2011 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.
A new field wind tunnel was used to determine fine dust emissions on organic soils in Michigan and Florida at the request of the Natural Resources Conservation Service. This research included the use of rare earth elements (REE) to identify the source areas of mobilized sediment. Data analysis of the REE is currently underway. Variations in emissions between the soils were quantified by the field wind tunnel experiment, and while only preliminary, these can be linked to soil properties. Organic matter (OM) content affects erodibility, and this can explain differences in dust production. The largest erodible fraction results in a high concentration during initial blow-offs. Abrasion does not significantly increase emission rates from high OM soils due to their high mechanical stability. The relative enrichment of enzyme activity in eroded sediment is demonstrated for end member OM content soils, indicating implications for soil sustainability.
Our participation in the GRACEnet continues. Dryland research plots under different cropping systems and tillage treatments are in their 8th year. We are having a very dry year. By late June we have had only 1.19 inches of rainfall, and no crops have been planted. Field measurements for water infiltration were performed in the fall of 2010.
Cotton seedlings of different ages were placed in laboratory wind tunnels to determine the effects of windblown sand abrasion on plant survival and subsequent recovery. In further experiments in FY 2010, plants were additionally subjected to mechanical clipping in order to separate the effects of windblown sand abrasion-induced drought stress from simple loss of plant leaf area. These data will be used to advise farmers when cotton fields suffering from windstorms and sand erosion should be replanted with a new crop in order to be economically viable.
A method to determine the probability of wind erosion from dust source areas. In 1961, an underground nuclear test, called Project Gnome, was conducted beneath the Mescalero Sands east of Carlsbad, New Mexico, resulting in an unintentional venting of radioactive materials to the surface. Although remediation activities have been conducted, low levels of radionuclides are still detectable in surface soil samples, and when the wind blows, radionuclide contamination is sometimes detected in ambient dust samples. Recently, an attempt was made to monitor wind-driven processes at the Project Gnome site, with the primary goal of determining the minimum wind speed, or threshold wind speed, at which sands are detached and transported. The site was monitored continuously for 112 days, and during active periods, and average threshold values were found to be around 10 m/s. This new information provides key data that researchers can use to evaluate the probability of wind erosion from a source area when combined with local wind data.
Speeding up soil quality recovery detection in sandy soils under dryland production. Since the 1940s much of the land in the Southern High Plains region has been planted solely to cotton using conventional tillage practices, resulting in declining soil quality. In order to sustain future agricultural activities in this area, conservation practices such as minimum tillage and cotton rotations with sorghum are being implemented to reduce erosion and restore soil quality in dryland production. But it often takes many years before improvements can be seen. At Lubbock, Texas, we found that introducing a rotation of cotton with high biomass crops, such as forage sorghum and a winter rye cover crop, produced increases in microbial biomass C and N, and the activities of enzymes important for nutrient cycling in as little as three years. It took over five years to show improvements under rotations of cotton and grain sorghum compared to cotton monoculture. This is new information that growers and researchers can consider when identifying cropping systems that will result in improved soil quality and functioning.
Van Pelt, R.S., Zobeck, T.M., Baddock, M.C., Cox, J.J. 2010. Design, construction and calibration of a portable boundary layer wind tunnel for field use. Transactions of the ASABE. 53(5):1413-1422.
Stout, J.E. 2012. A field study of wind erosion following a grass fire on the Llano Estacado of North America. Journal of Arid Environments. 82(3):165-174.
Acosta Martinez, V., Lascano, R.J., Calderon, F.J., Booker, J.D., Zobeck, T.M., Upchurch, D.R. 2011. Dryland cropping systems influence microbial biomass and enzyme activities in a sandy soil in a semiarid region. Biology and Fertility of Soils. 47(6):655-667.
Hagen, L.J., Van Pelt, R.S., Sharratt, B.S. 2009. Estimating the saltation and suspension components from field wind erosion. Aeolian Research. 1:147-153. Available online: http://www.sciencedirect.com/science/journal/18759637.
Ma, L., Hsieh, D., Zobeck, T.M., Holder, H.D., Thompson, J. 2011. Optical properties of aeolian dusts common to West Texas. Aeolian Research. 3(2):235-242.
Stout, J.E., Arimoto, R. 2010. Threshold wind velocities for sand movement in the Mescalero Sands of southeastern New Mexico. Journal of Arid Environments. 74(11):1456-1460.
Panebianco, J.E., Buschiazzo, D.E., Zobeck, T.M. 2010. Comparison of different mass transport calculation methods for wind erosion quantification purposes. Earth Surface Processes and Landforms. 35(13):1548-1555.
Baddock, M.C., Zobeck, T.M., Van Pelt, R.S., Fredrickson, E.L. 2011. Dust emissions from undisturbed and disturbed, crusted playa surfaces: cattle trampling effects. Aeolian Research. 3(1):31-41.