Final report for ONC19-057
This project was developed after hearing a cover crop farmer at a local watershed meeting argue that no matter how many benefits cover crops have, the largest farmers will never use them because they have too many acres to do this amount of management. Field salad completes its life-cycle almost completely outside of the corn and soybean growing season potentially removing the management barrier to using cover crops.
This project will assess field salad’s ability to function as a cover crop in a corn and soybean rotation without additional management. Corn and soybean yields will be compared with and without a field salad cover crop under three different kinds of management (organic, no-till, and conventional). Weed pressure under these different scenarios will also be measured.
Developing field salad as a cover crop has the potential to address all three of NCR-SARE’s goals. It protects our natural resources by helping expand cover crop adoption beyond current levels. Field salad may improve the lives of farmers by making cover crops an option for farmers who are not normally involved in these kinds of conservation practices. Farm profitability could also be improved by decreasing the cost of using cover crops.
Action Objectives: Determine whether field salad is compatible with organic, no-till and conventional cropping systems. In particular, can it re-establish itself, not negatively impact yield, provide additional soil cover, and does it offer any weed suppression.
Learning Objectives: Presentations on the study's results and farmer co-operator experiences will look to reach farmers who have not yet tried cover crops, especially those who thought cover crops involved too much management. Farmers attending these meetings will be asked to fill out a survey on their attitudes and experiences with cover crops and whether learning about field salad changes them.
Year 1- 2019
To test how field salad grows in-field we used a randomized controlled block design comparing control plots to plots that have been seeded with field salad. The control plots used the farmer's normal farming practices. The treatment plots had the farmer's normal practices plus the field salad cover crop. This study was repeated on three farms with different cropping systems (conventional, no-till, and organic). There are 4 replicate pairs on each farm.
The plots are 100 feet square and were seeded with a hand seeder. We had initially planned for larger plots. However, with the record breaking wet spring in 2019 the fields were harvested late. Since the fields were not able to be seeded until November, we held back part of the seed in case the plots needed to be reseeded. The plots have all germinated, so the extra seed will be given out to farmers as part of our outreach at the end of the grant.
All of the fields in this study will be growing corn in 2020. The conventional and no-till fields grew soybeans last year. The organic farm grew a summer cover crop mix last year that was tilled in.
The plot layouts can be seen here - Randomized controlled block plot design
Residue measurements were taken in February using the line-transect method. A 50 foot measuring tape was laid on a diagonal across each plot and at each foot marker it was recorded as either touching or not touching some sort of ground cover. Only one side of the tape was used to measure residue. These measurements were then converted to a percent coverage.
In the spring, 2 foot square quadrats will be used to measure the field salad's biomass. In the fall, larger 3 foot square quadrats will be used to compare the yields of the control verse treatment plots.
Year 2- 2020
Spring of 2020 biomass samples were taken from our no-till and organic fields using a quadrat. While there had been some seedlings on the conventional field when we measured residue over the winter, there were no field salad plants in the field come spring. The larger samples from the organic field were dried at the U of I dryer prior to weighing. The smaller samples from the no-till field were dried in a microwave.
In the fall, we took yield samples from our no-till corn field by harvesting four 17’ 5” samples of corn from each plot to be combined into one sample. The sample weigh was taken, and then a 1/10th subsample was brought back to the university for threshing. The weight of the whole sample was then extrapolated from the subsample. Details of our harvesting and calculations can be found in the following document Yield Sampling Methods. We had planned to use similar methods on our organic soybean field. Unfortunately, at the last minute that field was accidentally harvested prior to our measurements.
Field salad was reseeded in the no-till and conventional till fields in the fall of 2020, New plots fall 2020. Field salad in the conventional field germinated, but then died. In the No-till field, it grew, but was sprayed before it could mature and produce seed. The spring of 2020 was very cool, which appears to have delayed maturity. The soybeans in the organic field were not planted until after the field salad had matured. Although the field salad plants were smaller than in other fields, they were able to produce seed. This field was tilled before planting. However, field salad was able to successfully reseed itself in the fall of 2020 and these plants are seen growing in the spring.
Residue measurements were taken in the fall using the same methodology as the previous year, using a 50 ft measuring tape.
Year 3 - 2021
We continued to use the quadrat method to take biomass measurements. This year, we sampled from the no-till, organic and conventional fields. The no-till and organic fields had other cover crops planted on both the control and treatment plots. Cereal rye was planted across the no-till field, while the organic field had a more complex mix that included grasses, cole crops, and legumes. All of the samples were dried in a microwave before being weighed. Sample B from the organic field began to smoke and therefore may not be accurate. Including or excluding sample B had little impact on the average sample weight.
A soybean harvest was sampled from the no-till and conventional fields. Two rows of 8’ 8.5” were harvested for a total of 17’ 5” from each plot. The beans were threshed and seed weights and moisture levels measured with the help of staff and equipment from the University of Illinois Department of Crop Sciences.
After combining sample E from the conventional field we decided to lop off the roots of the samples before combining to get cleaner samples. Sample E was then cleaned and measured again for moisture and weight. Averages were calculated with the dirty sample E and with the cleaned sample E which brought the control average weight from 67 to 63. We ended up excluding sample E. Interestingly, this had the same result as using the average of the dirty and clean sample. All of the no-till samples had their roots lopped off in the field. The organic farmer uses a longer rotation including a summer fallow period where only cover crops were grown, and therefore had no yield to report.
Year 1- 2019
One of the benefits of field salad is that despite a wet season pushing harvest back significantly we were still able to get the cover crop to germinate in the fall. As expected, it has mainly stayed at a seedling stage in this first season. In future years, when the cover crop has more time to establish in the fall, we anticipate it producing greater over winter cover.
With the weather cycling between 50 degree days and snow storms it was difficult to find days where the soil was firm enough to go into the field but where there was not snow or ice on the ground. The fields were mostly clear of ice and snow on the day we took our measurements. However, three of the plots on the organic farm had ponding and ice covering a significant portion and so we were not able to get measurements for those plots. Again, because the cover crop was still in the seedling stage, we did not expect to see significant differences in soil coverage between the control and treatment plots.
The conventional fields had more residue than expected with their high levels of tillage. Interestingly, most of the residue was from corn, even though the previous crop was soybeans. Discussions with the farmer revealed that he had been having difficulty with his residue not breaking down. The organic farm had tilled in a summer cover crop mix and seeded a winter cover crop mix of cereal rye, brassicas, and clover. There was a mixture of the tilled cover crop residue and the winter cover crop in the field. There were also traces of corn residue. The no-till field had a thick thatch of soybean stubble covering the entire field. The field salad seedlings seemed to grow better in fields with higher residue. It was often found under clusters of crop residue or at the base of the other cover crops.
The residue levels between treatment and control plots were comparable, with the conventional field having the greatest in-field variation. The conventional field had an average of 67% and 63% cover on the control and treatment plots respectively. The no-till field had a full cover across the field with an average of 100% on the control fields and 99% on the treatment fields. The organic fields had an average of 91% on the control plots and 92% on the treatment fields.
The individual residue measurements can be seen here - Residue- 2_11_20
Year 2 -2020
The average biomass samples for the no-till field were greater for the treatment group with 35g, vs. 27g for the control group, see No-till Biomass-2020. One of the plots in the control group had significantly more biomass, mostly due to grass weeds, than the other plots and may be skewing the results. When this plot was removed the remaining control plots had an average biomass of 39g which is closer to the treatment group. In the organic field, the control plots had higher biomass than the treatment group, with 539g and 496g respectively, see Organic biomass 2020. The organic fields were also seeded with a cover crop mix that included cereal rye. This accounts for the much higher biomass weights seen in this field.
While the field salad in the conventional field died, there were a few field salad plants on the edge of the field. Interestingly, these were larger and more mature than the plants on the no-till or organic fields.
In the 2020 growing season field salad did not grow on the conventional field, and the main crop was accidentally harvested early on the organic field. The average yield was not substantially different, with the control having an average of 246 bu/ acre and the treatment having an average of 241 bu/acre corn, see No-till yield data 2020.
In the organic field, field salad was able to reseed itself. This is despite having heavy competition from the cereal rye that was also planted. The field salad plants were small, but they were still able to mature and produce seed. Being buried with tillage did not prevent field salad seeds from germinating the next year. Since the conventional and no-till fields had to be reseeded, we took the opportunity to reorient the plots to make them easier to harvest yield data in the future.
The conventional and no-till corn fields had residue levels in the 90’s for both the control and treatment plots. The organic soybean plots had slightly lower residue levels of 85% for the control and 77% for the treatment. These lower levels are attributable to soybeans producing less residue than corn. Residue values can be found here, Residue-Fall 2020.
Year 3 - 2021
As expected in the conventional field there was substantially more biomass in the treatment plots than the control plots with an average of 56g vs 12g, see 2021 Conventional Biomass. In the no-till plots, the control plots had slightly higher biomass than the treatment with 55g vs. 47g, see 2021 No-till Biomass. The organic field saw the same trend, with slightly lower biomass measured in the treatment plots with 109g vs 116g in the control, see 2021 Organic biomass.
The field salad produced significant biomass in the conventional plots, with an average biomass weight comparable to that of cereal rye. When field salad was mixed with cereal rye, the rye appeared to still be the dominant species growing. However, field salad plants were still present. Growing the two species together appears to have reduced the overall biomass produced, but increased the diversity.
Field salad seeds float which leads to a denser population at the bottom of a field than midfield. Biomass and yield samples have been taken mid-slope to account for this. Despite the seed's ability to float, plants are not observed to grow beyond the first 6-12 in of grass surrounding the field. In situations where the slope empties directly into a stream, this may be more of a concern.
In the fall we took yield samples from both the no-till and conventional fields. In the conventional field the yields were similar with an average of 64 bu/acre in the treatment vs. 65 bu/acre in the control, see 2021 Conventional Soy Yield. In the no-till field on the other hand, the treatment plots had a much higher average yield than the control with 61 bu/acre vs. 50 bu/acre, see 2021 No-till soy yield.
Growing a field salad and cereal rye cover crop mix appears to have more benefit than using cereal rye alone in the no-till field before soybeans. We suspect that the yield increase seen in the no-till field salad treatment plots was due to its interaction with cereal rye, since this same benefit was not seen in the conventional field where field salad was grown alone as a cover crop. Our first thought was to look back at the lowered biomass weights in the field salad no-till plots. We thought perhaps having fewer cereal rye plants lowered any allelopathic effect it is having on the soybeans. However, cereal rye is known for having an impact on corn yields more than soybeans and therefore seems unlikely to cause such a dramatic yield difference.
Another option is that having a mixed cover crop provided more soil health benefits and better nutrient cycling than cereal rye alone. Field salad is known for accumulating nitrate over the winter. When the field salad plants die back in the spring, they may provide additional nitrogen to the soil. This could compensate for nitrate that may be immobilized by soil organisms processing the high carbon material from the cereal rye. In addition to not being tilled, this field has had overwintering cover crops as a part of its rotation for several years now. It may therefore have more diverse or active soil biology and be in a better place to react to increased cover crop diversity than a conventional field.
Due to multiple blizzards in February, we have not yet been able to get residue measurements for this winter.
Year 4 - 2022
During harvest, we were able to see that field salad had reseeded itself in both the no-till and conventional field. However, the distribution of field salad in the no-till field was spotty and concentrated at the bottom of slopes. This is likely due to the seed’s ability to float and be transported during rain events. The distribution of plants that had reseeded in the conventional field showed similar patterns. Despite this concentration of reseeded plants in low areas, the size and shape of both plots remained intact, allowing observers to clearly differentiate between the treatment and control strips, as in the picture below:
There is a narrow window of time when weather conditions favor field salad germination and when most conventional growers apply herbicides for pre-planting weed control. Conventional farmers must manage a tight timeline between the maturation of the cover crops, herbicide applications, and planting. During the spring of 2022, herbicides were applied to the no-till field prior to the field salad cover crop setting seed. While the conventional farmer adjusted his management timeline by choosing to leave the field salad intact and no-till plant their corn into the trial plots. This allowed for the cover crop to be seen at a field day.
Educational & Outreach Activities
On May 23rd, 2022 six farmers and landowners attended a cover crop walk and educational tour of the conventional test plots which was hosted by Prairie Rivers Network and the farmer Ed Karr. Ed spoke about his experience using field salad as a cover crop and Prairie Rivers Network’s Agricultural Programs Specialist, Catie Gregg, explained the purpose of the project.
The participants were able to walk the field, examine plant samples and discuss how field salad could be used as a cover crop in different cropping systems. The field salad had bolted and allowed for the viewing of mature plants with seeds and provided a good understanding of how densely they were distributed throughout the field. Attendees were generally interested in learning more about incorporating similar cover crops into their farming systems. One participant, a seed dealer, offered to sell any harvested seed as part of aerial seeding cover crop mixes.
The event was promoted by our networks including the Idea Farm Network, farmer-led learning network in Illinois.
While 4 farmers are involved in the project, we are still conducting the research phase of our project and therefore have not engaged in any outreach activities about our results.
This preliminary research on the use of field salad as a cover crop provided insights into some of the benefits and challenges of its use. This project asked many questions to assess whether field salad could be a low management cover crop, including whether field salad would–
- germinate from a fall broadcast seeding,
- provide cover over winter,
- provide additional biomass to the system,
- suppress weeds, and
- be able to reseed itself in systems that used tillage, cover crops, and herbicides.
We learned that field salad can be successful in field settings. Field salad can provide biomass similar to cereal rye when grown alone and can be added to other cover crop mixes. It can also reseed itself, even in systems that use tillage. However, this study showed that the use of field salad as a cover crop did not provide sufficient cover over winter, this is largely due to the small size of the plants during this time of year. It also did not appear to suppress weeds very well and may be overpowered by grass cover crops. Growers that use field salad as a cover crop will need to adapt their weed management practices to ensure that it is able to reseed before herbicide applications occur.
The biggest challenge working with conventional and no-till growers, has been the types of herbicides they use and the timing of their application. Since fields may be sprayed weeks before planting, the window between allowing field salad to set as a cover crop and planting is very small. When this study began we questioned if there was enough time for the field salad to set seed before planting. When field salad reseeds itself, it starts growing in August, which is much earlier in the season than the initial planting. This shift in the timing of plant growth and maturity can make it more vulnerable to spring herbicide applications. In the spring of 2019, the conventional farmer in our study sprayed the pre-emergent herbicide, Volley ATZ. At this time, the field salad seed appeared to have germinated. However, upon field inspections in the spring of 2020, we could not find any living field salad plants. In this case, the timing and type of herbicide applied impacted the survival for the field salad.
Farmers may have to make adjustments to their weed management practices when using a field salad cover crop. For example, as mentioned previously, in 2022 the conventional grower decided to no-till plant the trial plot in order to allow the cover crop to set seed and did not use herbicide prior to planting.
One of the most interesting results– the no-till treatment plots had higher yields than the control. Since field salad is known to be a nitrogen accumulator, future research should look into whether using a field salad cover crop prevents nitrate from leaving the field or releases nitrate for the cash crop in the spring. However, it is important to note that there may be different results depending on whether the field salad is grown alone or with other cover crops.
Our goals were to reach farmers who have not yet tried cover crops, especially those who thought cover crops involved too much management and see whether this demonstration could influence their perspective. However, all of the farmers who attended the field walk already used cover crops. Most of them appeared to be very innovative, open to trying new things, and interested in whether field salad could be a part of their rotation. We did not end up distributing a survey to the participants because the group was small, and it was clear everyone used cover crops already. It was much better in that moment to have a group discussion to share the project findings and to have everyone share their experiences with cover crops.
Ironically, the farmer who probably gained the most new experiences with cover crops was the conventional farmer who participated in the project. Initially, he offered to participate in the project because he knew the PI from her previous work at his county’s Soil and Water Conservation District. This reinforces previous observations that found conventional farmers are more likely to try conservation practices when they are asked to participate by someone they know and have built some trust with the project administrator.
One of the most interesting results was that the no-till treatment plots had higher yields than the control. Since field salad is known to be a nitrogen accumulator, future research should look into whether using a field salad cover crop prevents nitrate from leaving the field or releases nitrate for the cash crop in the spring. However, it is important to note that there may be different results depending on whether the field salad is grown alone or with other cover crops.