Prediction of post harvest nitrogen status and fertilizer nitrogen recommendation for rice - rice cropping sequence under integrated nitrogen nutrition system

摘要

Soil test based fertilizer recommendation results in maximising the fertilizer use efficiency. For each crop the soil has to be tested. Under practical conditions it is difficult. It has therefore become necessary to predict the changes in the soiltest values after each crop of the sequence. An attempt was made in the present study to predict the post harvest nitrogen status based on initial soil test values and to recommend fertilizer N for targeted yield of rice-rice cropping sequence. A field experiment was carried out at Tamil Nadu Agricultural University Farm, Coimbatore during the year 1995-96 with rice IR 20 as test crop. The green manure and FYM were incorporated at 15cm depth and allowed to decompose 7 days after application. Azospirillium was mixed with 40 kg sand and applied before transplanting through soil application. Half of the quantity of N as urea and 60 kg P_2O_5, and 50 kg K_2O as per soil test basis were applied as basal and the remaining N was applied in two splits of equalquantities on 30 and 60 days after planting respectively. The initial and post harvest surface soil samples from all the plots were collected and analysed for alkaline KMnO_4-N (Subbiah and Asija, 1956). Treatment-wise grain and straw yields were recorded. Grain and straw samples were analysed for N content (Piper, 1966) and total N uptake was computed.