Evaluation of nitrogen availbility in soil

Abstract

The objective of the present work was to evaluate the nitrogen availability in soils of the Federal District of Brazil. The extractants showing the highest correlations with mineralized nitrogen (six-week incubation in the lab) were the following: 025 N NaOH (r = 970): 2M KCL 100ºC/buffer pH = 11.2 (r = .963); 2M KCI 1000(, = .959); buffer solution pH = 11.2 (r = 939) and H₂O₂/MnO₂ (r = 925). These extractants showed high (p > .01) correlations among themselves. However, the multiple linear correlation coefficients between absorbed nitrogen and extracted nitrogen were: 2M KCL 100°C (R = .817); H₂O₂/MnO₂ (R = .810); butler solution pH = 11,2 (R = .792) and 2M HCL 100 ºC/buffer pH = 11.2 (A = .742). In the nitrogen fertilization field trial, high correlations were observed between grain yield and soil nitrogen (mineral and organic) at the depth ranges of 0 cm 25 cm and 0 cm - 50 cm, as extracted with 2M HCL 100ºC, butler solution pH = 11.2 or H₂O₂/MnO₂ . The critical level estimated by means of a linear-plateau model (Braga 1983) varied according to soil depth and extractant.