While plant growth derives from components in the air in the form of carbon dioxide, water in the soil and sunlight, all plants (not just cotton) also need mineral nutrients to grow. The primary nutrients are nitrogen, phosphorus, and potassium; other secondary and micro nutrients also play a role. Cotton's fertility requirements are similar to other crops, as is illustrated in Figure 1, showing actual, average fertilizer use for major crops in the United States.

Figure 1 – Fertilizer use of major crops in the United States (from USDA, National Agricultural Statistics Service Agricultural Chemical Usage Data).

There are various methods to meet the fertility requirements of cotton including the use of nitrogen-fixing cover crops, manures and soluble fertilizers. While alternative sources to soluble fertilizers may seem a sustainable solution, relying on them as a sole source of fertility can compromise yields or lead to the leaching and runoff of nutrients, because the timing that will impact the release of the nutrient to the plant has a high level of uncertainty.

Nitrogen is particularly prone to leaching and runoff and has become a water-quality concern for agriculture. For cotton producers, this is both a financial and an environmental issue. Nitrogen that leaves the field does not get used by the plant and becomes, literally, money down the drain. While nitrogen contamination is a concern, the good news is that nitrate concentrations entering the Mississippi River in the Cotton Belt are lower than concentrations to the north (see Figure 2).

Figure 2 – Nitrate concentrations entering the Mississippi river (adapted from U.S. Geological Service Fact Sheet 135-00)