Soil sulfur fractions dynamics and distribution in a tropical grass pasture amended with nitrogen and sulfur fertilizers |
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| Authors: | Fabiana Schmidt Fabiano Daniel De Bona Cristiane Prezotto Silveira Francisco Antonio Monteiro |
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| Institution: | Soil Science Department, “Luiz de Queiroz” College of Agriculture, University of S?o Paulo, 13418–900 Piracicaba – SP, Brazil |
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| Abstract: | Soil sulfur (S) partitioning among the various pools and changes in tropical pasture ecosystems remain poorly understood. Our study aimed to investigate the dynamics and distribution of soil S fractions in an 8‐year‐old signal grass (Brachiaria decumbens Stapf.) pasture fertilized with nitrogen (N) and S. A factorial combination of two N rates (0 and 600 kg N ha–1 y–1, as NH4NO3) and two S rates (0 and 60 kg S ha–1 y–1, as gypsum) were applied to signal grass pastures during 2 y. Cattle grazing was controlled during the experimental period. Organic S was the major S pool found in the tropical pasture soil, and represented 97% to 99% of total S content. Among the organic S fractions, residual S was the most abundant (42% to 67% of total S), followed by ester‐bonded S (19% to 42%), and C‐bonded S (11% to 19%). Plant‐available inorganic SO4‐S concentrations were very low, even for the treatments receiving S fertilizers. Low inorganic SO4‐S stocks suggest that S losses may play a major role in S dynamics of sandy tropical soils. Nitrogen and S additions affected forage yield, S plant uptake, and organic S fractions in the soil. Among the various soil fractions, residual S showed the greatest changes in response to N and S fertilization. Soil organic S increased in plots fertilized with S following the residual S fraction increment (16.6% to 34.8%). Soils cultivated without N and S fertilization showed a decrease in all soil organic S fractions. |
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| Keywords: | Brachiaria decumbens fertilization sulfur fractionation tropical soil |
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