Project : USDA ARS

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Research Project: Evaluating Management Strategies to Increase Agroecosystem Productivity, Resilience, and Viability

Location: Agroecosystem Management Research

2022 Annual Report

Objectives
Objective 1: Evaluate impacts of conservation tillage practices and crop diversity on soil carbon sequestration, greenhouse gas emissions, and soil microbial communities. Subobjective 1A: Determine how crop rotation diversification affects soil organic carbon. Subobjective 1B: Quantify soil greenhouse gas emissions from different management and cropping systems. Subobjective 1C: Quantify soil microbial communities from different management and cropping systems. Objective 2: Quantify the impacts of modified management practices of integrated crop-livestock systems to improve agricultural productivity in a temperate environment.. Subobjective 2A: Determine soil physical, chemical, and biological quality changes under integrated crop-livestock (ICL) systems. Subobjective 2B: Determine soil greenhouse gas fluxes from ICL systems. Objective 3. Quantify water management and nutrient management effects on the productivity of crop and feedstock production systems. Subobjective 3A: Determine water use in annual and perennial systems used for bioenergy. Subobjective 3B: Evaluate nitrogen use efficiency on long-term cropping systems. Objective 4: Operate and maintain the Platte River – High Plains Aquifer Long-Term Agroecosystem Research (LTAR) network site using technologies and practices agreed upon by the LTAR leadership. Contribute to the LTAR working groups and common experiments as resources allow. Submit relevant data with appropriate metadata to the LTAR Information Ecosystem. Subobjective 4A: Establish and instrument LTAR research sites. Subobjective 4B: Contribute data to the LTAR database as requested.

Approach
An integrated, systems approach is needed to improve agricultural systems toward greater sustainability to meet societal demands for food, feed, fiber, and fuel. Soil and crop management strategies that optimize the capacity of cropland and grassland soils to store carbon while minimizing greenhouse gas emissions from nitrogen fertilizer and other management practices are required. Past research has increased crop nutrient and water use efficiencies through best management practices coupled with the development of better germplasm. More improvements are required to adapt to climate variability and change, increased competition for limited water resources, and increased demand by a growing population and improved standard of living. Further, a better understanding of how genetics, management, and environmental conditions affects soil organic carbon dynamics, including impacts on soil microbial structure and function, is needed to improve or maintain critical soil functions and associated ecosystem services. Research activities will investigate the role of agronomic practices on soil properties and greenhouse gas fluxes (Objective 1), quantify productivity and soil quality in integrated crop-livestock systems (Objective 2), determine nutrient and water management effects on crop and feedstock production systems (Objective 3), and operate and maintain the Platte River—High Plains long-term agroecosystem research site in collaboration with University of Nebraska-Lincoln (UNL) (Objective 4). Although each objective has a specific research focus, we recognize that a systems-based approach is required and will integrate these research objectives, as needed, to improve our current understanding of integrated agricultural systems. Results will be shared with producers, consultants, extension educators, state and federal regulatory agency personnel, and other scientists. Products resulting from this project plan will contribute to improved soil, crop, and integrated crop-livestock management relevant approaches and tools applicable to temperate regions within sub-humid and semi-arid environments.

Progress Report
Progress has been made in all four objectives and subobjectives. Under Objective 1A, substantial progress has been made that determined crop rotation diversity increases soil organic carbon more than nitrogen fertilizer rates. For Objective 1B, soil greenhouse gas (GHG) data have been collected using static chamber methodology and data have been summarized and presented. Greenhouse gas data along with soil samples have been summarized and preliminary data reported. Under Objective 1C, metagenomic/metatranscriptome assembly data have been published indicating the time of sampling, host plant species, and nitrogen fertilization had major effects on microbiomes. For Objective 2A, substantial progress has been made with soil samples completed, analyzed, and archived. Soil samples have been summarized for soil biological property analysis to better understand regional impacts from current integrated-crop livestock management practices. For Objective 2B, substantial progress has been made with the publication of integrated crop-livestock management effects on greenhouse gas emissions. Results indicate that incorporating perennial grasses into integrated crop livestock systems will provide the most effective GHG mitigation outcomes. For Objective 3A, soil matric potential water sensor values have been presented comparing perennial grass and corn. Under Objective 3B, substantial progress has been made with the publication of nitrogen use efficiency data and grain yield in an irrigated continuous corn system. Further research on the relationship between crop diversity and nitrogen use efficiency across multiple environments is ongoing. For Objective 4A, baseline Long-term Agroecosystem Research (LTAR) cropland soil data have been analyzed and checked for quality control. Under Objective 4B, existing business-as-usual and aspirational experimental sites are fully instrumented to measure carbon dioxide flux, weather data, and collect phenocam data. Long-term Agroecosystem Research study plot sites have been established with aspirational and business-as-usual treatments.

Accomplishments
1. Soil resources are greater with crop diversity. Crop rotation has been used for centuries, but how these practices specifically affect soil organic matter and soil microbial communities are still unclear. ARS scientists in Lincoln, Nebraska, found that across sites in the U.S. and Canada, crop rotations affected soil organic matter chemistry in similar ways and that soil organic matter sources were largely microbial in origin. Results highlight how more diverse crop rotations contribute to improved soil health and crop productivity.

2. Ground-truthing agroecosystem process models improves predictive capacity. Models help society understand climate change but a major challenge in these models is accurately representing soil processes that affect soil organic carbon (SOC) storage. Current models often use assumed, instead of measured, values for different types of SOC which each have different rates of decomposition and stability. A cross-location collaboration between the Woodwell Climate Research Center (formerly Woods Hole Institute) and USDA-ARS scientists in Lincoln, Nebraska, updated the Daily Century (DAYCENT) model with measured SOC data from several long-term USDA-ARS research locations. The updated model indicated that managed grassland and cropland soils in the Great Plains today have lost respectively 4% and 40% of their original SOC content. Further, the updated model showed even higher predicted SOC losses under all future climate scenarios compared to the original DAYCENT model. These results will be of great interest to producers striving to adapt agricultural practices to a changing climate.

U.S. DEPARTMENT OF AGRICULTURE

Agroecosystem Management Research: Lincoln, NE