Using cover crop mixtures to improve soil health in low rainfall areas of the northern plains

2012 Annual Report for SW11-099

Project Type: Research and Education
Funds awarded in 2011: $354,405.00
Projected End Date: 12/31/2015
Region: Western
State: Montana
Principal Investigator:
Dr. Perry Miller
Montana State University

Using cover crop mixtures to improve soil health in low rainfall areas of the northern plains


We are testing the effects of cover crop mixtures (CCMs) grown during the summer fallow period on soil biological, chemical and physical parameters, and wheat yield. CCMs include plant functional groups that 1) fix N, 2) provide ground cover, 3) have deep tap roots, or 4) have fibrous root systems. One experiment tests presence/absence of plant functional groups, grown in place twice in three years, on four farms. A field-scale design compares conventional fallow with CCM effects on soil water and nitrogen, and wheat yield on six cooperator’s farms. This research provides basic information on agro/economic impacts of CCMs.

Objectives/Performance Targets

1. Position this project for maximal success by gaining familiarity with growth characteristics of targeted candidate species for CCMs by growing crops locally in 2011, prior to potential award of this grant.

1a. We will produce seed of 8–12 crop species at Bozeman to gain greater familiarity with plant growth habit and obtain seed of known quality for research project.

1b. To ensure success of our field research, we will monitor nearby farm fields of CCMs, as time and budget permits, to gain familiarity with sampling CCMs and with practical field challenges.

2. Quantify the effects of CCMs (compared with fallow) on grain yield, quality and economic return.

2a. We will determine differences (with 90% confidence) in yield and quality of grain following each CCM compared to fallow for four plot studies and six field scale studies following the second year of the study.

2b. Based on grain yield, quality, seed costs, equipment costs, NRCS payments, etc. we will determine if the net economic return is different among the treatments. Our performance target is to identify soil-building CCMs that produce similar or more profit in a CCM-wheat system than fallow-wheat, because otherwise adoption is relatively unlikely.

3. Determine the effects of CCMs on soil quality using fallow as a control.

3a. Soil quality indicators that we will measure include biological (potentially mineralizable N (PMN), microbial biomass, enzyme activities, mycorrhizal colonization levels and infectivity potential, and earthworm density), physical (wet aggregate stability, temperature, compaction), and chemical (available nitrogen and phosphorus).

3b. Comparing CCMs with single functional groups to those with subsets or the entire set of functional groups, we will identify the functional group(s) that most contributed to any soil quality change detected.

3c. Indicators that are different between each CCM and fallow after the third year of the study will be identified. Our performance target is to identify which CCMs most improve different aspects of soil quality, allowing farmers to customize a CCM depending on their soil needs.

4. Introduce growers and agricultural professionals (“audience”) to the potential sustainable aspects of CCMs.

4a. We will conduct one field day and two workshops during the first year of the project, focusing on general CC principles and any regional research results (for example from ND). Our first performance target is to directly reach 200 people with these events and indirectly reach another 800 by asking our audience to take handouts to neighbors, friends and colleagues, and by producing a video of the field days that will be accessed online.

4b. Our second performance objective will be to increase the audience awareness and understanding of potential benefits of CCMs. We will assess this with audience evaluations.

5. Educate audience about effects of CCMs on subsequent crop and economics.

5a. In the winter after the wheat phase of this study, we will conduct three to four more workshops to share yield, quality and economic results, have one radio interview with a PI, and produce a CCM webpage to share our findings. Our first performance target is to directly reach 300 people with these events and reach another 2000 indirectly.

5b. Our second performance target will be to increase our audience’s understanding of the agronomic and economic effects of CCMs in our region. This will be assessed with evaluations.

6. Educate audience about the effects of CCMs on soil quality, including functional group benefits, based on our study.

6a. In the year of the second CCM crop, we will host another field day, conduct two to three more workshops to discuss our soil quality results, and prepare an Extension fact sheet on our findings. Our first performance target will be to directly reach 300 people with these events and 1,200 indirectly.

6b. Our second performance target will be to increase the understanding of plant functional groups and to assess this with our educational evaluation plan.

7. Enhance adoption, if study results warrant, of CCMs.


Research in 2012 went as planned, with plot studies managed near Amsterdam (45o 43’ 7.3” N, 111o 22’ 4.2” W) and Conrad, MT (48o 12’ 47.0” N, 111o 29’ 38.2” W), adjacent to farmer-managed field studies. A third farmer-managed study was grown near Dutton, MT (47o 57’ 7.5” N, 111o 24’ 11.5” W). We were able to seed CCMs at the beginning of April to provide the maximum growth window prior to a pre-set June 15 crop insurance cutoff date, intended to protect ‘fallow’ level coverage for 2013 crops. Two key problems were associated with this early seeding window. First, a problematic weed, downy brome (Bromus tectorum), proved difficult to kill completely with glyphosate application during that cool time of year. Consequently this weed affected CCM growth at both locations, but especially at the site east of Conrad, MT. Rescue treatments of a grassy herbicide were used at both locations in the CCM treatments that did not include a grassy functional group. More importantly, despite average to slightly warmer than average growing temperatures in 2012, insufficient CCM growth was present prior to June 15. After consultation with collaborating farmers, it was determined that the June 15 crop insurance cutoff date is not crucially important to their planning, and so in 2013 we will delay seeding until early May and set termination according to plant biomass goals.

The farmer-managed fields were each planted at different windows and with different cover crop species mixtures. The Conrad site was also planted at the beginning of April and also beset with downy brome, which forced termination earlier than desired. The Dutton site was planted in late April in very dry soil, and so seed germination was delayed until after a significant mid-May rainfall event. This site was terminated in July. The Amsterdam site was sown at the beginning of June and terminated in early August.

Accomplishments specific to each objective:

Objective 1

Preliminary research was conducted in 2011 at the Bozeman experimental farm to examine growth of purported ‘root’ crops at different planting dates, with and without fertilizer N. Three commercially available lines of tillage radish grew similarly and produced large roots only at the mid-June seeding date. Beet did not grow well at the early planting date. Turnip was highly susceptible to flea beetles at all planting dates. Seed was harvested successfully at Bozeman for many, but not all, of the species used in this experiment. Radish is challenging to thresh to separate seeds from pods without damaging the seed. Two grower fields were sampled to measure CCM biomass proportions, soil water and N, and subsequent wheat yield. CCM biomass was found to be strongly biased in favor of N-fixing pea in both fields, which may be expected in typically N-limited cereal stubble. This raises a key question of whether some amount of starter N is required to obtain balanced CCM biomass proportions, and we are fertilizing at experimental sites with very low available N. In one case were it was measured, wheat yield did not differ statistically (P=0.14) between CCM (53.6 bu/ac) and chem fallow (60.4 bu/ac), although grain protein was greater (P=0.02) for fallow (12.6%) than CCM (11.4%).

Soil quality parameters associated with Objective 3 will begin to be measured in spring 2013, as planned, on three CCM treatments (full mix, pea only and fallow). Because soil parameters are slow to change, we are making the majority of soil quality measurements after the CCM treatments have been grown for the second time, in place, in 2014. This is a deliberate strategy to fast-forward the soil change response.

Towards Objective 4, we conducted a field day on June 14 at our Gallatin Valley site. With cooperation from NRCS, we attracted approximately 50 attendees for our two-hour field day. Dr. Jones also has given two presentations on cover crops since this project commenced. One was at the Winter Trend Series (Shelby, MT, 12/6/2011), put on by the local NRCS Conservation Districts, and the second was at the Northern Pulse Growers Association Pulse Days (Billings, MT, 12/13/2012). These two events were attended by approximately 150 people total; thus we reached our goal of 200 direct contacts. We have hired a videographer who has interviewed five growers to date and taken both aerial and ground shots of one of our sites to be used in the video. He will interview researchers for the video when we have more useful results, and we will release the video in the third year of the study via You-tube and for distribution at meetings as a DVD.

Dr. Jones’s Winter Trend Series presentation on cover crops was evaluated. Of those who filled out the evaluation (n=16), 100% said they had a better understanding of the topic covered and that they would share some aspect of his program with at least one other person. In addition, 83% of respondents said this information would cause them to change a management practice.

Objectives 2 and 5 begin delivery in 2013 after the first wheat test crop phase, while Objective 6 and 7 must wait until the final year of the study.

Impacts and Contributions/Outcomes

It is premature to comment on regional impacts from this research. However, we have already learned of limitations associated with using an early spring growth period prior to the existing summer fallow insurance cutoff date of June 15. We have also learned the challenge associated with achieving balanced biomass proportions among all components in the CCM within a field setting. Since this is the first replicated research on CCMs in Montana, negative or positive results can be expected to yield economic value. Negative results may save farmers from losses over a larger scale by avoiding the use of CCMs, while positive results may help direct desired change in soil parameters, with farm-specific benefits anticipated.


Herb Oehlke
22 miles east of Conrad
Conrad, MT 59425
Office Phone: 4066272184
Chad Doheny
2490 22nd Lane NE
Dutton, MT 59733
Office Phone: 4067884122
Carl Vandermolen

56 Park Plaza Road
Bozeman, MT 59715
Office Phone: 4065871288
Will Roehm
east of Great Falls, next to Maelstrom Air Force base
Great Falls, MT 59405
Office Phone: 4067883199
Jane Holzer
Montana Salinity Control Association
PO Box 909
Conrad, MT 59425
Office Phone: 4062783071
Jim Bjelland
21 miles east of Conrad
Conrad, MT 59425
Office Phone: 4067883666
Susan Tallman
M.Sc. Student
Montana State University
334 Leon Johnson Hall
Bozeman, MT 59717-3120
Office Phone: 4065873977
Clain Jones
Assistant Professor
Montana State University
334 Leon Johnson Hall
Bozeman, MT 59717-3120
Office Phone: 4069946076
Dr. Cathy Zabinski
Associate Professor
Montana State University
334 Leon Johnson Hall
Bozeman, MT 59717-3120
Office Phone: 4069944227
Roger Benjamin

10 miles NW of Fort Benton
Fort Benton, MT 59442
Office Phone: 4067885142