Experiments were conducted to determine methane emission from a rainfed lowland rice field (water depth about 3-30 cm) and an irrigated shallow rice field (4-6 cm), both planted to the same cultivar, cv. 'Gayatri,' as influenced by fertilizer management practices. Methane emission peaked from 100 to 125 days after transplanting followed by a decline in rainfed lowland field plots. Application of prilled urea did not enhance methane emission significantly over that of the untreated control. Subsurface application of urea supergranules was, however, effective in reducing the methane flux over that of the control. Methane emission was lowest in plots treated with the mixture of prilled urea and Nimin (a nitrification inhibitor). Under irrigated shallow conditions, the application of prilled urea and green manure (Sesbania rostrata), singly and in combination, significantly increased methane emission over that of the control. Cumulative methane efflux from control and prilled urea treated lowland rice field was about 4-10 times higher than that in irrigated shallow fields. These results suggest that by virtue of their readily mineralizable carbon and ninhydrin reactive nitrogen, these substrates can serve as positive indicators of methane emission potential of rice fields.

Continuous mono-cropping of rice has resulted in decline or stagnation of yield output due to the occurrence of multiple nutrient deficiencies and worsening of soil physicochemical properties accompanying increased pressure of insect pests and diseases. The basic concept of integrated nutrient management (INM) is maintenance or adjustment of soil fertility and supply of plant nutrients to an optimum level for sustaining the desired crop productivity through optimisation of benefits from all possible sources of plant nutrients in an integrated way. Augmenting a rice-based cropping system with pulses is a prevalent and indigenous cropping system under rainfed conditions. Considering the above facts, experiments were conducted to evaluate the impacts of integrated nutrient management on productivity of aromatic rice–greengram cropping system and nutrient balance of the post-harvest soil for agricultural sustainability under rainfed conditions in two consecutive years (2017–2018 and 2018–2019) with six main plots and three subplots. The experimental findings revealed that the treatment comprised of 50% recommended dose of fertiliser (RDF) through chemicals + 50% recommended dose of nitrogen (RDN) through farmyard manure (FYM) increased the plant height, tillers, dry matter accumulation, leaf area and leaf area duration, and yield parameters in short grain aromatic rice. Similarly, preceding application of 50% RDF + 50% RDN through FYM to rice and further application 75% RDF + Rhizobium+ phosphate solubilizing bacteria (PSB) to greengram increased the growth characteristics and yield parameters—such as pods/plant, seeds/pod, grain yield, stover yield, and harvest index—in greengram. It was concluded that the treatment consisting of 50% RDF (chemical fertiliser) + 50% RDN (FYM) to rice and 75% RDF + Rhizobium + PSB to greengram increased the productivity of the rice–greengram cropping system. Furthermore, the adoption of INM has positively impacted post-harvest soil nutrient balance.

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A field study was carried out during rabi seasons in 2017-18 and 2018-19 after harvest of rice to reveal the residual effect of integrated nutrient management on nodulation, yield, quality and available nutrient status in soil after harvest of greengram at Instructional Farm of College of Agriculture, Odisha University of Agriculture and Technology, Bhubaneswar. The maximum number of root nodules/plant at 30 DAS and 45 DAS in greengram (5.86, 6.19 and 12.49 and 12.94in 2017 and 2018 respectively) were recorded in the subplot treatment of 75% RDF+ rhizobium + PSB and lowest values were obtained in 75% RDF treatment. Similarly in main plot, residual effect of 50% RDF+50% RDN through FYM showed significantly higher number of root nodules/plant during both the years of study which remained at par with 75 % RDF+ Green manuring. Lowest values were obtained from only RDF treatment. Residual effect of 50 % RDF+50 % RDN through FYM showed significantly higher protein % (24.2 and 24) and protein yield (194.3 and 196.2) during both the years of study which remained at par with 75 % RDF+ Green manuring treatment. Residual effect of 75 % RDF+ Green manuring treatment recorded higher increase in soil organic carbon (4.87 g/kg), available N(225.7 kg/ha), Available P (26.2 kg/ha) and available K (296.0 kg/ha) than all other treatment combinations. The residual treatment 50% RDF+25% RDN through FYM recorded the lowest values of soil nutrient status after harvest of greengram. Similarly the sub plot treatment receiving 75% RDF+ Rhizobium+ PSB recorded significantly higher soil organic carbon (4.67 g/kg), available N(217.1 kg/ha), Available P (22.8 kg/ha) and available K (291.8 kg/ha) than 100% RDF and 75% RDF.

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