Abstract
Abstract Inherently poor soil fertility and non-adoption of fertilizer recommendations based on soil test and yield targets by farmers limit the productivity and profitability from monsoon rice in Bangladesh and much of South Asia. In the Level Barind Tract (LBT; AEZ-25) and the High Ganges River Floodplain (HGR; AEZ-11) agro-ecological zones (AEZs) of Bangladesh, monsoon (aman/kharif) season transplanted rainfed rice (known as T. aman rice) is grown in large areas after maize, wheat and/or mungbeans, with residues of each crop removed from the field after grain harvest. This results in lower grain yield and lower profits in these AEZs as compared with other AEZs. Nutrient management, based on soil test, yield targets, or integrated use of inorganics and organics for each AEZ together with retention of crop residue, has the potential to increase rice yield, reduce production cost and increase income. With this hypothesis, this study was conducted to determine the optimum nutrient management practices for achieving higher yield, maintaining apparent soil nutrient balance, and obtaining high profits from monsoon rice. Twelve nutrient management options were evaluated, of which the first six were: (i) 80-16-44-12-2 kg ha-1 of N, P, K, S, Zn respectively for a high yield goal (T1; ‘HYG’); (ii) 56-12-32-8- 1.5 kg ha-1 respectively for a medium yield goal (T2; ‘MYG’); (iii) 65-13-32-9-2 kg ha-1 respectively plus 5 t ha-1 cowdung as integrated plant nutrient management system (T3, ‘IPNS’); (iv) 67-14-41-9-2 kg ha-1 respectively as a soil test-based fertilizer management strategy (T4; ‘STB’); (v) 40-9-11-0-0 kg ha-1 respectively as per farmers’ practice (T5; ‘FP’) and (vi) 0-0-0-0-0 kg ha-1 as a control (T6; ‘CON’). The remaining six treatments were the same as above but each also included the crop residue incorporation (CRI), i.e., (vii) T7, ‘HYG+CRI’; (viii) T8, ‘MYG+CRI’; (ix) T9, ‘IPNS+CRI’; (x) T10, ‘STB+CRI’; (xi) T11 ‘FP’+CRI’; and (xii) T12, ‘CON+CRI’. In both AEZs, STB plus CRI resulted in the highest rice yield (p≤0.05) followed by ‘STB’ and ‘IPNS+CRI’. In comparison with ‘FP’ and ‘CON’, each without CRI, balances were positive (p≤0.05) for P, S, Zn and B but were negative for N and K in ‘HYG’, ‘MYG’, ‘IPNS’ and ‘STB’ with or without CRI. In both AEZS, STB nutrient management had the highest (p≤0.05) net returns (526 & 487 US$ ha-1, respectively), highest benefit cost ratio (BCR; 3.54 & 3.36) and highest marginal benefit cost ratio (MBCR; 10.47 & 10.19). These were followed by STB+CRI’ and ‘IPNS’, while they were lowest (p≤0.05) for CON and FP. We recommend that nutrient application, based on soil test with incorporation of mungbean residue, followed by IPNS, could be the best strategies for achieving high yield, improving soil fertility and for fetching a higher profit from monsoon rice in Bangladesh and similar soils and growing environments of South Asia.
Highlights
Rainfed monsoon rice is the most important crop to feed the ever-growing population in South Asia and SouthEast Asia
The farm gate prices of products were collected from local farmers and markets to compute gross return, gross margin, net returns, benefit cost ratio (BCR) and marginal benefit cost ratio (MBCR), as described in detail in other papers, using the following equation: MBCR= Gross Return (Specific Management ) − Gross Return (Control)
Similar to the results of the current study, Ali et al (2003) and Basak et al (2008) reported that ‘soil test based (STB)’ with crop residue incorporation (CRI) management resulted in the highest number of productive tillers (NPT) m-2 in T. aman rice in MustardBoro rice-T. aman and in Mustard-Boro rice-T. aman rice cropping patterns respectively
Summary
Intensive cropping with modern varieties, for example, three rice crops per year, induces micronutrient deficiency in soils due to uptake by plants and leaching by monsoon rains and irrigation (Jahan et al 2016) This risk can be attenuated by the addition of organic manures (Baruah and Baruah 2015; Jahan et al 2016) and incorporating crop residues (Devi et al 2017) as well as inclusion of legumes in rotation, without any yield penalty (Hua et al 2015; Hossain et al 2016). Development of site-specific (AEZ-based) nutrient recommendations to achieve target yield and high profits from monsoon rice without declining the soil fertility would probably be the best fertilizer management practice in rice. This study was, conducted to determine the nutrient management practices for obtaining higher rice yields and economic returns, without declining the soil nutrient balance, for monsoon rice in Bangladesh and similar rice-growing environments in South Asia and SE Asia
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