Plant nutrient management for enhanced productivity in intensive grain production systems of the United States and Asia

Are present nutrient management recommendations for the world's major cereal cropping systems adequate to sustain the productivity gains required to meet food demand while also assuring acceptable standards of environmental quality? To address this question, the current nutrient management approaches and their scientific basis in large-scale, mechanized maize (Zea mays L.)-based cropping systems of the USA and more labor-intensive, small-scale irrigated rice (Oryza sativa L.) production systems in Asia were evaluated. The principal challenges in both systems are similar: (1) there is no compelling evidence for significant increases in the genetic yield potential in both systems during the past 30 years, (2) farm yields are presently about 40-65% of the attainable yield potential, and (3) nutrient management mostly relies on approaches that do not account for the dynamic nature of crop response to the environment. Because average farm yield levels of 70-80% of the attainable yield potential are necessary to meet expected food demand in the next 30 years, research must seek to develop nutrient management approaches that optimize profit, preserve soil quality, and protect natural resources in systems that consistently produce at these high yield levels. Achieving these goals will require novel strategies for more precise plant nutrient management tailored to the technologies, dynamics and spatial scales relevant to each system. Significant advances in soil chemistry, crop physiology, plant nutrition, molecular biology, and information technology must be combined in this effort. Future field-oriented plant nutrition research must be of a more strategic, interdisciplinary, and quantitative nature. Systems approaches at micro-to meso-scales are required for gaining a more quantitative understanding of crop response to nutrients based on interactions among the essential crop nutrient requirements and on response to dynamic environmental conditions.