Current and Future Best Management Practices for Nitrogen and Phosphorus Fertilizer Application

Background/Question/Methods

Agriculture faces the challenging dilemma of meeting global demand for food, fiber and fuel in a locally sustainable manner.  Nutrient management is a key factor to help the world grow the food it needs. The objective of this presentation is to discuss the agronomic technologies and practices related to nitrogen (N) and phosphorus (P) management that are currently available to a Midwestern producer, and to foresee those that will be available in next twenty years for sustainable crop production.  Fertilizer source, moment of application, as well as the use of spatially optimal nutrient rate, are critical tools to achieve this goal. Recent estimates clearly indicate that N and P balances are negative in the Mid-West and this is substantiated by the decrease in soil test P over the last five years. New enhanced efficiency N sources have shown promising results to improve the synchrony between crop N demand and nutrient supply. Similarly, more efficient and nutritionally balanced complex P fertilizers that improve P use efficiency have become recently available. Even though it is recognized that spring application of fertilizer increases nutrient use efficiency, in many cases it is not practical for producers. Deep, precise placement of fall applied P fertilizer addresses these issues but requires sophisticated equipment.  Precision Agriculture allows the producer to apply the optimal rate within a field, thus increasing fertilizer use efficiency. However, it encompasses a complex set of technologies that require many steps, more management and more precise recommendations than those required for uniform fertilizer application. The adoption of this technology has been more rapid for P than N due to the complexity of the N cycle and the lack of a good estimate of soil N supply, among other factors.

Results/Conclusions

Policies that promote the adoption of proven, cost-effective practices and technologies (soil testing, grid sampling, smarter equipment) will be more successful than those designed to control nutrient application rate. Future research requires an integrated approach to develop and evaluate the productivity and nutrient loss of new cropping systems. Unfortunately, most projects tend to focus on single or few factors and fail to represent real world conditions.