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Research Project: Precision Farming for Development of Sustainable Dryland Cropping Systems of the Central Great Plains Region

Location: Central Great Plains Resources Management Research

2021 Annual Report

Objective 1: Develop management practices incorporating the latest technology developments for a field size aspirational four year, dryland crop rotation system with precision nutrient, agrichemical, weed control and crop population management. Sub-objective 1a. Identify and quantify production parameters most important in affecting economic yields across a dryland field-scape. Sub-objective 1b. Develop methods for quantifying optimal precision N management for specific management zones in wheat-based dryland rotation. Sub-objective 1c. Develop methods to quantify optimal corn populations for specific management zones in a four-year aspirational rotation. Sub-objective 1d. Develop and evaluate new tools for assessing soil quality across a field-scape using spectral scanning (FTIR) and other quick methods. Sub-objective 1e. Evaluate the use of drone based data for the quantification of crop water stress in dryland crop rotations. Objective 2: Compare yields, economic returns, and environmental impacts of the aspirational rotation system, to a dryland rotation system currently used by producers of the region. Sub-objective 2a. Quantify and compare grain yields and economic returns from a precision-managed four-year aspirational no-till rotation with a “business as usual” reduced-till wheat-fallow rotation. Sub-objective 2b. Quantify and evaluate changes in soil quality as affected by both management systems across the field-scape. Objective 3: Evaluate potential alternative crops and management practices for introduction into the aspirational wheat based dryland rotation system. Sub-objective 3a. Continue evaluations of germplasm and potential alternative crops for inclusion into wheat-based dryland systems. Sub-objective 3b. Evaluate new agronomic practices for inclusion into aspirational wheat-based dryland rotations.

Dryland farmers in the central Great Plains have the technical means to collect much of the field data needed for precision farm/field management. These data often available in a map format or “data layer” include field grain-yield maps, soil-color maps, electrical conductivity (EC), pH, topographical-elevation field maps, and soil-series maps. However, most dryland producers do not have a science-based, unbiased collection of quantitative recommendations for interpreting how to best use those field data layers. The lack of reliable quantitative recommendations makes it difficult to manage field-scape variability for maximizing net returns. In this project, researchers will use a replicated set of field sized plots that show substantial variability in productivity as one moves through a given field. Using this large field experiment we will develop the mathematical relationships between yield, and inherent field variability and climate variability that are key to a field’s annual productivity. This research will provide a quantitative understanding of how N inputs in dryland rotations can best be optimized across variable field landscapes and variable climate for improving farm gate income. With that science based knowledge researchers will build reliable decision support tools to help guide producers on precision farm management in semi-arid wheat base dryland rotations. This research will also focus on precision optimization of dryland corn populations that match inherent field and climate variability. Soil health monitoring of the rotation treatments and the testing and development of quick methods for assessing soil quality will also be included as important research aspects of the project.

Progress Report
Objective 1: Crop yield and topography data collected in the first two project years were used to develop 3 management zones (high, medium, and low yield potential) in each aspirational (ASP) and business-as-usual (BAU) crop-rotation field. We installed neutron probe access tubes to allow weekly soil-water measurement across the management zones in each ASP and BAU field. Soil water measurements will be used to calibrate hydrologic models, evaluate crop water use efficiency, and understand how spatial variability within fields affects grain yield. Thousands of soil samples collected on 30-m grids in each BAU and ASP field have been analyzed for general soil chemical properties, which has allowed creation of geospatial maps showing distributions of soil physical and chemical variables. Unmanned aerial vehicles (UAVs) were used to collect detailed spatial data in each field to document crop condition at different times during the growing season. With installation of a second eddy covariance tower this year, we now are measuring evapotranspiration over both BAU and ASP field conditions. Preliminary analyses using random forest machine learning (ML) and principle component analysis (PCA) statistics were used to explore interactions of grain quality and yield, topography, and gridded soil physical and chemical variables. Results will establish the factors that best predict crop yields, which will improve management-zone delineation and management-decision recommendations. All these activities are setting the stage for a long-term comparison of BAU wheat-fallow crop production to more-intense, precision-managed, multi-crop ASP rotations under dryland conditions. Data and preliminary results were disseminated to producers and stakeholders at the Customer Focus Group meeting and to the scientific community in conference presentations. Objective 2: Field management data, including crop inputs, field operations, operational costs, and crop yields, were compiled in a database for the first 3 years of the project. Soil quality/health analyses were completed on initial gridded soil samples. Mid-project, gridded soil sampling was omitted, partly due to staffing limitations and COVID restrictions, and partly because sampling conducted at the end of the complete 4-year crop-rotation cycle (2022) will allow us to fully meet project objectives. Intensive long-term milestone soil sampling of off-site fields (Kansas and Nebraska) was completed to assess long-term effects of management on soil physical and chemical properties (soil health) in semi-arid dryland cropping areas. Data and preliminary results were disseminated to producers and stakeholders at the Customer Focus Group meeting and to the scientific community in conference presentations. Objective 3: Wheat and rye variety trials are in progress, and the genetics by environment by management (GxExM) study was started this year. A new stakeholder-driven study was initiated on persistence of volunteer triticale in alternative dryland rotations. We continued data collection and analysis from wheat field trials, rye/triticale studies, canola study, feed barley, and cowpeas in collaboration with Colorado State University. In addition, we conducted a comprehensive sampling of soil in 288 Alternative Cropping Rotation (ACR) plots for a soil-health assessment after 30 years of various cropping systems. Selected pairs of wheat-rotation-plot data from the long-term ACR study are being evaluated with datasets of air temperature and precipitation to better understand climate impacts on yields in dryland agroecosystems. Identification of the key factors that have historically influenced yields (e.g., timing and amount of precipitation, maximum and minimum air temperatures during key growth stages, exposure to temperatures above a threshold) is the first step towards identifying effective management strategies to adapt to the changing climate.

1. Coal char applied to crop lands reduces nitrogen loss and increases soil organic carbon. Coal-fired power plants generate 130 million tons of coal ash in the United States and 500 million tons worldwide, but only 16% is utilized. Coal ash contains mercury, cadmium, arsenic, and other contaminants and creates a major industrial-waste disposal issue. New uses of coal ash in agricultural production could benefit power plants, farmers, and environmental stakeholders. ARS scientists in Akron, Colorado, worked with researchers at University of Nebraska-Lincoln to develop recommendations for coal char use as crop soil amendment. Optimal one-time additions of coal char to different types of soils resulted in an increase in soil carbon content, important to climate change mitigation and soil health, and greater conservation of nitrogen, an important fertilizer resource. At recommended rates of coal ash application, 10,000 square miles of cropland, 2.6% of cropland in the United States, would be needed annually to dispose the entire United States coal ash production. These promising findings point to the need for systematic, coordinated efforts across the range of cropland sites where coal ash could be used.

2. Cropping system partially offsets tillage-related degradation of soil organic carbon and aggregate properties in a 30-yr rainfed agroecosystem. Land management practices, such as tillage practices and crop rotation, can reduce soil losses and enhance land sustainability. ARS scientists in Akron, Colorado and Lincoln, Nebraska, found that no tillage and corn-soybean crop rotation improved soils properties down to 1 foot. Over the 30-year study, no till increased soil organic carbon annually by 1 ton per acre more than tillage, and continuous corn increased soil organic carbon by 0.27 ton per acre more than continuous soybean. Soil aggregate stability, which reduces soil erosion, was increased by 22% by no-tillage vs. plow and by 10% by soybean-corn rotation vs. continuous soybean or corn. Shifting Nebraska continuous corn and soybean acreage to corn-soybean rotation could offset carbon emissions of about 2200 people (U.S.) while reducing losses of productive soil from crop fields and reducing environmental impacts from stream sedimentation.

3. Potential amendments for improving productivity of low carbon semi-arid soil. Manure, coal char, and biochar are organic amendments that can replace commercial fertilizer to enhance crop production and increase soil organic carbon. ARS scientists in Akron, Colorado, collaborated with scientists from University of Nebraska-Lincoln to assess organic amendments in semi-arid Great Plains cropland production. Char (10 to 60 tons per acre), biochar (2.5 to 5 tons per acre), and composted manure and municipal compost (15 to 30 tons per acre) enhanced dry (pinto) bean yield by 250 lb per acre, corn yield by 1,400 lb per acre, and sugar beet by 616 lb per acre compared with unamended soil. Soil organic carbon also increased 7 to 60% with organic amendment. Adapting 1% of Nebraska crop land to organic amendment could enhance dry bean production to 1.25 tons ($1100) per year, corn to 7,000 tons ($1.5 million) per year, and sugar beet to 3,000 tons ($90,000) per year. Increased yield following these amendments could be related to improved micronutrient uptake and soil organic carbon. At 20 tons of ash per acre, 10,000 square miles of cropland, 2.6% of cropland in the United States, would be needed annually to dispose the entire United States coal ash production. This research shows the dual benefits by recycling the organic by-products (char, biochar, animal manure, and municipal compost) in agricultural land and enhancing land productivity. Long-term net returns must evaluate the tradeoff between increased crop yields and improved soil health with increased transport costs and potential salt or toxic compound build-up.

Review Publications
Panday, D., Mikha, M.M., Sun, X., Maharjan, B. 2021. Coal char effects on soil chemical properties and maize yields in semi-arid region. Agrosystems, Geosciences & Environment. 4(1). Article e20145.
Panday, D., Mikha, M.M., Maharjan, B. 2020. Coal char affects soil pH to reduce ammonia volatilization from sandy loam soil. Agrosystems, Geosciences & Environment. 3(1). Article e20123.
Schneekloth, J., Calderon, F.J., Fonte, S., Nielsen, D.C. 2020. Tillage and residue management effects on irrigated corn (zea mays) performance and water cycling in a semiarid cropping system of Eastern Colorado. Irrigation Science. 38:547-557.
Maharjan, B., Panday, D., Blanco, H., Mikha, M.M. 2021. Potential amendments for improving productivity of low carbon semi-arid soil. Agrosystems, Geosciences & Environment. 4(3):1-10.
Jin, V.L., Wienhold, B.J., Mikha, M.M., Schmer, M.R. 2021. Cropping system partially offsets tillage-related degradation of soil organic carbon and aggregate properties in a 30-yr rainfed agroecosystem. Soil and Tillage Research. 209. Article e104968.