Submitted to: Trade Journal Publication
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/16/2005
Publication Date: 3/1/2008
Citation: Allen, V., Brown, C.P., Segarra, E., Green, C.J., Wheeler, T.A., Acosta Martinez, V., Zobeck, T.M. 2008. In search of sustainable agricultural systems for the Llano Estacado of the U.S. Southern High Plains. Agriculture, Ecosystems, & Environment. 124:3-12.
Interpretive Summary: Crop production on the Llano Estacado of the Texas High Plains depends on irrigating with water pumped from the underground Ogallala aquifer at rates that have far exceeded the amount going back to groundwater for many years. This region produces over 20% of the U.S. cotton crop production. The common practice is to grow cotton continuously, which is economically risky and contributes to wind erosion and uses much ground water. Although there are many cattle found in this region, not many people raise livestock and grow crops at the same time. This type of farming is called an integrated crop-livestock system. Integrated crop-livestock systems could improve use of soil nutrients, reduce soil erosion, improve how we use the water, and interrupt pests growth. In this study, we compared two type of farming: 1) a system of continuously growing only cotton, typical of the region; and 2) a farm that included a cotton and forage rotation, and a perennial pasture system. Angus cross stocker beef steers (initial body weight 249 kg) grazed the perennial warm-season grass WW-B. Dahl in sequence with rye and wheat from January to mid-July when they were sent to the feedlot for finishing. Grass seeds were harvested from bluestem in October. Cotton in the alternative system is grown in a two-paddock rotation with the wheat and rye. Cotton was harvested from both systems in October. At the end of five years, the alternative system reduced needs for irrigation by 23% and for nitrogen fertilizer by 40% compared with the conventional cotton-only system. Fewer chemical inputs including pesticides were required by the alternative system. Soil with perennial grass pasture was higher in soil organic matter, had more stable clods that were more difficult to break apart in water, and more soil microbes than soil where continuous cotton was grown. Systems that depend less on irrigation and use fewer non-renewable resources and fewer chemicals that take energy to produce appear possible, but further improvements are required to ensure.
Technical Abstract: Crop production on the Llano Estacado of the Texas High Plains uses precipitation and supplemental irrigation with water pumped from the Ogallala aquifer at rates that have far exceeded recharge for many years. Over 20% of the U.S. cotton (Gossypium hirsutum) crop is produced in this once vast grassland. Most of this cotton is produced in monoculture systems that are economically risky and contribute to wind induced erosion and depletion of ground water resources. Although large numbers of cattle are found in this region, little integration of livestock and crop production exists. Integrated crop-livestock systems could improve nutrient cycling, reduce soil erosion, improve water management, interrupt pest cycles, and spread economic risk through diversification. Two whole-farm scale systems compared 1) a cotton monoculture typical of the region; and 2) an alternative integrated system that included cotton, forage, and Angus cross stocker beef steers (initial body weight 249 kg). Steers grazed the perennial warm-season grass WW-B. Dahl (Bothriochloa bladhii) in sequence with rye (Secale cereale) and wheat (Triticum aestivum) from January to mid-July when they were sent to the feedyard for finishing. Grass seed were harvested from bluestem in October. Cotton in the alternative system is grown in a two-paddock rotation with the wheat and rye. Cotton was harvested from both systems in October. At the end of five years, the alternative system reduced needs for supplemental irrigation by 23 percent and for nitrogen fertilizer by 40 percent compared with the conventional cotton monoculture. Fewer chemical inputs including pesticides were required by the alternative system. Soil with perennial grass pasture was lower in predicted soil erosion and was higher in soil organic carbon, aggregate stability, and microbial biomass than soil where continuous cotton was grown. Profitability was greater for the alternative system until cotton lint yields reached about 1500 kg ha-1 for the continuous cotton system and differences between the systems became larger as depth to ground water increased. Systems that are less dependent on supplemental irrigation and less consumptive of non-renewable resources and energy-dependent chemical inputs appear possible, but further improvements are required to ensure sustainability of agricultural systems for the future in the Texas High Plains.