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Technologies for sustained production growth - Narrowing of yield gap
India has been successful in raising the genetic yield of rice twice through introduction of plant type based high yielding varieties since mid 1960s and exploitation of hybrid vigour since early 1990s. It is sad that on both the occasions, we failed to harness the full potential of the new varietal technologies given the wide yield gap seen between yields achievable in experimental fields and what is actually achieved by farmers. Of the estimated potential yield of 10 t/ha possible in the semidwarf varieties under irrigated ecology, often less than one half of it is only harvested by farmers. Yield gap analysis done at macro level reveals the gap between actual and achievable yields to vary from 30 to 65%.
In majority of the rice growing states, the gap is more than 35%. Whereas in Punjab, Tamil Nadu, Haryana and Andhra Pradesh, actual yield has been found to be close to achievable yield, in states like Bihar, Eastern Uttar Pradesh, Orissa etc, the gap is too wide. Narrowing the yield gap is the most potential near-term strategy to raise the production level substantially. Bringing down the gap even by 30 to 40% in the irrigated ecology would help add no less than 20 million tonnes to the nation’s rice production by 2010. The strategy, if extended to the favourable rainfed shallow lowland ecology, would enable addition of another 10 million tonnes. In translating the strategy into so contemplated production advance, what is required is precise diagnosis of factors that contribute to the gap in a given area and correction of them. At macro level, major the factors that contribute to the gap could be inherent nutrient supplying capacity of soil, the level of consumption of fertilizer nutrients and the extent of their distorted use, soil and water quality, extent of adoption of high yielding varieties and pace of spread of new generation varieties, quality seed availability and effectiveness of extension service, while at micro (farmer) level the yield gap is largely due to differences in the level of compliance of the recommenced package of practices.
Development of data-base based on extensive survey and analysis to know in order of importance the various checks that contribute to reduction from the highest yield achievable in a given location, would help plan appropriate remedial strategy to narrow down the gap and maximize thereby productivity and production. Of the several extension strategies designed, experimented with and extensively adopted for maximizing the harvestable potential of varietal technologies ‘Integrated Crop Management’ (Improved form of the System of Rice Intensification), designed and promoted by the Food and Agriculture Organization of the United Nations Organization, is an effective one. Fashioned with two broad objectives viz (i) maximization of productivity by narrowing the yield gap and (ii) sustainable production by optimal use of inputs, ICM is site and farmer specific. Strict adoption of the key checks (cultivation practices from seed to grain) identified on the basis of their yield enhancing potential in a given situation is crucial for consolidating the inherent yield potential of the variety concerned. In case of rice, 10 core and optional checks have been identified as crucial. They include use of quality seed, transplanting relatively young and robust (12-15day old) seedlings, wide space planting at 2-3 seedlings per hill, soil stirring 3-4 times at 10 day interval from 15DAT for effective weed management, intermittent irrigation during vegetative phase where practicable, need based nutrient management integrating organic sources where available, integrated pest management with emphasis on need based use of chemical pesticides and timely harvest and post-harvest care.
The ICM strategy being practiced across the rice world including in India, has been found to be an effective integrated strategy in narrowing down the yield gap at macro and micro levels as well as in input saving through enhanced use efficiency. It has been confirmed from studies conducted in different countries that ICM economises seed, water and fertilizer respectively by 60, 30 and 40%. Reservation against adoption of this system on account of availability and cost of labour for labour intensive transplanting of young seedlings at recommended spacing and number of seedlings per hill has now been overcome to an extent by mechanizing transplanting. Correction of wide differences in rice productivity between states and districts within states is yet another opportunity and means to add sizeably to rice production. Of the 563 rice growing districts in the country, barring 218, all are of moderately low (1500-2000kg/ha), low (1000-1500kg/ha) and very low (<1000kg/ha) productivity. The 365 (>60%) districts yielding less than the national average are largely in the rainfed eastern, central and western states. They include mainly Assam with 23 out 26 districts with low yields, Bihar (28/38), Madhya Pradesh (40/48) Chattisgarh (16/16), Jharkhand (18/22), Orissa (20/30), Maharashtra (25/32), Eastern Uttar Pradesh (20/31). In most of these states lack of ideal high yielding/improved varieties adapted to abiotic stress conditions like undesirable water regimes characterized by drought and submergence, soil salinity and low fertilizer consumption seem to bring down the productivity. Popularization of high yielding varieties reasonably adapted to such stresses now available, production and supply of quality seed, enhanced fertilizer consumption and correction of soil problems, development of crop life-saving irrigation facilities for drought prone areas are the means at regional level to maximize rice productivity and production.