Site-specific nutrient management for intensive rice cropping systems in Asia

• Published in: Field crops research 2002-02, Vol.74 (1), p.37-66
• Main Authors: Dobermann, A, Witt, C, Dawe, D, Abdulrachman, S, Gines, H.C, Nagarajan, R, Satawathananont, S, Son, T.T, Tan, P.S, Wang, G.H, Chien, N.V, Thoa, V.T.K, Phung, C.V, Stalin, P, Muthukrishnan, P, Ravi, V, Babu, M, Chatuporn, S, Sookthongsa, J, Sun, Q, Fu, R, Simbahan, G.C, Adviento, M.A.A
• Format: Article
• Language: English
• Subjects: Indigenous nutrient supply; Nitrogen use efficiency; Profitability; Rice; Site-specific nutrient management
• ISSN: 0378-4290; 1872-6852
• DOI: 10.1016/S0378-4290(01)00197-6

Irrigated rice ( Oryza sativa L.) yield increases in Asia have slowed down in recent years. Further, yield increases are likely to occur in smaller increments through fine-tuning of crop management. On-farm experiments at 179 sites in eight key irrigated rice domains of Asia were conducted from 1997 to 1999 to evaluate a new approach for site-specific nutrient management (SSNM). Large variation in initial soil fertility characteristics and indigenous supply of N, P, and K was observed among the eight intensive rice domains as well as among farms within each domain. Field- and season-specific NPK applications were calculated by accounting for the indigenous nutrient supply, yield targets, and nutrient demand as a function of the interactions between N, P, and K. Nitrogen applications were fine-tuned based on season-specific rules and field-specific monitoring of crop N status. The performance of SSNM was tested for four successive rice crops. Average grain yield in the SSNM increased by 0.36 Mg ha −1 (7%) compared to the current farmers’ fertilizer practice (FFP) measured in the same cropping seasons or 0.54 Mg ha −1 (11%) compared to the baseline FFP yield before intervention. Average nutrient uptake under SSNM increased by about 10% in the same seasons or by 13% (N) and 21% (P, K) compared to the baseline data. Yield increases were associated with a 4% decrease in the average N rate, but larger amounts of fertilizer-K at sites where the previous K use was low. Average N use efficiencies increased by 30–40%, mainly through the use of improved in-season N management schemes. Across all sites and four successive rice crops, profitability increased by US$ 46 ha −1 per crop or 12% of the total average net return. The performance of SSNM did not differ significantly between high-yielding and low-yielding climatic seasons, but improved over time with larger benefits observed in the second year. Average profitability increased from US$ 32 ha −1 pre crop in the first year to US$ 61 ha −1 pre crop in the second year due to improvements in the SSNM approach and re-capitalization of P and K applied in the first year. SSNM required little extra credit for financing, and remained profitable even if rice prices are somewhat lower than current levels. Further, scope for improvement exists at many sites by alleviating other crop management constraints to nutrient use efficiency. Profit increases ranged from US$ 4 to 82 ha −1 per crop among eight rice domains. However, pro