Role of Phosphorus in Cotton Production

The cotton plant does not produce more roots in areas with high nutrient content in the same way as cereals, creating a challenge of where it is best to apply P to make the plants absorb it with ease. In general, only 20-30 percent of the applied P-fertilizer is used by the crop in the application year, and the remaining P will be bound up in the soil and may be used for later.

Phosphorus normally exists in two “pools” in the soil. One is the slow release pool where the P is quite immobile and in compounds such as calcium phosphate. The slow release pool will deliver P to the other pool, called the fast release pool and in this way the slow release pool gets depleted over time. The fast release pool delivers P into the soil solution from where the plants supply themselves.

The fertilizer strategy must replace the P taken away by the crop each year. Due to P’s immobility, it is important to apply P fertilizers in a way that a large as possible volume of soil is treated, so broadcasting is preferred to row applications. Incorporation can also be beneficial.