Donald J. Boquet and B. Rogers Leonard
Despite its success throughout history, cotton as a crop in the U.S. suffers from many problems for many different reasons. There are seedling, stem, root and boll rot diseases, a diverse group of insect species that feed on leaves, plant juices, immature fruit and bolls, and dozens of competing weed species. Adverse weather in early spring is hard on this tropical plant, and rainy periods during late summer and fall often cause yield losses through boll rot and delayed harvest. Costs of production for cotton are among the highest for agronomic crops, but prices received for cotton in the past several years were lower than in the 1960s.
Research-based information and technology developed by the LSU AgCenter have been important factors in maintaining profitability in the Louisiana cotton industry. In 1929, a group of north Louisiana cotton farmers who recognized the need for problem-solving research purchased land near St. Joseph in the Mississippi River Delta and donated it to the Louisiana Agricultural Experiment Station. This station, known today as the Northeast Research Station, has continuously conducted research on the Mississippi River alluvial soils and is internationally recognized as one of the leading cotton research organizations in the country. In 1958, the Northeast Research Station established a substation in Winnsboro on loess soils (wind-deposited silt loam), known today as the Macon Ridge Research Station.
Another research station active in cotton research is the Red River Research Station near Bossier City. Established in 1948, the Red River Station is uniquely situated to conduct research in two areas of consequence to the region—cotton insect pests and poultry litter. Evaluation of the technology to control insect pests with less reliance on insecticides is one of its missions. Northwest Louisiana is also proximate to extensive poultry production that generates thousands of tons of animal waste each year. If not properly disposed of, this waste poses serious environmental problems. Research on the safe and beneficial use of poultry litter is providing benefits to agricultural interests and to the public in northwest Louisiana.
With the recent return of cotton production to central Louisiana, cotton research at the Dean Lee Research Station near Alexandria has taken on new life. It is more difficult to produce cotton in this area of the state because growing conditions are influenced by the sea breeze effect of the Gulf of Mexico. Research at this location focuses on the interactions of weather with production input variables.
These four research stations are involved either directly or collaboratively with LSU AgCenter departments, including agricultural economics, agronomy, entomology, plant pathology and crop physiology, and other research organizations. Louisiana Cooperative Extension Service faculty are also located in north Louisiana at the Scott Research and Extension Center in Winnsboro because of the concentration of the crop in northeast Louisiana.
Cotton Breeding Continues
Improving the genetics of cotton varieties to make them more suitable for Louisiana conditions has been a long-term commitment of the AgCenter. The cotton breeding program in Louisiana was one of the first such research efforts established at a land-grant university, dating back to the 1920s.
Because cotton is a tropical perennial species, it requires considerable genetic manipulation to develop into a productive annual crop for a temperate environment. Breeding new varieties, however, involves much more than adapting cotton types to the environment. Cotton is unique in that acceptable fiber quality, and not only yielding ability, must be bred into varieties. Fiber quality is composed of several distinct genetically complex properties, each of which must be separately bred and selected for. Development of pest-resistant plants that can overcome infestations of insects and nematodes to minimize use of pesticides also is important. The Louisiana breeding program has used unique plant traits such as leaf shape and color, bract shape and nectar-producing inhibition to discourage insect pests. The only current cotton varieties for the South resistant to root-knot nematode were developed in the LAES cotton breeding program. The contributions of the LAES cotton breeding program are reported in this issue. Read Improving Cotton Varieties in Louisiana.
Best Management Practices Help with Profits
Historically, cotton in the Mid-South has been monoculture and grown as a summer annual crop in fields that were intensively tilled. Fields were left fallow in winter, which, because of our wet climate, exposed the soil to potential runoff losses of sediment and nutrients. This runoff can contribute to nonpoint-source pollution of surface water bodies.
Since 1991, the AgCenter, Natural Resources Conservation Service, Louisiana Farm Bureau and other organizations have cooperated to develop management practices that protect the soil and minimize field runoff. Agricultural practices designed to reduce runoff from agricultural land are referred to as best management practices (BMPs). These BMPs had to be implemented without compromising the long-term productivity or profitability of farms.
The development of agronomic BMPs that improve crop productivity while also protecting water quality has been the focus of several projects. On the highly erodible land of the Macon Ridge area, research has proved the benefits of using reduced tillage and winter cover crops to protect the land. Soil loss from research plots planted using the BMPs of winter cover crops of wheat or hairy vetch and no-tillage practices has been negligible, while soil loss from plots without cover crops and conventionally tilled exceeded seven tons per acre per year.
In addition to the environmental benefits, winter cover crops and no-till BMPs increased cotton yield and decreased production costs. These practices are called productive BMPs because they protect water quality, but, equally important, the research shows they more than pay for themselves in increased yields and cost savings. Therefore, the implementation of these BMPs on individual farms to ensure the desired societal benefits of clean water can be done without adverse effects on farm profitability. The benefits of BMPs are discussed in this issue beginning. Read Conservation Tillage, Cover Crop BMPs for Cotton.
In other BMP research at the Red River Research Station near Bossier City, researchers are examining ways to beneficially use waste from Louisiana’s largest animal industry in an environmentally safe manner. Poultry litter applied to cotton fields in conjunction with conservation tillage produced higher yields than cotton grown using the conventional methods that did not employ BMPs. Soil organic matter content and the nutrient status of the soil were also improved. As an added bonus, inorganic fertilizer nitrogen was not needed where poultry litter was applied. This research demonstrates that production of a potentially harmful waste can be turned into a BMP by safely returning the waste to agricultural row cropland in a manner that improves the soil and cotton yields.
Defoliation Timing Critical
Once bolls are mature, a critical operation remains before the cotton can be picked. Harvest aids must be applied to remove leaves and temporarily halt plant growth to allow picking of the seedcotton. This process of defoliation improves the efficiency of harvesting and preserves fiber quality. Proper timing is essential to avoid yield reductions from too-early termination of growth and too-late termination that compromises harvest timing and fiber quality. Determination of the optimal defoliation timing has been described as more of an art than science. The various methods for determining the proper time of defoliation to achieve a balance between yield and quality concerns are discussed in Cotton Defoliation: The Science of the Art.
Louisiana’s highly productive soils have one major limiting factor—erratic summer rainfall. Supplemental irrigation is essential for profitable cotton production in most years on some soils (loess) and for insurance against exceptionally dry years on other soil types. In most of Louisiana, water from wells or surface sources is readily available for irrigation. Determining the need for and scheduling irrigation is not straightforward, however, because dry weather is sometimes followed by rainfall. When this happens, any benefits of the apparent needed irrigation are negated and, in fact, irrigation may cause a yield loss. Some of the ways to avoid these irrigation problems and optimize the benefits of irrigation are being evaluated at the Northeast Research Station.
Integrated Pest Management
More than most other crops, cotton requires protection from insects, nematodes and diseases. Until the last decade, more pounds of pesticide per acre were used on cotton in a given year than on any other agronomic crop. The integrated pest management (IPM) system has moderated pesticide use on cotton. In recent years, highly target-specific pesticides that can be used at low dosages (ounces rather pounds per acre) have become available. Genetic engineering has produced cotton plants resistant to insect pests and tolerant to applications of selected herbicides. In addition, a better understanding of cotton pest biology and interactions in agricultural environments has improved the ability of producers to adapt crop protection solutions to each individual need. The ultimate goal of LSU AgCenter scientists with responsibilities for improving cotton IPM is to develop practical crop protection solutions into existing production systems with minimal effects on nontarget organisms and the environment.
Weed Management Changes
Weed management in cotton has changed considerably in the past decade. The adoption of conservation tillage practices has reduced the emphasis on tillage as weed control and increased reliance on herbicides. Producers are using pre-plant herbicide applications, called burndowns, to establish weed-free seedbeds. Novel herbicides used in post-emergence, over-top applications have been successful in controlling broadleaf weed problems such as morningglory and pigweed without injury to cotton plants. Producer acceptance of herbicide-tolerant cotton has simplified weed management in cotton by reducing the emphasis on pre-plant, soil-applied and post-directed herbicides. In 2001 and 2002, herbicide-tolerant cotton varieties accounted for more than 75 percent and 55 percent, respectively, of the total planted acreage in Louisiana. Extensive research programs in the AgCenter have defined cotton plant and pesticide characteristics that enhance the differential selectivity between crop safety and weed control.
Insect Management Goes Hi-Tech
The evolution of cotton insect pest management strategies has followed a trend similar to that of weed management. Research on highly selective novel insecticides, environmentally friendly insecticide delivery systems, transgenic insect-resistant cotton varieties and insect ecology has provided information to develop cost-effective alternatives to recommended insect pest management practices. The eradication of the boll weevil as a cotton pest has greatly reduced the application frequency of nonselective insecticides. In the absence of these treatments, which were toxic to a broad spectrum of insects, innocuous insects have emerged as significant pests that now are capable of limiting yield. Current research focuses on the development of site-specific insect management with insecticide prescriptions. Adapting precision agricultural technologies to cotton insect pest management strategies could further reduce insecticide inputs with economic and environmental benefits.
Tillage Practices Affect Disease Management
The dynamics of cotton disease management have shifted with changing tillage practices and short-season varieties. Although the pathogens plaguing cotton plants have not changed, the dynamics of cotton diseases have. Increased use of conservation-tillage practices has altered the soil environment, leading to an increase in the diversity of soil organisms. The effects of increased microbial interactions on specific plant pathogens are complex and not completely understood. Some pathogens may increase in the altered environment, and others may decrease. Research is continuing to evaluate the effects of disease pathogens, but general uncertainty has prompted producers to re-evaluate
the need for additional fungicides at planting.
The impact of reduced-tillage practices on nematode populations is also not completely understood, but research is under way. The reniform nematode has emerged as the state’s No. 1 nematode pest, replacing the root-knot nematode. Current research efforts are targeting management of this pest.
The sporadic occurrence of late-season maladies has had mixed effects on cotton development. Bronze wilt is usually associated with specific short-season cotton varieties and can reduce yields drastically. Boll dangle or vascular cavitation, in contrast, destroys many young bolls but is associated with high-yielding varieties and is apparently not yield-limiting.
Improved Technology Sustains Cotton Industry
Innovations in technology have greatly changed the way cotton is grown, improving production efficiency from pre-plant operations through harvesting. Although no single technology can be said to have saved the cotton industry, all of the improvements in technology during the past 50 years together have enabled the cotton industry to survive, if not prosper. Perhaps the greatest change in technology is use of transgenic seed with insect and weed control attributes, which transfer the cost and the burden onto producers of making what used to be mid- and late-season decisions at planting time. Despite problems and high cost, the use of transgenic varieties is the most rapidly adopted technology change in agricultural history.
The adoption of environmentally friendly conservation tillage practices also has had profound effects in revolutionizing cotton production practices. Although promoted for environmental benefits, conservation tillage improves efficiency and makes it easier and less costly for producers to grow cotton. Likewise, larger cotton pickers and more effective harvesting equipment such as boll buggies and modules have improved the efficiency of harvesting cotton. The improved technology has benefited cotton growers, but at a high cost.
The articles in this issue are examples of research and extension efforts put forth by LSU AgCenter scientists to provide solutions to problems being experienced by the Louisiana and the Mid-South cotton industry. These scientists are integrating their results into holistic, intensive and sustainable cotton production systems. All of the cotton varieties—and agricultural production systems in general—are developed so that they meet the economic and environmental challenges that face Louisiana agriculture.
Donald J. Boquet and B. Rogers Leonard, both Professors, Macon Ridge Research Station, Winnsboro, La.
This article was published in the spring 2003 issue of Louisiana Agriculture.