AGRI-BRIEFS   AGRONOMIC NEWS ITEMS

From Agronomists of the Potash & Phosphate Institute 655 Engineering Drive, Suite 110 Norcross, Georgia 30092-2837 Phone (770) 447-0335

Spring 2002, No. 2

Seeding decisions in many areas will depend on moisture captured from over-winter and spring precipitation. Spring soil moisture assessment, measuring the depth of moist soil by in field probing, is going to be critical in many areas. Having 3 to 4 inches of stored soil water provides the foundation to support profitable crop yield if supplemented with adequate growing season precipitation and crop nutrients.

Soil testing fields is also going to be critical after a summer of drought. Estimating the amount of residual nutrients in the soil after a dry year can be difficult. Soil testing to a depth of 12 to 24 inches to assess soil residual nitrogen is critical to reducing the guesswork on fertilizer application. Measured soil phosphorus and potassium levels are not likely to change much between years, even with a drought. These nutrients are less mobile in the soil and react in such a way that they become available to future crops in rotation.

Nutrients can play a major role in reducing the impact of moisture stress on crops. Nitrogen deficiencies have an impact on the ability of a crop to convert available water into yield, referred to as water-use efficiency. Under low moisture growing conditions, early uptake of nitrogen enhances both shoot and root development which is critical to final yield formation. Phosphorus is important in stimulating seedling root development. This helps the plant explore more soil, increasing the recovery of nutrients and water.

Potassium is often referred to as the regulator nutrient, influencing the water dynamics in plants. In its association with some 60 enzyme systems in the plant, potassium helps to regulate water loss when the crop is subjected to temperature and water stress. Where potassium deficiencies exist, crops are more prone to rapid desiccation, leading to lost yield potential. Chloride has been shown to improve disease resistance or tolerance in cereal grains. Adequate chloride can minimize root diseases like take-all, improving the ability of the cereal seedling to capture more nutrients and water. Early season disease control is ultimately reflected in final grain yield potential and crop quality.

Balance is the key to optimizing crop response under both high and low stress conditions. While many soils may have residual nitrogen from the 2001 drought year, it is critical that nitrogen be balanced with phosphorus and potassium so that soil and fertilizer nitrogen will be used more efficiently.

Start with a soil test to assess the soil residual nutrients. Be sure and evaluate the crops you grow for their specific nutrient demands based on crop type, yield goal, and management practices. While the weather can often limit production, a crop with a good balance of nutrients will produce optimum yield levels, regardless of conditions.