Estimation of native soil N released to paddy rice using biological and chemical indices

everal methods have been proposed for estimating potentially available N from native soil N mineralization. However, no rapid technique has been sufficiently reproducible to be implemented in a soil testing program in Arkansas. Therefore, the objective of this study was to develop a chemical method sufficiently rapid for routine use in estimating N availability in paddy rice (Oryza sativa L.). Soils were collected from the rice-growing region of Arkansas during 1990 and 1991. 'Newbonnet' rice was grown at each location without N fertilizer to attribute the N availability to the rice. Greenhouse studies were also implemented to determine total N uptake (TNU) from native soil N. Anaerobic incubations were performed as an index of potentially mineralizable N. Extraction with 1.0 M HCl, 0.5 M oxalic acid...