THE INFLUENCE OF CULTIVATION ON THE DISTRIBUTION OF NITROGEN IN SOILS OF THE USTOLL SUBORDER

Abstract

Four pairs of matched virgin and cultivated Ustoll profiles were analyzed for organic C, total N, nonhydrolyzable N, hydrolyzable NH4+-N, hexosamine N, and alpha amino acid N to determine the distribution of these fractions throughout the profile and the changes that occur in the distribution upon cultivation. The data demonstrated that the effects of cultivation on soil N and C contents can be detected to depths of more than 120 cm in soils of the Ustoll suborder. Losses of organic C and total N upon cultivation were greatest in the surface and decreased with increasing soil depth. An increase in organic C and total N occurred in the deepest portions of three of the four cultivated soils, compared to the virgin counterparts. The concentrations of the four organic N fractions also decreased with depth. The proportion of hexosamine N and amino acid N remained constant with depth, however, while the proportion of hydrolyzable NH4+-N increased with depth, and the proportion of nonhydrolyzable N decreased with depth. Cultivation decreased the concentrations of all four N fractions. It also decreased the proportions of total N that were nonhydrolyzable N and amino acid N, but it increased the proportion of hydrolyzable NH4+-N. © Williams & Wilkins 1977. All Rights Reserved.