Enhancing Cropping System Sustainability by Minimizing Ammonia-N Losses from Biological and Chemical Inputs

Project Overview

Project Type: Research and Education
Funds awarded in 2010: $190,009.00
Projected End Date: 12/31/2013
Grant Recipient: Montana State University
Region: Western
State: Montana
Principal Investigator:
Dr. Richard Engel
Montana State University

Annual Reports


  • Agronomic: hay, wheat


  • Animal Production: feed/forage
  • Crop Production: conservation tillage
  • Education and Training: demonstration, extension, farmer to farmer, on-farm/ranch research, participatory research, workshop
  • Farm Business Management: budgets/cost and returns
  • Soil Management: green manures, soil analysis

    Proposal abstract:

    Ammonia (NH3) volatilization from chemical fertilizer and legume green manure nitrogen (N) inputs represents a significant pathway of N loss to the environment. On-farm measurements of NH3 losses from these sources have rarely been conducted. This Research and Education project will quantify NH3 losses from urea fertilizer and following legume manure termination using a micrometeorological method, and develop management strategies to minimize losses. Studies will be conducted at three farms with crucial grower participation. Results will be shared with the agricultural community at field days, workshops, and in popular farm media. Currently, there is a large gap in knowledge about the magnitude of NH3 losses from farms in the Northern Great Plains (NGP), that when filled, will improve agricultural sustainability and environmental quality. Based on preliminary studies showing average N loss from urea of 24%, the value of that lost N extrapolated across the state equates to approximately $30,000,000 in Montana alone. ?

    Project objectives from proposal:

    1. Quantify on-farm ammonia loss from urea fertilizer applications (chemical) and legume termination (biological) from NGP dryland cropping systems.

    Our performance target will be to determine the fraction of applied urea fertilizer that is lost as NH3 for applications to winter wheat applied between fall to early spring. Two or three different application timing dates will be compared at each farm site, e.g. Oct, Dec-Jan, and March-Apr We have conducted preliminary studies that indicate losses can be quite large from cold soils (up to 40%). Our study will identify the environmental and soil conditions that are most conducive to high NH3 losses. Our second performance target will be to determine the fraction of N in legume manure that is lost as NH3 following its termination by glyphosate spraying and mowing. Most studies on NH3 volatilization have utilized enclosures or chambers rather than the micrometeorological techniques being proposed here. Micrometeorological approaches are widely recognized as providing more reliable estimates of gas N losses than enclosures, because they do not disturb the environment or soil processes that affect gas exchange at the ground, provide continuous measurements over time, and provide a measure of gas loss over a larger footprint than enclosures (Denmead, 1983).

    2. Identify mitigation strategies or production practices that will minimize ammonia-N losses where losses are found to be significant from inorganic and organic N inputs.

    Our performance target is to mitigate NH3 losses to ? 5% of the N input. We will evaluate different mitigation strategies based on comments and input received from our participating cooperators, area growers and ag-professionals. For example, our urea studies may evaluate: i) subsurface urea banding at seeding; ii) pre-plant broadcast applications followed by direct seeding; and iii) enhanced efficiency fertilizers that include urease inhibitors. Under strategy ‘i’, most no till air-seeders have the capacity to apply both fertilizer and seed. Placement of fertilizer urea below the soil surface is a known strategy for mitigating NH3 emissions to the air. Under strategy ‘ii’, many air-drills are configured with hoe-style openers that create considerable disturbance at the soil surface. The level of disturbance may be sufficient to cover urea prills on the soil surface, thereby mitigating NH3 losses. Under strategy iii, enhanced efficiency fertilizers have gained popularity in recent years because of their potential to enhance crop N use efficiency. Recently, NRCS programs such as the Conservation Stewardship Program (CSP) have targeted agricultural air quality issues including NH3 pollution. The CSP provides enhancement points to growers for adopting practices that improve air quality including enhanced N fertilizers that contain urease inhibitors.

    Few reports are found in the literature that utilized micrometeorological methods to quantify NH3 volatilization losses in the field from legume green manures. Therefore, we make no prejudgments about what we might find. Incorporation of crop residue is the most effective approach for mitigating NH3 losses. Under a strict no till scenario tillage is not an option, however, this practice may need to be considered should NH3 losses prove significant.

    3. Develop and execute an educational outreach program to producers and agricultural professionals that will improve their understanding of on-farm N cycles and N loss mitigation, thereby leading to enhanced sustainability and environmental quality.

    Our performance target is to achieve direct contact with 1000 people (or people-hrs) and indirect contact with another 5,000 people through radio, news releases, and trainings by ag-professionals and farmer to farmer communication. Our education outreach programs will target ag-professionals who are involved in outreach to their grower clients. Therefore we anticipate there will be a multiplier effect to our direct contact hours.

    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.