1a. Objectives (from AD-416):
1. Develop adaptive management practices and document their benefits to optimize yield and enhance ecosystem services for CGPR dryland agricultural systems most vulnerable to adverse changes in climate. 2. Extend the applicability of adaptive management practices across the CGPR using the development and evaluation of site-specific technologies and process modeling for field scales. 3. Develop and evaluate practices for remediation/restoration of degraded soils in the CGPR.
1b. Approach (from AD-416):
There are 27 million acres of cultivated dryland in the Central Great Plains region (CGPR). The primary limitation for cropping in the CGPR is a variable drought dominated climate. Despite system improvements toward more intensive cropping, 58% of the region’s dryland is still winter wheat-summer fallow (WF). Unfortunately, WF is not economically /environmentally sustainable. Our objective is to develop sustainable dryland systems for the CGPR. A central research theme is adapting the region’s cropping systems to the ever-changing semi-arid climate. The unit works to achieve that objective using a long-term “core experiment,” the Alternative Crop Rotation (ACR) study. This field study compares 23 rotations for their economic, agronomic, and drought-mitigating effects and their effects on soil quality. In support of the core experiment, several satellite experiments evaluate the agronomic and economic potential of alternative crop species; quantify crop water use; evaluate changes in soil quality; develop management for remediating degraded soils; and evaluate nutrient use efficiency in these systems. The combined efforts of the “core” and “satellite” experiments will result in sustainable, climate-adaptive cropping systems for the region and will provide a quantitative knowledge of production limitations of the CGPR to climate change. Introducing biological and market diversity with broadleaf bio-diesel/oilseeds will reduce pest pressures inherent to the current grass-dominated rotations. Economic savings from improved cropping systems, reductions in agri-chemical use, and reductions in soil loss resulting from this research are estimated at $6-$35 per acre annually. Assuming 25% adoption of this technology will result in annual regional savings of $40 -$236 million.
3. Progress Report:
Progress of project approved June, 2011: Sustainable Dryland Cropping Systems for the Central Great Plains. Scientists at the USDA-ARS Central Great Plains Research Station (Akron, CO) with ARS and University Collaborators have begun several experiments to reach objectives of the approved project. Objective 1: Develop adaptive management practices to optimize yield and enhance dryland systems most vulnerable to changes in climate. The team has established new simulation modeling exercises, crop water use and N use efficiency experiments, modified alternative rotation plots, and established new crop residue management studies (stripper header management). A new canola rotation was established in 2012 to determine how to best fit canola into wheat rotations. To quantify water use by alternative crops, scientists are analyzing water use data sets of millet, sorghum (both new and old data sets). To improve wheat nitrogen use efficiency (NUE) a wheat cultivar by N management experiment was established with university collaborators (CSU). A grant was funded this summer 2012, to evaluate oilseed germplasm and to evaluate select cultivars in an oilseed stress trial. The Sunflower sequencing experiment is in its second year and will be planted this fall to winter wheat. Scientists are monitoring soil water recharge and will have an assessment of how well wheat performs after various summer crops in 2013. We finished the skip-row sorghum experiments. The graduate student has just written up and defended her thesis this past April. The slot tillage experiment was established in 2011. Progress was made evaluating soil organic matter quality (measured mid-IR spectroscopy) resulting in a published manuscript. Scientists made progress in publishing manuscripts evaluating soil organic carbon as influenced by tillage, and organic amendment. An organic wheat rotation experiment was established in 2011. Biochar experiments were established with USGS collaborators in 2012. Objective 2: Extend the applicability of adaptive management practices across the CGPR using site-specific technologies and process modeling for field scales. Progress is in learning software and purchasing hardware to conduct site specific N management across a landscape. We have grid sampled (for chemical/physical properties) land intended for the research. Several simulation models have been used to extend data gathered at Akron, CO to other soils and climates in the CGPR. This resulted in one peer reviewed manuscript published this past year. Objective 3: Develop and evaluate practices for remediation of degraded soils in the CGPR. Because of the 2012 summer drought no decisions about the direction of the experiment will be made until after the 2013 growing season. In the initial experimental design, 8 manure amendments were applied at rates large enough to provide adequate nutrients for dryland crops for 6 years. Because of the drought we need one more year to complete one cycle of the experiment. Preliminary analyses of yields and soil parameters have been summarized in station annual reports. Two manuscripts have been published.
1. Regional estimates of dryland canola production potential in the central Great Plains. Spring canola production has the potential to diversify dryland crop rotations in the central Great Plains. Canola oil can be used as a biodiesel feedstock or used directly as an on-farm fuel for equipment that has been converted to run on straight vegetable oil (SVO). ARS scientists in Fort Collins and Akron, Colorado developed and tested a spring canola cropping systems model and then used it with long-term weather data from nine central Great Plains locations covering approximately 45,000 square miles to evaluate the potential profitability of spring canola. Simulation results indicated that dryland spring canola could be profitable across a large portion of the central Great Plains under certain soil moisture conditions. This simulation study reduces the need for costly and time-consuming long-term field studies at multiple locations.
2. New methods for understanding wind erosion effects on soil productivity. Wind erosion combined with tillage damages the productivity of farm soils. Scientists from Akron, Colorado, Lubbock, Texas, and Alabama A&M University determined wind erosion effects on soil organic matter and soil microbiology. These methods were used in wind-tunnel erosion experiments of several soils. The results show that wind eroded dusts, which travel long distances, carry with them a particular kind of soil organic matter that is important for soil fertility. A detailed description of soil chemistry and microbiological changes that occur during wind events was obtained. These data will aid in the development of soil management and conservation practices in agricultural systems.
3. Evaluating soil environmental effects on the root growth of crops. Scientist at Akron, Colorado and collaborators summarized in a book chapter the important soil physical factors that limit crop root growth. The research showed that a new way to characterize the soil environment (the Least Limiting Water Range (LLWR)) is a more sensitive method to describe how changes in soil physical condition affect root growth than other methods currently being used. The purpose of the chapter was to encourage further investigation of soil effects on root and plant growth that is often neglected in current research programs.
4. New methods to measure soil microbial communities and soil organic matter chemistry. Soil microbes are responsible for nutrient cycling and contaminant removal. ARS scientists from Akron, Colorado and Lubbock, Texas, and scientists from Texas Tech University used novel physical (diffuse reflectance spectroscopy) and biological (DNA pyrosequencing) methods to determine soil microbe diversity and organic matter chemistry in select farm soils. We learned that specific bacteria species inhabit specific soil environments and that nutrients in each of these environments are not uniformly utilized by the soil bacteria. Such data are important because they provide insight on optimal soil nutrient management to maintain agricultural productivity while ensuring environmental quality.
5. Canopy cover and leaf area index relationships for wheat, triticale, and corn. Computer simulation models are valuable tools for assessing management and weather effects on crop production. The recently developed computer model AquaCrop from the United Nations Food and Agriculture Organization is useful for assessing crop production under varying temperature and water availability conditions, but it has not been properly calibrated with respect to leaf area (a common measure of plant growth). ARS scientists at Akron, CO generated mathematical relationships between leaf area index and canopy cover for winter wheat, corn, and triticale. The relationships matched the shape of an exponential rise to a maximum value. The mathematical relationships are useful for completing modeling studies with data sets in which leaf area index has been recorded. Additionally, the relationships are useful as a low cost method to predict leaf area index from canopy cover measurements made with an inexpensive digital camera.
6. Evaluating variability in manure decomposition characteristics. The rate at which animal manures decompose affects fertilizer management in manure amended crop land. Different animal manures decompose at different rates and the rate of decomposition is related to the soil-enzyme activity of the manure amended soil. Scientists at Akron CO, Hays KS, and Bowling Green KY, quantified how different organic amendments affected soil enzyme activity during manure decomposition. Scientist documented variable soil-enzyme activity that was directly related to manure type. The value in this research is in knowing that subtle differences in manure bio-chemistry can have important impacts on nutrient cycling and soil fertility management in manure amended fields.
7. Use of computer simulation models to assess crop yield and profitability of new dryland crops. A more efficient use of the limited precipitation, characteristic of the Central Great Plains is a continual challenge. Corn, canola, proso millet, foxtail millet and triticale when used in rotation with winter wheat have the potential to more efficiently utilize summer rainfall than the traditional winter wheat summer fallow system. ARS scientists in Fort Collins and Akron, Colorado used the Root Zone Water Quality Model (RZWQM2) along with long-term weather data from Akron, CO and Sidney, NE to evaluate the yield variability and potential profitability of these crops under varying water availability conditions. Net returns were generally greater for the two forage crops than the three grain crops. Study results will be useful for the selection of an appropriate crop and planting period (spring or summer) and will help to assess risk in intensive cropping systems.
Calderon, F.J., Mikha, M.M., Vigil, M.F., Nielsen, D.C., Benjamin, J.G., Reeves III, J.B. 2012. Diffuse-reflectance mid-infrared spectral properties of soils under alternative crop rotations in a semiarid climate. Communications in Soil Science and Plant Analysis. 42:17, 2143-2159.