Changing markets, technology, and attitudes are creating opportunities for new paradigms
supporting wider adoption of soil-building practices, but there is little science-based information
about integrating livestock and cover crops into irrigated crop rotations. While a few producers
in the sugarbeet/malting barley production area of northwestern Wyoming and south central
Montana experiment with cover crops following barley harvest for soil cover and livestock
forage, uncertainties about costs and benefits, and how to navigate options, mean that intensive
tillage and expansive bare soil are still the norm in this region. To address questions about effects
of different cover crop options on subsequent cash crops, soil quality, forage yield and quality,
and farm economics we will establish an on-station trial in a producer-driven long-term rotation
experiment at the University of Wyoming Powell Research and Extension Center, an on-farm
experiment with at least five producers, and innovative education programs and products. We
will evaluate four types of cover crops following barley in systems where sugarbeet is the
subsequent crop. Cover crop types include volunteer barley regrowth, replanted barley, soil
building mix, and livestock production mix. The on-station experiment will be embedded in the
long-term rotation experiment where half of each cover crop plot will remain unharvested and
half will be harvested for hay. The on-farm experiments will be established after harvest of
irrigated barley where producers winter graze replanted barley. On-farm plots will be split, with
half ungrazed in 0.1-acre exclosures and half winter grazed with the rest of the field. The
participatory research will creating settings for farmer inquiry, peer-to-peer learning, and lasting
relationships. We will optimize those opportunities by 1) expanding our technological exchange
created for the long-term rotation experiment; 2) field-based hands-on workshops; 3) Extension
and research publications; and 4) impact evaluation with on-going responsive adjustments to
research and extension activities.
This project will provide producers with knowledge to implement soil-building practices for
more sustainable irrigated cropping systems. Specific objectives include quantifying and
comparing effects of four types of cover crops (volunteer barley, replanted barley, and two cover
crop mixes) and three residue treatments (hay, grazed, and no harvest) on:
1. Yield and quality of subsequent crops;
2. Soil quality and organic matter cycling;
3. Forage quality and quantity of the four cover crop types;
4. Water use efficiency in subsequent sugarbeets;
5. Costs and benefits of different cover crop/forage options;
A cover crop mix planted after barley harvest in sugarbeet-barley rotations will improve soil quality compared with no cover crop and with replanted or volunteer barley regrowth. Further, soil quality improvements will vary with management of cover crops for green manure, hay, or grazing.
During the 2019 growing season we tracked the plots established in 2018 through sugarbeet planting and harvest on the six cooperating farms and on the University of Wyoming Powell Research and Extension Center (PREC) at Powell, WY. We established new cover crop plots in the barley phase of the on-station long-term rotation experiment at PREC and sampled soils, biomass, yields, and trace-gas emissions through the 2019 season. We worked with the six farmers to establish another year of the on-farm plots, but the cold, wet spring in the study area caused barley harvest be delayed too much to allow time for cover crop planting at two of the farms. Hail destroyed the barley crop just before harvest at another, causing the farmer to opt out of establishing plots because the large amount of barley seed on the ground would not have allowed meaningful evaluation of cover crop performance. Cover crops were planted and grazing exclosures established at three of the farms. However, one of those suffered from a grasshopper infestation that destroyed the cover crops before appreciable biomass was produced. The cover crops established well at another of the farms, but when we went back to collect biomass and soil samples, we found that the field had been severely overgrazed; so much so that the cattle broke down our exclosure, even though we had reinforced it with heavy wire panels and extra T posts. The third farm at which cover crops were planted did well and we were able to collect soil samples and biomass data inside and outside the grazing exclosure.
M.S student Taylor Bush and new Ph.D. student Dixie Crowe worked with the farmers to locate and establish new plots at each farm, and with the PREC farm crew to plant the on-farm and on-station plots, as well as to sample soils and harvest sugarbeets from the plots established in 2018.
We established a paired-site study in on fields of two of our cooperating farmers who had been practicing cover crops and conservation tillage for at least 10 years, and on adjacent fields under conventional practices. The purpose of this extra experiment was to evaluate longer-term effects of the practices and to generate additional results not affected by annual climatic variability during the study period.
We had begun to plan field workshops with two of the cooperating farmers, but the many problems that prevented successful establishment of cover crops caused us to decide to postpone the workshops until 2020.
During the 2020 season we intend to continue the on-station experiment by tracking the sugarbeets that follow the 2019 cover crops and by establising a new set of cover crop plots in the 2020 barley phase of the crop rotation experiment. We also plan to expand upon the paired site study and have identified additional study sites on farms in the study area. We do not intend to repeat the on-farm cover crop/grazing experiment because it is proving to be too expensive and variations in weather and farming practices are limiting our ability to collect meaningful data.
While 2019 was a very difficult year for establishing and growing cover crops following barley because of delayed barley harvest, it was a good year for sugarbeets, particularly for research plots, which are typically harvested earlier than commercial plots. We have collected a great deal of data on the yield and quality of both cover crops and sugarbeets, which Taylor is currently compiling and analyzing for his M.S. thesis defense this spring. Dixie is compiling a great amount of trace-gas data. She will continue the on-station study and will expand upon the paired-site study begun by Taylor.
Preliminary analyses of mineral and biologically active soil nitrogen indicates some differences among the four cover crop practices (no cover crop [conv], cover crop mix [CC], replanted barley [RB], and volunteer barley [VB]). Figure 1 shows preliminary results from on-station plots from samples collected at cover crop (CC) planting and biomass harvest in 2018, followed by sugarbeet (SB) planting and harvest in 2019. The trend suggests that the vigorous growth of nitrogen-hungry replanted barley (RB) suppressed plant-available N at sugarbeet planting time. The legumes and more decomposable biomass in the cover crop mix (CC) may have accelerated decomposition to supply similar amounts of mineral N as typical no-cover-crop practices, but under CC, additional N was likely conserved for later mineralization. Compared with no cover crop, all three cover crop treatments had less than half as much mineral N remaining at sugarbeet harvest. This is likely due to increased microbial activity in the cover crop plots, which causes immobilization of mineral N; or capture in biological form. Some equipment problems have delayed analyses of microbial biomass in our soil samples, but we will be able verify whether that is the case.
Figure 1. CC plant was August, 2018, CC harvest, October 2018, SB plant, April 2019, SB harvest, September 2019. Conv, no cover crop; CC, cover crop mix; RB, replanted barley; VB, volunteer barley.
The paired-site study revealed soil carbon storage advantages of long-term conservation practices. Near-surface soil organic carbon content was variable and did not follow expected trends of higher concentrations under conservation systems at the Fromberg, MT, site (Figure 2).
Figure 2: SOC content in 0 to 15 cm depth at two paired sites near Fromberg, MT, and Ralston, WY.
But deeper sampling shows increased soil carbon below the surface and overall higher carbon storage in the conservation systems compared with the conventional, intensively tilled systems with no cover crop practices (Figure 3).
Figure 3. Overall soil carbon storage (0-60 cm) at the two paired sites.
We believe that this pair-site approach may provide more compelling results that our series of one-year studies at the on-farm sites, which are difficult to manage due to climatic and management variability. We are in the process of expanding the number of paired sites and the types of analyses in order to fully evaluate the effects of cover crops following barley in this region. We believe that, together with the ongoing on-station trials at PREC, this will better meet our project objectives.
We have an active “network for technological exchange” with frequent communication among researchers and cooperators. We have planned mini-field days and field workshops for 2020. We did not hold field days or workshops in 2019 because of the problems described above . Next year we are hopeful for the success of the cover crop establishment so that meaningful educational events can be planned. While we do not intend to continue the on-farm plot experiments, we will continue to collaborate with the farmer to plant workshop events that showcase their use of cover crops following barley.
Educational & Outreach Activities
Posters on the project were presented at the PREC field day and at the Soil Science Society of America meeting.
- Cover crop establishment, composition, and management was discussed in depth at the meeting on May 30, 2018. All the farmers, researchers, educators, and students learned a great deal from one another.
Cover crop selection, establishment, and management.
Outcomes of the project will provide information on how to integrate cover crops and grazing or haying into crop rotations in ways that will add addition revenue streams while improving soil quality and agroecosystem biodiversity.
The farmers we are working with on this project are progressive in that they are already utilizing some form of conservation tillage, cover crops, and livestock integration. But they’re practices and experiences vary a great deal, so having them all in the same room each year to discuss the project with researchers, educators, students, and others is extremely valuable to all of us.