Assessing the Contribution of Nutrients to Yield of Hybrid Rice and Maize through Omission Plot Techniques in Bihar

India is the second largest producer of rice in the world with production of 100 million tons in 2010-11. Rice occupies 44 Mha i.e. 22% of the total cropped area. However, at the current rate of population growth, in India the requirement of rice is estimated to be around 150 million tons within next fifty years. To make India self sufficient in rice, it is needed to improve the productivity to a greater extent, compared to the existing condition. The task is quite challenging and the options available are very limited. Among the various possible genetic approaches to achieve this target, hybrid rice technology is the most feasible and readily adaptable one. Commercial success of hybrid rice in China has clearly demonstrated the potential of this technology to meet the ever-increasing demands for rice all over the world. Efforts to develop and use hybrid rice technology in India, through Indian Council of Agricultural Research (ICAR) started since 1989, with launching of a mission oriented project. Within a short span of seven years, half a dozen hybrids each from public and private sectors are made available for commercial cultivation. Hybrid rice has yield advantage of more than 30% over conventional varieties. In India, the area under hybrid rice is 2 million hectares i.e. approximately 5% of total rice area in 2011-2012 (The Hindu, 2012). The state of Bihar (India), covers an area of 92.83 lakh hectares, nearly 2.83% of the total geographical area of the country and located between 240 19' 10" to 270 31' 15" north latitude and 830 19' 50" to 880 17' 40" east longitude. The total cultivable area of the state is 78.97 lakh hectares. During 2010-11, rice and maize were grown in 30.46 and 6.78 lakh hectare with production of 10.90 and 27.28 q/ha, respectively. In Bihar, the area under rice is 3.5 million ha i.e. 45% of gross cropped area and area under hybrid rice is 0.4 m ha i.e. 11 % of the area under rice cultivation (2011 – 2012). However, the productivity of rice in the State is still far below the National average of 2.10 tonnes/ha. In addition, maize is rapidly emerging as a favourable option for farmers in South Asia as a non-traditional component crop of rice and wheat based systems (Majumdar et al., 2012). During the year 2011-12, the productivity of rice and maize was 24.9 and 30.3 q/ha, respectively in Bihar. However, there is a need to improve the productivity of rice and maize in order to ensure food security for the growing population. Achievement of attainable yield in these two crops are often constarints by imbalanced and inadequate use of essential plant nutrients. Due to increasing population in years to come, the emerging problem of essential nutrients deficiency may intensify because of poor farming practices, imbalanced use of fertilizers, restricted recycling of farm wastes etc., and intensive cultivation to produce extra food, fiber, fuel fodder, fruits, etc. The decline in factor productivity of applied nutrients, a measure of nutrient use efficiency as yield of harvested portion divided by amount of fertilizer nutrient applied, are major reasons for productivity stagnation in rice-based systems in the Upper Gangetic Plain region of India (Yadav 2000; Tiwari et al., 2006). Surveys conducted by the Department of Soil Science, Rajendra Agricultural University, Pusa, Samastipur, Bihar (India) indicate that current farmer fertilization practices are creating nutrient imbalance in soil-plant systems, besides increasing pest incidence, cost of production, and environmental problems. In soils of Bihar, the nutrient deficiency is increasing day by day and in general soils are low in N, Zn, S, B and medium to low in K and P. This might be due to imbalanced application of NPK fertilizers without taking proper care about secondary and micronutrients. Widespread multi-nutrient deficiencies (K, S, Zn, and B) and sporadic deficiencies of Fe, Mn, Cu, etc. within the soils of the intensively cultivated IGP, owing to constant depletion, have become major constraints for improving productivity (Singh et al., 20
11). N, P and K are the three primary nutrients for plant growth; farmers tend to apply more fertilizer N due to its lower price and visible impact on crops as compared to other nutrients. This has led to increasing deficiencies of P and K as a result of suboptimal application or unbalanced use in the intensive cereal based system (Dutta et al., 2012). On the other hand, long-term experiments and other studies indicate that crop productivity can be sustained with balanced fertilization. Rice crop is the maximum consumer of nitrogenous fertilizer as nitrogen plays an important role in increasing the productivity of rice. However, nitrogen use efficiency (NUE) for rice is as low as 30-40%. Low use efficiency of nitrogenous fertilizers is due to various nitrogen loss mechanisms, namely, ammonia volatilization, leaching, surface runoff, and denitrification. Split application of the nitrogen fertilizer to rice may increase NUE. Along with N, rice also needs application of P and K at right rate and time. However, at the present increase in P and K fertilizer prices, the applications of these nutrients are reduced drastically. As a result the growth of the plants is hampered due to imbalanced fertilization. The inherent soil supplying capacity of NPK and their application requirements vary between farmers’ field plots due to long term variable management practices. The availability of N, P, K and other essential nutrients in farmers’ fields could be assessed by the “Omission Plots” techniques where a particular essential nutrient is omitted from the fertilization schedule keeping the supply of other limiting nutrients in ample quantity. A relatively long-term study (three years) with continuous omission of N, P and K nutrients from selected plots respectively, might be a very good indicator of the soil nutrient supplying capacity. Similar studies in a large number of farmers’ fields in a region could provide an indication of the extent of variability in nutrient supplying capacity of soil of a region. Hybrid rice and maize extracts comparatively high amounts of mineral nutrients from soil. Hence, to cater uptake needs of these crops, soil nutrient reserves alone are not sufficient making it implicit to supply them through fertilizers. In general, the fertilizers applied are either insufficient or imbalanced and often not based on soil supplying capacity. Therefore, the present study will be emphasized on the evaluation of nutrient response on hybrid rice and maize with following objectives- i. To evaluate the soil supplying capacities of different nutrients (N, P, K, and Zn) under hybrid rice-maize cropping system. ii. To estimate the nutrient requirement of high yielding hybrid rice – hybrid maize cropping system. iii. To develop an optimum nutrient management strategy for sustaining high productivity in hybrid rice – hybrid maize cropping system. iv. To assess the economics of fertilizer application in variable crop response scenario. v. To generate awareness among the farmers about improved nutrient management practices in the rice – maize cropping system.