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

Spring 2001, No. 8


Crop stress due to inadequate moisture has long been recognized as one of the major yield limiting factors in southeast agriculture. This stress has been more severe during the past three years and is anticipated to carry over into the 2001 season for regions such as southwest Georgia. Sandy, low exchange capacity, low water holding soils are common throughout the region and are most susceptible to moisture stress. Field research reveals that best management practices (BMPs) help plants to better withstand stress from inadequate moisture. Providing a balanced crop nutrition program is one of those BMPs. The reasons are based on sound science.

The depth and density of a plant’s root system are major factors regulating a crop’s ability to access and utilize moisture stored in the soil. Phosphorus is best known for stimulating early root growth and seedling vigor. However, research also documents that potassium applied to low testing soils will result in a more effective plant root system. Thus, a highly fertile soil is needed to develop a quality root system early that can best access available soil moisture throughout the plant growth cycle.

Rapid seedling growth provides earlier soil shading by the plant’s canopy. This does two things. It reduces the amount of soil moisture lost by evaporation, and it allows more of the soil moisture to pass through the plant for growth and yield development. Early row closure also means greater leaf area exposure for the capture of sunlight. Well nourished plants can better convert this light energy into plant sugars and produce more yield per unit of available soil moisture.

Stress forces such as high temperature, diseases, nematodes, and/or weeds can further increase the injury from plant moisture stress. When these stresses can be minimized, plants can better utilize available water. Research shows that plants with inadequate potassium have lower resistance to certain diseases, slower recovery from root injury by nematodes as well as reduced effectiveness by some crop protection products. Such interactions with other management practices are best attained by having the right amount of each essential nutrient readily available when needed by the plant.

Residue management can improve soil/crop moisture relations. Reduced tillage helps to slow the process of residue breakdown. Adequate nutrition is the fuel that creates the quantity of crop residue needed to improve both water infiltration and the water storage capacity of a soil. A balanced fertilization program for higher grain yield will, at the same time, generate more residue for better soil water relations for the following crop.

The products of today’s decisions will be harvested this fall. Moisture availability and use is but one of the big challenges. Low crop prices and rising input costs must also be added to the water issue. A top goal must be to harvest the best possible yield to keep unit costs down. Indiscriminate cost reduction is a one way street away from success.

A healthy, well nourished crop is essential if the highest return is to be received from each and every input investment. We know that nutrition contributes at least one third of a crop’s production…sometimes more. It happens because of the previously mentioned interactions and influence on proper plant growth. For a crop to grow and produce to its genetic potential requires a minimum level of basic raw materials such as nitrogen, phosphorus and potassium. The plant is unaware of the cost of inputs or of its market value at maturity. It becomes, then, a grower’s decision to provide the nutrients essential for best growth for the desired level of production. For years, sound science merged with grower experience has demonstrated that a fertile soil containing the proper balance of nutrients can best cope with crop stress and deliver top profit crop production.

For more information, contact Dr. Noble R. Usherwood, Southeast Director, PPI, 233 Kenilworth Circle, Stone Mountain, GA 30083. Phone: (404) 294-0137. E-mail:
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