Cotton growers are making great strides in reducing soil erosion, which, when unchecked, depletes one of agriculture’s most fundamental resources. A variety of farming techniques, such as conservation tillage—mixing and disturbing the soil as little as possible—and planting winter, or cover crops, have been implemented and improved upon to better conserve soil by preventing erosion — and by actually helping to encourage soil creation.
According to the U.S. Department of Agriculture (USDA), total soil loss on cultivated cropland across the country decreased by nearly 40 percent from 1982 to 2003. This trend is indicative of modern agricultural technologies that enabled the preservation of more soil and the concurrent development of higher-quality soil.
Over the last 10 years, cotton has made great strides in reducing the use of tilling and in adopting the practice of growing winter or cover crops. Scientific research shows that these improved conservation tillage practices dramatically reduce soil erosion, and actually bring these activities into balance with soil creation.
Modern production practices allow cotton growers to achieve high levels of soil conservation and input efficiencies that both increase yield and reduce production cost. The environmental and economic benefits, coupled with mandatory regulations and requirements for compliance, are strong incentives for producers to take every practical measure possible to protect the soil.
Cotton is highly tolerant of soil and water salinity (salt content) and can be grown with water and soil resources that would otherwise be unsuitable for other food, feed, and fiber crops. Cotton’s high level of tolerance of salinity lets producers make use of drainage or reclaimed water that otherwise would require environmentally-challenging waste disposal, another achievement of modern farming technology in practice.
In the 1930s on the Great Plains of the U.S., poor farm management practices combined with severe drought resulted in huge soil losses due to wind erosion, which led to what we now call the Dust Bowl. During this period in U.S. history, the need for careful soil management was realized, and that need played a part in the creation of what is now called the National Resource Conservation Service (NRCS). The NRCS — originally called the Soil Conservation Service — is a part of the U.S. Department of Agriculture (USDA) and functions to develop conservation farming techniques and practices that help preserve the nation’s soil resources and assist growers in implementing these practices.
Modern agriculture now uses many management practices to preserve soil, including:
- Wind breaks, or planting trees in lines along crop fields to reduce wind erosion
- Contour farming, where crop rows are oriented perpendicular to the natural slope of the land to reduce water erosion
- Conservation tillage, which preserves crop residue on the surface of the fields and reduces the number of tillage operations — i.e., decreasing the number of times fields are cultivated to control weeds or plowed to disturb the soil.
Through the years, erosion-control methods have remained fundamentally important to cotton growers to protect the soil surface and manage the influence of water and wind.
The implementation of erosion-control methods is not only vital in maintaining agricultural viability, but is also in the best interests of cotton growers for financially sound economic development and future sustainability. The cost to replace soil functions and remedy off-site damage due to soil erosion has been estimated at $19 per ton of soil; however, the cost caused by productivity losses is even greater.
In agriculture production, the two guiding principles of soil preservation are: 1) minimize topsoil lost to erosion; and 2) improve soil health. Typically, both of these objectives are accomplished by increasing organic matter with winter, or cover crops, and minimizing the amount of tillage used on the soil.
To control weeds and diseases, traditionally producers were forced to remove all plant residues and weeds from the soil surface prior to planting, and then continue to cultivate the soil while the crop was growing to control late emerging weeds. While tilling does control some disease and weeds, it also loosens the soil. Today, thanks to seed treatment fungicides, herbicides and herbicide tolerant cotton, diseases and weeds can be controlled without tilling, allowing what is referred to as “no-till” and conservation tillage systems to be adopted.
Cotton has made great strides in reducing tillage and using winter, or cover crops. The number of acres of cotton produced with reduced-tillage systems has been increasing for the last 10 years. Today, according to a study done by Cotton Incorporated, two thirds of growers say they use some form of conservation tillage. In addition to preserving the soil, reducing tillage significantly reduces fuel use and its associated cost to growers.
In addition to carbon dioxide, water, and sunlight, all plants need mineral nutrients to grow. The primary nutrients needed are nitrogen, phosphorus, and potassium, though other secondary and micronutrients also play a role.
There are various methods to meet the fertility requirements of cotton, including the use of nitrogen-fixing cover crops, manures and soluble fertilizers. While alternative sources to soluble fertilizers may seem a sustainable solution, relying on them as a sole source of fertility can compromise yields or lead to the leaching and runoff of nutrients, given the level of uncertainty in the timing of the nutrient’s release to the plant.
Excess nitrogen is particularly prone to leaching and runoff and has become a water-quality concern for agriculture. For cotton producers, this is a fiber quality, financial, and an environmental issue. Excess nitrogen delays harvest, which generally reduces fiber quality. Additionally, nitrogen that leaves the field does not get used by the plant and therefore becomes, quite literally, money down the drain. Nitrogen contamination is a real concern, and highly advanced scientific calculations are used to practice the most accurate application of this element.
In addition to the tremendous progress that has been made in reducing tillage operations and encouraging organic matter increase in the soil, other modern technologies are also being used to detect and manage crop nutrient needs, including Global Positioning System (GPS) receivers, multi-spectral images and ground-based sensors to map out soil property variations in the field.
The use of these combined technologies is often referred to as “precision” or “site-specific” agricultural management — “precision ag” for short. Although basic soil properties, such as soil texture, cannot be changed outright, more accurate and advanced measurements lead to increased efficiency and productivity. Today, almost 73% of U.S. cotton growers indicate that they employ some type of precision technology in their management, with most reporting that they use it for the site-specific application of soil nutrients.
One precision ag approach is to use a ground-based sensor (such as an electrical conductivity, or EC, sensor) to map the variability present in soil type within the field.
The Veris Electrical Conductivity Sensor is a modern agricultural tool that is used to test soil electrical conductivity and soil texture, a factor which has a major impact on agricultural productivity, including water holding capacity, topsoil depth, and nitrogen-use efficiency. This is an effective way to map soil texture because smaller soil particles such as clay conduct more current than larger silt and sand particles. Soil EC measurements have been used since the early 1900s, and the process is now mobilized and aided by GPS.
As the cart containing the EC sensor is pulled through the field, one pair of coulter-electrodes injects a known voltage into the soil, while the other coulter-electrodes measure the drop in that voltage. The result is a detailed map of the soil texture variability that guides growers’ crop selection and zones. Soil samples are taken to analyze the nutrient need of each soil type present.
Once the map is created, it is loaded into the fertilizer applicator controller and then each soil type receives only the amount of nutrient that is required in that area of the field. This ensures over-application does not occur and that crop needs are exactly met.
The latest research effort is focusing on the use of sensors to detect the condition of the crop and vary the amount of nutrient applied in the fields in real time. This eliminates the time spent creating and loading maps, and will provide even greater precision by letting the plant signal its individual needs.
For cotton growers, maintaining soil resources has a big impact on how productive their land will be and how economical their products will be. But, beyond just being a fiscally sound idea, preserving soil quality is actually part of the U.S. federal environmental standards for soil management. Specifically, producers of “program crops,” such as cotton, must submit a Conservation Compliance Plan to the U.S. Government for approval.
The 1985 Food Security Act introduced the Conservation Compliance and Sodbuster programs to minimize soil erosion. In 1995, 90 million acres of cropped Highly Erodible Lands (HEL) in the U.S. were subject to conservation plans. Approved plans are mandatory for any grower wishing to participate in the crop program, and enforcement is strict. Thus, for many U.S. cotton producers, sustainable practices are not only a good idea but also the law.