Objective 1: Evaluate management practices that prevent soil degradation by soil erosion in semiarid cropping and rangeland systems. • Sub-objective 1A: Investigate soil redistribution and dust emissions from agro-ecosystems including rangelands and native plant communities under the stressors resulting from climate change. • Sub-objective 1B: Evaluate management systems in terms of multi-decadal erosion rates estimated from radioisotope inventories. Objective 2: Evaluation of management practices to increase soil water availability and contribute to higher water and nutrient use efficiencies. • Sub-objective 2A: Partitioning of evapotranspiration to water evaporation from soil and crop surfaces for dryland and irrigated cropping systems across different N fertilizer management strategies. • Sub-objective 2B: Investigate changes in groundwater quantity and quality that may affect cropland production in semiarid and arid regions. Objective 3: Development of management practices that contribute to maintaining microbial diversity and functions needed to improve soil health, ensure ecosystem sustainability, and maintain crop productivity under a changing climate. • Sub-objective 3A: Compare the effects of different management practices in semiarid regions on soil health indicators including the microbial community size, diversity and functions. • Sub-objective 3B: Characterize the effects of climatic events on soil health and the effects of future climate change (CO2, temperature and rainfall) on agro-ecosystems by measuring root biomass, soil microbial diversity and soil organic matter pools.
Sustainable agriculture, with an emphasis on the conservation of natural resources, is a challenge in the semiarid climate of the Southern High Plains (SHP). Of concern are developing cropping systems that cope with climate change, depletion of aquifers used for irrigation, and growing seasons characterized by frequent droughts and erratic rainfall. Record-breaking drought in 2011 and record-breaking rainfall amounts in 2015 forced agricultural producers to seek economically viable cropping systems, while struggling to adapt to extreme weather events. Climate change is expected to impose general global challenges but, clearly, solutions to these problems will be site specific. For example, one of our research goals is to examine the effects of elevated atmospheric CO2 concentration on soil biodiversity and carbon sequestration in soils of the SHP. Given environmental constraints of the SHP, few crops other than cotton are viable and management choices in the face of unpredictable extreme weather events are difficult. With the ongoing decline in irrigated area and a return to more dryland farming dictate our research emphasis on rainfall capture and careful management of other limiting input factors. Our overall goal is to develop sustainable agricultural systems that optimize productivity, conserve water, control soil erosion and improve soil quality for agricultural production in semiarid regions in a changing climate. Needed are cropping systems that incorporate management practices that reduce soil degradation by controlling soil erosion while increasing soil health, rainfall capture and improve economic productivity with limited water.
During the first year of our project plan (2016–2017), necessary arrangements, including site selection, were made for all experiments of our objectives. For example, field sampling equipment was constructed and installations were made at the Sevilleta National Wildlife Reserve in central New Mexico for Objective 1 related to the evaluation of management practices that prevent soil degradation by reducing wind and water erosion in semiarid cropping and rangeland systems. These installations will provide year-round sampling of aeolian sediments. We currently have permits to sample a state park near Monahans, Texas and are investigating access to sites in southeastern New Mexico. The event-wise sampling will require sites that are within 200 miles of Big Spring, Texas. Four reference sites were sampled. Sampling equipment was constructed and tested for use in semi-remote (no tractor access) locations. Sites for possible sampling are being identified and we are seeking permission from the prospective land-owners to sample. For study 1 of Objective 2, development of a graphical user interface (GUI) for the spatial interpretation of weather data was only partially initiated then halted due to lack of support from the vacant position. Data were downloaded from the USDA Natural Resources Conservation Service – Soil Survey for study 2. Elevation data and weather data have also been downloaded and organized as input to the model. Grid scale data from Texas A&M University has been formatted to fit into the model however the GUI is needed to proceed. Study 3 had been delayed because the collection of data at the landscape scale has not been initiated. Study 4 had good progress as two rain events have been investigated by taking both soil cores as well as plant tissue samples to determine if the cotton plant was using rain water and if so at what depth in the soil profile the water originated. For Subobjective 2b, permission was obtained from landowners in five counties to access 21 wells at sites located on the Southern High Plains and sampling has begun. Samples are collected; weather permitting, from all sites every two weeks. Depth to water measurements are obtained using a Solinst "electric line" water level meter whenever the wells are not operating. When the wells are in operation, water samples are obtained from faucets on the well. If a well is off then pencil bailers are used to obtain water samples. Water samples are then filtered through a 0.2 mm filter and tested for pH and electrical conductivity. A portion of each water sample is stored for future analyses. We initiated different soil samplings and setting up CO2 chambers in Objective 3 for the development of management practices that maintain microbial diversity and functions essential to soil health, ecosystem sustainability, and crop productivity under a changing climate. We conducted a soil sampling in long-term research plots comparing different cover crops and conservation tillage practices for semiarid, sandy soils, as this information was not available for this region. We also continue our samplings in producers’ fields initiated in 2013 to represent an evaluation of soil health after the extreme drought experienced in 2011-12. We successfully established the experiment with elevated CO2 chambers in the field on Runner-type cultivar of peanut. Soil samplings from this new experiment and experiments conducted in previous years will provide a comprehensive overview of the effects of elevated CO2 in soil microbial communities and functions.
1. Well sampling preliminary results. The Ogallala Aquifer is among the largest aquifers in the world and it is being depleted at a rapid rate. Along with the loss of the stored volume of water, there is also some indication that water quality may be changing and these changes could influence irrigated crop production. ARS scientists in Lubbock, Texas, are investigating possible changes of groundwater quality. In the early stages of this project, water quality was sampled every two weeks at several locations across the Texas High Plains. Preliminary results show: while wells are actively pumped, the water quality can change, however, it is not always decreasing in quality. The goal is to continue to study both long-term and seasonal variations in groundwater quality at locations across the Southern High Plains.
2. Winter cover crops and crop rotations promote soil microorganisms. Continuous cotton is a standard crop practice on the Southern High Plains, however this monoculture may not be the best for soil microorganisms, which play important roles in healthy soils. ARS scientists in Lubbock, Texas evaluated the impacts of alternative cropping systems compared to intensively-tilled continuous cotton in a low organic matter sandy soil. Phase I showed improved soil health within 5 years when higher plant residue are returned to the soil by rotating cotton with grain sorghum with and without a rye winter cover crop. Phase II addressed what happens to the soil microbial component once the management is changed back to grow cotton one out of three years. Soil fungi declined with the reintroduction of cotton and increased tillage. Rotations with winter cover crops had still higher microbial biomass and enzyme activities compared to continuous cotton. This study demonstrates the vulnerability of microbial communities in sandy soils in a semiarid to cropping systems that do not retain crop residues after harvesting.
Lanigan, D., Stout, J.E., Anderson, W. 2016. Atmospheric stability and diurnal patterns of aeolian saltation on the Llano Estacado. Aeolian Research. 21:131-137. doi:10.1016/j.aeolia.2016.04.001.
Acosta Martinez, V., Cotton, J.E. 2017. Lasting effects of soil health improvements with management changes in cotton-based cropping systems in a sandy soil. Biology and Fertility of Soils. 53(4):1-14. doi:10.1007/s00374-017-1192-2.
Sweeney, M.R., Zlotnik, V.A., Joeckel, M., Stout, J.E. 2016. Geomorphic and hydrologic controls of dust emissions during drought from Yellow Lake playa, West Texas, USA. Journal of Arid Environments. 133:37-46. doi:10.1016/j.jaridenv.2016.05.007.
Li, C., Fultz, L., Kucera, J.M., Acosta Martinez, V., Horita, J., Strauss, R., Zak, J., Calderon, F., Weindorf, D. 2017. Soil carbon sequestration potential in semi-arid grasslands in the conservation reserve program. Geoderma. 297:80-90.