Effect of fertilizer levels and organic sources of nitrogen on production potential of hybrid rice (Oryza sativa) and soil properties under system of rice intensification

A field experiment was carried out during the rainy (kharif) seasons of 2010 and 2011 at Varanasi, Uttar Pradesh, to study the performance of hybrid rice (Oryza sativa L.) PHB 71 to fertilizer levels and nitrogen levels applied through organic sources on production potential, nutrient uptake and soil physic-chemical properties un- der system of rice intensification (SRI). The experiment was laid out in a split-plot design keeping 3 fertilizer levels [50%, 75% and 100% recommended dose of fertilizer (RDF)] in main plots and three levels of nitrogen (15, 30 and 45 kg N/ha) applied through 2 organic sources (FYM, farmyard manure and VC, vermicompost) in sub-plots com- prising 18 treatment combinations replicated thrice. An application of 100% recommended dose of fertilizer (RDF) increased effective tillers/m2 (10.1%), filled grains/panicle (18.6%), test weight (11.0%), grain yield (19.0%) and straw yield (24.2%) over the 50% RDF. As regards the 3 levels of N (15, 30 and 45 kg/ha) through organic sources, an application of 45 kg N either through VC or FYM resulted in higher values of yield attributes, grain and straw yields than 30 kg N/ha either through VC or FYM. Further, increasing fertilizer levels from 50% to 100% RDF, significantly enhanced the nutrient uptake (NPK) by grain and straw as well as soil organic carbon content and available NPK at harvesting. However, 45 kg N/ha applied either through FYM or VC resulted in the maximum NPK uptake by the crop and enhanced soil electrical conductivity, organic carbon as well as available N, P and K content of the soil, but reduced the soil pH at the end of two crop cycles. Interactive effect on grain yield was found significant between fertilizer levels and organic sources applied at varied N levels. Application of 75% RDF + 45 kg N/ha through VC resulted in markedly higher grain yield but remained at par with 100% RDF applied in con- junction with 30 or 45 kg N/ha as FYM and VC both. The integration of 100% RDF accompanied with 30 kg N/ha through VC gave the maximum net returns ( 59,804/ha).