ESTIMATING POTENTIALLY MINERALIZABLE SOIL NITROGEN FROM A CHEMICAL INDEX OF SOIL NITROGEN AVAILABILITY1

Abstract

The feasibility of estimating potentially mineralizable soil nitrogen, N0, from direct or indirect measurements of NH4+-N produced by hydrolysis of soil organic nitrogen during 16-h autoclaving (121.degree. C), Ni, was investigated for 13 groups of soils comprising 475 surface and subsurface samples representing 54 soil types. The regressions of N0 on Ni for different soil groups were pooled, and the resulting equation was N0 = 4.1 (.+-. 1.0) Ni + 6.6. Apparently, therefore, the coefficient, 4.1, provides a means of reasonably estimating N0 from the chemical index, Ni, for a broad range of soils, with certain specified exceptions. Estimates of N0 from Ni together with measurements of residual mineral, plant-available N may provide a basis for developing improved N fertilizer recommendations.