Nitrogen Release from Isobutylidene Diurea: Soil pH and Fertilizer Particle Size Effects1
- T. D. Hughes2
Soil-isobutylidene diurea (IBDU) mixtures were incubated to determine the effects of soil pH and IBDU particle size on N release patterns. Such information is needed for predicting rates and freqnencies of application. All incubations were conducted at a temperature of 21 ± 0.5 C. and 28 ± 2% soil moisture. Evidence was obtained lot excluding urea-N concentrations from calculations of N recovery, thus all recoveries were based on concentrations of (NH+4 + NO−3)-N.
Nitrogen release patterns from 0.7 to 0.8 mm IBDU particles in soil at initial pH's of 5.7, 6.8, and 7.7 were determined. After four weeks of incubation, the amount of N released was equivalent to one-third of the IBDU-N for soil at pH 5.7, however, lesser amounts were released in soil at pH's 6.8 and 7.7. Differences in N release were due to differences in NH+4-N concentrations, whereas concentrations of NO−3-N were not related to soil pH throughout the 10-week incubation period. Thus, N release from IBDU was affected by soil pH shortly after fertifizer application, but this effect disappeared as soon as the NH+4 accumulation was exhausted by nitrifying organisms.
Fertilizer particle size had pronounced effects on N release in soil of initial pH's 5.7 and 7.4. Nitrogen recoveries of 75% after 10 weeks, 58% after 21 weeks, and 50% after 32 weeks were obtained for IBDU particle diameters of 0.6 to 0.7 mm, 1.0 to 1.2 mm, and 1.7 to 2.0 mm, respectively.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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