Abstract
Efficiency is exceptionally low for nitrogen (N) fertilizers in flooded rice
ecosystem. A greenhouse pot study was conducted to determine nitrogen availability in soils from rice based cropping systems. Various parameters of N availability used were organic matter, total N, organic N and ammonium nitrogen, which were negatively affected by soil characteristics such as soluble salts (EC), soil pH and time content
(CaCOj) except organic matter. Nitrogen fertility status as judged by the various Navailability parameters under different cropping sequences followed the order: riceberseem > rice-wheat > rice-fallow. Dry matter yield and N uptake by rice were significantly correlated with ammoniacal-N and mineral forms of nitrogen. Total N was also significantly correlated with N uptake. This study is very useful to identify N availability parameters for fertilizer recommendations but further research is needed to evaluate these parameters under field conditions.
M.S. Zia, M. Aslam, Rehmatullah, M.B. Khan, M.B. Baig , A. Ali. (1998) Assessment of nitrogen availability in calcareous soils under rice based cropping systems, The Journal Soil & Environment , Volume 15, Issue (3-4).
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