1a. Objectives (from AD-416):
The long-term objective of this project is to develop environmentally viable practices, guidelines, and cropping systems that farmers and land managers can apply to control water and wind erosion, enhance soil quality and sustain productivity. Specifically, over the next three years we will focus on the following two objectives. Objective 1: Determine temporal variations of soil characteristics in native grasslands, Conservation Reserve Program (CRP) lands, and croplands, and contribute to multi-location ARS GRACEnet project. Subobjective 1A: Characterize physical, chemical, and biological properties of soils as affected by alternative management and land uses for cotton production. Subobjective 1B: Integrate physical, chemical, and biological properties for adaptation of the Precision Agricultural Landscape Modelling System (PALMS) model. Objective 2: Quantify the effects and interactions of wind and water erosion on agricultural landscapes, including physical, chemical, and biological properties of eroded sediments. Subobjective 2A: Quantify wind and water erosion on eroding landscapes, and characterize physical, chemical, and biological properties of the eroded sediments. Subobjective 2B: Develop improved methods and instrumentation for assessing erosion rates and processes, and quantify abrasion damage and recovery of cotton seedlings from wind-blown sand.
1b. Approach (from AD-416):
Information will be provided on how soil quality and functioning are affected under alternative management, which includes conversion of continuous cotton to the Conservation Reserve Program (CRP), perennial pastures with warm-season grasses for livestock cotton production systems or cotton rotations with other crops. Management impacts will be evaluated based on several soil quality and functional attributes such as soil water infiltration, aggregate stability, carbon sequestration, soil microbial community structure and diversity, and enzymes involved in nutrient cycling. C sequestration assessments will contribute to the ARS GRACEnet (Greenhouse Gas Reduction through Agricultural Carbon Enhancement network) project. This project will also quantify interactions of wind and water erosion on agricultural landscapes and will determine physical, chemical, and biological properties of eroded sediments. Enzyme activities, microbial community composition, and chemical characteristics of fine particle dust from agricultural soils will be used to identify the sources and origin of dust. The time fractions equivalent method for determining the threshold condition for soil movement in the field under natural wind and soil conditions will be evaluated and further refined. Morphological traits that promote resistance to injury caused by abrasion of plants by sand particles during wind storms will be identified and the most resistant varieties of selected common crops will be determined for enhancing crop productivity in this region.
3. Progress Report:
During the first year of this project, the region experienced a historical drought comparable to the dust bowl of the 1930s. This has delayed two of the three studies related to investigations of the physical, chemical, and biological properties of soils as affected by alternative management and land uses for cotton production under dryland and irrigated cropping systems. We conducted soil samplings in July 2011 to specifically characterize the effects of this drought on soil organic matter and microbial community diversity by evaluating a sandy soil (67% sand content) and a high clay content soil (38% clay) under different management practices. The integration of livestock and cotton cropping into the whole farming system as an alternative for cotton monoculture practice, had some progress because samplings were initiated in 2010 before the drought began. Information on the relationships between soil bacterial community structures and the quantity and quality of soil organic carbon within different aggregate size-fractions of soil was elucidated. Our findings will expand knowledge on how C is sequestered in these semiarid soils. The PALMS landscape model has been calibrated to two soil series of the Texas High Plains: Pullman and Amarillo. The calibration was done by comparing measured and calculated values of soil water content for several soil depths and for two growing seasons for the two soil series. This comparison indicated necessary adjustments to input parameters related to soil physical properties. We made significant progress on the evaluation of the chemical and biological species composition of eroded sediments from wind and water erosion as an index to evaluate soil functioning as affected by management and the source of erosion. Our preliminary findings shows that eroded sediments remove the active labile organic soil particulates containing key microorganisms involved in soil biogeochemical processes, which can have a negative impact on the quality and functioning of the source soil. Wind tunnels studies in several states across the country have been completed. A new hand-held wind-erosion sampling system was designed for rapid deployment in the field. The new system consists of lightweight retractable shaft with an anemometer mounted on top and a saltation sensor mounted on the bottom.
1. Wind erosion of organic soils is related to soil properties. Organic soils (Histosols) are found in 42 states, with a total of 21 million ha in the United States. These soils, when intensively cropped, are subject to wind erosion, resulting in loss of crop productivity and degradation of soil, air, and water quality. Estimating wind erosion on Histosols has been determined by USDA-Natural Resources Conservation Service (NRCS) as a critical need, yet little is known about rates of wind erosion and the effects of soil properties on these soils. ARS scientists at Lubbock, Texas, performed field wind tunnel tests on organic and organic-rich soils in Michigan and Florida and found that surface soil organic matter level significantly affected wind erodibility and fine dust emissions. In addition, variations in soil erosion were linked to other soil properties. Simple models based on one or more soil properties were developed to estimate soil loss by wind erosion from organic and organic-rich soils. This information will be used in the ARS Wind Erosion Prediction System used by NRCS for wind erosion prediction in the US.
2. Reduced tillage in dryland improves soil quality in less than 10 years. Sustainable soil management systems are needed to provide a productive and environmentally safe food supply. Soil quality assessment indexes are used to better understand the effects of cover crops and tillage on effects related to soil and water conservation. In this study, ARS scientists at Lubbock, Texas, quantified the effects of tillage and the addition of diverse grains and cover crops in dryland systems on soil quality parameters and water infiltration rates after 8 and 10 years of production. Adding more biomass to a cotton crop rotation improved soil quality for agricultural production. Overall, though, soil properties were more sensitive to cropping system differences than tillage differences (conventional versus no tillage) and demonstrated the importance of crop rotations for improving soil quality in dryland cropping systems. Although soil microbial properties were not sensitive to tillage practices, measurements related to soil quality, including organic matter content, soil density, wet and dry aggregate stability, and soil strength, showed a separation of these systems due to tillage. This study demonstrated that benefits of reduced tillage practices to improve soil properties and quality for agricultural production can take less than 10 years for dryland cropping systems.
3. Windblown sand does more than simply defoliate cotton. Millions of hectares of crops are exposed to windblown sand abrasion each year and often require expensive replanting by farmers. A prevailing hypothesis is that this damage is similar to a mechanical loss of leaves on the crop. Scientists at the Wind Erosion and Water Conservation Laboratory, Big Spring, Texas, showed that crop survival and recovery from this damage is far slower than would be expected from a simple loss of crop leaf area and likely involves a short-term, high-intensity water stress resulting from sand particles rupturing plant cells. These new data can be used to help advise farmers on whether or not cotton fields suffering from wind storms and sand abrasion damage need to be replanted.
4. Wind erosion steals good bacteria from agricultural fields. Scientists from ARS in Lubbock, Texas, and Akron, Colorado, demonstrated how wind-eroded sediments carry away not only soil particles but also beneficial microbes needed in soil processes that recycle nutrients, detoxify soil, and build soil organic matter. The scientists reported that different eroded sediments resulting from variations in soil erosion remove different bacteria and kinds of organic C. Bacteria traveling in fine dust differed from those carried in coarser sediments greater than 106 microns in size. These are important findings for soil functioning because different bacteria participate in different soil processes. While fine dust can travel extremely long distances at great heights, coarse sediments rarely move far from the soil surface and travel shorter distances, suggesting that they - and their associated microbes - should be fairly easy to retain with cover cropping and other soil conservation measures.
Acosta Martinez, V., Mikha, M.M., Sistani, K.R., Stahlman, F., Benjamin, J.G., Vigil, M.F., Erickson, R. 2011. Multi-location study of soil enzyme activities as affected by different manure types, rates, and tillage application practices. Agriculture. 1(1): 4-21.