It's important to know mobile nutrient patterns, especially nitrate-N. Fertilizer Recommendations Traditional fertilizer recommendations are based on regionally developed response curves. These response curves served well when managing fields as a single management unit. But ongoing research clearly demonstrates that fertilizer response may vary across landscapes within the same field, even when soil nutrient levels are the same. These traditional response curves may be too simplistic for a site-specific system. Assigning target yields and expected moisture availability by soil management unit may aid in refining recommendations.
Field research continues to determine appropriate recommendation strategies.
Knowing your soil nutrient variability may be useful even when variable-rate application is not being considered. Directed bulk spreading of nutrients may be well justified to areas of the field identified as requiring more nutrients than those supplied through the standard whole-field fertilizer program. Likewise, sampling may detect areas where excessive nutrients are accumulating. This may be due to poor crop growth caused by salinity or lack of available soil moisture. Reducing fertilizer applications to these areas will reduce costs and prevent loading of nutrients that may be harmful to the environment.