Evaluation of rapid tests for assessing nitrogen availability in wheat soils. 2. Effect of factors associated with field sampling, sample treatment and laboratory analysis

Abstract

An evaluation of biological and chemical tests of potentially available soil nitrogen has been made through a study of factors associated with field sampling, sample treatment, and laboratory analysis Variations in time of sampling, fineness of grinding, and the conditions and period of storage of air-dry samples were generally shown to affect the values obtained by both biological and chemical methods, but not the degree of correlation with plant uptake of nitrogen. These findings, together with information gained on method precision and spatial variability and analytical considerations, led to the choice of organic carbon as the best of the methods tested.