Higher Nitrogen Use Efficiency in Diversified Cropping Systems?
Title: The Root of the Matter–Are Changes in Corn Root Morphology Responsible for Improved Yield and Higher Nitrogen Use Efficiency in Diversified Cropping Systems?
Location: Iowa State University Marsden Farm
Time Period: 2019-2021
Research Team: Matt Liebman, Matt Woods, and Virginia Nichols
Project Description: There is an important need to develop sustainable alternatives to the corn-soybean cropping system that dominates the upper Midwest, as evidenced by recurring problems with water quality, susceptibility to weather extremes, and low profitability. Many of the shortcomings of the existing corn-soybean system are due to its sole reliance on short-season annual crops and the exclusion of deep-rooted perennial crops like alfalfa that provide long periods of living cover. We hypothesize that much of the benefit of alfalfa-based cropping systems to corn and to the environment derives from the joint effects of improving soil physical conditions to promote corn root growth while increasing the N-supply power of soil, especially in deeper soil layers. To test this hypothesis, we will measure soil physical properties, corn root architecture, soil N dynamics, and corn performance in a long-term experiment in Boone Co., IA, that includes a 2-year corn-soybean rotation and a 4-year corn-soybean-oat/alfalfa-alfalfa rotation. We expect that soil resistance to corn root penetration will be lower, corn root systems will be larger and deeper, and the rate of potential nitrogen mineralization from soil organic matter will be greater for corn following alfalfa than following soybean. Empirical data from these research plots will be used within the Agricultural Production Systems Simulator model (APSIM), which can assess the impact of various soil, climate, and crop management factors on crop productivity, nitrate leaching, and nitrous oxide emissions to the atmosphere. Insights from this project will inform strategies promoting higher agronomic productivity, greater N use efficiency, and lower potential for N discharges to water and air. The objectives of the proposed work are aligned with the Iowa Nutrient Research Center's call for the evaluation of "new techniques and strategies that add knowledge leading to cost‐effective reduction of nonpoint source N."
Publications: Nichols, V.A., M. Liebman, and S.V. Archontoulis. 2019. Modeling the roots of the rotation effect. Abstracts of the 2019 American Society of Agronomy Meeting. On-line at: https://scisoc.confex.com/scisoc/2019am/meetingapp.cgi/Paper/118379.
Funders: Iowa Nutrient Research Center
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