Our goal is to enhance the sustainability of dryland cropping systems in SW Colorado and SE Utah by growing cover crops during the fallow period between two cash crops. Our objectives are to: 1) test the growth and performance of different cover crop species/mixtures across distinct site and management contexts; 2) assess the impacts of cover crops on soil fertility, soil moisture, cash crop yields, and overall farm profit; and 3) disseminate project results and contribute to improved soil health management in the region. In order to accomplish these objectives, we established two field trials at the Southwest Colorado Research Center (SWCRC) and eight research and demonstration trials on farmers’ fields. These trials encompass two crop rotations (winter wheat-fallow and winter wheat-safflower-fallow), two tillage regimes (conventional tillage and no-till), as well as conventional and organic crop production systems. To date, 19 summer or early fall-planted and five spring-planted cover crop mixtures have been tested. It is too early to draw conclusions as to the feasibility of cover crops in dryland cropping systems in the project area, some key preliminary findings/outputs are:
- Late summer or early fall-planted cover crops produced considerably more biomass than the spring-planted cover crops. For example, plant biomass of spring-planted mixtures averaged 713 lbs/ac in 2017, while fall-planted mixtures exceeded 4000 lbs/ac in 2016 at the SWCRC. We also found that if cover crops are planted too early after wheat harvest and before adequate moisture is available then volunteer wheat tends to dominate plant canopy and biomass.
- Some species performed poorly (e.g. teff, flax, sun hemp, balansa clover) and the notion that the more species (i.e., higher diversity) is always better may not hold true in the project area. We also note that climate in the region (semi-arid with short growing season), seed cost, and proper management (i.e., planting date, seeding depth, inoculation) are all key considerations for developing high performance cover crop mixtures.
- Preliminary results from the SWCRC indicated a 27% yield penalty for wheat following cover crops vs. fallow, and that this is likely due to temporary immobilization of soil nitrogen and reduced soil moisture at planting. We note that yield penalties were lower (19 & 22%) for two on-farm trials for which we have early results. No fertilizer was applied to the wheat and this will be reconsidered moving forward. While inputs costs were higher for the cover crop treatments, we feel that continued management refinements will help to reduce costs.
More detailed results and analysis will be included in a CSU-AES Technical Bulletin that will be published in early 2018. Project concepts and highlights have been presented at multiple events including: three field tours, one field day, six workshops, two growers’ meetings, two research center conferences, and two ASA-CSSA-SSSA annual meetings. Many of these presentations, along with project announcements, interviews, and useful links are available on the project website at http://drylandcovercrops.agsci.colostate.edu. Attendance to the outreach events has been generally good. Moreover, the attendees appear to have gained knowledge on cover crops, soil health, and management practices. These and other indicators bode well for the adoption of cover crops and other soil health improvement practices in the region.
1. Evaluate the performance of cover crops and determine their effects on soil moisture, soil fertility, weed control, soil biology, soil erosion, and on the succeeding cash crop.
- Establish field trials on farmers’ fields and at the Southwestern Colorado Research Center (Research Center).
- Collect baseline data at the start of each trial.
- Measure soil and plant characteristics annually to determine if and how cover crops affect dryland cropping systems in SW Colorado and SE Utah.
2. Assess the economic feasibility of cover crops in dryland cropping systems. Partial budget analysis will be used to track changes in revenue that result from the operational and input costs associated with planting cover crops. Analysis will include measuring return on investment following cover crops, accounting for changes to yield or quality of cash crops. This will determine where a cover crop strategy produces a profit or loss to the operator. Indirect costs and benefits of cover crop management will be documented.
3. Educate farmers and others about cover crops and disseminate project results (all participants). This will be achieved via:
- Yearly field tours and workshops
- A project documentary video
- Factsheets, CSU-AES Technical Bulletins, and refereed journal articles
- Presentations at growers meetings, workshops, and other relevant events in Colorado and Utah.
4. Gauge the project’s impact by how well the outreach events are attended, feedback from each event, and the number of acres planted to cover crops since this project started. NRCS will continue to track the number of additional applications for cover crop grant assistance and will assist with long term monitoring of cover crop practice adoption.
Cover crops grown during the fallow period between two cash crops such as winter wheat and safflower will achieve one or more of the following benefits: (1) reduce soil erosion, (2) improve soil fertility and biological activity and/or (3) suppress weeds, without negatively impacting the profitability of the cropping system.
A total of 10 field trials have been conducted on farmers’ fields and at the Southwestern Colorado Research Center in Montezuma and Dolores counties in Colorado and in San Juan County, UT. All these trials are located on fields that have been historically farmed in a dryland annual cropping system. They encompass two crop rotations (winter wheat-fallow and winter wheat-safflower-fallow), two soil management practices (conventional tillage or CT and no-till or NT), and conventional and organic crop production systems. In the on-farm trials, cover crops were planted in either a large block or in large strips, with one or more control strips left fallow for comparison. The trials at the Southwestern Colorado Research Center were established on small plots with three replications.
Cover crop mixtures were developed with the participating farmer, NRCS staff, and research center staff. To date, 19 summer/fall-planted cover crop mixes and five spring-planted cover crop mixes have been tested. These mixes include legumes (e.g., pea, hairy vetch, clovers, sainfoin, and dry bean), grasses (rye, ryegrass, triticale, barley, oat, corn, sorghum sudan grass, pearl millet, and teff), brassicas (canola, rapeseed, radishes, forage collards, and turnip) and other broadleaves (flax, safflower, sunflower, buckwheat, and sunn hemp). The number of species in each mix varied from three to 10. The cover crop mixes were planted in fallow in the summer or early fall after wheat harvest or in the spring after the snow melts and the soil is dry enough for field operations. The only test where a cover crop, namely yellow sweet clover, was interseeded with winter wheat was not successful due the slow and low growth of yellow sweet clover before it was terminated in the spring when winter wheat was sprayed to control weeds. Seeding dates varied from July 29th to December 6th and from April 2nd to April 20th. Terminations dates were around June 10th in 2016 and June 20th in 2017. Seeding rates ranged from 10 to 43 lbs/acre and seed cost from $10/acre to $48/acre. The goal was to explore as many cover crop species and mixes as practical to determine their performance and their impacts on soil health and on the cash crop. We also wanted to test different management practices, so that we can narrow down the choice of species for the project area. This was important because of the lack of research-based information on cover crops in dryland cropping systems in the project area.
Soil mapping and baseline soil characterization was accomplished in the summer or early fall of 2015. Detailed soil and plant measurements are done each year to assess the impact of cover crops on soil quality and health and on the cash crop. They include:
- Gravimetric soil water content before planting cover crops and before planting the cash crop. Sampling depth varies from 2.0 to 4.0 feet, depending on the type of trial (on-farm vs. research center trials) and on soil condition.
- Soil water infiltration rate with Cornell Sprinkle Infiltrometer. The infiltrometer was calibrated at each site to provide a rainfall rate of approximately 0.5 cm/min. Measurements are generally done in August or September.
- Soil test analysis to measure soil pH, organic matter, nutrient availability (major and some minor nutrients), and cation exchange capacity. Soil samples are taken at a depth of 0 to 6 inches prior to planting cover crops or the cash crop. The same soil samples are used to run the Haney soil health test, which provides an alternate method to assess soil nutrient (NPK) availability.
- Plant biomass and canopy cover: The Line-Point Intercept method is used to calculate canopy cover and ground cover prior to cover crop termination. Plant biomass is determined by clipping plant matter in a 1.24 ft.-radius range hoop, placed at the beginning of the Line-Point Intercept transect. A subsample is dried at the oven at 60 deg. C for 24 hours (plants are fairly dry by the time we place them in the oven) to determine dry matter.
- Cash crop yield and quality. Grain yield in the fallow and cover crop treatments is provided by the cooperating farmer or we estimate it by taking several samples in the field, threshing them, and weighing the grain. The grain protein (wheat) or oil (safflower) content is determined in the laboratory.
It is too early to draw conclusions regarding the effects of cover crops on soil health or quality or on their agronomic or economic viability but some trends are starting to emerge.
- Fall-planted cover crops produced more biomass than spring-planted cover crops, which can be expected due to the longer growing season for the fall-planted cover crops. Dry matter of spring planted cover crops were generally less than 1000 lbs (average of 713 lbs/acre at SWCRC#2, 692 lbs/acre at Barry Middle, 704 lbs/acre at Barry WSW, and 242 lbs/acre at Crowley). Summer of fall-planted cover crops averaged 4479 lbs/acre at SWCRC#1 in 2016 and 3438 lbs/acre at SWCRC#2 in 2017. The latter had a predominance of volunteer wheat. In two other fields that were monitored in 2017 but are not part of the project, fall-planted cover crops averaged 3007 lbs/acre in one field and 1857 lbs/acre in the other field on May 16, 2017. Winter triticale or winter rye were the dominant species in these fields. In one of the project on-farm trials, cover crops were planted on July 29, 2015, approximately one week after winter wheat was harvested. They produced 400 lbs/acre of dry matter in one field and 968 lbs/acre in another field before they were killed by a hard freeze in late October. The cover crop mix included warm season species such as sunflower, sorghum sudangrass, and Proso millet. More biomass was produced in the spring by the species (e.g., purple top turnip and yellow sweet clover) that survived the winter. The challenges of planting cover crops too early after wheat harvest are soil moisture availability and weed control, particularly volunteer wheat. Volunteer wheat was a major contributor to plant canopy and plant biomass in at least two trials. It can be considered a cover crop, except that it harbors diseases and insects (e.g., RWA, western bean cut worm) and will out compete other cover crop species and limit plant diversity. The time interval from wheat harvest until there is enough moisture to trigger seed germination varies from year to year and will determine how soon after wheat harvest one can control volunteer wheat and plant cover crops. That interval can be shortened with no-till management. No-till will also conserve moisture compared to conventional tillage. Volunteer wheat has not been much of an issue in spring-planted cover crops.
- The more plant biomass is produced, the higher the uptake of soil moisture and nutrients. This was the case in six field tests whereby the amount of available N and moisture was markedly higher in the fallow treatment than in the cover crop treatment(s) prior to wheat planting. In three of these trials where winter wheat was planted in 2016 and harvested in 2017, wheat yield was substantially lower in the cover crop treatment than where no cover crops were planted. The difference was highly significant at the SWCRC#1 trial which had three replications.
- On the upside, there were fewer weeds in cover crop mixtures that had a good stand and produced a significant amount of biomass.
- In the short-term, it appears that cover crops take up more nutrients than they contribute. This was certainly true for N. The question then is, “should there be restitution of the depleted nutrient e.g., by applying N fertilizer to the cash crop based on soil test recommendations?”. This may not make up for the loss of soil moisture or may even exacerbate it by promoting vegetative growth at the expense of grain production. Water in the project area is undoubtedly the most limiting factor to crop production. The expectation is that in the long term, cover crops will enhance soil organic matter, which will increase soil water holding capacity. It would also improve soil structure, increase soil cover and soil biological activity, and thus increase soil water infiltration and reduce soil evaporation. Soil moisture storage and nutrient cycling will be enhanced, which would offset cover crop seed cost and management. Microbial biomass was generally higher in the cover crop than in the fallow treatment but the difference was either non-significant or its significance could not be established due to the lack of replications. Water infiltration rate was significantly higher (P=87%) in the cover crop than in the fallow treatment at the SWCRC trial #1 in 2016 but there were no significant or apparent trends at the other test sites in 2016 or 2017.
- The notion that the more species (diversity is important) in the cover crop mix, the better it is for soil health may be tough to achieve in the project area due to economic considerations and to limitations such as water scarcity and the relatively short growing season. Some species have not done well enough to warrant their inclusion in the cover crop mix in the future. They include teff, flax, sun hemp, crimson clover, berseem clover, and balansa clover. Hairy vetch shows promise but its contribution to plant canopy and biomass was negligible at most test sites. Yellow sweet clover did well in two fields in the fall of 2015 and spring of 2016 but at other fields its stand was poor or nonexistent. Among the legumes, peas did the best. Winter rye performed well as did winter triticale. Spring barley and oat get established easily if there is adequate moisture but in our tests, they did not produce much biomass, which has more to do with the length of the growing season than with the species themselves. Sorghum sudangrass, corn, sunflower, pearl millet, and possibly other warm season plants will put up significant growth if planted soon after wheat harvest. This was the case in only one test where cover crops were planted in late July and the first freeze did not occur until late October, which was two to four weeks later than normal. Among the brassicas, Winfred turnip did the best. Rapeseed and canola either did not get established or were planted too late to survive the winter. Both do well in monoculture in SW Colorado with best management practices and favorable weather conditions. Small-seeded cover crops such as canola, rapeseed, and yellow sweet clover present challenges due to their seed size. They cannot be planted deep (e.g., more than half an inch) or their emergence may suffer. This can be exacerbated by soil crusting after a rain event. A poor stand will diminish the small-seeded cover crops ability to compete with weeds and with other cover crop species, and to overwinter. Ideally, the smaller seeds should be placed in a separate drill box (small seed box) than the larger seeds but so far in this project, all the cover crop seeds were mixed before planting them, which may affect seed flow and distribution. Another consideration in selecting cover crop species and mixtures adapted to the project area is flowering and seed maturity. Cover crops are usually terminated before any of the species makes viable seeds. In 2016, cover crops were terminated around June 10th but in 2017, they were terminated around June 20th, which was late since some of the species (e.g., oats and barley) made seeds.
It is too early to assess the impacts of this project on dryland farming in the project area but there has been more interest in soil health as evidenced by the number of workshops, conferences, and other related events and by the number of attendees to these events. More acres have also been planted to cover crops since the start of this project, although we do not yet have exact numbers to back this up.
The ultimate goal of this project is to develop cover crop mixtures and management practices that will enhance the productivity, economic viability, and environmental benefits of dryland farming in SW Colorado and SE Utah. We have made inroads towards this goal but more time is needed, given the arid and variable nature of the climate in the project area. Moreover, this is the first project of its kind in the project area with its unique features and challenges, which makes it difficult to extrapolate research results from other farming environments where cover crops have been tested and incorporated into dryland crop rotations.
We use a participatory approach to conduct research and to educate agricultural producers and others about the potential benefits of cover crops in the project area. The approach consists of having a select number of farmers test cover crops on their fields and share their findings with neighbors and other agricultural producers. These farmers decide what cover crop species to plant and when, with assistance from the USDA-NRCS in their county. A large amount of data is collected and analyzed by the project staff to quantify the effects of these cover crops on the soil, cash crop, and the cropping system as a whole. The results are discussed by the project participants and presented to the larger community at meetings, tours of the test sites, workshops, conferences, etc. Information about the project, presentation excerpts, videos, and useful links are posted on the project’s website on a regular basis.
Educational & Outreach Activities
We organized a number of educational and outreach activities and participated to others.
- Field tours and field days:
- June 9, 2016: Cover crops field trials
- August 18, 2016- CSU-SWCRC Field Day: Cover crops, alternative crops, soil and water management and conservation, orchard management
- May 30-31, 2017: Cover crops field trials
- Exploring Innovations and Efficiencies, SW Ag Seminar, 5-6 December 2015, Cortez, CO. The emphasis was on soil health and farming sustainability in Colorado, Utah, and New Mexico.
- Dryland Cover Crops and Soil Moisture Management, Four State Ag Expo, March 18, 2016, Cortez, CO. Presentations by Dr. Abdel Berrada, Dr. David Nelson, Dr, John Holman, and Kevin Larson; and panel discussion.
- Following in the Footsteps of Successful Farmers, SW Ag Seminar, October 22, 2016, Dolores, CO. Topics: soil health, cover crops, land conservation, weed control
- Soil Health Workshop, February 9, 2017, Dove Creek, CO. Cover crops projects in Colorado, soil health assessment, panel discussion.
- Dryland Farming and Cover Crops in SW Colorado, August 24, 2016, Durango Colorado. Sponsored by the La Plata County Conservation District.
- Presentations at the above seminars, plus the:
- Dove Creek Conservation District meeting on April 25, 2017.
- CSU-AES Research Center Conference in Ft, Collins in January 2016 and 2017.
- CSU-SWCRC Annual Advisory Meeting in February 2016.
- ASA-CSSA-SSSA Annual Meetings in Phoenix, AZ in 2016 and Tampa, FL in 2017.
- The New Mexico Sustainable Agriculture Conference in Los Lunas, NM on December 13, 2018.
- Upcoming events & publications
- Soil health seminar in Monticello, UT on February 8, 2018. Exact title has not been announced yet.
- CSU-AES Technical Bulletin
- Project website: The project’s website, http://drylandcovercrops.agsci.colostate.edu, is generating interest in cover crops and soil health from a broad audience (consumers, farmers, ag professionals, general public). After the release of the marketing flyer (e.g., flyer to advertise the project) in the community and local ag-related events, Google + reached almost 10,000 hits globally. The launch of project interview videos are increasing traffic 25% through YouTube and is expected to increase by the end of the year.
- Other: At the 2017 Soil Health Workshop, surveys were provided to attendees. Four questions asked the attendees to rank their knowledge, interest, and willingness to try cover crops, before and after the workshop. By attending the Soil Health Workshop, attendees appear to have gained knowledge on cover crops, soil health, and management practices. Additionally, it appears that we are targeting the correct groups within our region, because participants had a strong interest in cover crops and a strong willingness to use cover crops, even at the beginning of the workshop. We feel the results of the survey are promising regarding the adoption of cover crops in the region.
- soil biology
- soil and water conservation
- soil quality
- cover crops
- farming sustainabilty