Sterling Brooks Blanche, Donald J. Boquet, Sarah Sterling, Dustin L. Harrell, Boyd Padgett, T.K. Udeigwe, Howard P. "Sonny" Viator and Clayton A. Hollier

The Louisiana Soybean Variety Testing Program plays an important role in the soybean industry in Louisiana. LSU AgCenter researchers conduct the trials annually to evaluate commercial soybean varieties for yield potential, agronomic performance and resistance to diseases. The trials provide Louisiana soybean producers, seed companies and other interested in variety selection with unbiased results on the performance of soybean varieties in the major production regions of Louisiana.

Importance of the variety trials
One of the most important decisions that soybean producers make is that of variety selection. Planting the best possible variety in each specific situation is a major step toward achieving profitable soybean production. In practice, variety selection is not such an easy task. In 2010, more than 200 commercial varieties and experimental lines were entered into the program. It is difficult to sort through such a large group of varieties, considering that the performance and profitability of soybean varieties can be affected by many factors, including geographic location, soil texture, weather patterns and management practices. Many of the varieties tested in the program are found not to be adapted to Louisiana and, if planted, will produce much lower economic returns compared with top performing varieties. In fact, only a relatively small number of varieties are top performers that consistently yield among the top 10 percent. The program aids producers in this important component of soybean production by "narrowing the field" and providing sound, unbiased information on the yield and agronomic characteristics expected for each of the varieties.

Testing methods
To evaluate the performance of soybean varieties in Louisiana, 18 trials are conducted annually in six locations across the major soybean production regions of the state (See map). The tests are conducted at LSU AgCenter research stations so they can be closely monitored for data collection and to ensure that factors contributing to variation can be minimized. Any factor such as variations in soil texture or insect and weed pressure that occur in the trial can confound the results and arbitrarily affect the rankings of the varieties.

The relative maturities of different soybean varieties can vary greatly. To group soybean varieties of similar maturity, three tests (an early, medium and medium-late variety trial) are planted at each location. All tests are planted in a randomized complete block design with four replications at each location to identify all sources of variation and accurately quantify the differences among varieties. Statistical analyses are performed to aid in interpretation of the results and to discern which varieties are truly superior.

A broad range of information is collected that can help producers understand what to expect from each variety. Yield is the most important factor to consider, but other data that should be considered include standability and plant height (yield potential will not be realized if plants fall down), relative maturity group (it is important to know when plants will reach harvest maturity) and disease ratings (producers can select resistant varieties and minimize yield losses and fungicide applications). In recent years, other factors such as seed quality and the degree of plant greenness at maturity have been recorded.

Interpreting the results
Profitable soybean production begins by producing maximum yields, and this is the primary factor in variety selection. However, it is important to realize that a host of factors affect the yield performance of varieties. A single variety is rarely the best variety in all locations and situations. For example, some varieties are adapted to irrigation in northern Louisiana, while others may do well in dryland situations in southern Louisiana. Therefore, variety performance should be evaluated by producers in two ways: 1) averaged across all possible years and locations and 2) in locations similar to the targeted production location.

The performance and consistency of a variety in different years and locations is a strong indicator of future production potential and is the most important criteria used in selection. Data from a single year, while meaningful, is not as good an indicator as performance over multiple years and locations. Because it is unlikely that future growing seasons will be identical to any single location report, selecting a variety that is high-yielding across many environments can increase the probability of success. Consider that for varieties tested for three years, we will have information on their performance in 18 different locations.

Other factors that affect a variety’s performance can be evaluated with information from the variety testing program. Varieties differ in their levels of disease resistance. In locations where a specific disease is a perennial problem, producers are advised to raise resistant varieties. Relative maturity is another factor to consider. In most cases, producers spread their risk and coordinate their planting and harvest capabilities by planting varieties from different maturity groups.

More specific information is available for variety selection such as seed quality ratings, variety ratings for green bean syndrome, and resistance to salt damage.

The Soybean Variety Testing Program provides a wealth of information for the Louisiana soybean industry. LSU AgCenter scientists are constantly updating and modifying these trials to provide the maximum benefit to all segments of

the soybean industry. Louisiana soybean producers who use the program results for variety selection will greatly increase their chances of planting superior varieties and optimize their yield and profit potential.

Acknowledgments
Millie Deloach, Grayson Close, Darrell Franks, John Stapp, Tim Talbot, James Leonards, Ronald Regan, Jacob Fluitt, Al Coco, Jim Hayes and Greg Williams