2007 Annual Report 1a.Objectives (from AD-416) Knowledge of the effects of cropping systems on selected soil properties is needed to optimize productivity and develop sustainable agricultural systems. The effects of alternative dryland and irrigated crop and livestock systems on water infiltration, soil aggregation, and other soil properties will be defined through the following sub-objectives. 1.1 Determine the effect of agricultural management practice factors such as crop type, irrigation amount and type, tillage intensity, and residue cover on water infiltration aggregate stability carbon sequestration, soil microbial community structure, and enzymes that affect soil function. 1.2 Validate and further refine the Soil Conditioning Index and Soil Management Assessment Framework to assess the sustainability of management practices and systems. Wind erosion and dust emissions are controlled by biological and physical processes and characteristics that must be determined to develop successful methods of dust mitigation. We will investigate basic biological and physical processes and characteristics of wind erosion and airborne dust needed to develop mitigation strategies using the following sub-objectives. 2.1 Quantify total airborne soil mass transport and fine particle dust emissions as affected by soil texture and cropping system. 2.2 Determine enzyme activities, microbial community composition, and chemical characteristics of fine particle dust from agricultural soils to identify the sources and origin of dust. 2.3 Validate and further refine the time fraction equivalent method for determining the threshold condition for soil movement in the field under natural wind and soil conditions. 2.4 Identify morphological traits that promote resistance to injury caused by abrasion of plants by sand particles during wind storms and determine the most resistant varieties of selected common crops. 1b.Approach (from AD-416) Agricultural management practice factors such as crop type, irrigation amount and type, tillage intensity, and residue cover will be correlated with water infiltration, aggregate stability, carbon sequestration, soil microbial community structure, and enzymes that affect soil function. The soil conditioning index and soil management assessment framework, used to assess the sustainability of management practices and systems, will be evaluated and refined. Total airborne soil mass transport and fine particle dust emissions as affected by soil texture and cropping systems will be quantified. 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. 4.Accomplishments Important Soil Quality Index Evaluated: The United States Department of Agriculture, Natural Resources Conservation Service (USDA-NRCS) has proposed the Soil Conditioning Index (SCI) to predict the effects of management actions on soil organic matter, a soil quality indicator. ARS scientists from Lubbock, Texas, evaluated the SCI to test the effects of different land uses in semiarid, hot, sandy soils. The SCI successfully identified fields with the highest levels of organic matter and when no-tillage or a limited amount of tillage was done from fields that were more aggressively tilled. This accomplishment identifies an important limitation of the new index used to determine compliance for U.S. farm programs. (NP 202; Component 1, Soil Conservation and Restoration) Managing Soil Properties through Dryland Cropping Systems with Different Cropping Intensities: In some areas of the Southern High Plains available irrigation water is becoming scarce due to the small amount groundwater recharge occurring to the Ogallala aquifer. Changes in soil quality indicators (i.e., organic matter content) can improve the potential of soils to store water for crop production in dryland cropping areas. ARS scientists from Lubbock, Texas, evaluated a High Biomass Crop dryland study and have shown that soil microbial populations and microbial chemical properties important for plant fertility are higher in winter cover crop rotations, compared to continuous cotton or cotton-sorghum systems. Continuation of this study is important for the long-term evaluation and confirmation of these trends, and their implications in water management and crop productivity in dryland farming. (NP 202; Component 1, Soil Conservation and Restoration; Component 3, Soil water; Component 4, Soil Biology) Alternative Crop Rotations Were An Improvement Compared to Wheat-fallow for the Central Great Plains: Although the winter wheat-fallow rotation is the main cropping system in the semiarid region of the Central Great Plains, other cropping systems are being suggested because systems with less tillage and fallow (no crop) can provide more residues that can increase soil organic carbon and other properties related to improved soil quality. ARS scientists from Lubbock, Texas, and Akron, Colorado, compared soil microbial properties under different native pastures and different intensities of cropping after 15 years of management in Akron, Colorado. The study showed that native pasture and undisturbed grass plots showed higher soil carbon due to soil microbes in the topsoil when compared to the cropping systems. This accomplishment is important for long-term agricultural activities in semiarid regions by showing that the combination of no-tillage and continuous cropping with reduced fallow frequency had a positive effects on soil quality parameters. (NP 202; Component 1, Soil Conservation and Restoration; Component 3, Soil water; Component 4, Soil Biology). Cesium From Fallout Used to Estimate Wind Erosion: Wind erosion robs the soil of essential plant nutrients and water holding capacity and negatively affects soil productivity. The release of radioactive chemicals from atmospheric testing of nuclear weapons during the 1950s and 1960s has created a convenient way of measuring soil redistribution in the landscape that occurred during the last 40 years. Cesium (137Cs) was one chemical deposited in fallout on soil surfaces as a result of atmospheric testing. The activity of 137Cs in an eroded soil profiles compared to that from an uneroded reference sites has been used by water erosion researchers to estimate long-term erosion and deposition rates. This study investigated whether or not wind erosion and deposition estimates based on 137Cs activities would agree with measured erosion and deposition. ARS scientists from Lubbock, Texas, found that certain simple models used to predict erosion based 137Cs amounts tended to overestimate long-term rates of soil loss and either under- or over-estimated long-term deposition rates depending on the nature of the sites. The results indicated that models having a soil particle size correction factor are more appropriate for wind erosion and deposition estimates than other simple models. (NP 202; Component 1, Soil Conservation and Restoration). Cotton Seedling Damage and Recovery from Wind Erosion: Millions of acres of crops are exposed to wind-blown sand damage each year, and in many instances the harm is thought to be severe enough to require replanting. ARS scientists from Lubbock, Texas, conducted four sand damage (abrasion) treatment experiments, with different amounts of time for the blowing sand, on cotton seedlings. The studies found that when the plants were recovering from the damage, the growth rate of treated plants was greater than that of untreated controls. These findings suggest that cotton breeders selecting for traits that lend resistance to and/or recovery from sand abrasion damage should focus on the following two plant traits:. 1)an ability to use the root to repair the damaged canopy and/or. 2)an ability of newly formed leaves to be more efficient in taking carbon dioxide out of the air. (NP 202; Component 1, Soil Conservation and Restoration) 6.Technology Transfer Number of web sites managed 1 Number of non-peer reviewed presentations and proceedings 10 Number of newspaper articles and other presentations for non-science audiences 19 Review Publications Ravi, S., Zobeck, T.M., Over, T.M., Okin, G.S., D'Ordorico, P. 2006. On the effect of moisture bonding forces in air-dry soils on threshold friction velocity of wind erosion. Sedimentology. 53:597-609. Ravi, S., D'Ordorico, P., Herbert, B., Zobeck, T.M., Over, T.M. 2006. Enhancement of wind erosion by fire-induced water repellency. Water Resources Research. 42:1-9. Stout, J.E. 2007. Simultaneous observations of the critical threshold of two surfaces. Geomorphology. 85(2):3-16. Van Pelt, R.S., Zobeck, T.M. 2007. Chemical constituents of fugitive dust. Environmental Monitoring and Assessment. 130(1-3):3-16. Van Pelt, R.S., Zobeck, T.M., Ritchie, J.C., Gill, T.E. 2007. Validating the use of 137cs measurements to estimate rates of soil redistribution by wind. Catena. 70(3):455-464. Acosta Martinez, V., Mikha, M.M., Vigil, M.F. 2007. Microbial communities and enzyme activities in soils under alternative crop rotations compared to wheat-fallow for the Central Great Plains. Applied Soil Ecology. 37:41-52. Baker, J.T. 2007. Cotton seedling injury and recovery from wind blown sand abrasion: I. Duration of exposure. Agronomy Journal. 99(2):556-561.