Selecting the Right Nutrient Rate: Basis for Managing Fertilization Programs

Selecting the "right" nutrient rate for fertilization programs is one of the most important decisions growers face. On one hand, increasing fertilizer prices and environmental concerns have increased the awareness of accurately managing fertilization programs, thus reducing fertilizer amounts during cropping seasons. By contrast, many growers fear not obtaining the desired crop performance and economic returns, especially when fertilization is assumed as "inexpensive insurance" to improve yields, thus leading to overfertilization. The objective of this paper was to provide general principles for selecting and monitoring the right nutrient rate within the framework of the "4R" nutrient management concept (right rate, right source, right placement, and right timing) to protect environmental quality while maintaining productivity. Some methodologies to determine, apply, and adjust fertilization rates during the growing season were discussed, including in-season monitoring procedures, such as petiole sap testing, plant diagnostic analysis, leaf color evaluation, and plant growth index.