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Sulphur mineralization during decomposition of organic matters in soil and its relationships with C and N dynamics

Abstract : Although sulphur defiencies have become common in recent years, compared to nitrogen there has been little conceptualization to help design S fertilization strategies for cropping systems. Recently, as S deficiency in cropped soils has increased, more research has been done to better quantify and model the turnover of S, the role of soil biomass and the relationship with C dynamics. In first part of this work, a laboratory study was carried out to determine sulphur, carbon and nitrogen mineralization rates in soil samples obtained from representative soils in France. Their relationship with some of the soil properties was investigated to find a predictor of mineralized S in soils. The results suggest that the mineralization of sulphur is predominantly driven by heterotrophic microbial activity. A predictive equation for S mineralization is proposed, based on soil C and clay content, soil pH and initial soil sulfate. The objective of the second part was to quantify the impact of soil S availability on crop residue decomposition and S immobilization. To do so, the effect of S availability was tested by varying the initial S-SO42- content in a presence of a single rate of residue addition (rape straw) and by increasing the rate of C addition at a single level of soil S availability (wheat straw). No limitation of residue decomposition was obtained suggesting low S demand of microbial biomass during decomposition. The effect of the chemical quality of plant residues was then investigated. We used four residues of different biochemical compositions and sulphur contents decomposing in non limiting sulphur conditions, to assess the relationship between S mineralization and residue decomposition. The residues were taken from arable, pasture and forest situations (wheat stem, young mustard, beech leaf, tall fescue) were selected so as to cover a wide range of S contents. The data allows us to quantify relationships between residue C/S and S accumulation in soil and the net S mineralization associated to plant residue decomposition. In the last part of this work, we evaluated the possibility of using our data to adapt a sub-module of biotransformation of C and N (soil-plant model STICS) to predict S mineralization during residue decomposition. A S balance was also calculated for 4 agricultural situations using mineralization data, in order to design a tool for fertilizer S recommendation.
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Submitted on : Thursday, February 12, 2009 - 8:00:00 AM
Last modification on : Thursday, February 12, 2009 - 8:00:00 AM
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Hamid Niknahad Ghar Makher. Sulphur mineralization during decomposition of organic matters in soil and its relationships with C and N dynamics. Sciences of the Universe [physics]. AgroParisTech, 2008. English. ⟨NNT : 2008AGPT0051⟩. ⟨pastel-00004764⟩

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