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 in several experiments are achieving objectives of the project. Objective 1: Develop adaptive management practices to optimize yield and enhance dryland systems vulnerable to changes in climate. The unit’s publication of the simulation modeling of the adoption of canola for the Central Great Plains is in review. The stripper header management studies are near completion. The four year canola rotation established in 2012 is in its second year with an objective to determine how to fit canola into wheat, corn and millet rotations. The wheat nitrogen use efficiency (NUE) by wheat cultivar experiment established with university (CSU) collaborators is in its third year of data collection. The first year of the grant funded oilseed stress trial was established during the extreme drought of 2012. The 2012 drought precluded the measurement of meaningful differences in cultivars. Scientists monitoring soil water recharge after Sunflowers now have an assessment of how well wheat performs after various summer crops grown under irrigation in 2012. The skip-row sorghum by variety and seeding rate experiment is complete and the graduate student wrote her first draft of a manuscript to submit for publication by August 2013. The 2012 drought precluded the measurement of meaningful differences in the slot tillage experiment established in 2011. Progress was made evaluating soil organic matter quality (measured mid-IR spectroscopy) resulting in a second published manuscript. Scientists made progress in publishing manuscripts evaluating soil organic carbon as influenced by tillage, and organic amendment. The organic wheat rotation experiment established 2011 provided no measurable treatment differences due to drought. Biochar experiments established with USGS collaborators in 2012 are near completion. Objective 2: Extend the applicability of adaptive management practices across the CGPR using site-specific technologies and process modeling for field scales. Progress is still in learning software and purchasing hardware to conduct site specific N management across a landscape. The sequestration cut has made it difficult to move forward with this project simply because we don’t have the technician hours available. Because this is a new effort it has become low priority until additional funding becomes available to hire the additional technical help. 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. Preliminary analyses of yields and soil parameters have been summarized in station annual reports. Two manuscripts have been published. In the fall of 2013 all plots will be sampled to an 8 foot depth (2.4 m) to assess nutrient changes from manure application over the last 6 years and to evaluate other physical/chemical properties in this experiment.
1. Decision support tools for assessing production risk of corn, canola, proso millet, foxtail millet, and triticale in the Central Great Plains. Diversification of the traditional winter wheat-fallow production system requires the introduction of different crops that may be new to farmers. Farmers need a tool to help them assess the potential risk in producing these alternative crops. ARS scientists at Akron, CO developed Excel spreadsheet-based decision support tools that provide farmers with the probability of achieving given yields of corn, canola, and proso millet for grain and foxtail millet and spring triticale for forage at several central Great Plains locations. The tools use yield estimates from crop simulation models that use historical weather data over many years to provide information about yield variability and probability of producing a given yield. The user simply selects the desired crop, location, and soil water content at planting from drop-down menus. After the user enters the target yield the tool displays the probability of achieving at least that yield. The tool is extremely simple to use and allows the user to make an assessment of the risk involved in growing a new and unfamiliar crop to diversify the cropping system.
2. Using the Least Limiting Water range to identify soil physical effects on plant productivity. Management practices that minimize soil physical limitations to crop growth create an environment for maximizing crop yields. Scientists at Akron, CO combined several soil physical characteristics into a single parameter called the Least Limiting Water Range (LLWR). This parameter was useful for quantifying management effects on soil physical quality and more importantly providing the relationship between crop growth and soil physical quality. The scientists identified the specific LLWR most favorable to root and shoot growth of corn. This is important because management practices like irrigation and residue management affect the time and duration that the soil environment is maintained within a water range most favorable to healthy crop development.
3. Infrared spectroscopy a useful tool for determining the quality of soil organic matter. Soil organic matter (SOM) is a key aspect of soil quality and soil fertility. Its presence in soil therefore greatly affects crop yields. While it has been shown that increases in SOM are beneficial, less is known about how the chemical composition of SOM affects crop yields. ARS scientists at Akron, CO have shown that Mid-Infrared Spectroscopy (MidIR) can quickly and inexpensively characterize changes in the chemistry of SOM. Scientists at Akron documented that MidIR can be used to detect increases in important chemical attributes like sugars, aromatics, and proteins in SOM. The amount of these components in SOM determine the unique fertility of a soil and their presence affects the rate of SOM decomposition; which in turn tells us how likely the SOM of a specific soil will increase, maintain or decline. The ability to monitor a soils SOM for these components allow farmers, extension workers and scientists to gage how best management practices affect soil fertility and enhances soil sustainability.
4. Defining limitations for sorghum production in the Eastern Colorado High Plains. Sorghum is an important warm season grain crop in the southern high plains region of western Kansas and south eastern Colorado. It is drought tolerant and well adapted to semi-arid climates. However, its adoption by farmers in north east Colorado has historically been insignificant. Low adoption is primarily because cooler temperatures in north eastern Colorado during grain filling have resulted in inconsistent yields and quality. ARS scientists at Akron, CO in collaboration with Colorado State University quantified the affect row spacing, population and maturity rating has on sorghum yields and days required to reach physiological maturity. With all maturity groups tested wide row spacing resulted in an increase in grain quality and at one location improved grain yields. Early and medium early maturing hybrids had at least a 75% chance of reaching physiological maturity at all three eastern Colorado locations tested. At the warmest locations (Akron and Stratton Colorado) they had at least an 89% probability of reaching physiological maturity. The research is important because it quantifies the expectation for success and failure of typical sorghum germplasm in the semi-arid high plains region.
5. The method used to calculate soil carbon is important. Because of the inherently large variability of soil density with depth and location, any estimate of the total amount of soil organic carbon (SOC) stored in a soil requires both a SOC concentration measurement and a corresponding measurement of soil bulk density. The problem is in how to best combine soil density measurements with measurements of SOC concentration to calculate total SOC. Scientists at Akron evaluated three methods to calculate total SOC. These were an equivalent soil mass approach (ESM) a minimum equivalent soil mass approach (MESM), and the fixed-depth approach (FD). They found that overall the MESM approach was favorable for calculating SOC from a single sampling event. Also they found that the ESM approach and the MESM approach were both better than the fixed depth method for calculating total SOC. However, because so much of the early literature has used only the FD approach, the FD calculation should still be included in futures reports. This inclusion enables a comparison of recently reported SOC measurements versus those reported previously on long term soil management. Futhermore, researchers working to quantify changes in SOC as affected by changes in soil management will benefit from this research because they are now better informed about potential errors in making SOC measurements.
6. The availability of plant nutrients in composted dairy manure is less than expected. In collaboration with Colorado State University, ARS scientist in Akron measured the release of nitrogen (N) from composted dairy manure applied to mixtures of perennial grasses at 10 ton per acre for 2008 and 5 ton per acre for 2009. A control treatment with no composted dairy manure was also included. There were no observed differences in the amount of N released (N mineralization), total forage production, or N uptake between controls and compost-amended soils. This data suggests that N mineralization rates from composted dairy manure were considerably lower than expected and thus may not supply enough N to meet the N demand of perennial forage grasses.
Mikha, M.M., Vigil, M.F., Benjamin, J.G. 2013. Long-term tillage impacts on soil aggregation and carbon dynamics under wheat-fallow in the central Great Plains. Soil Science Society of America Journal. 77:594-605.