Predicting overwinter nitrate-N changes at the subfield scale in leaching-susceptible, agricultural soils

Project Overview

GW18-179
Project Type: Graduate Student
Funds awarded in 2018: $25,000.00
Projected End Date: 01/31/2021
Grant Recipient: Montana State University
Region: Western
State: Montana
Graduate Student:
Major Professor:
Dr. Clain Jones
Montana State University
Major Professor:
Dr. Patrick Carr
Montana State University

Commodities

  • Agronomic: wheat

Practices

  • Crop Production: fertilizers, nutrient cycling, nutrient management, water management
  • Education and Training: on-farm/ranch research, participatory research
  • Farm Business Management: budgets/cost and returns
  • Soil Management: nutrient mineralization, organic matter, soil analysis, soil chemistry, soil microbiology, soil physics, soil quality/health
  • Sustainable Communities: infrastructure analysis

    Proposal abstract:

    Nitrogen fertilizer is generally the largest input cost for producers in Montana and in much of the
    western United States. Despite this fact, scientists, producers, and their advisors have not
    established a consistent and well-tested system for determining areas of fields that are more or less
    responsive to nitrogen fertilizer. This proposal attempts to develop such a system. We will employ
    novel remote-sensing techniques to investigate subfield-scale changes in soil nitrate-nitrogen (N)
    during winter months. Restricting the period of inquiry to the months between September and
    April (henceforth ‘overwinter’) will eliminate or minimize impacts of confounding variables such
    as crop uptake, fertilizer inputs, and denitrification, allowing for direct estimates of variables such
    as leaching and mineralization. Temporally intensive overwinter sampling will facilitate
    development of a model to predict overwinter N changes (ONCs), which are known to range from
    +61 to -23 lb/ac in this region. Such a model will serve to minimize over- and under-fertilization
    for the many farmers applying constant rates of fertilizer in spite of—or in lieu of—soil test results.
    Complicating the situation further is the threat of warmer and wetter Montana winters, which could
    feasibly exacerbate ONCs. This research will have implications for 1) grower profits through
    enhanced N use efficiency, reduced N surpluses, minimization of suboptimal yields caused by
    under-fertilization, and improved methods of variable rate fertilizer application.; 2) water quality
    via minimization of N surpluses and N leaching; and 3) climate change impacts on modern farming
    practices by strengthening awareness among farmers of how altered precipitation and temperature
    patterns interact to affect N use efficiency, water quality, and soil health.

    Project objectives from proposal:

    1. Quantify subfield-scale variability in ONCs toward improved precision ag methods such as
    variable rate fertilizer application.
    2. Develop a model to predict ONCs and to notify farmers when large ONCs are likely to have
    occurred in order to minimize economic and environmental injuries resulting from uninformed
    fertilizer management decisions.
    3. Demonstrate to farmers the economic and environmental benefits of soil testing and the
    implications of changing precipitation and temperature patterns for modern farming practices.

    Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.