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This article in AJ

  1. Vol. 68 No. 1, p. 103-106
    Received: Mar 8, 1975

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Nitrogen Release from Isobutylidene Diurea: Soil pH and Fertilizer Particle Size Effects1

  1. 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 + NO3)-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 NO3-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.

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