Sulfur Uptake from Fertilizer Fortified with Sulfate and Elemental S in Three Contrasting Climatic Zones
2020
Fien Degryse | Roslyn Baird | Rodrigo C. da Silva | Christopher B. Holzapfel | Claudinei Kappes | Monica Tysko | Michael J. McLaughlin
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 (SO<sub>4</sub>-S) in S-fortified monoammonium phosphate fertilizers by various crops at three sites in Argentina, Brazil, and Canada. The S sources were labeled with <sup>34</sup>S, and the <sup>34</sup>S 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 SO<sub>4</sub>-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 SO<sub>4</sub>-S in the first year, but higher in the second year. In the Argentina and Canada sites, the cumulative recovery of SO<sub>4</sub>-S was >65% and that of ES was 20−25%. In the Brazilian site, the cumulative recovery of SO<sub>4</sub>-S was 9% and that of ES 16%. The higher recovery of ES than of SO<sub>4</sub>-S in the Brazilian site was attributed to leaching of added SO<sub>4</sub>-S and relatively fast oxidation of ES due to the warm climate. These results suggest that ES may be more suitable than SO<sub>4</sub>-S as a fertilizer S source in warm humid climates, while inclusion of SO<sub>4</sub>-S in the fertilizer is recommended in colder climates as slow oxidation limits the initial availability of ES.
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