Nitrogen availability for flooded rice by the direct steam distillation method

Abstract:

The objective of this work was to evaluate the ability of the direct steam distillation (DSD) method to extract alkaline hydrolyzable nitrogen fraction in the soil and to predict N availability in rice paddies. Twenty-five soil samples were collected at the 0-20-cm soil depth, with contrasting texture and contents of soil organic matter. The mineralization of N by anaerobic incubation was determined in a laboratory, and leaf-N content and N accumulation by rice plants were obtained in a greenhouse by simulating flooding conditions in pots. These variables correlated with N extracted by the DSD method. Soil-N contents obtained with the method, as well as available N after 28-day anaerobic incubation and N accumulated by rice plants after 45 days, showed high values. The evaluation of a more labile N fraction by the DSD method improves the estimation of N availability, in comparison to methods that only assess soil organic matter contents, which indicates that the DSD method has potential for evaluating N availability in rice paddies.

Index terms:
Oryza sativa; nitrogen fertilization; soil analysis; soil fertility evaluation; anaerobic incubation; soil organic matter