Nitrogen-supplying capacity of soils for rice and wheat and nitrogen availability indices in soils of northwest India

Nayyar, A.B.jay-Singh; Yadvinder-Singh

Communications in soil Science and plant analysis 7(7-8): 961-976


ISSN/ISBN: 0010-3624
DOI: 10.1080/00103620600583984
Accession: 016490359

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Quantitative assessment of soil nitrogen (N) that will become available is important for determining fertilizer needs of crops. Nitrogen-supplying capacity of soil to rice and wheat was quantified by establishing zero-N plots at on-farm locations to which all nutrients except N were adequately supplied. Nitrogen uptake in zero-N plots ranged from 41.4 to 110.3 kg N ha(-1) for rice and 33.7 to 123.4 kg N ha(-1) for wheat. Availability of soil N was also studied using oxidative, hydrolytic, and autoclaving indices, salt-extraction indices, light-absorption indices, and aerobic and anaerobic incubation indices. These were correlated with yield and N uptake by rice and wheat in zero-N plots. Nitrogen extracted by alkaline KMnO4 and phosphate borate buffer and nitrogen mineralized under aerobic incubation were satisfactory indices of soil N supply. For rice, 2 M KCl and alkaline KMnO4 were the best N-availability indices. Thus, alkaline KMnO4 should prove a quick and reliable indicator of indigenous soil N supply in soils under a rice-wheat cropping system.