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Abstract
The concerns for sustainable soil productivity and ecological stability in relation to the use of chemical fertilizers have become an important issue. The fertilizer consumption of the nation is 74 kg/ha whereas it is 13 kg/ha in northeastern region (as high as 44.4 kg/ha in Manipur and as low as 1.7 kg/ha in Arunachal Pradesh). The marginal farmers in northeastern region are more than 60% of the farming community who are unable to use the inorganic fertilizer and hence the productivity of rice has been very poor (less than 1 tonne/ha) in the region. Organic manures are reported to enhance the fertilizer efficiency and reduce the requirement of inorganic fertilizers. Traditional green manures (Sesbania aculeate), organic manures (FYM) and problematic weeds (Ipomoea Carnea and Gliricidia maculata) may serve as alternative source of nutrients to the plants and may supplement any chemical fertilizers. Most of the green manure plants contain from 0.3 to 0.8% nitrogen (CitationKhan et al., 2000). Integrating fertilizer nitrogen with legume green manure as alternative source of nutrients can aid development of sustainable agricultural management system. A series of experiments was conducted from 1993 to 1999 for integrated nutrient management by using the different sources of organic manures, green manures and chemical fertilizers and their combinations to study the effect on productivity of rice (cultivars CR-1009 and CR-1018, ‘Gayatri’) under rainfed lowland and varying irrigation regimes. The experiment was conducted during kharif season at Water Technology Deras Research Farm, Mendhasal (Bhubaneswar). Green—manuring with Sesbania aculeata increased rice yield by 7 q/ha. An increase of 3 q/ha was observed in comparison to beushening (Beushening is a cross ploughing in standing water under lowland rice ecosystem when rice plants are approximately 45 days old) without fertilizer and green manure treatment—which is a farmer's practice in this coastal region. Grain yield was higher in continuous submerged (5 ± 2 cm) treatments in comparison to intermittent irrigation (where irrigation was given to a depth of 7 cm and was reflooded after 2 days of disappearance of ponded water) treatments. However, the treatments of inorganic fertilizer (urea) in split dose gave a better yield under intermittent irrigation. Both sources of nitrogen i.e. organic or inorganic or their combination proved better than control (no nitrogen). Application of organic manures like Sesbania aculeate and Ipomoea carnea or their combination with urea was found superior to other green and organic manures. Gliricidia maculata gave higher grain yield in comparison to control (no nitrogen).