Yield reductions due to water limitations are often associated with more frequent and longer drought spells during critical stages of crop development. In many parts of the world, lack of enough water makes it difficult or even impossible to grow crops.

In the U.S. Southeast, improving crop performance under water deficit is still one of the big challenges in crop production.

Soybeans are often not irrigated (less than 5 percent of the land area in the major producing countries have access to irrigation), so the crop is vulnerable to variations in rainfall.

In West Tennessee, more than 95 percent of soybeans are grown under a rainfed condition.

Based on results from other researchers, soybean varieties that express certain drought-tolerant traits produce higher yields under drought conditions, and computer simulation studies have shown that planting more drought-tolerant soybean varieties would have the potential to increase yields about 70 percent or more in rainfed locations in the United States.

As a crop physiologist with the University of Tennessee, I am interested in identifying soybean varieties that carry the stomata related drought-tolerant traits that have proved valuable in corn and North Carolina soybeans and have been found in Spanish-runner and Virginia type peanut. Varieties used in my research are chosen from both commercial and breeding lines.

With the support of UT AgResearch, two rainout shelters were installed at the West Tennessee Research and Education Center in Jackson, Tenn., that would allow researchers to simulate water deficit in the field at key times during the growing season.

Preliminary greenhouse results indicated a wide range of water saving potential as some varieties closed stomata early during soil drying, indicating a few varieties may be able to “save” water during drought, potentially reducing drought’s impact on crop growth and yield.

When these varieties were grown under rainout shelters, they continued to show differences in the transpiration rate (water loss through leaves) under dry-air conditions at midday in the field.

Results of simulated drought work in the field will be useful to help breeders develop more drought-tolerant lines as well as identify existing commercial soybean varieties that have better tolerance to drought.

Avat Shekoofa, is Assistant Professor, Crop Physiologist-Water Stress and Irrigation, Department of Plant Sciences ,University of Tennessee Institute of Agriculture.