Fractions of organic nitrogen and relations with the potentially mineralizable nitrogen of soils

Abstract

From the knowledge of the forms of nitrogen in soils and their transformations is possible to evaluate the contribution of organic forms for the N available to plants. It is intended, with this project, to assess the forms of organic N in soils and correlate it with the potentially mineralizable nitrogen (N0) and the amounts of N accumulated in maize plants. The fractions of N will be determined in seventeen soils (Oxisols and Ultisols) by the quantification of N released from organic compounds during acid hydrolysis and separated into five fractions: N-total hydrolyzable, N-NH4+ hydrolysable, N-amino acids, N-amino sugars and N-unidentified. The fractions obtained in 17 soils will be correlated with potentially mineralizable nitrogen of soil (N0) obtained in incubation experiments in the laboratory, long term, in variable temperatures (10/14h 23/28oC, 18/23oC 10/14h and 28oC) and N uptake by corn plants in a greenhouse experiment, using the same 17 soils. With these results it is expected to determine which nitrogen´s tanks of most contributes to the supply to nitrogen from plants, and methods offer simple and fast extraction. (AU)