- Agronomic: grass (misc. annual), medics/alfalfa, rye, vetches, wheat
- Crop Production: cover crops, fallow, irrigation, no-till, strip tillage
- Soil Management: soil quality/health
The imminent depletion of the Ogallala Aquifer demands innovative cropping alternatives to prevent dramatic losses of income when water levels are insufficient for irrigated row-crop production in the Southern High Plains. Integrating winter cover crops with summer crops maximizes land productivity and system profitability by improving water infiltration, stabilizing soils, and increasing potential income channels. Even though the benefits of cover crops for nutrient retention and erosion control are well recognized, adoption has been slow because of concerns that cover crops withdraw soil water to the detriment of the summer crop. This small-plot experiment tested the interacting effects of irrigation and tillage management techniques with five cover-crop species on soil water depletion and productivity of the cover and subsequent summer forage crop. The overall aim was to compare the success of residue management schemes in reducing irrigation needs for the water-limited Southern High Plains region. The overall recommendation that culminated from this work is that West Texas producers should plant rye as a cover crop. Dryland rye produces modest yield, even in a dry year, but light irrigation should be used to ensure good forage yield if the winter grazing is desired. The impact of this project is two-fold: strengthen rural communities by ensuring the persistence of profitable agriculture in the region, and stabilizing the soil surface from excessive wind erosion and desiccation.
Statement of Problem, Rationale and Justification
The purpose of this project was to investigate five cover crop species as potential complements to a warm-season beef-stocker grazing system. Historically, producers in the Texas High Plains generate income from beef cattle, cotton, and grain crops. Agriculture in the region relies on supplemental irrigation from the Ogallala Aquifer, an aquifer stretching across eight states and underlying more than 170,000 square miles (HPWD, 2014). Unfortunately, the vitality of the Ogallala is threatened since extraction rates of around 12 inches per year greatly exceed the annual estimated recharge rate of 0.5 inch (HPWD, 2014). With strong gusting winds and limited precipitation (18 inches annually), it is not surprising that many soils are prone to severe erosion, especially during the winter months when most annual croplands are fallow. Integrating winter cover crops will allow producers to take advantage of otherwise fallow land by managing cover crop residue to stabilize and enhance soil resources.
Forage-based livestock systems have proven to be economical and resource-efficient options for the High Plains (Allen et al., 2012). Cover crops are just one possible alternative management strategy to better utilize depleting water supplies from the Ogallala Aquifer and sustain on-farm resources. Allen et al. (2012) reported moderate success in grazing winter cereals as part of an integrated crop-livestock system. Most cereals mature rapidly in the spring, making them difficult to manage as they tie up nutrients and deplete soil water if not properly managed. This trial compared five winter-annual forages harvested under four combinations of irrigation and tillage treatment.
While traditional cattle ranches once dominated Texas agriculture, the industry continually evolves to adapt to new technology and environmental conditions (Kelton, 2007). Fences, wells, and windmills were once considered novel ideas that revolutionized agriculture in the High Plains. Row crop production is now most prevalent, but the imminent disappearance of aquifer resources should encourage producers to seek innovative alternatives to safeguard against dramatic losses of income when pumping capacity is insufficient for irrigated crops. Forage-livestock systems are a viable option for the future of West Texas agriculture, and the inclusion of cover crops managed as surface residue could preserve the economic viability of High Plains agriculture.
The impact of this project is two-fold: strengthen rural communities by ensuring the persistence of agriculture in the region, and stabilizing the soil surface from excessive wind erosion and desiccation. Cattle production is crucial to the region’s agriculture community (Butler and Muir, 2012). This research can help rejuvenate the region’s ranching heritage but do so by promoting forage-based livestock systems that are potentially more productive and profitable than traditional rangelands, and more water-frugal when integrated into a row-crop dominant ecosystem. Texas plays a major role in agriculture, especially in the beef industry since the state had 12.4% of the nation’s cattle in 2014 (NCBA, 2015). Without the adoption of more sustainable, resource-efficient management practices, agriculture cannot persist on the Southern High Plains.
Project Relevance to Sustainable Agriculture
The region’s climate presents challenges for agricultural producers. Precipitation is limited (15-20 inches annually, 22% of evaporative demand). Gusting winds and intense rainfall accompany storms, which provide most of the region’s precipitation, but erode exposed soils. High rates of evaporation quickly diminish already limited soil water resources in this semi-arid climate.
Environmental and economic advantages of cover crops are widely reported (Clark, 2012; NRCS-Texas, 2013; Idowu and Grover, 2014). Reducing soil erosion, increasing water infiltration, and supplying organic matter and nutrients to successive crops are the most relevant benefits for the High Plains. Grass species are more adept in scavenging nutrients and produce larger volumes of residue that break down slowly, compared with broadleaf-type species (Clark, 2012). Legumes fix atmospheric nitrogen (N), some of which carries over to subsequent crops, and the legume residue has a lower carbon-to-N ratio, allowing N to be released more readily than from grasses (Clark, 2012). Although less common, the biofumigation and biodrilling potentials of brassica species are an attractive option for winter-annual ground covers (Clark, 2012). The five species selected for this trial were developed for or found to be adaptable to the Southern High Plains. The target uses of these cover crops serve the dual roles of stabilization and enhancement of soil plus their use as a grazeable spring forage. Teff response is evaluated as a summer-annual forage and as an indicator species for responses by other summer cash crops.
Even though the benefits of cover crops are well recognized, adoption has been minimal. Erratic weather patterns and unpredictable market conditions make producers hesitant to plant crops that may not generate immediate economic benefits (Butler and Muir, 2012; Idowu and Grover, 2014). There is a dogma among landholders in the Southern High Plains that cover crops extract too much water from the soil profile, hindering productivity of the successive cash crop. Managing the cover as a residue that improves soil productivity for longer-term benefits can help negate concerns.
Idowu and Grover (2014) proposed utilizing no- or minimal-tillage practices with cover crops to minimize concerns. Minimizing soil disturbance and maintaining ground coverage can improve soil health and promote water infiltration while reducing evaporative losses. Unger and Vigil (1998) reported that significant declines in soil water storage reduced subsequent crop productivity, but acknowledged that water use by cover crops could be counterbalanced by benefits of no- or reduced-tillage systems. This research investigated the interacting effects of irrigation and tillage with five cover crops on soil water depletion and productivity of the cover and subsequent forage crop to identify the most successful cover crop practices in the drought-prone Southern High Plains.
The research will provide knowledge to spark future development of a more sustainable agricultural landscape in West Texas. Producers will receive information that facilitates their decision-making on how to fit cover crops into their crop and livestock systems.
Allen, V.G., C.P. Brown, R. Kellison, P. Green, C.J. Zilverberg, P. Johnson, J. Weinheimer, T. Wheeler, E. Segarra, V. Acosta-Martinez, T.M. Zobeck, and J.C. Conkwright. 2012. Integrating cotton and beef production in the Texas Southern High Plains: I. Water use and measures of productivity. Agronomy Journal 104:1625-1642.
Butler, T.J., and J.P. Muir. 2012. Perspective on forage legume systems for the tallgrass and mixed-grass prairies of the Southern Great Plains of Texas and Oklahoma. Crop Science 52:1971-1979.
Clark, A. (Ed.). 2007. Managing cover crops profitability, 3rd Edition. Sustainable Agriculture Network, Beltsville, MD.
HPWD. 2014. Water planning. High Plains Underground Water District. http://www.hpwd.org/water-planning/ (online, accessed 5 July 2014).
Idowu, J., and K. Grover. 2014. Principles of cover cropping for arid and semi-arid farming systems. Guide A-150. New Mexico State University Cooperative Extension Service. Las Cruces, NM.
Kelton, E. 2006-2007. Ranching in a changing land. In: Texas Almanac- The Source For All Things Texan Since 1857. http://www.texasalmanac.com/topics/agriculture/ranching-changing-land (online, accessed 11 Feb 2015).
Li, Y., V.G. Allen, J. Chen, F. Hou, C.P. Brown, and P. Green. 2013. Allelopathic influence of a wheat or rye cover crop on growth and yield of no-till cotton. Agronomy Journal 105:1581-1587.
NCBA. 2015. Beef industry statistics. National Cattlemen’s Beef Association. http://www.beefusa.org/beefindustrystatistics.aspx (accessed 11 Feb 2015).
NRCS-Texas. 2013. Winter cover crop species adapted to North-Central West Texas and Southwestern Oklahoma. Plant Materials Technical Note No: TX-PM-13-01. USDA, Knox City, TX.
Unger, P.W. and M.F. Vigil. 1998. Cover crop effects on soil water relationships. Journal of Soil and Water Conservation 53:200-207.
Project objectives:div style="margin-left:1em;">
- Compare persistence and productivity of five winter cover crop species under four water and tillage treatment combinations for ability to conserve soil water and promote growth of summer forage.
- Compare residual effects of cover crops and winter management strategies on the productivity and nutrient status of a subsequent no-till, irrigated summer teff hay crop. Potential effects include nitrogen supplied by legumes, allelopathy from wheat and rye, and depletion of ground water resources.
- Compile research conclusions into fact sheets readily available to producers through the TAWC outreach program and to be demonstrated at Texas Tech Research Field Days.