Long‐term Impact of Tillage Practices and P Fertilization on Soil P Forms

10 CSA News July 2014 Conservation tillage practices (minimum or no-till) are characterized by minimal soil disturbance and mixing and have been used more frequently in recent years to reduce off-site losses of nutrients associated with eroded particles, including phosphorus (P). However, by maintaining crop residues and fertilizers on the soil surface, the relatively immobile nutrients that do not readily move down the soil profile remain at or near the soil surface. Therefore, no-till (NT) management systems often result in high concentrations of nutrients at the soil surface (0–5 cm) but sharply decreasing concentrations below this depth. Studies have shown that NT management has induced the stratification of soil organic carbon (C), potassium, and P. Stratification of P is of particular environmental and agronomic concern. Studies that characterize P stratification and determine its causes can guide producers to use management practices such as tillage and fertilization so that plant nutrient requirements are met while minimizing the potential for P loss.