Location: Wind Erosion and Water Conservation Research
2024 Annual Report
Objectives
Objective 1: Determine changes in the factors associated with soil health across agroecosystems that are transitioning to dryland agriculture. Our aim is to provide new information on changes of soil organic matter that result in water conservation leading to better soil health-based management decisions.
Sub-objective 1A: Validate a method and categorize soil health across a range of management strategies by simultaneous measurements of key enzyme activities affecting soil biochemistry.
Sub-objective 1B: Examine effects of diverse management practices on microbial soil health and functions related to soil biogeochemical cycling and organic matter dynamics.
Sub-objective 1C: Define and measure soil degradation in various agroecosystems resulting from vegetation change and disturbance and how those factors affect soil crusting, surface erodibility, precipitation capture efficiency, and microbial transport on the fugitive dust.
Objective 2: Assess effects of climatic factors on water limited biotic and abiotic agroecosystem characteristics and processes affecting crop, water, and soil health management.
Sub-objective 2A: Use crop models to evaluate irrigation strategies that maximize water use efficiency and profits in US Southern High Plains cotton production.
Sub-objective 2B: Test whether nighttime CO2 enrichment or high frequency, short-term pulses of CO2 affect plant growth, leaf area or crop water use.
Sub-objective 2C: Define and inspect the theoretical dryland crop production limits achieved by soil management.
Sub-objective 2D: Model conservation agriculture (CA) effects on US Southern High Plains dryland cotton production.
Objective 3: Fundamental investigations of the quality and quantity of various sources of water for agricultural production in the Southern High Plains including groundwater, surface water, and rainwater.
Sub-objective 3A: Develop a method for assessing the value of rainfall, groundwater, and surface water for agricultural uses based upon water chemistry.
Sub-objective 3B: Assess the effects of salty irrigation water on soil surface crusting, erodibility, and soluble dust emissions.
Approach
The challenges that confront Southern High Plains (SHP) agricultural producers are associated with the rapid decline of the Ogallala Aquifer (OA) water table and intermittent rainfall that often is less than the amount required to sustain crop production. The water table’s decline combined with the region’s semi-arid climate is driving a transition from partially irrigated to almost entirely dryland agricultural production. In both marginally irrigated and dryland systems crop management will shift towards optimizing the remaining irrigation resources and adopting innovative crop and soil management approaches. The problems confronting SHP producers during this transition will require solutions that are specific to semi-arid agriculture, minimize risk, and support economic and environmental sustainability. In addition to identifying solutions appropriate for current climate conditions, management decisions will also depend on new knowledge of soil and crop interactions in an evolving CO2 environment. Thus, our project addresses climate factors associated with current highly variable SHP precipitation patterns and rising CO2 levels. Our research will quantify and provide a better understanding of the impacts of soil degradation, climate uncertainty, and changing water availability and quality in semi-arid agriculture. Specifically, we will: 1) develop and validate methods for soil health metrics and use them to evaluate management practices that promote water conservation; 2) account for climate variability when evaluating management practices that affect crop yield, water use and soil health; and 3) develop a method for evaluating water quality of the various sources of water used for production and increase understanding of soil salinity effects on surface crusting, erodibility, and hygroscopic dust emissions emanating from such surfaces. Our results will provide the knowledge needed to sustain agricultural production during the transition to dryland systems in the SHP and in other semi-arid production regions.
Progress Report
Our research project plan addresses field experiments conducted in the Southern Texas High Plains (STHP) region. This region is a “working laboratory” used to investigate best soil and water resource management practices for semi-arid dryland production and their applicability to other regions also experiencing a transition from deficit-irrigation to dryland management due to climate change. This transition has been exacerbated due to frequent droughts and record ambient temperatures experienced in the past decade. Our second year of research was successful in making significant progress on our three objectives to provide a better understanding of soil management practices, with emphasis on soil health, across diverse climatic regions including semi-arid, to evaluate current and future climate variability via modeling, and long-term effects of a deteriorating water quality on semi-arid agriculture. For Objective 1, we focused on determining factors and management associated with improved soil health and mitigation of wind erosion and degradation, and we made progress in our three Sub-objectives. For Sub-objective 1A, we worked in a multi-location project with 22 ARS collaborators and with 15 ARS locations across the USA to evaluate chemical, physical, and biological properties of the soils within a wide range of climatic zones, soil types, and diverse management comparisons (cover crops, manure, conservative tillage). We are working on data analysis to establish linkages between soil microbial community composition related to functions for soil organic dynamics, aggregation, and biogeochemical cycling across regions. Our results show that across the different locations evaluated in the nation, the strongest relationship among measured soil properties was between total EL-FAME (indicator of soil microbial community abundance) and soil organic carbon (SOC) compared to relationships observed between total EL-FAME and soil pH and clay content. Our region in Lubbock, Texas, was within the three locations (Lubbock, Texas; Florence, South Carolina; and Parlier, California) showing the lowest mean SOC and represented coarse textured soils under warm temperatures. Reduced tillage, cover cropping, and manure increased total EL-FAME and SOC, whereas crop diversity had no detectable effect. Abundance of bacterial fatty acid biomarkers had stronger statistical relationships to SOC than fungal biomarkers, but fungi exhibited more sensitivity to management than bacteria. For Sub-objective 1B, our team conducted soil samplings in 31 producer-sites transitioning from deficit-irrigation to dryland cropping systems, and from no-tillage and wheat winter cover cropping to cotton production that will be compared to reference sites in the Conservation Reserve Program and the common practice of irrigated tilled cotton monoculture. We also collected surface soil samples from several agroecosystems including soils without saline irrigation-water and soils with saline irrigation-water, which were cropped to alfalfa or a cotton maximum rotation. We also collected surface soil samples from several grazing histories in fire affected rangelands. For Sub-objective 1C, we investigated several rainfall simulator designs and purchased stainless steel to construct the simulator.
We made considerable progress on Objective 2 that addresses the effects of climatic factors on water in limited biotic and abiotic agroecosystem characteristics and processes affecting crop, water, and soil health management. In Sub-objective 2A we used several simulation models to evaluate how improvements on soil health properties would impact crop yield under dryland conditions and evaluated the effect of variable deficit-irrigation at different crop growth stages to improve grain yield and water use efficiency in grain sorghum. The scientist in charge of Sub-objective 2B dealing with “carbon dioxide (CO2)" enrichment on plant growth, leaf area and crop water use, retired and this research program has been shifted towards dryland cropping systems in Martin County and surrounding counties of the STHP. For Sub-objective 2C, defining the theoretical dryland crop production limits achieved by soil management practices, data from various databases were successfully identified, collated, and formatted for crop modeling. We did an analysis of dryland cotton lint yield as a function of historical rainfall at the county level for the STHP and used a simulation model to evaluate the water balance of two major soil series of the STHP indicating that the soil series Amarillo, predominant in this region, represents a higher risk for dryland production compared to the Pullman soil series. We also sampled these soil types used in dryland production and we completed the characterization of their soil physical and hydraulic properties including the calcic horizon known as caliche. These properties are summarized in the report titled “Soil Hydraulic Properties – Martin County”. These properties are important as they are used as input to several soil and crop models to quantify theoretical limits of crop production in semi-arid environments. For Sub-objective 2D, we have different efforts using models to quantify the effects of conservation agriculture (CA) on STHP dryland cotton production. Our first goal (G2D.1) is using pedotransfer functions and the CROPGRO-Cotton model (also known as the Generic Crop Growth Model) to estimate the effects of varying soil organic carbon levels on the soil water retention properties of the two benchmark STHP soils and simulate the related effects on cotton lint yield. Our second goal (G2D.2) was to use models considering crop development, soil nutrients and soil water balance including the CROPGRO-Cotton (Generic crop growth model) and CERES-Wheat (Crop Environment Resource Synthesis model) to estimate the degree to which winter wheat cover crops compete with STHP dryland cotton for soil moisture and evaluate management strategies that might minimize this competition. Our studies in Martin County Texas showed that in a dry year, a rye cover crop planted at low density in 30-60 inch spacing will only use 0.5-inches of water during the winter compared to the evaporation of soil water from a bare soil in an adjacent field under conventional tillage. While the cotton emerged in both fields of our study, the cotton failed in both fields due to lack of rain after June 4th and thus we were not able to evaluate lint yield differences between fields. This is an ongoing experiment in production fields, and we will continue to evaluate the effect of cover crops. Our emphasis of research on dryland cropping systems was due to an interest by stakeholders that prompted our redirection. As a result, a large dryland cropping system project collaborating with stakeholders is in place and we are currently recruiting a scientist to lead this effort. This dryland cropping systems project consists of working on producer’s fields and the main objective is to address their research needs which are mainly related to crop covers, crop rotations, and tillage operations. To date we have the collaboration of 36 producers and their combined production fields cover more than 100,000 acres. In selected fields we have installed weather stations, rain gauges and sensors to measure soil water content. Our long-term goal is to establish a relation between rainfall and cotton lint yield as a function of the different management systems in the producer’s fields. Unfortunately, severe droughts in 2022 and 2023 failed to provide adequate moisture to harvest a cotton crop. This is an ongoing project that has the support of cotton and sorghum commodity groups, and of their respective stakeholders, and our facility in Big Spring, Texas, will serve as a site that will be used for small plot demonstrations and to disseminate our research findings.
For Objective 3, Sub-objective 3A, ARS scientists from Lubbock, Texas, made considerable progress on sampling of groundwater, surface water, and rainwater in the High Plains and in the Rolling Plains of Texas. As of June 2024, we collected a total of 280 groundwater samples of the Ogallala aquifer, 523 rainwater samples on the high plains of the Llano Estacado, and 928 surface water samples within the upper Brazos watershed. All these samples were analyzed to determine the concentration of dissolved solids and oxygen levels. Additionally, rainfall samples were collected from the Beaufort rain gauges at the Big Spring Field Station and limited sampling of surface water was accomplished when the streams contained flowing water. Within Sub-objective 3B, with the goal to assess the effects of salty irrigation-water on soil surface crusting, erodibility, and soluble dust emissions, we made progress on laboratory testing of the three soil textures and 3 levels of salinity and sodicity under relative humidities of less than 40% and relative humidities of more than 70%. We also tested field sites irrigated with saline irrigation water and adjacent unirrigated soils for dust emissions using a Portable In-Situ Wind Erosion Laboratory.
Accomplishments
1. Quantification of soluble inhalable dust from saline and sodic soils. As the Ogallala Aquifer is depleted, rebounding saline water from the red beds below has caused the water to become increasingly saline. As this water is used to irrigate area soils, researchers need to know the effect of surface salt accumulation on soluble inhalable dust production from these fields. Inhalable dust adversely affects human health and may also be deposited on adjacent lands and watersheds without salinity problems or into freshwater bodies. In order to investigate the effects that irrigation with saline water will have on soil erodibility and dust emissions including soluble dust, an ARS scientist at Lubbock, Texas, along with collaborators from The University of California at Berkeley and Temple University utilized a laboratory wind tunnel equipped with a total dust recovery system at the ARS Big Spring field site. Soils of three distinct textures ranging from loamy sand to clay loam were packed into stainless steel soil trays and treated with water of varying salinities and sodicities. The treated soil trays were oven dried, allowed to equilibrate to either high (greater than 60%) or low (less than 40%) relative humidities and were tested for threshold velocities and then transferred to the dust recovery wind tunnel for testing at a centerline velocity of 12 meters per second and coarse silica abrader. The team found that salinity armored the surface crust, thus increasing the threshold velocity required to initiate saltation and also resulted in reduced erodibility and dust production. Increasing salinity did however increase the soluble portion of dust. This demonstrates that as long as the salts in the irrigation water are not toxic, salinization of irrigated soils provides little concern for human health from emitted dust.
2. Soil biological health responds rapidly to residue additions or minimized soil disturbance in low organic matter soils. Maintaining soil health and sustainable crop production is challenged by climate variability and wind erosion in semi-arid regions. To understand the initial effects of the transition of tilled cotton systems to no-tillage with winter wheat as a cover crop, an ARS scientist from Lubbock, Texas, led an effort with scientists from New Mexico State University and Texas Tech University to conduct a soil health assessment on 18 commercial grower sites from 2019 to 2022 in the Southern Texas High Plains. After two years, compared to tilled systems, no-till systems had significant increases in ester-linked fatty acid methyl ester bacterial and saprophytic and arbuscular mycorrhizal fungal markers, enzyme activities of nutrient cycling, and various soil organic matter pools, under both center-pivot irrigation and dryland. Similar increases were also observed in two dryland sites sampled before and up to two years after transition to no-till. The study demonstrates the potential of no-tillage and cover crops to improve soil health in cotton production in semi-arid regions, and a framework for a soil health assessment that links different soil health indicators with functions related to soil organic matter, soil water, and biogeochemical cycling.
3. Investigation of upper Brazos River and tributaries. The number one agricultural product in the state of Texas is “beef cattle.” To raise cattle requires two critical resources – grass and water. In the Rolling Plains to the east of Lubbock, there are numerous cattle ranches that benefit from spring-fed streams discharging from the Ogallala aquifer that provide natural watering places for cattle. The Ogallala aquifer is also a key source of irrigation water for the vast acreage of cropland on the Texas High Plains. Thus, there are two different and both important agricultural systems in the Texas High Plains competing for the same underground water supply. Scientists from ARS in Lubbock, Texas, collected and analyzed numerous water samples at multiple sites on the Double Mountain Fork and Salt Fork of the upper Brazos River. The focus of the study was on the spring-fed streams to the east of the Texas High Plains and how they were affected by seasonal pumping on the Texas High Plains. The research showed that stream flow tends to follow a well-defined seasonal pattern. For example, the spring-fed streams of the upper Brazos flow more continuously during the winter when spring discharge is at a peak. However, during the summer growing season, when farmers on the High Plains are irrigating crops, this research suggests that spring discharge is reduced along the eastern edge of the Texas High Plains and many streams in the ranch lands of the Rolling Plains dry out, leaving little water for livestock in the summer when water is needed most. These research findings will raise awareness of coordination needed within different farmer activities in this region to conserve water from the Ogallala aquifer.
4. Historical wells on the Llano Estacado. Scientists from ARS in Lubbock, Texas, addressed historical changes in wells on the Llano Estacado since 1914. An early investigation of the Ogallala Aquifer, conducted in 1914, provides important clues regarding groundwater conditions prior to intensive pumping of the Aquifer for irrigation. By combining these early observations with later measurements obtained by federal scientists, state agencies, and local water districts, it was possible to obtain long, detailed, and nearly continuous records of a receding water table at various locations across the Llano Estacado. This research is critical to provide a more precise definition of the rate of depletion of the Ogallala Aquifer under a changing climate.
5. Increasing our understanding of the sustainability of dryland cropping systems. Dryland cropping systems in the Southern Texas High Plains (STHP) face several challenges under frequent droughts. ARS scientists from Lubbock, Texas, established a collaboration with 36 producers in Martin and surrounding counties in the STHP that covers more than 100,000 acres in dryland production. A network of 40 weather stations and 43 rain gauges were installed in several fields to collect data on the effect of management of inputs on cotton lint yield. These inputs include, crop rotations, ground cover, and tillage operations. Emphasis is given to evaluate profitability and risk assessment on how the cropping system interacts to produce the crop of interest, mainly cotton and sorghum. As part of this study, a portable and disposable weather station that cost about $200 per unit is being used. Results showed that these weather stations are suitable for hourly and daily measurements of air temperature and humidity, wind speed and rainfall. The measurement of solar radiation is more complicated and will require extrapolation from measurements made with more accurate sensors. The measurement of rainfall, as expected is related to the intensity of the rainfall event and we are exploring the used of doppler technology as a means of getting accurate measurements for rainfall events more than 1-inch. The overall effort led to the development of an “AgroClimate Dashboard” with day-to-day weather information and heat units as it relates to crop management that will assist dryland producers in the STHP to make their management decisions.
Review Publications
Burger, W., Van Pelt, R.S., Grandstaff, D., Wang, G., Sankey, T.T., Li, J., Sankey, J.B., Ravi, S. 2023. Tracing spatial and temporal dynamics of post-fire sediment transport and redistribution using multiple rare earth element tracers: Insights into grassland management. Earth Surface Processes and Landforms. 128(11). https://doi.org/10.1029/2023JF007274.
Lascano, R.J., Goebel, T.S., Gitz, D.C., Stout, J.E. 2024. Evaluation of a wireless solar powered personal weather station. Agricultural Sciences. 15(1). https://doi.org/10.4236/as.2024.151003.
Acosta Martinez, V., Cotton, J.E., Slaughter, L., Ghimire, R., Roper III, W.R. 2023. Soil health assessment to evaluate conservation practices in semi-arid cotton systems at producer sites scale. Agronomy Journal. 7(3). https://doi.org/10.3390/soilsystems7030072.
Ogunleye, A., Thapa, V.R., Aryal, D., Acosta Martinez, V., Ghimire, R. 2023. Response of soil microbial communities to different cover crops options for semi-arid regions. Agricultural and Environmental Letters. 8(2). https://doi.org/10.1002/ael2.20118.