50 Indian Journal of Agricultural Sciences 83 (2): 170–5, February 2013/Article Effect of organic nitrogen sources on yield, nutrient uptake and soil health under rice (Oryza sativa) based cropping sequence S K YADAV 1 , YOGESHWAR SINGH 2 , M K YADAV 3 , SUBHASH BABU 4 and KALYAN SINGH 5 Institute of Agricultural Sciences, Banaras Hindu University, Varanasi, Uttar Pradesh 221 005 Received: 28 July 2012; Revsied accepted: 26 December 2012 ABSTRACT A two year of field experimentation was carried out at Varanasi from 2005–07 to study the effect of organic nitrogen sources on yield, nutrient uptake and soil health under rice (Oryza sativa) based cropping sequence. The soil was sandy clay loam in the texture with pH 7.4, moderately fertile, being low in organic carbon (0.50%), available nitrogen (185.5 kg/ha). The experiment on rice based cropping sequences with 3 organic N nutrition treatments was laid out in split plot design with three replications. Seven rice based cropping sequences [rice-potato-onion; rice-green pea-onion; rice-potato- cowpea (green pod); rice-green pea – cowpea (green pod); rice-rajmash (green pod)- onion; rice-rajmash (green pod)- cowpea (green pod) and rice-maize (green cob)-cowpea (vegetable)] were assigned to main plots and three treatments comprising nitrogen application (control; organic manure; organic manure + bio-fertilizer) were allocated to sub plots. The system productivity was the highest (355.73 q/ha) with rice–potato–onion cropping sequence under investigation. Among the manurial treatment, organic nitrogen nutrition with biofertilizers had the highest rice grain equivalent yield (353.08 q/ha) and net monetary return (` 292 454). The application of organic manure alone or along with biofertilizers inoculation significantly improved the N, P, K and S uptake by cropping sequence over control. However maximum improvement in soil health related to soil organic carbon, available nutrient status, soil micro-organism population were observed in organic nitrogen sources alone or along with biofertilizers. Key words: Biofertilizers, Cropping sequence, nutrient uptake, Organic manure, Soil health Improving global crop productivity and product quality together with taking care of environmental quality and human wellbeing are the main challenges for the immediate future. Such a goal depends on agricultural development and policy and can be achieved by providing the right nutrient source at the right rate, the right time and the right place. Food crops grown using organic inputs having less or no chemicals are being preferred over conventionally produced food by the end users. Food materials produced organically has got it place in food market in developed and developing countries (Urkurkar et al. 2010). Organic production systems maintained and improved the soil health through stimulating the activity of soil organisms. Organic manures are also helpful in alleviating the increasing incidence or deficiency of secondary and micronutrients and are capable of sustaining crop productivity. Azotobacter naturally fixes atmospheric nitrogen in the rhizosphere while the use of phosphate solubilizing bacteria (PSB) will be helpful in increasing the availability of fixed phosphorus in soil. Application of organic manure not only improves the soil organic carbon for sustaining the soil physical quality but also increases the soil nitrogen. However, nitrogen use efficiency is very low particularly in rice and is difficult to sustain in the soil system due to volatilization, leaching and denitrification losses. Hence N is the element to be first trust in sense of organic farming (Magar 2004). These evidences suggest that the use of organic manures like farmyard manure, vermicompost and poultry manure could be a key factor for achieving and maintaining high level of production in rice based cropping sequences. Therefore, an investigation was conducted to find out effect of organic nitrogen sources on yield, nutrient uptake and soil health under rice (Oryza sativa) based cropping sequence. MATERIALS AND METHODS A field experiment was conducted during 2005–06 and Based on a part of Ph D thesis of the first author submitted to BHU, Varanasi during 2010 1 Scientist (e mail: sanjaybhu05@rediffmail.com), Central Potato Research Station (CPRI), Shillong, Meghalaya 793 009; 2 Junior Scientist-cum-Assistant Professor (e mail: singhyogeshwar@ gmail.com), RAU, Bihar 848 125; 3 Technical Officer (manoj.agro@yahoo.co.in), Department of Geophysics; 4 Scientist, (email:subhiari@gmail.com) ICAR-RC-NEH-Sikkim Centre, Tadong, Gangtok, Sikkim 737 102; 5 Dean (e mail: singhkalyanbhu@ rediffmail.com)