Control of Water Content in Laboratory Determination of Mineralizable Nitrogen in Soils

Abstract

Abstract A simple, convenient method was developed to control precisely moisture content in soil samples during aerobic incubation for determination of mineralizable N. The sample is contained in a polystyrene filter unit with a filter membrane having a bubble point pressure well above the 33‐kPa suction tension normally used for equilibration. Equilibration at seven moisture tensions (5‐67 kPa) gave soil water contents that were very similar to those obtained by conventional pressure plate measurements. Nitrogen mineralization values obtained at different tensions varied as expected, but reproducibility of three determinations on four Chernozemic soils was good (C.V. = 3.9%) at all tensions used.