Abstract
Field trials with labeled fertilizers can be used to provide information on fertilizer efficiency, residual value, and nutrient fate. We assessed the uptake from elemental S (ES) and sulfate S (SO4-S) in S-fortified monoammonium phosphate fertilizers by various crops at three sites in Argentina, Brazil, and Canada. The S sources were labeled with 34S, and the 34S abundance in the plant tissue was analyzed at an early stage and at maturity over two consecutive years. At the sites in Argentina and Canada, the recovery of ES in the crop was smaller than that of SO4-S in the first year, while the opposite was true in the second year. At the Brazilian site, the recovery of ES was similar to that of SO4-S in the first year, but higher in the second year. In the Argentina and Canada sites, the cumulative recovery of SO4-S was >65% and that of ES was 20−25%. In the Brazilian site, the cumulative recovery of SO4-S was 9% and that of ES 16%. The higher recovery of ES than of SO4-S in the Brazilian site was attributed to leaching of added SO4-S and relatively fast oxidation of ES due to the warm climate. These results suggest that ES may be more suitable than SO4-S as a fertilizer S source in warm humid climates, while inclusion of SO4-S in the fertilizer is recommended in colder climates as slow oxidation limits the initial availability of ES.
Highlights
Sulfur is an essential element for all crops
Soybean grown in the second year showed no significant differences in biomass yield between the MAP and MES10 treatments at either stage
Low contribution of fertilizer S to crop uptake was likely caused by dilution of S in the labile S pool, leaching shortly after application and slow oxidation
Summary
Sulfur is an essential element for all crops. Sulfur deficiency has become more common, due to decreased atmospheric inputs, increasing yields, and a shift to high-analysis fertilizers with no or little S.As a result, S fertilization has become more important [1]. Sulfur is an essential element for all crops. Sulfur deficiency has become more common, due to decreased atmospheric inputs, increasing yields, and a shift to high-analysis fertilizers with no or little S. S fertilization has become more important [1]. Used S fertilizer sources contain either SO4 -S (e.g., ammonium sulfate, (NH4 ) SO4 ; gypsum, CaSO4 ·2 H2 O) or elemental S (ES). Sulfate is readily available to plants, but is vulnerable to leaching because of its weak adsorption in most soils [2]. Several studies have confirmed considerable leaching of fertilizer SO4 -S [3,4], but field data are scarce
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