Investigating the Legume Green Fallow Alternative on North-Central Montana No-Till Operations

Project Overview

Project Type: Graduate Student
Funds awarded in 2010: $24,250.00
Projected End Date: 12/31/2010
Grant Recipient: Montana State University
Region: Western
State: Montana
Graduate Student:
Major Professor:
Dr. Perry Miller
Montana State University

Annual Reports


  • Agronomic: hay, wheat
  • Animals: bovine


  • Animal Production: feed/forage, winter forage
  • Crop Production: application rate management, conservation tillage, continuous cropping, fallow, no-till, nutrient cycling, organic fertilizers, tissue analysis
  • Education and Training: extension, on-farm/ranch research, participatory research
  • Farm Business Management: budgets/cost and returns, feasibility study
  • Natural Resources/Environment: biodiversity, soil stabilization
  • Production Systems: agroecosystems
  • Soil Management: green manures, nutrient mineralization, organic matter, soil analysis, soil quality/health
  • Sustainable Communities: sustainability measures


    We conducted an on-farm study with north-central Montana no-till wheat producers using legume green manures (LGM) as a summer fallow alternative. Soil water, nitrogen and wheat yield response following LGM and fallow treatment were evaluated, and collaborating producers were interviewed. Wheat yields following LGM treatment were less than following fallow, as was grain protein when wheat was fertilized with N; LGMs conversely increased grain protein when wheat was unfertilized. Wheat yield depressions were attributed to LGM's temporarily limiting soil N available to subsequent wheat. Producers interviewed noted that seed costs and lack of immediate wheat yield benefits were formidable challenges to LGM adoption.


    Summer fallow practice has been a common management strategy employed over the past century to store soil water and stabilize wheat yields in dryland northern Great Plains (NGP) cropping systems. Summer fallow serves this purpose well, but it also can precipitate net declines in soil organic matter, saline seeps (Nielsen and Calderon, 2011) and nitrate leaching (Campbell et al., 2006). While summer fallow acreage has steadily declined since the early 1970s in much of the northern Great Plains (Carlyle, 1997; Tanaka et al., 2010), north-central Montana represents a region where summer fallow practice remains steadfast, with ~80% of cropland remaining in a summer fallow–wheat rotation (USDA-FSA, 2010). Half-season legume green fallow crops (legume green manure, hay or forage) used to replace summer fallow may be a water-conservative way to intensify north-central Montana agroecosystems (Miller et al., 2006) while concomitantly reducing N fertilizer dependence and increasing soil and water conservation. Past plot-scale studies established that green fallow crops can threaten soil water available to subsequent wheat (Army and Hide, 1959; Brown, 1964; Biederbeck and Bouman, 1994; Aase et al., 1996; Brandt, 1996; Zentner et al., 1996), but that this risk is reduced if green fallow crops are terminated early before full bloom stage and no-tillage practices are used (Zentner et al., 2004; Miller et al., 2006). Nonetheless, legume green fallow crop adoption is currently negligible in north-central Montana.

    We conducted a participatory research project with five no-till wheat producers trialing legume green manures (LGMs) as a summer fallow replacement in north-central Montana. This study has an original focus on treatments exclusively using no-till management, early legume termination and participatory research at the field-scale. Our objectives were to assess the agronomic viability of using no-till, early-terminated LGMs to replace summer fallow under farmer management and at the field-scale, and to better understand LGM adoption from the producer’s perspective. Soil water use, soil N levels and wheat yield response following LGM and summer fallow treatments were assessed. Producers were interviewed upon completion of the project to elucidate potential challenges to replacing summer fallow with a LGM crop.

    Project objectives:

    1) Quantify the effects of LGMs on soil N, soil water use and the effect they have on the following wheat crop compared to summer fallow.

    2) Assess how no-till management and early termination may affect LGM management.

    3) Assess LGM management over regionally varied sites and management practices by different producers.

    4) Conduct a marginal economic assessment of LGM management compared to standard summer fallow under no-till management.

    5) Assess producer initiative to continue LGM management based on results of the study.

    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.