Closing yield gaps in maize production in Southeast Asia through site-specific nutrient management

Rising incomes and changing dietary requirements are swiftly transforming maize (Zea mays L) in Southeast Asia from a food staple into an important industrial commodity. Increased maize production is required to meet rising demands, but additional production should come from the sustainable intensification of existing farmlands to minimize the undesirable effects of agriculture on the environment. We hypothesize that maize yields, profit, and N use efficiencies can be significantly increased through site-specific nutrient management (SSNM), thereby reducing yield gaps in the region. Through a combined approach of simulation modeling and on-farm research in at least 65 sites in 13 major maize-producing domains across Indonesia, Vietnam and the Philippines from 2004 to 2008, we were able to (a) quantify maize yield gaps and yield responses to fertilizer application, (b) evaluate the agronomic and economic performance of SSNM, and (c) evaluate the incremental profitability of SSNM in various production and grain and fertilizer price scenarios. The average exploitable yield gap between the attainable yield and current farmers' yield in Southeast Asia was about 0.9 t ha(-1). Yield responses to fertilizer application across the region followed the order N> >P> K. Yield response to N was higher in irrigated sites than in rainfed sites (6 t ha(-1) versus 2 t ha(-1)), while P and K fertilizer responses were similar across production systems (<2 t ha(-1)). Yield with SSNM was 1.0 t ha(-1) (+13%) higher than the current farmers' fertilizer practice (FFP) measured in the same cropping seasons. Yield increases were associated with a 10% decrease in the average N rate, but with increased application of K at sites where the previous K rates were low. Average N use efficiency increased by 42%, mainly by adjusting the rates and timing of N application to the stages of crop development. Across all sites and seasons, profitability increased by US$167 ha(-1) per crop, which was equivalent to 15% of the total average net return. Opportunities for achieving higher income over the FFP (>= US$100 ha(-1) season) were greatest in highly favorable rainfed environments; less favorable rainfed areas were vulnerable to unfavorable market prices. We conclude that SSNM has the potential to close existing yield gaps in the maize production systems of Southeast Asia by improving yield, nutrient use efficiency, and profitability. (C) 2013 Elsevier B.V. All rights reserved.