Targeted yield precision model assessment for rice-rice crop sequences in Farmers

Journal of Soil Science and Plant Nutrition, 2016, 16 (1), 31-47 RESEARCH ARTICLE Targeted yield precision model assessment for rice-rice crop sequences in farmers’ fields in humid, sub-tropical northeastern India K.N. Das*, A. Basumatary and S. Ahmed *Department of Soil Science, Assam Agricultural University, Jorhat 785013, Assam, India. Corresponding author: Abstract On-farm trials were conducted based on an autumn rice-winter rice crop sequence in 21 farmers’ fields from 2012–2014 in humid, sub-tropical northeastern India i) to verify the suitability of the formulated appropriate site-specific target yield-based fertilizer prescription models over available technology and ii) to analyze the economics of the adoption of these models to enhance the productivity and profitability of rice-rice crop sequences. The results revealed that treatments based on the targeted yield precision model with and without integrated plant nutrient supply (IPNS) components ensured higher grain yield, additional yield gains and additional net profits over the farmers’ practice and conventional fertilizer recommendations. The achievements of the prefixed targets were >100% in autumn rice and 96 to 106% in winter rice. The IPNS treatments guaranteed a better a benefit: cost ratio (1.7 to 2.3) vis-a-vis without IPNS. The targeted yield precision model for fertilizer recommendations was more precise to achieve the targeted yields, which additionally led to higher profits. The targeted yield approach was effective up to 4.0 and 5.0 tons ha−1 yield targets without IPNS in autumn rice and with IPNS in winter rice, respectively, in humid sub-tropical northeastern India. Keywords: Autumn rice, winter rice, fertilizer recommendations, targeted yield, IPNS 1. Introduction Sustainable, high yield agriculture is India’s top- Information on the optimum doses of fertilizer most agenda for food security, profitability and for crops is essential to enhance farm profitability environmental safety. However, most, if not all, under different soil-climate conditions. Because of farming strategies must be refined to sustain increasing input costs and decreasing commodity productivity and prevent the ever-increasing problems prices, the farmers are currently looking for related to soil fertility deterioration. Fertilizer is new ways to increase efficiency and cut costs. one of the costliest inputs in agriculture, and the According to Dobermann et al. (2003), the decision use of right amount of fertilizer is fundamental for on fertilizer use requires knowledge of the expected farm profitability and environmental protection. crop yield in response to the nutrient application, 31 32 Das et al. which is a function of crop nutrient needs, the supply considers the indigenous nutrient supply of the soil, of nutrients from indigenous sources, and the fate of productivity targets that are capable of sustained the fertilizer applied. Rice fulfils 43 percent of the high yields, and how to restore soil fertility. With caloric requirement for more than 70 percent of the this approach, the present food grain production Indian population. To meet the demands of increasing could be achieved. population and to maintain self-sufficiency, the Rice (Oryza sativa L.) is the most important food grain present production level of 102 million tons must be in India and contributes 41.5% to the total food grain increased to 125 million tons by the year 2020. This production. Rice, which is at present grown mainly rate of increase signifies the contribution of fertilizers during the kharif seasons, dominates the agriculture to the production of rice to meet the food requirements scenario in Assam; winter (Sali) rice occupies 1.749 of the hungry mouths of the country. However, an million hectares, and autumn (Ahu) rice occupies annual net negative balance of approximately 10 0.464 million hectares with a productivity of 1674 kg/ million tons of nutrients is currently reported in ha compared with the national average of 2240 kg/ha. India. The loss of major nutrients can be high in rice One reason for lower productivity of rice in the state fields, particularly rain-fed rice, where water flowing is the imbalanced application of N, P and K nutrients. from field to field during periods of high rainfall not The high cost of fertilizers remains a constraint for the only reduces the nutrient use efficiency but can also farmers that prevents them from applying adequate degrade the environment (Kapoor et al. 2008). This amount of fertilizers to their crop. Of the total cultivable shift in soil fertility and deterioration in soil health is area of Assam, Inceptisols occupy approximately further aggravated by indiscriminate and imbalanced 49.3%, are mostly acidic and contain high amounts of fertilization of N, P and K and it can only be corrected Fe and Al oxides and hydroxides. Fixation of applied with a proper manure-fertilizer schedule based on a P by these oxides and hydroxides is a common soil fertility evaluation (Santhi et al. 2011). To realize problem that hinders the uptake of P by crops, with higher response and benefit:cost ratios, the soil test- consequent nutrient imbalances. However, Yin and based application of plant nutrients is inevitable, Liang (2013) reported that applying organic fertilizer allowing the nutrients to be applied in proportion could increase the content of the phosphorus fractions to the magnitude of the deficiency of a particular of paddy soil and in presence of microorganisms Al-P nutrient. Correcting the nutrient imbalance in the soil and Ca-P could be transformed into moderately labile helps to harness the synergistic effects of balanced organic phosphorus. Awareness among farmers of the fertilization. Many researchers have prescribed field- appropriate N, P and K application rates for rice in specific balanced amounts of N, P, K and based on such soils is critical to improve productivity. Thus, the crop-based estimates of the indigenous supply the present investigation was performed in farmers’ of these nutrients and by modelling the expected fields i) to verify the suitability of the formulated yield response as a function of nutrient interaction appropriate site-specific target yield-based fertilizer (Dobermann and White 1999; Witt et al. 1999; Bera et prescription models over available technology and al. 2006; Jai Paul et al. 2011; Singh et al. 2014; Regar ii) to analyze the economics of these models for their and Singh 2014). Site-specific nutrient management adoption to enhance productivity and profitability in rice-rice crop sequences. Journal of Soil Science and Plant Nutrition, 2016, 16 (1), 31-47 Targeted yield precision model for rice-rice crop sequences 2. Materials and Methods 33 levels of phosphorus (0, 30, 60 and 90 P2O5 kg ha-1), three levels of potassium (0, 60 and 120 K2O kg ha-1) 2.1. Det (...truncated)