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 second year of this project (2012–2013), the region continued to experience an extreme drought following the 2011 historical drought and heat wave comparable to the dust bowl of the 1930s. This has caused modifications on 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 have been analyzing soil samplings taken in July 2011 and March 2012 to specifically characterize the effects of the record 2011 drought/heat wave on soil organic matter and microbial community diversity. Preliminary data are demonstrating enzyme activities were highest during the peak drought/heat wave conditions captured with our July 2011 sampling compared to March 2012 (when drought conditions were less intense and temperatures were lower), which explains the significant reductions in soil total C from July 2011 to March 2012. The PALMS landscape model was calibrated for the two major soil series, Pullman and Amarillo, of the Texas High Plains. 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. The merging of two models PALMS and Cotton2K, both written in the Fortran language, has further expanded our ability to evaluate how inputs of water and nitrogen can be used to increase lint yield production using site-specific recommendations. The group established a Material Transfer Research Agreement (MTRA) with a company to evaluate the EXO-Skin sap flow sensor and SapIP wireless data-logging system, to measure the transpiration of cotton under laboratory and field conditions. We made significant progress determining organic C sources lost in different sized wind-eroded sediments to evaluate soil functioning as affected by wind erosion. Our preliminary findings showed that finer dust sediments (mean diameter of 35 micrometer), which travel far distances from the soil source than higher size sediments (i.e., saltation size material, <175 micrometer mean diameter), will carry away higher levels of labile aliphatic-carbon compounds and clays, which can have greater negative impacts on soil processes and the future sustainability of agroecosystems. Wind tunnels studies have been conducted in several states across the country. 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. New model allows ability to predict how water and nitrogen inputs will affect cotton yields. A mechanistic simulation model is a process whereby the variables that impact the calculations of the water, energy, carbon and nitrogen balance of the soil-plant-atmosphere system are selected and compared to measured values. From a theoretical basis, soil water and the functions that characterize the soil hydraulic properties are the most important variables that impact the water and energy balance of the system. Therefore if a model is calibrated it can be used in a predictive mode. Investigators at Lubbock, Texas, calibrated the PALMS model for the two major soil series of the Texas High Plains, Amarillo and Pullman series. A difficulty in this process is the correct characterization of the relation of soil water content and water potential and with hydraulic conductivity, otherwise known as the soil hydraulic properties. Results showed that the default parameters set to characterize the soil hydraulic properties with the Rawl's functions were adequate to calculate accurate values of soil water content across a wide range of environmental conditions. Furthermore, merging the two models (Cotton2K and PALMS) has provided a tool that can be used to evaluate how inputs of water and nitrogen, which are closely linked, can be used to increase cotton lint yield production using site-specific recommendations.
2. New hand-held dust storm sampler also records wind speed. A scientist at the USDA-ARS lab in Lubbock, Texas, developed a new hand-held wind-erosion sampling system that consists of a retractable shaft with an anemometer mounted on top and a saltation sensor mounted on the bottom. The system is lightweight, mobile, and was designed for rapid deployment in the field. By using the Time Fraction Equivalence method, developed previously by the same scientist, the new system has been programmed to directly output a value of threshold velocity, the wind speed at which soil movement is initiated. Recently, a company in Big Spring, Texas, has expressed interest in manufacturing the hand-held sampling system based on the ARS design, making this technology more readily available to scientist working in the soil sciences.
3. Soil quality may be permanently impacted by drought/heat events. A unit scientist in Lubbock, Texas, conducted soil samplings during the 2011 historically extreme drought and heat wave that occurred in the Southern High Plains of Texas. During November 2010 to August 2011, this region received only 39.6 mm of precipitation (vs. the historical average of 373 mm) and experienced the hottest summer since record keeping began in 1911. Several enzyme activities important in biogeochemical cycling were evaluated at four sites under two soils (loam and a sandy loam) with a management history of monoculture (continuous cotton) and rotation (cotton and sorghum or millet). During the drought/heat wave, enzyme activities continued to be a fingerprint of the soil management history, as all activities were higher in the rotation compared to monoculture for both sites. However, the decline of enzyme activities and soil organic matter over time suggests that such extreme drought/heat wave may result in adverse effects on soil quality, affecting the long-term sustainability of these low organic matter agricultural soils. This research also shows the need to expand our understanding of climate change in agroecosystems.
Cotton, J.E., Moore-Kucera, J., Acosta Martinez, V., Burow, G.B. 2013. Early changes due to sorghum biofuel cropping systems in soil microbial communities and metabolic functioning. Biology and Fertility of Soils. 49(4):403-413.