Crops and Soils

Crops and Soils

Water Conservation on the High Plains

Crops and Soils

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Over 30 percent of the nation's cotton crop is produced in the Southern High Plains region of Texas, primarily as a monoculture crop under conventional tillage practices. Intensive tillage operations have been associated with accelerated decomposition of soil organic matter (SOM) and subsequent loss of carbon to the atmosphere as carbon dioxide.

Cultivated intensively since about 1940, irrigated agricultural production in the Texas High Plains has been at the expense of high water use that has exceeded the recharge potential of the Ogallala Aquifer in an already low-rainfall region. This practice has provided high economical profit but has come at the expense of soil exposure during winter fallow periods leading to increased wind soil erosion and significant reductions in SOM content. Today, regional challenges imposed by impending loss of the Ogallala Aquifer for irrigation, low fertility soils, high soil erosion, and stressful climatic conditions have prompted producers to reconsider their production options.

Researchers with Texas Tech University are aiming to assess the capacity of long-term, integrated crop and livestock systems in the Texas High Plains to enhance soil quality and functioning by evaluating soil microbial diversity and its link to soil processes including carbon sequestration and greenhouse gas fluxes.

While the potential to sequester carbon is strongly associated with water, this semi-arid region is positioned to play an important role because degraded soils whose SOM reserves have been depleted due to soil mismanagement hold the largest potential for soil organic carbon sequestration. In addition, many any acres are available in this vast landscape to contribute to sequestering carbon and with impending scarcity of water for irrigation, cropland is increasingly being returned to grass production. Perennial forages protect fragile soils, convert atmospheric carbon to SOM, and reduce water and fertilizer requirements compared with current cropping practices. Pastures have the potential to store significant amounts of soil organic carbon because their dense and deep root systems contribute to aggregate formation and the inclusion of carbon within, which is less susceptible to oxidation and eventual loss to the atmosphere. With this in mind, Texas Tech University researchers are exploring perennial forage systems that may provide an important means for carbon storage in the Texas High Plains where degradation of SOM exceeds the rate of stabilized carbon formation due to the production of low residues seen in intensively tilled cotton monoculture systems.

Integrating Legumes with Grass to Improve Forage-Livestock Systems

cattle grazing on a grass/legume mix

Taking a “systems research” approach, Texas Tech University researchers – backed by over a decade of producer-driven field studies -- have compared cotton monoculture to diversified crop/livestock systems. What they have found is that systems based on or inclusive of forages and livestock require less water for irrigation and livestock use than systems based entirely on row crops. Research continues at the Texas Tech New Deal Research Station with field trials pertaining to the integration of forages and livestock into a predominant row crop region as a means of reducing water extraction from the Ogallala Aquifer, building soil organic matter, stabilizing soil from wind erosion, and diversifying income.

Following severe drought in the Texas High Plains in 2o11 and 2012 and pasture recovery in 2013, grazing trials were restarted in 2014. A basic steer grazing trial was conducted from 2014-2016 comparing a grass-only system of Old World Bluestem (OWB) receiving nitrogen fertilizer to an alternative (and hypothetically more sustainable) grass/legume system for animal productivity and water use efficiency.

The study, funded under LS14-261 "Long-term Agroecosystems Research and Adoption in the Texas Southern High Plains -- Phase II," also included grazing some native and teff pastures, but were used in minor amounts and didn’t have an overall impact on the results.

The Performance of Cover Crops in Minimally Tilled Forage-based Grazing Systems

Cover crop trial plots

Forage-based livestock systems have proven to be economical and resource-efficient methods for High Plains agriculture. Long-term integrated crop/livestock systems help reduce overall water use and preserve soil health while maintaining marketable weight for animals that are proving profitable for farmers.

Integrating winter cover crops with summer forage crops could maximize land productivity and system profitability by improving water infiltration, stabilizing soils, and increasing additional potential income channels. However, adoption of cover crops has been slow because of concerns that cover crops withdraw soil water to the detriment of the summer crop, and they may not generate immediate economic benefits.

In a Southern SARE-funded Graduate Student Grant (GS15-152), “Evaluation of Winter Annual Cover Crops Under Multiple Residue Management: Impacts on land management, soil water depletion, and cash crop productivity,” Texas Tech University researchers investigated five cover crops species as potential complements to a warm-season beef-stocker grazing system. The impact of the project was two-fold: Stabilize the soil surface from excessive wind erosion and desiccation; and strengthen rural communities by ensuring the persistence of profitable agriculture in the region.

Soil Quality of Integrated Crop/Livestock Systems: Enhancing soil carbon sequestration and microbial diversity

Perennial grass and cotton field

Over 1/3rd of the cotton produced in the United States is grown in the Texas High Plains – a semi-arid region of the Texas Panhandle reliant for decades on water from the Ogallala Aquifer for irrigation. In addition to being a “thirsty” crop, cotton produces far less residue than other major crops and intensive tillage has been associated with accelerated decomposition of soil organic matter (SOM) and loss of carbon (C) to the atmosphere. In the Southern SARE-funded study (LS10-229), “Integrated Crop and Livestock Systems for Enhanced Soil Carbon Sequestration and Microbial Diversity in the Semi-arid Texas High Plains,” Texas Tech University researchers evaluated integrated crop/livestock systems for long-term soil quality by assessing microbial activity and soil carbon storage.

Cover Crops and Cotton in the Texas High Plains: SARE research summary, 2007-2009

Cotton and cover crops

The use of small grain cover crops, like rye and wheat, is important across the region in reducing soil erosion, managing weeds, and retaining soil nutrients and organic matter. In long-term integrated crop/livestock production systems research where cotton was grown in alternate rotation with small grains, research results showed that rye or wheat cover crops reduced the growth and lint yield of cotton compared to a monoculture cotton production system. In a Southern SARE-funded Graduate Student Grant (GS07-056), “Allelopathic Effects of Small Grain Cover Crops on Cotton Plant Growth and Yields,” Texas Tech University researchers investigated allelopathy as the possible cause of the observed suppression and to incorporate livestock grazing as a means of reducing the allelopathic effects on the cotton crop.

Water Use of Old World Bluestems in the Texas High Plains: SARE research summary, 2001-2003

Old World Bluestem

Old world bluestem grass species are widely grown in the Texas High Plains as they offer opportunities for livestock grazing. However, little information is available on their water-use efficiencies. In a Southern SARE-funded Graduate Student Grant (GS02-012), “Optimizing Water Use for Three Old World Bluestems in the Texas High Plains,” Texas Tech University researchers evaluated three old world bluestem species under dryland, and low, medium and high irrigation levels to determine water use efficiency, yield and nutritive value over a three-year period.

Published by the Southern Region of the Sustainable Agriculture Research and Education (SARE) program. Funded by the USDA National Institute of Food and Agriculture (NIFA), Southern SARE operates under cooperative agreements with the University of Georgia, Fort Valley State University, and the Kerr Center for Sustainable Agriculture to offer competitive grants to advance sustainable agriculture in America's Southern region. This material is based upon work that is supported by the National Institute of Food and Agriculture, U.S. Department of Agriculture, through Southern Sustainable Agriculture Research and Education, under sub-award numbers: LS97-082, LS02-131, LS08-202, LS10-229, LS11-238, LS14-261, LS17-286, GS02-012, GS07-056, GS15-152 and GS18-196. USDA is an equal opportunity employer and service provider. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture.