Organic Matter Amendments Research Articles

Evaluating soil resilience in long-term cultivation: a study of pre-Columbian terraces from the Paca Valley, Peru

This study evaluated the soil properties of pre-Hispanic stone-walled terraces by comparing soil quality along terraced catenas in the Paca Valley, a tributary of the Mantaro Valley, Peru. Micromorphological and bulk analyses of terrace soils revealed that despite terracing soil horizonation largely followed the catena. Upland terraced fields had deeper A-horizons with higher biotic activity than uncultivated controls, but less fine material and greater carbonate accumulation. Midslope fields were highly variable in depth and soil properties reflecting considerable substrate and anthropogenic variations in this growing zone. Silts and clay accumulated in valley bottom terraces where pedofeatures indicate an ongoing downhill movement of fine material. The distribution of soil separates down Paca hillsides demonstrates that terraces help moderate, rather than control, the erosion of key soil fractions required for long-term agricultural productivity. This study illustrates how the loss of fine material is partly mitigated by soil consolidation in dense topsoil peds, microaggregates and saprolite. These aggregates are retained by terraces and contribute to deep soil profiles. Nevertheless, many fields show signs of degradation, especially from insufficient organic matter amendment. In addition to farming itself, buried soils and associated artefacts in valley bottom fields indicate mass soil movement, a likely result of disruption caused by Inca road and terrace construction. The poor soil quality of many upland terraces also confirms that stone-walled terraces were constructed on mediocre substrates for farming, indicating a high labour investment for marginal agricultural returns in these areas. Overall, Paca Valley terraces improve topsoil retention and promote deep soil profiles. However, these fields present quite varied growing substrates. It is also apparent that over the last millennium, soil depletion from cultivation has compromised soil quality through loss of fine material and organic matter. Shifts in farming practice away from pre-Hispanic practices such as long-fallow and middening appear to exacerbate this trend.

Soil solarization with biodegradable materials and its impact on soil microbial communities

The application of soil solarization (SS), one of the most promising techniques for the control of soilborne pathogens, is seriously limited by the drawback regarding the disposal of the used plastic materials. A possible solution to this problem is the use of biodegradable plastics. The aim of this study was to make comparisons between the impact of SS performed with biodegradable materials and that of SS with plastic films and other pest management techniques (i.e. organic matter amendment, calcium cyanamide and Dazomet fungicide application) on crop productivity, soilborne disease incidence, weed suppression, and soil chemical (total N, NH 4-N, nitrate, available phosphorus, organic matter, hydrolysis of fluorescein diacetate) and microbial (cultivable Pseudomonas, DGGE fingerprinting of bacterial 16S- and fungal 28S rRNA gene fragments from total soil community DNA) parameters. We carried out field experiments in two types of soil with different textures (clay and sand) artificially inoculated with Fusarium oxysporum f.sp. lycopersici (vs. tomato) and Sclerotinia minor (vs. lettuce). The temperature of soils covered with solarizing materials was always higher than that of bare soils, but plastic cover was more effective and consistent in rising soil temperature compared to biodegradable materials. Plant growth promotion by SS was limited, especially compared to Dazomet and organic matter applications, and a positive effect was observed only for lettuce in the clay soil. Differently, both plastic and biodegradable solarizing materials were effective in reducing lettuce drop caused by S. minor. Weed development was significantly suppressed by Dazomet application and SS with plastic film, while control with biodegradable materials was limited. SS had a variable and limited effect on chemical and microbial parameters, with a general tendency to reduce richness of bacteria and fungi. Dazomet caused the most pronounced reduction of the microbial community diversity in both soil types and a significant stimulation of the fluorescent Pseudomonas group. Organic amendment significantly enhanced the organic matter content, the hydrolysis of fluorescein diacetate and the Pseudomonas population. Among all measured soil parameters, the size of the fluorescent Pseudomonas population emerged as the most important factor affecting crop productivity. The results of this experimentation show the potential of using biodegradable solarizing materials in place of plastic films, but also indicate the need for improving their properties to obtain performances comparable to those of other pest management techniques.

The effectiveness of four organic matter amendments for decreasing resin-extractable Cr(VI) in Cr(VI)-contaminated soils

This paper compared the effectiveness of four organic materials for decreasing the amounts of soil extractable Cr(VI) in Cr(VI)-contaminated soils using the DOWEX M4195 resin-extraction method. Organic matters were added into Cr(VI)-spiked soils [500 mg Cr(VI) (kg soil) −1] in the form of sugarcane dregs compost (SCDC), cattle-dung compost (CDC), soybean meal (SBM) and rice bran (RB), in the amounts of 0, 1%, and 2% by dry weight, respectively. The results indicated that adding only 1% organic matter to the studied soils could effectively decrease the amount of soil resin-extractable Cr(VI) after 12 days of incubation. The decrease of resin-extractable Cr(VI) by organic materials was mainly the result from the reduction of Cr(VI) to Cr(III) supported by the XANES spectroscopy. Among the four tested organic materials, SBM and RB had higher effectiveness in decreasing soil resin-extractable Cr(VI) than CDC and SCDC. This result may be due to the fact that SBM and RB have more dissolved organic carbon (DOC) and protein than CDC and SCDC. Therefore, it was concluded that the contents of DOC and protein are the main factors that determine the effectiveness of organic materials for decreasing the amounts of soil available Cr(VI) in Cr(VI)-contaminated soils.

Setting the Tempo in Land Remediation: Short-Term and Long-Term Patterns in Biodiversity Recovery

Land to be remediated, such as those affected by heavy metals or organic pollutants, can be remediated using biological approaches. These include, quarries and strip mines, or land impacted by oil pollution or other organic pollutants. Phytoremediation is usually a key component of bioremediation. However, without restoring soil organic matter, the soil biodiversity takes decades to recover. The soil organisms are a key component of soil function, and support plant growth. In addition, the soil microbiology is essential both for bioremediation and supporting phytoremediation. Using inexpensive sources of quality organic matter, it should be possible to accelerate recovery of ecosystem health and biodiversity. One potential source of untapped organic matter is municipal solid waste as a composted amendment. The organic matter amendment promotes soil structure and the creation of adequate habitat and substrate for the soil decomposition food web. Long-term chronosequence studies indicate that soil food webs tend to make a transition after about 20 years to a stable community structure. This approach could be used to gain carbon credits by restoring degraded or polluted soils.

The effect of sediment grain size on bacterial communities in streams

Sediment bacteria are ubiquitous and important to the cycling of organic matter and nutrients in streams. We experimentally investigated the effect of sediment grain size on bacterial communities by using artificial substrata of different sizes incubated in a northeast Ohio (USA) stream. We examined abundances of specific bacterial taxa with fluorescent in situ hybridization. In general, taxon abundances were highest on 5.0-mm particles and lowest on 0.1-mm particles, and all taxa responded similarly to particle size. Few differences in abundance were found between substrata incubated in a pool or riffle in the stream or between substrata with or without organic matter amendment. Particle surface area and particle packing (sediment permeability) both affected bacterial abundance in our experiments. However, our results suggest that other factors, such as chemistry of interstitial spaces and susceptibility to predation, also contribute to differences in abundance among substrata of different particle sizes.

Vegetation dynamics in response to organic matter loading rates in a created freshwater wetland in southeastern Virginia

Created wetlands are often limited in soil organic matter, a product that usually accumulates with long-term ecosystem succession. Although many studies have tested the effect of adding organic material to these systems, few have quantified the effect of various loadings of organic matter (OM) in created wetlands. The purpose of this study was to determine how vegetation composition, standing crop biomass, and woody vegetation development varied in a created freshwater wetland with respect to different loadings (0, 56, 112, 224, or 336 Mg ha−1) of a soil OM amendment. Soil C, N, and P were positively related to loading rate, as was soil surface elevation. Species richness, evenness, and diversity measurements, along with the Ellenberg Community Coefficient Similarity Index, suggested an overall similarity of plant assemblages regardless of loading rate. Standing crop biomass (580–790 g m−2) was not significantly correlated with OM loadings, but showed a significant curvilinear relationship with plot surface elevation. Woody vegetation development was correlated with OM loadings, plot elevation, and soil P, indicating a positive relationship with all three factors. An amendment loading of 112 Mg ha−1 provided the maximum benefit because it provided soil nutrient levels that were within the range of natural wetlands while also minimizing changes in soil surface elevation due to the added bulk material.

Differences in soil enzyme activities, microbial community structure and short-term nitrogen mineralisation resulting from farm management history and organic matter amendments

Changes in soil microbial biomass, enzyme activities, microbial community structure and nitrogen (N) dynamics resulting from organic matter amendments were determined in soils with different management histories to gain better understanding of the effects of long- and short-term management practices on soil microbial properties and key soil processes. Two soils that had been under either long-term organic or conventional management and that varied in microbial biomass and enzyme activity levels but had similar fertility levels were amended with organic material (dried lupin residue, Lupinus angustifolius L.) at amounts equivalent to 0, 4 and 8t dry matter lupinha−1. Microbial biomass C and N, arginine deaminase activity, fluorescein diacetate hydrolysis, dehydrogenase enzyme activity and gross N mineralisation were measured in intervals over an 81-day period. The community structure of eubacteria and actinomycetes was examined using PCR–DGGE of 16S rDNA fragments. Results suggested that no direct relationships existed between microbial community structure, enzyme activities and N mineralisation. Microbial biomass and activity changed as a result of lupin amendment whereas the microbial community structure was more strongly influenced by farm management history. The addition of 4tha−1 of lupin was sufficient to stimulate the microbial community in both soils, resulting in microbial biomass growth and increased enzyme activities and N mineralisation regardless of past management. Amendment with 8tlupinha−1 did not result in an increase proportional to the extra amount added; levels of soil microbial properties were only 1.1–1.7 times higher than in the 4tha−1 treatment. Microbial community structure differed significantly between the two soils, while no changes were detected in response to lupin amendment at either level during the short-term incubation. Correlation analyses for each treatment separately, however, revealed differences that were inconsistent with results obtained for soil biological properties suggesting that differences might exist in the structure or physiological properties of a microbial component that was not assessed in this study.

Surface Irrigation Reduces the Emission of Volatile 1,3-Dichloropropene from Agricultural Soils

Low-cost, practicable techniques are required to limit the release of volatile organic compound-containing fumigants such as 1,3-D to the atmosphere. In this study, we aimed to quantify 1,3-D diffusion and emission from laboratory soil columns maintained under realistic conditions and thereby assess the efficacy of soil irrigation as a technique for reducing emissions. In two soils (one relatively high, and one relatively low, in organic matter), irrigation led to a limiting of upward diffusion of the fumigant and to the maintenance of higher soil gas concentrations. Therefore, rather than being emitted from the column, the 1,3-D was maintained in the soil where it was ultimately degraded. As a consequence, emission of 1,3-D from the irrigated columns was around half of thatfrom the nonirrigated columns. It is concluded that surface irrigation represents an effective, low-cost, and readily practicable approach to lessening the environmental impact of 1,3-D fumigant use. In addition, the higher organic matter soil exhibited emissions of around one-fifth of the lower organic matter soil in both irrigated and nonirrigated treatments, due to markedly enhanced degradation of the fumigant. Organic matter amendment of soils may, therefore, also represent an extremely effective, relatively low-cost approach to reducing 1,3-D emissions.

Using Organic Matter with Chemical Amendments to Improve Calcareous Sodic Soil

Kangping soil in northeast China is a sodic soil characterized by a high pH and excessive sodium. The high pH and excessive sodium in sodic soils generally cause loss of soil structure, reduce hydraulic conductivity (HC), increase soil hardness, and make the soil unproductive land. After we mixed organic matter (rice straw) and chemical amendments (H2SO4, CaSO4, and FeSO4), a column experiment was conducted to evaluate the physical and chemical properties of the soil influenced by the changes in HC, penetrability of soil s`urface, pH, electrical conductivity, CO3 2‐, HCO3 −, Ca2+, Na+, sodium adsorption rate (SAR), available phosphorus (P) and iron (Fe), and leached P. Organic matter decreased the concentrations of CO3 2‐, HCO3 −, and Na+ in soil solution and increased the total volume of the leachate. Organic matter also reduced the amount of available Fe and increased the available P. However, organic matter did not affect the penetrability of the soil surface as much as soil hardness, HC, and SAR within the short period of this experiment. Among the chemical amendments, H2SO4 and FeSO4 were more effective than CaSO4 to restore HC, electrical conductivity, Na+, and SAR. The chemical amendments, compared with organic matter, significantly leached P from the soil in this study, but the leaching was independent of the concentration of available P in the soil. The CaSO4 had the strongest effect in increasing leached P from the soil without changing the concentration of available P in the soil. Organic matter with added CaSO4 leached P from the soil more than all other treatments.

Soil‐aggregate formation as influenced by clay content and organic‐matter amendment

AbstractNaturally occurring wetting‐and‐drying cycles often enhance aggregation and give rise to a stable soil structure. In comparatively dry regions, such as large areas of Australia, organic‐matter (OM) contents in topsoils of arable land are usually small. Therefore, the effects of wetting and drying are almost solely reliant on the clay content. To investigate the relations between wetting‐and‐drying cycles, aggregation, clay content, and OM in the Australian environment, an experiment was set up to determine the relative influence of both clay content (23%, 31%, 34%, and 38%) and OM amendments of barley straw (equivalent to 3.1 t ha–1, 6.2 t ha–1, and 12.4 t ha–1) on the development of water‐stable aggregates in agricultural soil. The aggregate stability of each of the sixteen composite soils was determined after one, three, and six wet/dry cycles and subsequent fast and slow prewetting and was then compared to the aggregate stabilities of all other composite soils.While a single wet/dry cycle initiated soil structural evolution in all composite soils, enhancing macroaggregation, the incorporation of barley straw was most effective for the development of water‐stable aggregates in those soils with 34% and 38% clay. Repeated wetting‐and‐drying events revealed that soil aggregation is primarily based on the clay content of the soil, but that large straw additions also tend to enhance soil aggregation. Relative to untreated soil, straw additions equivalent to 3.1 t ha–1 and 12.4 t ha–1 increased soil aggregation by about 100% and 250%, respectively, after three wet/dry cycles and fast prewetting, but were of less influence with subsequent wet/dry cycles. Straw additions were even more effective in aggregating soil when combined with slow prewetting; after three wet/dry cycles, the mean weight diameters of aggregates were increased by 70% and 140% with the same OM additions and by 160% and 290% after six wet/dry cycles, compared to samples without organic amendments.We suggest that in arable soils poor in OM and with a field texture grade of clay loam or finer, the addition of straw, which is often available from preceding crops, may be useful for improving aggregation. For a satisfactory degree of aggregate stability and an improved soil structural form, we found that straw additions of at least 6.2 t ha–1 were required. However, rapid wetting of straw‐amended soil will disrupt newly formed aggregates, and straw has only a limited ability to sustain structural improvement.

Effect of polysaccharides in slow filters integrated into closed hydroponic greenhouse systems

SummarySlow filtration is a widespread and environmentally sound method for the disinfestation of nutrient solutions in closed hydroponic systems. The efficacy of slow filters can be explained in part by straining and adsorption of pathogens onto filter material surfaces. Both mechanisms are influenced by choice of filter material, flow rate of the nutrient solution, biomass and extent of extracellular polymers on the filter skin. In a 2-year study, the total polysaccharide content and enzyme activity of the filter skin, and filter efficacy were monitored. Closed hydroponic systems using the nutrient film technique connected to slow filters were run with or without weekly inoculation with a fungal cell wall preparation (10.5 g m–2 of filter surface). This organic matter amendment increased the amount of total polysaccharide and enzyme activity within the filter skin. The fungal cell wall preparation did not accumulate, but was degraded rapidly. The total polysaccharide content (tPS; in mg g–1) of the filter skin increased linearly with time at 34.50 mg g–1 + 0.26 mg g–1 d–1 × days (d) (R2 = 0.556; P = 0.02) for untreated filters, and at 43.40 mg g–1 + 0.70 mg g–1 d–1 × days (d) (R2 = 0.826; P = 0.000) for treated filters. The extracellular polysaccharide content in the filter skin, determined after 16 and 20 weeks of slow filter operating time, ranged from 87.9 – 109.7 mg g–1 mineral wool (rockwool) sampled. The amount of extracellular polysaccharide was not influenced by the total polysaccharide content of the filter skin, by enzyme activity, or by addition of the fungal cell wall preparation. There was a trend towards higher filter efficacies when fungal cell wall preparations were added to the filter skin (treated: 98.3% ± 0.96; untreated: 97.9% ± 1.8); however, on the basis of the present data, no correlation between the assessed parameters and filter efficacies were observed.

Penagruh Lintasan Traktor Dan Pemberian Bahan Organik Terhadap Pemadatan Tanah Dan Keragaan Tanaman Kacang Tanah

The amendment of organic matter into soil can improve the soil condition and prevent soil comaction caused by tractor traffice. The aims of this research are to know the influence or tractor traffic and organic matter on nature of physical mechanic of soil, analyze the influence of tractor traffic and organic matter on performance of soil tillage and to know the influence of soil compaction on performance of peanut crop. This research was conducted in leuwikopo farm (dry land) and in the laboratory for soil analyze. The result show that tractor traffic and organic matter treatmen have effect to soil compaction and performance peanuut crop. The highest value of bulk density is 1.2 g / cm3 at 6 traffic with the organic matter doses 4 ton /ha /hatreatment. The biggest number of pods is 25 pod / tree there is at 2 traffic with pod / tree at 6 traffic without organic matter treatment. Keyword: Tractor traffic, organic matter, soil compaction. Diterima: 27 Pebruari 2006; Disetujui: 23 Juli 2006

Impact of salinity on soil microbial communities and the decomposition of maize in acidic soils

Soil salinity, as an increasingly important process of land degradation, is a major threat to microbial communities and thus strongly alters organic matter turnover processes. This study was conducted to determine the influence of salinity on the decomposition of maize and on the response of soil microbial communities. Soil samples were collected from two pasture sites in Heringen (Germany). One of the sites has previously been influenced by salinity caused by saline effluent from a potassium mine. These sandy soils were washed, resulting in equal levels of electrical conductivity. Moist soils were then incubated with 2% incorporated maize straw and at three levels of salinity (0, 15, 50 mg NaCl g − 1 soil) for almost 7 weeks at 25 °C. The amount of recovered maize derived particulate organic matter (POM) increased with increasing salinity, exhibiting reduced decomposition of substrate. Furthermore, inorganic N, which consisted almost exclusively of NH 4 +, increased with increasing levels of salinity. Corresponding to this, biological indices like soil respiration and microbial biomass decreased with increasing levels of salinity, underlining the detrimental effect of salinity on soil microorganisms. This effect was reduced after addition of maize straw, documenting the importance of organic matter amendment in counteracting the negative effects of salinity on microbial communities and related mineralisation processes. Addition of organic matter also led to a spatial differentiation of the microbial community in the soil, with bacteria dominating the surface of the substrate, indicated by a low glucosamine-to-muramic acid ratio. This ratio, however, was not altered by salinity. On the other hand, the ergosterol-to-microbial biomass C ratio was an evidence of fungal dominance in the soil. The ratio increased with elevated salt content, either showing a shift towards fungi, a change in fungal cell morphology, or accumulation of ergosterol in the soil. The metabolic quotient qCO 2 was higher in the soil previously subjected to osmotic stress, showing a physiologically more active population that is using substrate less efficiently. We assume that it might further reflect adaptation mechanisms to the increased osmotic pressure.

Restoration of Plant Cover in Subalpine Forests Disturbed by Camping: Success of Transplanting

Camping has severely impacted soil and vegetation in many natural areas. Effective techniques for restoring native vegetation are needed, particularly at high elevations. This study assessed the effectiveness of transplanting and restoration treatments designed to improve the physical, biological, and chemical properties of soils (scarification and amendments of organic matter, compost, and soil inoculum), and ameliorate microclimatic conditions (application of a biodegradable mulch mat) on six closed campsites in subalpine forests in Oregon. Most transplants (68%) were still alive seven years after transplanting. Mean area and height of surviving transplants increased 39% and 19%, respectively, over the seven years. Transplanting success varied among species. Graminoids survived most frequently, while tree species grew most rapidly. Only 45% of the shrub transplants survived and the canopy area of most survivors decreased. Shrubs constitute about 70% of the undisturbed groundcover. The soil amendments, particularly addition of compost and organic matter, increased the growth of transplants but had little effect on survivorship. Effects were most pronounced for graminoids and diminished after the fourth year of the experiment. The application of a biodegradable mulch mat had no effect. Transplanting locally collected plants is an effective means of accelerating the restoration of damaged campsites in these subalpine forests. However, the more elaborate treatments were only modestly successful in increasing transplanting success. They did not overcome the difficulty of restoring sustainable populations of the shrubs Vaccinium scoparium and Phyllodoce empetriformis.

HUMIC SUBSTANCES AND CLAY MINERALS IN ORGANICALLY-AMENDED SEMIARID SOILS

Unsuitable agricultural practices have resulted in a permanent soil degradation in some semiarid areas of southeastern Spain. Because addition of exogenous organic matter has been shown to generally cause an improvement in quality of these degraded soils, the objective of this work was to evaluate the efficacy of amendment with fresh sewage sludge, composted sewage sludge, and a mixture of fresh sludge and a commercial humic substance on restoring the quality of a degraded soil 7 years after a one-time amendment with 25 kg/m organic matter. The soil used in the study was a sandy Xeric Torriorthent. Because the experimental soil plots had a slope of 15%, the effect of soil slope on these properties was also determined. Soil samples were collected from the surface layer (0-20 cm) of the hill top (shoulder) and bottom of the hill (foot slope) portions of each plot. Chemical properties, mineralogy of the clay fraction, and humic and fulvic acid contents and composition were analyzed. The exogenous organic matter was apparently incorporated into the native soil humic and fulvic acids, resulting in a significant improvement of the overall soil chemical quality. Mineral composition and amounts and structure of humic acids varied between the shoulder and foot slope portions of soil plots, suggesting an effect of soil erosion on the distribution of these substances. Organic matter amendment seemed to limit soil runoff, but more research is needed to evaluate humic substance-clay mineral interaction effects on the formation of more stable soil aggregates and on the resulting impact on soil erosion at these sites.

Nitrate and Phosphate Removal Effects of Compost Amendments in Wetland Mesocosms

Constructed wetlands can remove nitrate and phosphate from runoff and shallow groundwater, and are often used as treatment alternatives or components of riparian buffers to remove nonpoint-source pollutants. Reducing conditions and organic carbon are necessary for denitrification to occur in wetlands, whereas phosphate is primarily removed by adsorption onto mineral substrates. The objective of this research was to investigate the effectiveness of mineral soils amended with organic matter to remove both NO3--N and PO43--P from nutrient-enriched water. Studies were carried out in a greenhouse at 14.4 1.7C using columns constructed from PVC pipe (15.2 cm inside diameter 51 cm tall). Triplicate columns were filled with mineral soil amended with 0%, 5%, 10%, or 20% compost by dry mass to provide additional organic matter. Each column was saturated (25 h mean retention time) with water enriched with 20 mg L-1 NO3--N and 10 mg L-1 PO43--P. Nitrate removal, calculated as first-order removal rate constants, increased significantly (p < 0.0001) with increased organic matter from 0% to 20% compost treatments. Experimental runs were repeated over a 3-month period; the effect of time on nitrate removal was also significant (p < 0.0001) and was observed for all treatments in this study. Phosphate removal significantly decreased (p < 0.0001) with increased organic matter additions. The greatest reduction of phosphate occurred during the first 6 h after saturating the columns. Our research demonstrates that organic matter amendments can significantly enhance the nutrient removal functions of saturated soils.

Interactions between the external mycelium of the mycorrhizal fungus Glomus intraradices and other soil microorganisms as affected by organic matter

The influence of organic matter on the interactions between external mycelium of the arbuscular mycorrhizal (AM) fungus Glomus intraradices, the bacterium Burkholderia cepacia and other soil microorganisms was studied in a root-free sand environment. Organic matter amendment, in terms of ground barley leaves, markedly increased the growth of the external mycelium of G. intraradices as estimated both with the fatty acid biomarker 16:1ω5 and hyphal length measurements. Mycelial proliferation of G. intraradices in sand with organic matter was unaffected by both inoculation with B. cepacia and a soil filtrate containing a mixed population of indigenous microorganisms. On the other hand, in the absence of organic matter, both inoculation with B. cepacia and the soil filtrate reduced the growth of G. intraradices, as estimated with measurements of 16:1ω5. In contrast, B. cepacia inoculation increased hyphal length density of G. intraradices in the absence of organic matter. Overall, the presence of external mycelium of G. intraradices increased the bacterial biomass and counteracted a suppressive effect of B. cepacia on the growth of saprotrophic fungi.

Evolution of water‐extractable copper in soil with time as a function of organic matter amendments and aeration

SummaryVariations in soil conditions can influence the speciation and hence availability of copper. We have followed the evolution of water‐extractability of both native and added copper in a clay‐loam topsoil over 5 months. The effects of addition of organic amendments, either leaf compost or lucerne straw, were studied. Soils were incubated under controlled conditions either moist and well‐aerated, or flooded. Other chemical properties were monitored (pH, redox potential, water‐extractable organic carbon, iron and manganese). Freshly added Cu was initially more soluble than native Cu, but the contrast decreased with time. Solubility was greater in flooded soils than in aerated samples. Solubility also increased with increasing pH, contrary to often‐reported trends. Although the extractability of added Cu increased with increasing dissolved organic carbon, as expected from the formation of complexes in solution, that of native soil Cu did not. Large, short‐lived flushes of Cu were associated with flushes of dissolved organic matter, particularly from decomposition of lucerne straw, but these relations were not always statistically significant when the entire data set was considered. The total amount of dissolved organic carbon is not a sufficiently sensitive probe to assess the extent to which Cu is solubilized by the formation of complexes in soil solution. The changing composition of soil and soil solution during incubation led to 10‐fold differences in the proportion of Cu that was water‐extractable. Single measurements of extractability can therefore never give an accurate estimation of mobility and availability of copper in soil.

Sorghum Quality, Organic Matter Amendments, and Health: Farmers’ Perception in Burkina Faso, West Africa

In West Africa, many people suffer from micronutrient deficiencies. Current interventions have low chances of succeeding. Therefore, a food chain approach including local practices is proposed. This article takes local ecological, cultural, and socio-economic aspects into account through a household survey in northern Burkina in 2002. Farmers’ knowledge was compared with available scientific information. Organic matter production is a function of the number of animals owned and the availability of labor and equipment. Organic resources are allocated to various fields according to soil texture and the crop to be grown. Farmers were unable to link micronutrient deficiency in the soil directly to food quality and human health. However, they indicated that some disorders (e.g., fatigue in adults, stunted growth of children, anemia) are associated with a low level of micronutrients in the diet. For the application of organic amendments to be modified to improve grain yield and food quality in the Sahel, the relation between organic amendment and food quality must be better understood by both scientists and farmers.

Evolution of Sr distribution coefficient as a function of time, incubation conditions and measurement technique

A thorough understanding of the dynamics of radiostrontium in soil is required to allow accurate long-term predictions of its mobility. We have followed the soil solution distribution of 85Sr as a function of time under controlled conditions over 4 months and studied the effect of soil moisture content and organic matter amendments. Data have been compared to redox conditions and soil pH. To fuel the ongoing debate on the validity of distribution coefficient ( K d) values measured in dilute suspension, we have compared values obtained from the activity concentration in soil solution obtained by centrifugation to data obtained in suspension with or without air-drying of the soil samples after incubation. The 85Sr adsorption properties of soil, incubated without prior contamination were also measured. There is some time-dependent adsorption of Sr. This is partly due to changing soil composition due to the decomposition of added organic matter and anaerobic conditions induced by flooding. There is also a kinetic effect, but adsorption remains largely reversible. Most of the observed effects are lost when soil is suspended in electrolyte solution.