Factors Affecting Cotton Variety Performance

BATON ROUGE, LA.
   One of the most important decisions that cotton producers make occurs before the growing season even begins. Variety selection, specifically which varieties are selected for each field and specific situation, will set the pace for the entire year. A closer look at factors affecting variety performance is necessary to consistently put the right variety in the right field.
   Selecting ideal varieties today is more complicated than in the past. They are offered with any number of genetic technologies and seed treatments, some of which may not be important to you and some of which are critical. Choosing among these technologies, such as Roundup Flex, Liberty Link, GlyTol, or Conventional, etc., can help narrow the field in selecting a variety. However, after the “technology” decision is made, there remains a large number of varieties that could potentially be planted on your farm.
   Research being conducted in Louisiana aims to categorize cotton varieties and to determine where they are best suited for maximum yield potential and fiber quality. One of these trials was conducted with Mr. Dennis Burns, LSU Ag- Center county extension agent, at an on-farm location in Tensas Parish to evaluate cotton variety performance on different soil types. Rather than averaging data from a soil type, e.g, clay soils, from throughout the state of Louisiana, we were able to test 6 cotton varieties on different soils within the same field. This is important because most of the other factors that affect the performance of varieties were constant (such as planting date, pest pressure, rainfall, nighttime temperatures, etc.).
   There were large differences in lint yields on different soil types. Averaged across varieties, the highest yields were obtained on a Tunica clay (1132 lb/A), followed by a Sharkey clay (999 lb/A), a Commerce silt loam (945 lb/A), and a Bruin silt loam (765 lb/A). The yields of the varieties, averaged across all of the soil types, ranged from 1281 to 746 lb/A. The highestyielding variety on average, Stoneville 5288, was also the highest-yielding for all soil types. However, some varieties bucked the trend of highest yields on the clay soils compared to the silt loam soils. Deltapine 1048 and Stoneville 5458 yielded higher on the Commerce silt loam, relative to their yields on the clays, than the other varieties. This suggests that their best fit is on lighter soils.
   Undoubtedly, yield potential is the most important characteristic to consider for variety selection. Another important consideration – a tiebreaker of sorts – is the level of stability/consistency of a variety. We estimated the consistency of cotton varieties across the soil types to evaluate how durable they would be in a range of conditions or in fields with variable soils. One important point to consider is that stability is a desirable trait, but it is only important if a variety has high yield potential in addition to consistent yields. The variety that was most consistent (interpret as equally adapted to all soil types) was Deltapine 1048, however, yields were somewhat lower compared to other varieties. Phytogen 485 was also very consistent. Stoneville 5288 and 5458 were consistent across soil types, which is important considering they both had high average yields across the field. The least stable varieties were Phytogen 565 and Deltapine 0935 (almost 2X as variable). Deltapine 0935 had high average yields on the clay soils, but yields were much lower on the loamy soils which contributed to the high levels of variability.
   Replicated small-plot research trials are an extremely important source of information when making variety selection decisions. These trials are used by seed company representatives making variety advancement decisions and by crop consultants and growers who are interested in evaluating relative varietal performance in local conditions. A major benefit of these trials is the ability to test a large number of varieties, including pre-release experimental lines, and get information on their growth and management curve. At the Dean Lee Research Station in 2010, we conducted 4 cotton variety trials: an early and a medium-full maturity trial on a Coushatta silt loam and a Latanier silty clay loam. In addition to yield and fiber quality traits, we gathered information to estimate the growth potential of the varieties in the trial for plant growth regulator management.
   Ultimately, there are many factors that should go into selecting a mix of varieties for your farm. Utilizing all available sources of information (University Variety Trials, previous performance in your area, etc.) is important. A variety might not always make a bumper crop, but investing the time to research the varieties and their characteristics can start things off on the right track. Δ
   DR. STERLING BROOKS BLANCHE: Assistant Professor, Cotton & Soybean Agronomy, LSU AgCenter