Advancing the Frontier of Legume Cover Crops and Building Integrated System Resilience in Semi-arid West Texas

View the project final report

Commodities

Practices

• Animal Production: grazing management
• Crop Production: cover crops
• Production Systems: integrated crop and livestock systems

Agronomic systems in the Southern Rolling Plains and Permian Basin regions of western Texas are dominate by cotton and winter wheat, followed by grain sorghum and non-alfalfa hay crops. The only legume crops of significant hectarage area alfalfa and peanuts, and the majority of production for each of these crops is contained in one or two counties. As cropping systems across this agricultural region are essentially void of legumes, synthetic fertilizer is the primary source of N for both cotton and wheat production. Overall, the lack of regionally adapted cover cropping practices contributes to greater inputs of synthetic N fertilizer, and also compromises potential opportunities to increase soil organic matter and soil health.

Adaptation and adoption of cover cropping practices has been extremely limited in semi-arid and arid western Texas. A common perception is that there is not enough precipitation in these regions to support a cover crop in addition to main crops. With increasing adoption of reduced tillage and conservation management practices, many growers are interested in the potential benefits of cover crops in their systems, but they lack regionally adapted information for precise and confident management of cover crops. A key benefit that would promote adoption is the potential for biological-fixed N to offset synthetic fertilizer inputs, and high-quality forage for integrated animal systems, making adaptation of legume cover crops an important focus for the region.

Legume cover crops have potential to offset N fertilizer inputs, provide a high-value supplemental forage source for the regional livestock industry, and improve the health of agricultural soils in the Southern Rolling Plains and Permian Basin of western Texas. The fallow period between harvesting wheat and planting cotton often exceeds eight months (July-February), and the fallow period in continuous wheat systems is generally July-October. Annual precipitation in this region has a bimodal distribution, with the majority of rainfall occurring in the late spring (April, May, June) and early fall (August, September, October). The fallow periods in wheat-cotton and wheat-wheat systems are a valuable opportunity to take advantage of fall precipitation and grow a cover-or dual-use crop.

We propose a research and extension effort, supported by on-farm projects and farmer cooperators, to investigate management options for legume cover crops in continuous wheat, wheat-cotton, and continuous cotton systems. Successful cover crop management can contribute surface residue, soil organic matter, and organic N, reducing fertilizer input costs. In addition to potential agronomic benefits and soil health, many cultivated legumes are high-protein forage crops that may offer dual-use potential in integrated animal systems. Texas is the leading state in goat, sheep, and cattle production for the U.S. All three of these livestock species are major regional enterprises in western Texas. Many cotton and wheat farmers also manage livestock on native rangeland or improved pasture, and wheat is often managed in a dual-use system to provide winter grazing, as well as a grain crop. The proposed cover crop practices could provide a high-quality forage source to supplement livestock production during critical periods.

Warm-season cover crop species of interest include: cowpea (Vigna unguiculate), mung bean (Vigna radiata), guar (Cyamopsis tetragonoloba), pigeon pea (Cajanus cajan), sunn hemp (Crotalaria juncea), and sesbania (Sesbania cannabina). Cool-season cover crops (in continuous cotton) include: red clover (Trifolium pratense), crimson clover (Trifolium incarnatum), hairy vetch (Vicia villosa), and Austrian winter pea (Pisum sativum). Growing these cover crop species in a biculture with common grass crops such as cereal rye (Secale cereale) in the winter and pearl millet (Pennisetum glaucum) in the summer may provide greater biomass, benefit to the soil, and potential foliage.

This research project will be conducted on four farms in the Southern Rolling Plains and Permian Basin regions of Texas. Across the four farms, each system (continuous cotton, continuous wheat, or wheat-cotton) will be represented at a minimum of two sites as follows: sites in McCulloch County and in Runnels County will have a continuous wheat system, sites in Tom Green County and Glasscock County will have a continuous cotton system, and the Tom Green County and Runnels County sites will also have a wheat-cotton system.

For all sites and systems, the experimental design will be a randomized complete block design with three replications. Cover crop treatments following wheat will be cowpea, mung bean, guar, sesbania, pigeon pea, and sunn hemp, as well as each species in a biculture with pearl millet. cover crop treatments in the continuous cotton system will be red clover, crimson clover, hairy vetch, and Austrian winter pea. Similarly, each species will be represented as a monoculture, and in a biculture with cereal rye. All trials will have a no-cover check, and a grass species only treatment (monoculture pearl millet following wheat, and monoculture rye following cotton). This will result in a total of 14 cover crop treatments in the systems following wheat, and 12 cover crop treatments in the system following cotton.