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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    Porosity, Bulk Density, and Volume Reduction During Drying: Review of Measurement Methods and Coefficient Determinations
    Qiu, J. ; Khalloufi, S. ; Martynenko, A. ; Dalen, G. van; Schutyser, M.A.I. ; Almeida-Rivera, C. - \ 2015
    Drying Technology 33 (2015)14. - ISSN 0737-3937 - p. 1681 - 1699.
    pore-size distribution - cooked beef product - mercury porosimetry - physical-properties - structural-properties - vacuum impregnation - image-analysis - porous-media - true density - shrinkage
    Several experimental methods for measuring porosity, bulk density and volume reduction during drying of foodstuff are available. These methods include among others geometric dimension, volume displacement, mercury porosimeter, micro-CT, and NMR. However, data on their accuracy, sensitivity, and appropriateness are scarce. This paper reviews these experimental methods, areas of applications and limits. In addition, the concept of porosity, bulk density and volume reduction and their evolution as a function of moisture content during drying is presented. In this study, values of initial porosity (¿0) and density ratio (ß) of some food products are summarized. It has been found that ¿0 is highly dependent on the type of food products, while ß ranges from 1.1 to 1.6. The possibility of calculating solid density based on food compositions has also been validated. The inter-predictions between porosity, bulk density and volume density have been made mathematically evident.
    Trade-offs around the use of biomass for livestock feed and soil cover in dairy farms in the Alaotra lake region of Madagascar. Special Issue: Biomass use trade-offs in cereal cropping systems: Lessons and implications from the developing world
    Naudin, K. ; Bruelle, G. ; Salgado, P. ; Penot, E. ; Lubbers, M.T.M.H. ; Ridder, N. de; Giller, K.E. - \ 2015
    Agricultural Systems 134 (2015). - ISSN 0308-521X - p. 36 - 47.
    cropping systems - conservation agriculture - physical-properties - zero-tillage - south-asia - residue - africa - maize - rice - productivity
    Conservation agriculture (CA) is promoted as a promising technology to stabilize or improve crop yields in Africa and Madagascar. However, small-scale farmers face difficulties to retain soil cover, mainly because of competing uses for the biomass produced, especially to feed cattle. To explore the relation between dairy production and CA we developed an optimisation model at farm level. Our aim was to explore trade-offs between CA practices and the size of dairy cow herds. Our model includes three main components: the farm, the crops and the cattle herd. The optimisation was made on the total net income for three years. Biomass produced by cropping activities can either serve as mulch or to feed cows. We applied a constraint on the minimum soil cover % to keep at the end of each year for CA fields: from 30% to 95%. We simulated two scenarios of milk market: a small milk market with low forage price and an open milk market scenario with higher price of forage. Three prototypes of farms were simulated with different proportion and size of four kinds of field. These three prototypes were: medium-sized farm with hillsides dominating, medium-sized farm with paddy fields dominating and small-sized farm with hillsides. Changing the degree of soil cover to be retained on CA plots did not significantly modify the total net farm income. It was more strongly influenced by the characteristics of the milk market. In case of a limited milk market it was not profitable to have more than seven cows because the expenses were not compensated by animal production. When setting minimum soil cover to 30% then all of the simulated results include biomass coming from CA cropping system even with 12 cows/farm. Conversely when setting this constraint to 95%, above 6/7 cows/farm forage come only from conventional fields. In all of the situations simulated even with 6 cows, with the current and twice the price for forage, it was possible to keep at least 50% of soil cover on 30–60% of the total farm area. CA was not feasible for farms with no irrigated paddy fields or when forage fetched a high price regardless of the constraint for % of soil cover to be kept on CA fields. Overall, CA systems can be beneficial for dairy cow farmers due to the forage produced, although the milk market and thus the value of biomass for forage, has a strong influence on CA practice at field level.
    Soil surface changes increase runoff and erosion risk after a low–moderate severity fire
    Stoof, C.R. ; Ferreira, A.J.D. ; Mol, W. ; Berg, J. van den; Kort, A. De; Drooger, S. ; Slingerland, E.C. ; Mansholt, A.U. ; Ritsema, C.J. - \ 2015
    Geoderma 239-240 (2015). - ISSN 0016-7061 - p. 58 - 67.
    critical shear-stress - random roughness - overland-flow - mediterranean ecosystem - physical-properties - water repellency - prescribed fire - burn severity - forest - wildfire
    Post-fire land degradation is to a large degree determined by what happens to soil properties and ground cover during and after the fire. To study fire impact in relation to fire intensity and post-fire soil exposure, a 9-ha Portuguese shrubland catchmentwas burned by experimental fire in the 2008/9 winter season. Previous studies reported on the significant increase in erosion after this fire, and discussed the role of reduced canopy interception and changed soil water repellency dynamics. Our objective was to assess whether fire-induced changes in soil physical properties and soil surface characteristics may have played an additional role in the increase in runoff and erosion observed after the fire. We sampled these properties before, immediately after, and up to one year after fire, and monitored soil temperatures during the fire using thermocouples. Despite the locally high fire intensity (N15.000kWm-1 in some places), soil physical changeswere not observed: topsoil bulk density, organic matter, porosity and saturated conductivity did not significantly change, likely because soil temperatures stayedlow with the 0.5 cm depth not exceeding 32.5 °C. Soil surface characteristics did change: Manning's n and randomroughness both decreased, increasing the risk and erosivity of overland flow. Results indicate that soil physical changes unlikely contributed to the increase in post-fire erosion observed in the catchment and that a highintensity winter burn does not necessarily lead to severe soil changes. Nevertheless, soil surface changes during and after fire contribute to an increase runoff and erosion risk in these areas
    Assessing the potential of biochar and charcoal to improve soil hydraulic properties in the humid Ethiopian Highlands: The Anjeni watershed
    Bayabil, H.K. ; Stoof, C.R. ; Lehmann, J.C. ; Yitaferu, B. ; Steenhuis, T.S. - \ 2015
    Geoderma 243-244 (2015). - ISSN 0016-7061 - p. 115 - 123.
    central rift-valley - organic-matter - physical-properties - land management - nile basin - agronomic performance - chemical-properties - climate-change - maize yield - retention
    Biochar has shown promise for restoring soil hydraulic properties. However, biochar production could be expensive in the developing world, while charcoal iswidely available and cheap. The objective of this study is therefore to investigate whether some of the charcoal made in developing countries can also be beneficial for improving soil hydraulic properties, and explore whether charcoal could potentially restore the degraded African soils. Laboratory and field experiments were conducted in the Anjeni watershed in the Ethiopian highlands, to measure soil physical properties including soil moisture retention and infiltration rates. Soils were dominantly clayey with pH in the acidic range, low organic carbon content, and steady infiltration rates ranging between 2 and 36 mm/h. Incorporation of woody feedstock (Acacia, Croton, and Eucalyptus) charcoals significantly decreased moisture retention at lower tensions (10 and 30 kPa), resulting in an increase in relative hydraulic conductivity coefficients at these tensions. While wood (oak) biochar decreased moisture retention at low tensions, corn biochar increased retention, but effects were only slight and not significant. Surprisingly, available water content was not significantly affected by any of the amendments. Overall findings suggest that wood charcoal amendments can improve soil hydraulic properties of degraded soils, thereby potentially reducing runoff and erosion.
    Mung Bean: Technological and Nutritional Potential
    Dahiya, P.K. ; Linnemann, A.R. ; Boekel, M.A.J.S. van; Khetarpaul, N. ; Grewal, R.B. ; Nout, M.J.R. - \ 2015
    Critical Reviews in Food Science and Nutrition 55 (2015)5. - ISSN 1040-8398 - p. 670 - 688.
    vigna-radiata l - amino-acid-composition - seed-coat color - var sublobata fabaceae - gram phaseolus-aureus - common indian pulses - l wilczek - green gram - physical-properties - in-vitro
    Mung bean (Vigna radiata (L.) R.Wilczek) has been intensively researched; scattered data are available on various properties. Data on physical, chemical, food processing, and nutritional properties were collected for whole mung bean grains and reviewed to assess the crop’s potential as food and to set research priorities. Results show that mung bean is a rich source of protein (14.6–33.0 g/100 g) and iron (5.9–7.6 mg/100 g). Grain color is correlated with compounds like polyphenols and carotenoids, while grain hardness is associated with fiber content. Physical properties like grain dimensions, sphericity, porosity, bulk, and true density are related to moisture content. Anti-nutrients are phytic acid, tannins, hemagglutinins, and polyphenols. Reported nutrient contents vary greatly, the causes of which are not well understood. Grain size and color have been associated with different regions and were used by plant breeders for selection purposes. Analytical methods require more accuracy and precision to distinguish biological variation from analytical variation. Research on nutrient digestibility, food processing properties, and bioavailability is needed. Furthermore, the effects of storage and processing on nutrients and food processing properties are required to enable optimization of processing steps, for better mung bean food quality and process efficiency.
    Vegetable production after flooded rice improves soil properties in the Red River Delta, Vietnam
    Everaarts, A.P. ; Neeteson, J.J. ; Pham Thi Thu, H. ; Struik, P.C. - \ 2015
    Pedosphere 25 (2015)1. - ISSN 1002-0160 - p. 130 - 139.
    sandy loam soil - physical-properties - farming systems - puddling depth - tropical asia - wheat system - constraints - opportunities - management - lowland
    Vegetable production in South East Asia often is in rotation with °ooded rice. The puddling of the soil with flooded rice production may result in unfavourable soil conditions for the subsequent production of dry land crops. To establish whether permanent vegetable production results in favourable soil conditions for vegetables, the effects of five different permanent vegetable production systems and a system of vegetable production in rotation with flooded rice on soil properties after flooded rice were studied in a 2-year field experiment. Bulk density at 0.05{0.10 m depth layer decreased with permanent vegetable production and vegetable production in rotation with flooded rice. The decrease in bulk density was in°uenced by the application of organic manure and rice husks, and especially by the number of crops cultivated, suggesting that frequency of soil tillage had a major effect on bulk density. Ploughing with buffalo traction after flooded rice, in combination with construction of raised beds, could reduce or totally eliminate negative effects of puddling on soil structure. Bulk density at 0.15{0.20 m soil depth was not influenced. Soil acidity decreased significantly in all systems. Soil organic carbon increased in all systems, but significant increase was only found in two permanent vegetable production systems. Available phosphorus (P) significantly increased in two permanent vegetable production systems, with a positively correlation to the amount of P applied. The significant decrease in bulk density and increase in pH (H2O), after only 2 years, showed that soil conditions after flooded rice could be improved in a short time under intensive vegetable production.
    Preparation, structure and stability of sodium caseinate and gelatin micro-particles
    Ince, A.E. ; Saglam, D. ; Venema, P. ; Linden, E. van der; Scholten, E. - \ 2015
    Food Hydrocolloids 45 (2015). - ISSN 0268-005X - p. 291 - 300.
    glucono-delta-lactone - whey-protein particles - light-scattering - physical-properties - beta-lactoglobulin - swelling behavior - phase-separation - ionic-strength - high-pressure - mixed gels
    Protein particles are promising candidates for texturing food products and can be produced in several ways. Here, we produced protein particles using a two-step emulsification method. This method is suitable to change the size of the particles and to control the protein concentration inside the particles. In this study, we prepared protein particles from two different protein sources, sodium caseinate (NaCas) and gelatin, that are gelled by acidification and cooling, respectively. The size and the internal protein concentration of the particles, their stability against heating and pH changes were studied. Although similar emulsification conditions were used to prepare the particles, NaCas particles were found to be 10 times smaller (average diameter 400 nm) than the gelatin particles (average diameter 4 µm). The internal protein concentration of the NaCas particles (16.8% w/w) is approximately twice as high compared to that of gelatin particles (7.6% w/w) (using an initial protein concentration of the solution of 10% (w/w)). The NaCas particle dispersions were found to be stable between pH 3 and pH 4. The particles disintegrated at pH values further away from the iso-electric point. Upon heating the dispersions at 90 °C, the NaCas particles were shown to be heat stable. Dispersions of gelatin particles were stable against aggregation at all pH values studied, except at pH 6, while the particles melted above 40 °C. Swelling of both particles was observed for both acidic and alkaline pH values. We conclude that emulsification method is robust for different protein sources used.
    Thermal shock and splash effects on burned gypseous soils from the Ebro Basin (NE Spain)
    Leon, J. ; Seeger, M. ; Badia, D. ; Peters, P. ; Echeverria, M.T. - \ 2014
    Solid Earth 5 (2014)1. - ISSN 1869-9510 - p. 131 - 140.
    semiarid environment - erosion processes - organic-matter - aggregate stability - physical-properties - sediment yield - fire - gypsum - ash - wildfire
    Fire is a natural factor of landscape evolution in Mediterranean ecosystems. The middle Ebro Valley has extreme aridity, which results in a low plant cover and high soil erodibility, especially on gypseous substrates. The aim of this research is to analyze the effects of moderate heating on physical and chemical soil properties, mineralogical composition and susceptibility to splash erosion. Topsoil samples (15 cm depth) were taken in the Remolinos mountain slopes (Ebro Valley, NE Spain) from two soil types: Leptic Gypsisol (LP) in a convex slope and Haplic Gypsisol (GY) in a concave slope. To assess the heating effects on the mineralogy we burned the soils at 105 and 205 degrees C in an oven and to assess the splash effects we used a rainfall simulator under laboratory conditions using undisturbed topsoil subsamples (0-5 cm depth of Ah horizon). LP soil has lower soil organic matter (SOM) and soil aggregate stability (SAS) and higher gypsum content than GY soil. Gypsum and dolomite are the main minerals (> 80 %) in the LP soil, while gypsum, dolomite, calcite and quartz have similar proportions in GY soil. Clay minerals (kaolinite and illite) are scarce in both soils. Heating at 105 degrees C has no effect on soil mineralogy. However, heating to 205 degrees C transforms gypsum to bassanite, increases significantly the soil salinity (EC) in both soil units (LP and GY) and decreases pH only in GY soil. Despite differences in the content of organic matter and structural stability, both soils show no significant differences (P <0.01) in the splash erosion rates. The size of pores is reduced by heating, as derived from variations in soil water retention capacity.
    Predictions of Glass Transition Temperature for Hydrogen Bonding Biomaterials
    Sman, R.G.M. van der - \ 2013
    The Journal of Physical Chemistry Part B: Condensed Matter, Materials, Surfaces, Interfaces & Biophysical 117 (2013)50. - ISSN 1520-6106 - p. 16303 - 16313.
    molecular-dynamics simulations - gel sol transition - aqueous-solutions - free-volume - glycerol-water - physical-properties - positron lifetime - light-scattering - phase-behavior - starch gels
    We show that the glass transition of a multitude of mixtures containing hydrogen bonding materials correlates strongly with the effective number of hydroxyl groups per molecule, which are available for intermolecular hydrogen bonding. This correlation is in compliance with the topological constraint theory, wherein the intermolecular hydrogen bonds constrain the mobility of the hydrogen bonded network. The finding that the glass transition relates to hydrogen bonding rather than free volume agrees with our recent finding that there is little difference in free volume among carbohydrates and polysaccharides. For binary and ternary mixtures of sugars, polyols, or biopolymers with water, our correlation states that the glass transition temperature is linear with the inverse of the number of effective hydroxyl groups per molecule. Only for dry biopolymer/sugar or sugar/polyol mixtures do we find deviations due to nonideal mixing, imposed by microheterogeneity.
    Structuring of expanded snacks based on patato ingredients : a review
    Sman, R.G.M. van der; Broeze, J. - \ 2013
    Journal of Food Engineering 114 (2013)4. - ISSN 0260-8774 - p. 413 - 425.
    glass-transition temperature - damaged starch granules - physical-properties - extruded products - bubble-growth - semicrystalline polymers - rheological properties - extrusion behavior - sodium-chloride - foaming process
    In this paper we review the current knowledge on the structuring via bubble expansion of starchy snacks, which are formulated on the basis of potato ingredients. These snacks are rarely discussed in scientific literature, but there are a scant number of patents dealing with various formulations and process descriptions. The general trends in the snack processing, we have described in a formal way using the Complex Dispersed Systems notation, augmented with a depiction of the processing pathway in the supplemented state diagram of starch. With this general framework in mind, we have compared the information given in the patents with scientific literature on cereal-based snacks. Based on this comparison we have formulated hypotheses about the functionality of the various ingredients with respect to the structuring of the potato snacks.
    Direct measurement of thermal effusivity of avian eggs and theur constituents: A photopyroelectric study
    Szafner, G. ; Bicanic, D.D. ; Kovacsne, K. ; Doka, O. - \ 2012
    Food Technology and Biotechnology 50 (2012)3. - ISSN 1330-9862 - p. 350 - 354.
    physical-properties - conductivity - parameters - products
    The front configuration photopyroelectric method has been used to determine, in a nondestructive fashion, thermal effusivity of the yolk and the white of eggs of several bird species as well as of the blends of a single egg yolk and egg white (also called liquid eggs) of different avian eggs. Statistically significant differences in thermal effusivity of egg whites were observed in ten out of twenty-one comparisons made. However, in the case of egg yolks, the differences were observed in twenty among twenty-one comparisons carried out. These observations are related to a varying fat content of egg yolk and a large amount of water found in egg white. The effusivity of the blends prepared from yolks and eggs varies because the contents of the yolk and white in avian eggs differ.
    Production of small starch granules by expression of a tandem-repeat of a family 20 starch-binding domain (SBD3-SBD5) in an amylose-free potato genetic background
    Nazarian, F. ; Trindade, L.M. ; Visser, R.G.F. - \ 2012
    Functional Plant Biology 39 (2012)2. - ISSN 1445-4408 - p. 146 - 155.
    physical-properties - size - morphology - evolution - quality - growth - tissue - plants - tuber
    Starch exists typically as semicrystalline granules of varying size. Granule size plays an important role for many industrial starch applications. Microbial non-catalytic starch binding domains (SBD) exhibit an affinity for starch granules on their own. Three different constructs were introduced in the amylose-free potato cultivar (Solanum tuberosum L. cv. amf) to investigate whether it is possible to produce smaller starch granules by an engineered, high-affinity, tandemrepeats of a family 20 starch-binding domain (SBD3, SBD4 and SBD5). A significant reduction in the size of starch granule was achieved in transgenic potato plants. Furthermore, it was shown that the SBDn expression can affect physical processes underlying granule assembly and the poorly understood granule formation. Expression of multiple linked SBDs resulted in amalgamated starch granules that consisted of many smaller granules. No significant alterations were observed with regard to rheological properties of starch granules.
    Comparison of risk assessment methods to determine the subsoil compaction risk of agricultural soils in the Netherlands
    Akker, J.J.H. van den; Hoogland, T. - \ 2011
    Soil & Tillage Research 114 (2011)2. - ISSN 0167-1987 - p. 146 - 154.
    mechanical strength - physical-properties - sidass project - part 1 - model - capacity - stresses - predict - values - time
    Subsoil compaction is a recognised threat in the European Soil Strategy and knowledge concerning the vulnerability of subsoils to compaction in Europe and the Netherlands is information required for the determination of priority areas (or risk areas) in the future European Soil Framework Directive. In Europe two risk assessment methods (RAM) are used in more than one country to determine the subsoil compaction risk. The first one (RAM-A) initially determines the susceptibility of soils to compaction as a function of texture and packing density. In the second step the vulnerability to compaction is determined as a function of susceptibility and climate. The second RAM (RAM-B) is a mechanistic model in which the soil mechanical strength determines whether a subsoil is susceptible to compaction. The RAMs are used to produce maps presenting the susceptibility and vulnerability to compaction of Dutch subsoils (RAM-A) and maps with the compression strength and maximal allowable wheel load of a Terra Tire to prevent compaction of Dutch subsoils (RAM-B). Both RAMs have weaknesses. RAM-A is an expert model and can be rather arbitrarily with results that are not in agreement with our experience. RAM-B suffers from lack of good data and probably underestimates subsoil strengths. Results of both RAMs are compared to each other and to a map showing the probability that the subsoil is already overcompacted. This probability map is based on bulk density data in the Dutch Soil Database (BIS). There is a good match between the results of both RAMs, however, the match with the probability map (presumed to be “reality”) is not good. In both RAMs sand and loamy sand soils are indicated as more vulnerable than clay soils, while in the probability map sand subsoils suffer less of subsoil compaction than clay soils. Of concern is that, according to the probability map, about 50% of the most productive and fertile soils of The Netherlands have overcompacted subsoils. --------------------------------------------------------------------------------
    A meta-analysis of long-term effects of conservation agriculture on maize grain yield under rain-fed conditions
    Rusinamhodzi, L. ; Corbeels, M. ; Wijk, M.T. van; Rufino, M.C. ; Nyamangara, J. ; Giller, K.E. - \ 2011
    Agronomy for Sustainable Development 31 (2011)4. - ISSN 1774-0746 - p. 657 - 673.
    no-till corn - soil chemical-properties - crop residue management - poorly drained soil - conventional tillage - loam soil - physical-properties - green-revolution - western nigeria - farming systems
    Conservation agriculture involves reduced tillage, permanent soil cover and crop rotations to enhance soil fertility and to supply food from a dwindling land resource. Recently, conservation agriculture has been promoted in Southern Africa, mainly for maize-based farming systems. However, maize yields under rain-fed conditions are often variable. There is therefore a need to identify factors that influence crop yield under conservation agriculture and rain-fed conditions. Here, we studied maize grain yield data from experiments lasting 5 years and more under rain-fed conditions. We assessed the effect of long-term tillage and residue retention on maize grain yield under contrasting soil textures, nitrogen input and climate. Yield variability was measured by stability analysis. Our results show an increase in maize yield over time with conservation agriculture practices that include rotation and high input use in low rainfall areas. But we observed no difference in system stability under those conditions. We observed a strong relationship between maize grain yield and annual rainfall. Our meta-analysis gave the following findings: (1) 92% of the data show that mulch cover in high rainfall areas leads to lower yields due to waterlogging; (2) 85% of data show that soil texture is important in the temporal development of conservation agriculture effects, improved yields are likely on well-drained soils; (3) 73% of the data show that conservation agriculture practices require high inputs especially N for improved yield; (4) 63% of data show that increased yields are obtained with rotation but calculations often do not include the variations in rainfall within and between seasons; (5) 56% of the data show that reduced tillage with no mulch cover leads to lower yields in semi-arid areas; and (6) when adequate fertiliser is available, rainfall is the most important determinant of yield in southern Africa. It is clear from our results that conservation agriculture needs to be targeted and adapted to specific biophysical conditions for improved impact.
    Assessment of the effects of fish meal, wheat gluten, soy protein concentrate and feed moisture on extruder system parameters and the technical quality of fish feed
    Draganovic, V. ; Goot, A.J. van der; Boom, R.M. ; Jonkers, J. - \ 2011
    Animal Feed Science and Technology 165 (2011)3-4. - ISSN 0377-8401 - p. 238 - 250.
    trout oncorhynchus-mykiss - extrusion conditions - physical-properties - rainbow-trout - aquaculture feeds - screw extrusion - replacement - products - cooking - starch
    Evaluation of feed ingredient functionality plays a vital role in modern fish feed manufacturing practice. The aim of this study was to examine the extrusion behaviour of blends containing alternative protein sources from plant origin to fish meal (FM), such as wheat gluten (WG) and soy protein concentrate (SPC), and the consequences for the physical attributes of the resulting feed extrudates. A mixture design was applied, varying the levels of protein sources included in the formulation from 50 to 450 g kg-1. Each diet was produced with added feed moisture content of 20, 26 and 32 g/100 g (wet basis). The partial least squares regression models were fitted and their performance was evaluated on the basis of R2 and the root mean squared error of cross-validation over the complete data set. A higher inclusion level of FM in the diet decreased the values of the extruder system parameters, such as torque, pressure at the die and melt temperature. In contrast, inclusion of SPC significantly increased the values of these extruder-related parameters. The viscoelastic properties of WG gave higher radial expansion; FM showed the opposite effect. The results show that the feed moisture was the dominant factor for extrudate density and oil absorption capacity. Products with higher breaking strength were observed with increasing levels of WG and SPC. Combining the product requirements for both extrudate density and hardness showed that the largest optimal compositional range is available at low feed moisture content. However, maximum FM replacement is possible at high feed moisture content
    Tillage and vegetative barrier effects on soil conservation and short-term economic benefits in the Central Kenya highlands
    Guto, S.N. ; Pypers, P. ; Vanlauwe, B. ; Ridder, N. de; Giller, K.E. - \ 2011
    Field Crops Research 122 (2011)2. - ISSN 0378-4290 - p. 85 - 94.
    contour hedgerow systems - water conservation - napier grass - andes region - leucaena-leucocephala - management-practices - spatial variability - physical-properties - northern thailand - intercrop system
    Minimum tillage and vegetative barriers can conserve soil and water resources in the steep-sloping highlands of East Africa but there has been little adoption by smallholder farmers. Soil conservation efficiency and short-term economic benefits provided by tillage and vegetative barriers were assessed over four cropping seasons to understand performance under local farming conditions. Minimum tillage was compared with regular tillage and vegetative barriers (leucaena and Napier) with no barriers. Maize and soybean yields were greater with than without vegetative barriers, except with Napier barriers when minimum tillage was practiced where strong root competition occured. Cumulatively for the four cropping seasons, Napier barriers with regular tillage conserved most soil (72%) followed by Napier with minimum tillage (53%). The least soil (1%) was conserved for minimum tillage without barriers and leucaena barriers were intermediate in decreasing soil erosion. The highest positive marginal rate of returns (MRRs) were realized under leucaena barriers with regular tillage (2.09) followed by Napier with regular tillage (1.32). Minimum tillage without barriers had the lowest positive MRRs (0.08). Future increase in the price of key inputs would have greater depressive effect on the MRRs of Napier barriers with regular tillage than leucaena barriers with regular tillage. Minimum tillage without barriers was inefficient in soil conservation particularly when rainfall was intense and had poor MRRs. Leucaena barriers conserved less soil than Napier barriers but were more economically attractive, demonstrating a clear trade-off between soil erosion that is likely to impact crop yields in the long-term and short-term economic benefits. Napier barriers with regular tillage present a win–win scenario due to efficient soil conservation and attractive economic returns provided future prices of labour and Napier cuttings remain stable.
    Soil fertility management: Impacts on soil macrofauna, soil aggregation and soil organic matter allocation.
    Ayuke, F.O. ; Brussaard, L. ; Vanlauwe, B. ; Six, J. ; Lelei, D.K. ; Kibunja, C.N. ; Pulleman, M.M. - \ 2011
    Applied Soil Ecology 48 (2011)1. - ISSN 0929-1393 - p. 53 - 62.
    fungus-growing termites - earthworm activity - microaggregate formation - nitrogenous fertilizers - physical-properties - agricultural soils - input management - feeding termite - carbon - dynamics
    Maintenance of soil organic matter through integrated soil fertility management is important for soil quality and agricultural productivity, and for the persistence of soil faunal diversity and biomass. Little is known about the interactive effects of soil fertility management and soil macrofauna diversity on soil aggregation and SOM dynamics in tropical arable cropping systems. A study was conducted in a long-term trial at Kabete, Central Kenya, to investigate the effects of organic inputs (maize stover or manure) and inorganic fertilizers on soil macrofauna abundance, biomass and taxonomic diversity, water stable aggregation, whole soil and aggregate-associated organic C and N, as well as the relations between these variables. Differently managed arable systems were compared to a long-term green fallow system representing a relatively undisturbed reference. Fallowing, and application of farm yard manure (FYM) in combination with fertilizer, significantly enhanced earthworm diversity and biomass as well as aggregate stability and C and N pools in the top 15 cm of the soil. Earthworm abundance significantly negatively correlated with the percentage of total macroaggregates and microaggregates within macroaggregates, but all earthworm parameters positively correlated with whole soil and aggregate associated C and N, unlike termite parameters. Factor analysis showed that 35.3% of the total sample variation in aggregation and C and N in total soil and aggregate fractions was explained by earthworm parameters, and 25.5% by termite parameters. Multiple regression analysis confirmed this outcome. The negative correlation between earthworm abundance and total macroaggregates and microaggregates within macroaggregate could be linked to the presence of high numbers of Nematogenia lacuum in the arable treatments without organic amendments, an endogeic species that feeds on excrements of other larger epigeic worms and produces small excrements. Under the conditions studied, differences in earthworm abundance, biomass and diversity were more important drivers of management-induced changes in aggregate stability and soil C and N pools than differences in termite populations. Highlights ¿ Application of farm yard manure + fertilizer improved aggregate stability and C and N stabilization in soil. ¿ Application of maize stover did not improve soil aggregation and C and N stabilization. ¿ Farm yard manure + fertilizer application enhanced earthworm diversity and biomass. ¿ Higher earthworm diversity and biomass enhanced aggregate and C and N stabilization. ¿ Earthworms were more important drivers of aggregate and C and N stabilization than termites.
    Impact of Manaus City on the Amazon Green Ocean atmosphere: Ozone production, precursor sensitivity and aerosol load
    Kuhn, U. ; Ganzeveld, L.N. - \ 2010
    Atmospheric Chemistry and Physics 10 (2010). - ISSN 1680-7316 - p. 9251 - 9282.
    secondary organic aerosol - cloud condensation nuclei - biomass-burning emissions - power-plant plumes - tropical south-atlantic - trace gas exchanges - rain-forest - tropospheric ozone - dry season - physical-properties
    As a contribution to the Large-Scale Biosphere-Atmosphere Experiment in Amazonia – Cooperative LBA Airborne Regional Experiment (LBA-CLAIRE-2001) field campaign in the heart of the Amazon Basin, we analyzed the temporal and spatial dynamics of the urban plume of Manaus City during the wet-to-dry season transition period in July 2001. During the flights, we performed vertical stacks of crosswind transects in the urban outflow downwind of Manaus City, measuring a comprehensive set of trace constituents including O3, NO, NO2, CO, VOC, CO2, and H2O. Aerosol loads were characterized by concentrations of total aerosol number (CN) and cloud condensation nuclei (CCN), and by light scattering properties. Measurements over pristine rainforest areas during the campaign showed low levels of pollution from biomass burning or industrial emissions, representative of wet season background conditions. The urban plume of Manaus City was found to be joined by plumes from power plants south of the city, all showing evidence of very strong photochemical ozone formation. One episode is discussed in detail, where a threefold increase in ozone mixing ratios within the atmospheric boundary layer occurred within a 100 km travel distance downwind of Manaus. Observation-based estimates of the ozone production rates in the plume reached 15 ppb h-1. Within the plume core, aerosol concentrations were strongly enhanced, with ¿CN/¿CO ratios about one order of magnitude higher than observed in Amazon biomass burning plumes. ¿CN/¿CO ratios tended to decrease with increasing transport time, indicative of a significant reduction in particle number by coagulation, and without substantial new particle nucleation occurring within the time/space observed. While in the background atmosphere a large fraction of the total particle number served as CCN (about 60–80% at 0.6% supersaturation), the CCN/CN ratios within the plume indicated that only a small fraction (16±12%) of the plume particles were CCN. The fresh plume aerosols showed relatively weak light scattering efficiency. The CO-normalized CCN concentrations and light scattering coefficients increased with plume age in most cases, suggesting particle growth by condensation of soluble organic or inorganic species. We used a Single Column Chemistry and Transport Model (SCM) to infer the urban pollution emission fluxes of Manaus City, implying observed mixing ratios of CO, NOx and VOC. The model can reproduce the temporal/spatial distribution of ozone enhancements in the Manaus plume, both with and without accounting for the distinct (high NOx) contribution by the power plants; this way examining the sensitivity of ozone production to changes in the emission rates of NOx. The VOC reactivity in the Manaus region was dominated by a high burden of biogenic isoprene from the background rainforest atmosphere, and therefore NOx control is assumed to be the most effective ozone abatement strategy. Both observations and models show that the agglomeration of NOx emission sources, like power plants, in a well-arranged area can decrease the ozone production efficiency in the near field of the urban populated cores. But on the other hand remote areas downwind of the city then bear the brunt, being exposed to increased ozone production and N-deposition. The simulated maximum stomatal ozone uptake fluxes were 4 nmol m-2 s-1 close to Manaus, and decreased only to about 2 nmol m-2 s-1 within a travel distance >1500 km downwind from Manaus, clearly exceeding the critical threshold level for broadleaf trees. Likewise, the simulated N deposition close to Manaus was ~70 kg N ha-1 a-1 decreasing only to about 30 kg N ha-1 a-1 after three days of simulation.
    Effects of fire ash on soil water retention
    Stoof, C.R. ; Wesseling, J.G. ; Ritsema, C.J. - \ 2010
    Geoderma 159 (2010)3-4. - ISSN 0016-7061 - p. 276 - 285.
    physical-properties - fly-ash - forest soil - hydrological properties - mediterranean soils - moisture retention - organic-matter - wildfire - erosion - texture
    Despite the pronounced effect of fire on soil hydrological systems, information on the direct effect of fire on soil water retention characteristics is limited and contradictory. To increase understanding in this area, the effect of fire on soil water retention was evaluated using laboratory burning and heating experiments. In addition, ash-infiltration and ash-incorporation experiments were performed to evaluate the effect of ash on soil water retention. While heating soil to 200 °C and below did not change soil properties, burning and heating to 300 °C and above increased bulk density, clay and silt content, and decreased organic matter and sand content. Burning and heating above 200 °C decreased the amount of water stored at the nine tensions considered, although the effect on soil water retention did not always increase with increasing temperature. Changes were largest for low tensions, i.e. between saturation and field capacity (10 kPa). Heating to 200 °C decreased the amount of plant available water, but despite reducing the amount of water stored at evaluated tensions, burning and heating to 300 °C and above increased the amount of plant available water. This may be caused by more complete combustion of organic matter at the higher temperatures and the production of ash. Direct incorporation of ash into soils did not alter soil texture but increased water retention from saturation to 310 kPa tension. Ash infiltration experiments interestingly had a similar effect, despite the fact that very little ash washed into the samples. Results from these experiments contribute to understanding post-fire changes in hydrological and erosion processes.
    Effects of land use-change on some properties of tropical soils - An example from Southeast Mexico
    Geissen, V. ; Sánchez-Hernández, R. ; Kampichler, C. ; Ramos-Reyes, R. ; Sepulveda-Lozada, A. ; Ochoa-Gaona, S. ; Jong, B.H.J. de; Huerta-Lwanga, E. ; Hernández-Daumás, S. - \ 2009
    Geoderma 151 (2009)3-4. - ISSN 0016-7061 - p. 87 - 97.
    organic-matter - physical-properties - microbial biomass - pasture - forest - carbon - deforestation - fertility - systems - landscape
    We studied the effects of land-use and land-cover changes on physical and chemical properties of soil in tropical South-East Mexico. In the study area of about 5500 km2, the dominant land use is pastureland (Pa seasonal agriculture (TA), fruit plantations (FP), sugarcane, (SC) secondary (SF) and primary forest (PF) and other not specified land-use types (undefined). From 1988 to 2003 severe deforestation took place and pastureland increased by 179% while primary forest decreased to 17% of the initial area. Based on topographic and soil maps we selected 176 sampling sites covering the combinations of topography and soil type. In 2005, we took soil samples in each selected site from two soil depths (0–20 cm and 20–40 cm). We analyzed fertility parameters like pH, texture and contents of organic carbon, total nitrogen and available phosphorus. Furthermore, we measured soil resistance against penetration in layers of 5 cm down to a depth of 40 cm. We estimated land-use changes between 1988 and 2005 using digital land-use maps derived from satellite and aerial photography interpretation. We compared soil properties of different soil types, soils under different current land use and under the influence of land-cover changes. Gleysols, Vertisols, Regosols, Luvisols and Leptosols showed clay to clay loam texture, whereas Cambisols were characterized by sandy clay loam texture. All soil groups in the study region were slightly acidic with pH(KCl) values between 5.3 and 6.2. Furthermore, they neither showed significant differences in available P content nor in C/N ratio. However, the investigated soil associations displayed different organic carbon and total nitrogen contents in the upper 20 cm depth. Soils under different current land use did not show any significant differences with respect to available phosphorus, organic carbon, total nitrogen and C/N ratio whereas the pH value was significantly higher under seasonal agriculture than under pasture. Land-use changes between 1988 and 2003 did not significantly influence the contents of available phosphorus and organic carbon or the C/N ratio. However, total nitrogen was significantly higher in soils which were changed from forest in 1988 to seasonal agriculture in 2003 (F-TA) than in soils changed from forest to pastureland (F-Pa) or from pasture to forestland (Pa-F). Furthermore, soils under land-use change F-TA were less acidic in both depths than soils under Pa-F, TA-Pa, or which remained pastureland over the whole time (Pa-Pa). Soils in pastureland were significantly more compacted in all layers than soils used for seasonal agriculture. Soils that were used for pastureland already in 1988 showed significantly higher compaction than most of the other soils. We conclude that land-use change in a period of 15 years did not lead to chemical soil degradation. However, permanent pastureland leads to a severe compaction of soils.
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