Application method influences the oxidation rate of biologically and chemically produced elemental sulfur fertilizers

Abstract

Elemental sulfur (ES) is commonly used as a fertilizer S source but needs to be oxidized to sulfate to become plant-available. We assessed how placement (surface applied or incorporated) affects the oxidation of ES fertilizers. The fertilizers included an ES powder, a suspension of biogenic ES particles, and three granular fertilizers: two ES-bentonite pastilles and one monoammonium phosphate fertilizer cogranulated with ES. The fertilizers were applied either on the surface (broadcast) or incorporated into two different soils in a column experiment, incubated at 25˚C.Prior to broadcasting, the granular fertilizers were dispersed in water for 48 h to simulate the effect of 30 to 40 mm of precipitation. The columns were leached weekly and the concentration of sulfates derived through ES oxidation was measured in the leachates. The half-lives of oxidation for the ES powder were 76 and 111 d for the incorporation and broadcast applications, respectively. The diluted biological ES suspension showed faster oxidation (8 and 30 d for incorporated and broadcast), probably because of its smaller particle size. Unlike the ES particles, the ES oxidation rates of the granular fertilizers were higher for the broadcast application than when incorporated in soil, particularly when they dispersed easily. One type of ES pastille showed little dispersion and its estimated half-life of oxidation was >1,000 d even when broadcast. Overall, the results show that ES oxidation depends on the degree of dispersion in the soil and that this is strongly affected by the fertilizer type and application method.

The Effects of Ammonium Phosphate with Different Sulfur Additions on Crop Yield and Nutrient Uptake in Calcareous Soil

“…In addition, the S fertilizer type also had an important effect on SUE. Matamwa et al [46] compared the effect of SO 4 −S and elemental S on SUE in their study and found that the application of SO 4 −S, such as single superphosphate and gypsum, results in higher SUE values than the application of elemental S, due to the slow oxidation of elemental S to SO 4 −S [50,63,64]. In this study, elemental S accounted for half of the S application, which was also a significant factor contributing to the reduced SUE.…”