Effect of Ammonium Thiosulfate and Liquid Fertilizer Droplet Size on Urea Hydrolysis
1988
Goos, R. J. | Fairlie, T. E.
Ammonium thiosulfate (ATS, 12-0-0-26S) has recently been shown to inhibit soil urease when mixed with liquid fertilizers such as urea-ammonium nitrate (UAN). The purpose of this research was to investigate the effects of soil water content (field capacity and wilting point), liquid fertilizer droplet size (0.01, 0.1, and 0.5 mL), and ATS addition to UAN (0 and 5% vol/vol) on urea hydrolysis by two soils incubated at 20 °C. Soil types were a Fargo silty clay (Vertic Haplaquolls) and an Embden loamy sand (Pachic Udic Haploborolls). Urea hydrolysis by both soils was slower at wilting point than at field capacity, and increasing the fertilizer droplet size further slowed urea hydrolysis. Adding ATS to UAN inhibited urea hydrolysis by both soils at both water contents. In general, the inhibitory effect of ATS on urea hydrolysis was greater than obtained by increasing droplet size. The inhibitory effect of ATS on urea hydrolysis was strongest at wilting point and with larger fertilizer droplet sizes. ATS was more effective in inhibiting urea hydrolysis in the Embden soil than the Fargo soil. Hence, the effect of ATS on soil urease will depend on how the fertilizer is applied and on environmental conditions after application.
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