambe maritima - crambe - beta maritima - plantago coronopus - matricaria perforata - eruca - groenten - landbouwgronden - innovaties - zoutwaterlandbouw - nederlandse waddeneilanden - proefprojecten - crops - saline soils - agriculture - crambe maritima - crambe - beta maritima - plantago coronopus - matricaria perforata - eruca - vegetables - agricultural soils - innovations - saline agriculture - dutch wadden islands - pilot projects
    Het project Zilte Landbouw Texel is in mei 2006 van start gegaan op het perceel nabij ‘De Petten’ op Texel. Er is gekozen om een Zilte Proeftuin aan te leggen op een nabij gelegen perceel waar gedurende twee jaar ongeveer twintig verschillende potentiële zilte gewassen zijn onderzocht op hun groei onder zoute condities en hun marktpotentie. De focus van de werkzaamheden op Texel van de Vrije Universiteit Amsterdam was gericht op Zeekool, Strandbiet, Hertshoornweegbree, Monniksbaard, Reukloze kamille en Wilde Rucola. Daarnaast heeft een langdurig onderzoek plaatsgevonden op de Afsluitdijk wat als referentie heeft gediend voor de natuurlijke groei van halofieten. In de kassen van VU zijn meerdere groei-experimenten onder gecontroleerde omstandigheden uitgevoerd, welke gebruikt zijn om de teelt van de verschillende gewassen op Texel verder te ontwikkelen. De teelt van vooral Zeekool, Zilte Rucola en Strandbiet is met succes opgeschaald en de producten zijn afgezet op de (lokale) markt. Door onder andere de promotie via verschillende kanalen en de unieke smaak van de zilte groenten is een vraag ontstaan naar de zilte gewassen die in veel gevallen het aanbod overtrof.
    Zilte Landbouw: aanpassen aan veranderende omstandigheden
    Rozema, J. ; Rijsselberghe, M. - \ 2010
    TransForum
    landbouwgronden - verzilting - zoute gronden - gewassen - zouttolerantie - innovaties - rentabiliteit - zoutwaterlandbouw - oude plantenrassen - regionale voedselketens - agricultural soils - salinization - saline soils - crops - salt tolerance - innovations - profitability - saline agriculture - old varieties - regional food chains
    De hoeveelheid zilte kwel in de Nederlandse kustprovincies neemt toe door stijging van de zeespiegel en de daling van de oude polders. Klimaatveranderingen en bodemdaling zijn hiervan de oorzaak. De druk op het steeds schaarser wordende zoetwater groeit hierdoor en voor de landbouw betekent dit dat de fysieke, financiële en maatschappelijke grenzen van zijn zoetwaterbehoefte bereikt zijn. Daarom brengt het project Zilte Landbouw in kaart welk toekomstperspectief gewassen die tegen zout water kunnen de landbouw in kustgebieden kunnen bieden.
    Het zout en de pap: een verkenning bij marktexperts naar langeretermijnmogelijkheden voor zilte landbouw
    Kempenaer, J.G. de; Brandenburg, W.A. ; Hoof, L.J.W. van - \ 2007
    Utrecht : InnovatieNetwerk (Rapport / InnovatieNetwerk nr. 07.2.154) - 93
    landbouw - innovaties - marktverkenningen - economie - zoute gronden - nederland - zoutwaterlandbouw - agriculture - innovations - market surveys - economics - saline soils - netherlands - saline agriculture
    De zeespiegelstijging en de bodemdaling in Nederland leiden ertoe dat steeds meer land - met name agrarisch land - verzilt. Dit rapport richt zich op het benutten i.p.v. bestrijden van verzilting.
    Drainage for a secure environment and food supply : 9th international drainage workshop, September 10-13 2003, Utrecht, The Netherlands
    Zeeuw, C.J. de; Vlotman, W.F. - \ 2004
    Wageningen : Alterra (Alterra-rapport 998) - 128
    drainage - ondergrondse drainage - zoute gronden - irrigatie - conferenties - wereld - drainage - subsurface drainage - saline soils - irrigation - conferences - world
    The 9th International Drainage Workshop; building blocks for Dutch and Global Water Policy. From September 10 - 13, 2003 Alterra-ILRI organised an international workshop where by means of Open Space Technology fifteen action plans were formulated by more than 115 participants to enhance integration of drainage into Integrated Water Resource Management. These action plans need to be elaborated for possible inclusion with Dutch and International water management plans. The main theme of the IDW was `Drainage for a secure environment and food supply`. A total of 85 papers and 30 posters were submitted, and these, including this report are presented on CD-ROM. This report contains the results of the first round of discussions; a total of 45 topics were identified by the participants for further discussion. On the thrid day finally 15 action plans emerged. The conclusions of the workshop are reflected in the Utrecht Declaration. This report is only digitally distributed and the information is also available via the website.
    Plant communities in saline environments - an introduction to the Festschrift for Sandro Pignatti
    Rodwell, J. ; Schaminée, J.H.J. - \ 2003
    Phytocoenologia (2003)2-3. - ISSN 0340-269X - p. 163 - 166.
    plantengemeenschappen - zoute gronden - zoutmoerassen - plant communities - saline soils - salt marshes
    Reuse of drainage water for rice and wheat growth during reclamation of saline-sodic soils in Pakistan under the national drainage program (NDP)
    Ghafoor, A. ; Boers, T.M. - \ 2003
    rijst - padigronden - hergebruik van water - irrigatie - pakistan - zoute gronden - rice - saline soils - paddy soils - water reuse - irrigation - pakistan
    Pakistan is facing scarcity of canal water for irrigated agriculture on 16 mha land. This problem is caused, among others, by the loss of surface storage capacity and by the current prolonged dry spell lasting over the several past years. Siltation of Mangla, Tarbela and Chashma Dams have caused a loss of . 5 km3 which is 25 % of the design capacity. Since this problem is increasing, there may be a gradual decrease of food production for a population of 140 million, which is expected to have doubled by 2025. Water shortage is the most serious for the provinces of Punjab and Sindh, where ground water is of hazardous quality and about 75 % of pumped ground water is not safe for irrigation without amendments. In this scenario, it appears wise and timely to study the prospects of growing food grains during reclamation of salt-affected soils using ground water to save good quality canal water for irrigating good soils. Under arid and semi-arid conditions of Pakistan with scarce and irregular rainfall, limited leaching of salts promotes soil salination followed by sodication, induced by irrigation with ground water of high EC, SAR and RSC without amendments or other agronomic management practices. In this way, 6 mha of soils have become salt-affected, of which 60 % are saline-sodic and needs a source of calcium for amelioration. For initial reclamation of salt-affected soils, low quality irrigation waters are generally useful and some times even better than canal water, due to favorable effects of electrolytes on infiltration rate and hydraulic conductivity. For a variety of reasons, farmers are not properly applying the technologies for reclamation and management of saline-sodic soils. To improve this situation on sustainable basis, Univ. Agri., Faisalabad has launched a three-year research study on reclamation of saline-sodic soils by reusing drainage water, in which farmers are participating. The experiments were started in June 2001 in the Fourth Drainage Project Area located in the Central Punjab and are funded by the National Drainage Programme. The reclamation technologies include split application of gypsum @ soil or water GR alone and in combination with FYM or green manure, and on-farm wheat seed priming. This paper will present preliminary results and recommendations pertaining to economical as well as sustainable reuse of drainage water on saline-sodic soils, farmers' constraints and limitations for adapting the required technologies in this regard on the basis of the on-going experiments.
    Strategies for productive use of brackish water for sustainable food grain productiuon [sic] in dry regions
    Zia, M.H. ; Ghafoor, A. ; Boers, T.M. - \ 2003
    irrigatie - pakistan - bodemchemie - zoutgehalte - zoute gronden - ontginning - oogstschade - irrigation - saline soils - soil chemistry - salinity - reclamation - crop damage - pakistan
    Due to unavoidable, prolonged irrigation with marginal quality water, secondary salinization of irrigated soils in Pakistan has necessitated to a need for better understanding of the water management alternatives. Although H2SO4 and gypsum have far been recognized for their benefits in treating brackish water but during field trials, their relative performance still remains controversial for counteracting the Na-hazards in soil/water system. As alternative sulfur burners are also being marketed but up till now there is not even a single field study published in some journal about their efficiency and economical viability for the treatment of brackish water. Therefore a field study was carried out to compare the effectiveness of sulfurous acid generator (SAG) and other water/soil applied amendments on a normal, calcareous, well drained, sandy loam soil. Rice 2001, wheat 2001-02, and rice 2002 were planted in rotation during the experimentation period with a total of 54 treated and 8 untreated irrigations (each of 7.5 cm). Tube well water used had EC = 3.24 dS m-1, SAR=17.23 and RSC = 5.44 mmolc L-1. The treatments were: T0) Brackish tube well water without any amendment; T1) All irrigation with water passed through SAG; T2) Alternate irrigation-one of SAG treated and one of tube well water, T3) One irrigation with SAG treated water and two with untreated tube well water; T4) FYM @ 15 t ha-1yr-1; T5) Soil applied gypsum to each crop equivalent to affect a decrease in WRSC of tube well water treated with SAG, and T6) H2SO4- fertigation at each irrigation equivalent to affect a decrease in RSC of tube well water with SAG. Water analysis after treatment with SAG (an average of 20 irrigations) revealed that SAG treatment affected only one parameter i.e. water RSC from 5.44 to 3.55, and had no beneficial effect on SARiw and ECiw. After three crops, a minor decrease (up to 2.5%) and increase (up to 5.3%) in soil pHs over initial values was noted at 0-15 & 15-30 cm depth. After three crops the soil ECe and SAR were maintained below the threshold levels and the treatments had non-significant differences. On the basis of three crops, net benefit was maximum, from T4 followed by T5, T3, T0, T2, T6 and T1. The use of sulfur burner/ sulfuric acid was found to be 5 times costlier than gypsum in our study. It is concluded that soil application of gypsum and/or farmyard manure to counter the sodic hazards of irrigation water will be useful as well as economical for rice-wheat rotation on a normal, calcareous well drained soil. However, for fine textured soils with low infiltration rates, to expect similar situation might not be correct for which additional studies are imperative.
    Netherlands Research Assistance Project : Final report : 1988 - 2000
    Anonymous, - \ 2001
    Wageningen : Alterra (Alterra-rapport 354) - 93
    zoutgehalte - drainage - zoute gronden - ontginning - programma-evaluatie - ontwikkelingshulp - beoordeling - ontwikkelingsprogramma's - pakistan - nederland - hydrologie - ontwikkelingssamenwerking - waterbeheer - Azië - salinity - drainage - saline soils - reclamation - program evaluation - development aid - assessment - development programmes - pakistan - netherlands
    The Netherlands research assistance project was implemented from 1988 till 2000. The project was a joint undertaking by the International Waterlogging and Salinity Research Institute (IWASRI), Lahore, Pakistan, and the International Institute for LandReclamation and Improvement (ILRI), Wageningen, the Netherlands. The project focused on drainage technical research during its first years, and on participatory drainage development in the last years.
    Towards improved water management in Haryana State : final report of the Indo - Dutch operational research project on hydrological studies
    Agarwal, M.C. ; Roest, C.J.W. - \ 1996
    Wageningen etc. : SC-DLO [etc.] - ISBN 9789032702625 - 80
    verbetering - india - irrigatie - uitspoelen - drainage door leidingen - zoute gronden - verzilting - natrium - bodem - buisdrainage - improvement - irrigation - leaching - pipe drainage - saline soils - salinization - sodium - soil - tile drainage
    Symposium on land drainage for salinity control in arid and semi-arid regions, February 25th to March 2nd, 1990, Cairo, Egypt
    Egypt. Ministry of Public Works and Water Resources, ; International Institute for Land Reclamation and Improvement, - \ 1990
    Cairo [etc.] : Ministry of Public Works and Water Resources [etc.]
    drainage - saline soils - leaching - egypt - drainage - zoute gronden - uitspoelen - egypte
    Operational research in water and salt management at Haryana Agricultural University, India : mission report of the Chief Technical Advisor 3 - 21 December 1988
    Roest, C.W.J. - \ 1989
    Wageningen : I.C.W. (ICW Note 1937) - 24
    drainage - india - irrigatie - uitspoelen - onderzoek - zoute gronden - irrigation - leaching - research - saline soils
    Salinity and flooding level as determinants of soil solution composition and nutrient content in Panicum hemitomum.
    Feijtel, T.C.J. ; Moore Jr., P.A. ; McKee, K. ; Mendelssohn, I. - \ 1989
    Plant and Soil 114 (1989). - ISSN 0032-079X - p. 197 - 204.
    chemische analyse - chemische samenstelling - verbetering - indicatorplanten - planten - polders - zoute gronden - verzilting - natrium - bodem - bodemaciditeit - bodem ph - vegetatie - wetlands - chemical analysis - chemical composition - improvement - indicator plants - plants - polders - saline soils - salinization - sodium - soil - soil acidity - soil ph - vegetation - wetlands
    De betekenis van chloride voor bomen: toxische gehalten in blad, naalden en grond : een literatuuroverzicht = The significance of chloride for trees: toxic concentrations in foliage and soil : a literature review
    Burg, J. van den - \ 1982
    Wageningen : De Dorschkamp (Rapport / Rijksinstituut voor Onderzoek in de Bos- en Landschapsbouw "De Dorschkamp" no. 323) - 123
    bosbouw - houtteelt - bosbouwkundige handelingen - groei - milieufactoren - bodemvruchtbaarheid - voedingsstoffen - bodemchemie - anorganische verbindingen - zoute gronden - alkaligronden - waterrelaties - wortels - bodemeigenschappen - bosschade - beschadigingen - erosie - planten - toxische stoffen - chloride - forestry - silviculture - forestry practices - growth - environmental factors - soil fertility - nutrients - soil chemistry - inorganic compounds - saline soils - alkaline soils - water relations - roots - soil properties - forest damage - injuries - erosion - plants - toxic substances
    Literatuurstudie over de relaties tussen het zoutgehalte in de bodem (het C-cijfer), het chloride-gehalte van blad en naalden, de groei en het optreden van zichtbare schadeverschijnselen. Voor een groot aantal geslachten en soorten zijn de C-cijfers, kritische chloride-gehalten en het chloride-gehalte, waarbij blad en naalden juist zichtbare schade gaan vertonen, opgenomen
    Drainage and reclamation of salt-affected soils in the Bardenas area, Spain
    Martinez Beltran, J. - \ 1978
    Landbouwhogeschool Wageningen. Promotor(en): W.H. van der Molen, co-promotor(en): P. Buringh. - Wageningen : ILRI - 322
    alkaligronden - drainage - verbetering - irrigatie - land - polders - ontginning - zoute gronden - verzilting - natrium - bodem - bodemkunde - solonchaks - spanje - iberisch schiereiland - onvruchtbaar land - alkaline soils - drainage - improvement - irrigation - land - polders - reclamation - saline soils - salinization - sodium - soil - soil science - solonchaks - spain - iberian peninsula - unproductive land
    Chapter 1

    The Ebro basin is situated in north-eastern Spain and forms a geographic unit bounded by high mountains. The Bardenas area lies in the Ebro basin and forms part of the Bardenas Alto - Aragón irrigation scheme, which was designed to make use of the surface water resources from the Pyrenees.

    Chapter 2

    The Ebro basin is a tertiary sedimentation basin in which the Ebro river and its main tributaries have incised alluvial valleys. The tertiary sediments consist mainly of mudstone, locally with interbedded gypsum layers, and very fine siltstone. Both sedimentary rocks are fine textured and, because they were deposited in a brackish lacustrine environment, contain harmful soluble salts.

    The main landscape-forming processes were erosion, transport, and deposition under semi-arid climatic conditions. The highest parts of the landscape consist of old tertiary formations which form the uplands of a dissected plain. At a lower level mesas occur, which consist of coarse alluvium covering the underlying tertiary sediments. Most of the eroded sediments were removed from the area but local sedimentation also occurred. Owing to the semi-arid conditions, both sediments and salts were deposited. The highest salt concentrations are found in the lowest parts of the alluvial formations, especially where the alluvium was derived from the eroded mudstone and siltstone. Between the residual uplands and the low-lying alluvial formations, piedmont and colluvial slopes occur.

    Within the Bardenas area ten major physiographic units were defined, each of them subdivided into minor components and indicated on the soil map.

    The Ebro basin is the driest part of northern Spain. The climate is semi-arid and becomes drier from the borders to the centre of the depression.

    The seasonal variation in temperature is great. Potential evapotranspiration exceeds total precipitation, which is extremely variable and is not concentrated in distinct rainy seasons. Wind velocity is high and both cold and warm dry winds are common. Evaporation thus occurs even in winter when temperatures are low.

    A great part of the area is cultivated, so that natural vegetation is restricted to residual and eroded soils not used for agriculture and to salt-affected soils where halophytes grow.

    Irrigated farming is influenced by soil conditions. Salt-free soils are under full irrigation, the main crops being maize, lucerne, sugar beet, and some horticultural crops.

    The cropping pattern on the saline soils depends on the degree of salinity. Barley and sugar beet are grown on moderately saline soils and lucerne on succesfully leached soils. On the higher lands, not under the command of the irrigation scheme, barley is grown.

    Chapter 3

    The study area comprises two drainage basins. The northern part drains to the Aragón river, the southern part to the Riguel river, which is a tributary of the Arba river.

    Drainage and salinity of the groundwater depend on the situation of each geomorphological unit and its relation to adjacent units. The groundwater in the fluvio-colluvial formations of the northern basin is shallow and highly saline. An ephemeral perched water table is found in the mesas, where the groundwater is non-saline. No shallow water table was found in other physiographic units.

    The irrigation water is of good quality as its EC is at the lower end of the C 2 -range. The SAR is also in the lowest range S 1 and the RSC is zero, so there is no danger of alkalinization.

    Chapter 4

    The physiographic approach was used to prepare the soil map. Each mapping unit is a broad association of soils having similar salinity hazards and possibilities of reclamation.

    Five main soil associations were distinguished:

    a) The residual soils of the siltstone outcrops, which have only a thin surface horizon overlying the hard siltstone.

    b) The soils of the mesas, which consist of a reddish loamy surface horizon overlying semi-consolidated coarse alluvium rich in calcium- carbonate but free of other salts. This in turn overlies the impervious mudstone. Texture and depth of the soil profile vary. Where moderately deep soils occur. a prosperous irrigated agriculture flourishes.

    c) The soils of the piedmont and colluvial slopes were developed from a mixture of fine colluvium. and material from the underlying tertiary sediments. They are generally deep and fine textured and have an intrinsic, though variable, salinity, increasing with depth. Because of the low permeability and the salinity of the subsoil, the most suitable irrigation method is sprinkling.

    d) The non-saline soils of the alluvial valleys of the main rivers. Soil conditions vary greatly, but the older terrace soils are usually shallower and less suitable for irrigation than the youngest deeper (alluvial) soils. In general, prosperous irrigated agriculture exists on these soils.

    e) The saline alluvial and fluvio-colluvial soils of valleys and fans, whose parent material was derived from denudation of the tertiary sediments. Soil conditions and the degree of salinity vary in each mapping unit, and consequently the possibilities of reclamation vary as well.

    Chapter 5

    The source of the salts is the intrinsic salinity of the parent materials and the secondary salinization in water-receiving areas that lack natural drainage. Under irrigation the mobilization and redistribution of salts continues and salinity increases.

    The saline soils of the area are mainly affected by sodium chloride, a component dominant in all samples. In addition, calcium and magnesium sulphates are found in the northern basin, while in the southern part, calcium and magnesium chlorides predominate over the sulphates.

    The SAR increases with the rise of EC. Soil alkalinity can therefore be regarded as a reflection of soil salinity since highly saline soils are sodic as well. Non-saline alkali soils were not found and pH-values greater than 8.5 do not occur.

    The results of crop tolerance field tests correspond well with the generally accepted levels for salt tolerance.

    The continued use of the slightly saline soils can be ensured by maintaining the present drainage system of open ditches and interceptor drains, and by keeping the soils under full irrigation. The normal percolation losses associated with basin irrigation will be sufficient to leach the salts from the rootzone.

    Sprinkler irrigation is suitable for the soils of the slopes, since no levelling is needed and the small water applications reduce the seepage of saline water. The only drainage system required is an interceptor drain between the slope and the adjacent valley.

    Chapter 6

    The saline alluvial soils require reclamation. For this purpose, they must be provided with a drainage system, followed by initial leaching to reduce their salt content.

    Because there was no local experience with such drainage and desalinization processes, it was decided to conduct an experimental reclamation. Two experimental fields were subsequently selected.

    The Alera field represents the poorly drained soils of the fluvio-colluvial formations of the northern basin. These are silty-clay soils whose porosity and permeability decrease with depth. Below a depth of 1.5 m the soil becomes almost impermeable. Salinity increases with depth, reaching values of between 20 and 35 mmhos/cm in the almost impermeable layer. Soil salinity in the surface layer varies.

    The Valareña field represents the saline soils of alluvial valleys and fans in the southern drainage basin. These are silty clay loam soils showing a marked stratification. At a depth of 2.5 m, coarse alluvium saturated with very saline groundwater occurs overlying impervious mudstone. Because of stratification, the hydraulic conductivity is highly anisotropic. Soil salinity is more uniformly distributed than in the Alera soils.

    The reclamation process consisted of the following phases:

    a) Theoretical design of the drainage system based on hydrological soil properties measured by conventional field methods and on assumed drainage criteria.

    b) Implementation of the drainage system in the experimental fields.

    c) Collection of field data, followed by determination of the actual hydrological soil properties and of the drainage criteria.

    d) Design of the definitive drainage system which will form the basis of recommendations for the reclamation of saline soils with similar conditions.

    Chapter 7

    After a detailed hydropedological survey, a drain spacing of 20 m at a depth of 1.5 m was calculated for both the Alera and the Valareña drainage systems. Both fields were subsoiled to a depth of 50 cm to improve their low infiltration rates.

    Piezometers were installed to monitor the water table. Precipitation was measured, as were the amounts of irrigation and drainage water. Soil samples were taken at fixed sites to determine the salinity during the leaching process.

    Chapter 8

    At the Valareña field, water flowed directly into the drain trench through the upper layer of soil, in which the stratification had been disrupted by levelling and subsoiling. Below this layer, there was no percolation of water and therefore no desalinization. These soils cannot be leached merely by the provision of a drainage system but also require deep subsoiling.

    At the Alera field, unsteady groundwater flow prevailed. At the end of tail recession, flow conditions approached those of steady flow. The discharge/hydraulic head relation had a parabolic shape showing that flow was restricted to the soil above drain level because the drains had been placed just above the impervious layer.

    The Boussinesq theory was very suitable to study the drainage of the Alera field. At the end of tail recession, if the term for flow below drain level was disregarded, the Hooghoudt equation could be applied.

    Drainable pore space was determined from the fall of the water table and the amount of drainage water during periods of low evapotranspiration. An average value of 4 per cent was found.

    The hydraulic conductivity was calculated from the discharge/hydraulic head relation using the Boussinesq and Hooghoudt equations for periods of low evapotranspiration. In general good agreement was found among the values obtained. It could thus be concluded that:

    - Hydraulic conductivity decreases with depth, becoming negligible below drain level.

    - The hydraulic conductivity between a depth of 0.5 m and drain level equals about 0.6 m/day, and is about 1.5 m/day in the upper layer.
    - For high water table conditions, the average hydraulic conductivity of the soil profile is 1 m/day.

    A comparison of hydraulic conductivity values obtained with field and laboratory methods and those obtained from the discharge/hydraulic head relation showed that:

    - The results obtained with the auger hole method (K = 0.2 m/day) were lower than those derived from the discharge/hydraulic head relation.

    - No satisfactory results were obtained from the inversed auger hole measurements above the water table.

    - The results obtained from laboratory measurements in undisturbed soil cores showed the anisotropy of the soil.

    The entrance resistance (W e ) of different combinations of drainage and filter materials was calculated from the drain discharge and the head loss of the water table measured in the drain trench (h i ). Another method, by which the head loss in the trench was calculated from the shape of the water table was also applied. Both methods gave similar results, yielding the following conclusions:

    - The W e -values remained fairly constant with time, except for plastic pipes-with an envelope of esparto or coconut fibre for which an increase in W e was observed.

    - The best combination was clay pipes with a gravel cover (W e =2 day/m).

    - Corrugated PVC-pipes with gravel covering and clay pipes without gravel may be used also (W e = 5 day/m).

    - Corrugated plastic pipes without a filter gave less satisfactory results (W e = 13 day/m).

    - Plastic pipes with coconut fibre and esparto filters showed an even higher W e than plastic pipes without a filter.

    - Barley straw is an unsuitable cover material since it rots easily and clogs the pipe.

    Chapter 9

    The desalinization of the Alera field started with an initial leaching, followed by the irrigated cultivation of moderately salt- resistant crops.

    The leaching efficiency coefficient was determined by comparing the actual desalinization process with theoretical models. Thus the leaching requirement could be predicted for different initial salt contents.

    To exclude the influence of slightly soluble salts, the desalinization curves were drawn in terms of chloride content. The correlation between chloride percentage and electrical conductivity was high.

    The following conclusions emerged from the study of the leaching process:

    - The leaching efficiency coefficient was not constant but increased with depth.

    - The leaching efficiency coefficient was higher at the beginning of the desalinization process and decreased gradually as the soil became less saline.

    - The calculated values reflected the differences in soil structure.

    - An average value of 0.5 was determined for the upper layer (0-50 cm), and a value of 1.0 for the deeper layer (50-100 cm).

    - The initial salinity was related to soil physical properties (infiltration rate and permeability) which, in turn, were dependent on the compactness of the soil.

    - For an initial EC e of 15 mmhos/cm, approximately 1000 mm of percolation water are required, which meant 1100 to 1400 mm of irrigation water. The leaching period could last up to 8 months, from early autumn to late May.

    - Deep subsoiling and local gypsum applications improved the structure of the upper soil layer.

    - The leaching of saline soils could be split into two phases: an initial leaching of the upper layer, followed by the irrigated cultivation of a moderately salt-resistant crop (sugar beet), during which percolation losses leached the deeper layers.

    - There was no risk of alkalinization during the leaching period.

    - To prevent secondary salinization after reclamation, good drainage conditions must be maintained and an irrigated crop rotation practised.

    Chapter 10

    From the relation between the depth of the water table, crop growth, and the mobility of agricultural machinery on the soil, and from a study of the groundwater regime in winter and during the irrigation season drainage criteria for unsteady-state conditions were derived. These criteria were converted to steady-state criteria for easier use in drainage projects.

    The following conclusions could be drawn from the study:

    - Little harm is done to winter cereals if a water table remains within a depth of 50 cm, for no more than 3 consecutive days.

    - With a water table between 75 and 100 cm, sugar beet grows well and is not harmed if a water table is within the top 50 cm for 3 to 4 consecutive days.

    - Lucerne is more sensitive than sugar beet to high water tables. For good yields, a water table must not remain longer than 3 days within the top 25 cm of soil, 4 or 5 days within the top 50 cm, and 5 or 6 days within the top 75 cm.

    - A water table depth shallower than 65 cm prevents the movement of machinery and hampers seed-bed preparation in winter.

    The following drainage criteria were assessed:

    a) In winter, a water table drawdown from the soil surface to a depth of 0.65 m in 8 days.

    b) In the irrigation season, a water table rise of 0.7 m caused by irrigation losses must be lowered in the 12 days between two consecutive irrigations, and must be deeper than 0.7 m after 7 days.

    Applying these criteria in the Boussinesq equation for unsteady flow and using the values for hydraulic conductivity and drainable pore space determined at the experimental field, a spacing of 25 m for drains installed at a depth of 1.2 m was obtained.

    Equivalent drainage criteria for steady flow are a minimum depth of 0.5 m for the unsaturated zone, with a corresponding hydraulic head midway between drains of 0.7 m and a drain discharge of 3 mm/day.

    If the entrance resistance was taken into account, the Ernst equation for steady flow and the Hellinga/de Zeeuw equation for unsteady flow could be used in calculating the drain spacing. The results obtained by both approaches agree well and allowed the following conclusions:

    - For drainage and filter materials with a high entrance resistance, the drain density (m/ha) required becomes twice that needed for materials with low entrance resistance.

    - Material with high entrance resistance involves much more risk of failure than a wider spacing with good material.

    Uitspoeling van chloor uit kasgronden
    Willigen, P. de - \ 1975
    Haren : Instituut voor Bodemvruchtbaarheid (Nota / Instituut voor Bodemvruchtbaarheid no. 18) - 19
    uitspoelen - zoute gronden - chloor - glastuinbouw - leaching - saline soils - chlorine - greenhouse horticulture
    Problems of waterlogging and salinity in the Indus Plains of Pakistan
    Bergman, M.J. ; Aart, R. van - \ 1974
    Wageningen : ILRI - 56
    evaporatie - verbetering - uitspoelen - pakistan - zoute gronden - verzilting - natrium - bodem - evaporation - improvement - leaching - saline soils - salinization - sodium - soil
    Zoute gronden
    Anonymous, - \ 1971
    Wageningen : [s.n.] (Literatuurlijst / Centrum voor landbouwpublikaties en landbouwdocumentatie no. 3303)
    bibliografieën - verbetering - polders - ontginning - zoute gronden - verzilting - bodemzouten - natrium - bodem - bodemzoutgehalte - solonchaks - bibliographies - improvement - reclamation - saline soils - salinization - salts in soil - sodium - soil - soil salinity
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