What agricultural practice helps to minimize phosphorus runoff?

Crop rotation with low-P crops is an effective agricultural practice for minimizing phosphorus runoff. When low-phosphorus crops are chosen as part of a rotation, they can help in reducing the overall phosphorus levels in the soil. These crops typically require less phosphorus for optimal growth, thereby decreasing the quantity of phosphorus that might be available for runoff during rain events or through irrigation.

Additionally, diverse root systems from various crops can improve soil structure and enhance water retention, which leads to reduced erosion and runoff. This practice ultimately helps maintain a balance in soil nutrient levels, ensuring phosphorus does not accumulate to high levels that could contribute to runoff problems.

The other options, such as intensive tillage, over-irrigating fields, and applying nutrients only in spring, would typically contribute to increased runoff and potential nutrient leaching. Intensive tillage can expose the soil to erosion and nutrient loss, while over-irrigation may create conditions for waterlogging or runoff. Similarly, applying nutrients in spring without considering crop needs can lead to excess phosphorus in the soil just before heavy rain, increasing the risk of runoff.