Relation of Mineralizable N to Organic N Components in Dark Loessial Soils

Mineralizable N and organic N components in different layers (0～15, 15～30,30～45, 45～60, 60～80 and 80～100 cm) of six soils with different fertilities sampled from YongshouCounty, Shaanxi Province, China, were determined by the aerobic incubation method and the Bremnerprocedure, respectively. Correlation, multiple regression and path analyses were performed to studythe relation of mineralizable N to organic N components. Results of correlation and regressionanalyses showed that the amounts of the N mineralized were parallel to, and significantly correlatedwith, the total acid hydrolyzable N, but was not so with the acid-insoluble N. Of the hydrolyzableN, the amino acid N and the ammonia N had a highly consistent significant correlation with themineralized N, and their partial regression coefficients were significant in the regressionequations, showing their importance in contribution to the mineralizable N. The amino sugar N, onthe other hand, had a relatively high correlation with the mineralized N, but their partialregression coefficients were not significant in the regression equations. In contrast, thehydrolyzable unknown N had no such relations. Path analysis further indicated that the amino acid Nand ammonia N made great direct contributions to the mineralized N, but the contributions of theamino sugar N were very low. These strongly suggested that the mineralized N in the soils tested wasmainly from the hydrolyzable N, particularly the amino acid N and ammonia N which are the majorsources for its production.

Mineralizable N and organic N components in different layers (0～15, 15～30, 30～45, 45～60, 60～80 and80～100 em) of six soils with different fertilities sampled from Yongshou County, Shaanxi Province, China,were determined by the aerobic incubation method and the Bremner procedure, respectively. Correlation,multiple regression and path analyses were performed to study the relation of mineralizable N to organic Ncomponents. Results of correlation and regression analyses showed that the amounts of the N mineralizedwere parallel to, and significantly correlated with, the total acid hydrolyzable N, but was not so with the acid-insoluble N. Of the hydrolyzable N, the amino acid N and the ammonia N had a highly consistent significantcorrelation with the mineralized N, and their partial regression coefficients were significant in the regressionequations, showing their importance in contribution to the mineralizable N. The amino sugar N, on the otherhand, had a relatively high correlation with the mineralized N, but their partial regression coefficients werenot significant in the regression equations. In contrast, the hydrolyzable unknown N had no such relations.Path analysis further indicated that the amino acid N and ammonia N made great direct contributions tothe mineralized N, but the contributions of the amino sugar N were very low. These strongly suggested thatthe mineralized N in the soils tested was mainly from the hydrolyzable N, particularly the amino acid N andammonia N which are the major sources for its production.