Phosphorus Interactions with Other Nutrients

one production factor influences the response to another factor. A positive interaction occurs when the influence of the combined practices exceeds the sum of the influences of the individual practices. Such positive interactions have served as the science-based justification for development of a “balanced” plant nutrition program. Positive interactions with P and other nutrients are well documented. In addition, P interactions have been identified with other practices such as crop varieties or date of crop planting. Positive interactions of P with other essential nutrients have been documented in research studies on many crops. Certain crop production practices along with environmental conditions can serve as indicators when P interactions might occur: • Higher crop yields place greater demand on soil nutrient reserves and applied fertilizer P. The objective is to supply nutrient needs during peak crop uptake periods. • Liming an acid soil alters nutrient availability to growing plants. It improves P availability to most crops. Liming can reduce availability of micronutrients such as iron (Fe), zinc (Zn), manganese (Mn), or boron (B) and increase the availability of the micronutrient molybdenum (Mo). • The shift to reduced tillage practices can alter the method of fertilizer application and often results in P accumulation in the surface zone of the soil. Lower tempera-