Getting the most out of cover crops: How timing of termination influences soil health, pest control, and improved crop production
One farmer and five outreach professionals met in person in April to discuss project goals and parameters to be considered for measurement. Individual meetings with all three farmers also occurred periodically throughout the summer. Preliminary results were presented and discussed with approximately 440 growers, extension personnel, and agricultural industry professionals from several northeastern states and Canada at five outreach events. All of the first-year data has now been collected and is currently being analyzed. We learned that in a dry year, terminating a cover crop at planting or later can contribute to reduced corn yields; that soybeans were less susceptible to potential yield reductions associated with planting green; and that sufficient nitrogen, planting depth, and soil moisture appear to be important for maintaining corn yield when planting green. A spring meeting date with all concerned investigators and farmer-cooperators is being planned for February.
As a result of these activities, on over 10,000 acres, fifty farmers who use no-till and cover crops will delay cover-crop termination in spring until or close to crop planting, thereby enhancing soil conservation and health, reducing crop losses to slugs and weeds, and improving cash crop establishment and yields.
- In summer 2015 (first summer of field research), preliminary results were presented and discussed with growers, extension personnel, and agricultural industry professionals from several northeastern states and Canada at five outreach events. Events included: Penn State Crop Management Extension Group Field Day, attended by 50 extension personnel; Southeast Agricultural Research and Extension Center Farming for Success Field Day (June 25), 200 attendees; Penn State Crop Diagnostic Clinic (July 28-29), attended by 110 farmers and ag industry professionals; Schrack Farms Field Day (September 1), attended by 50 farmers; and Cover Crops Field Day (September 23), attended by 30 farmers and consultants.
- Presentations are scheduled for Pennsylvania Agronomic Education Conference, January 22, 2016.
- A spring meeting date with all concerned investigators and farmer-cooperators is planned for February 2016.
Impacts and Contributions/Outcomes
Impacts and contributions/outcomes:
Comparing 2015 to the 1984-2014 30-year normal, spring rainfall (March, April, and May) was about 4 in. lower than normal at both the Rock Springs and Southeast weather stations. Meanwhile, summer rainfall (June, July, and August) was about 3.5 in. and 5.8 in. higher in 2015 at Rock Springs and Southeast, respectively. The dry spring impacted cash crop planting date and depth, and our farmer-cooperators suggested that we not delay cover crop termination time. Negative effects were seen mostly in the corn experiment, described below.
Though both research center locations had several additional treatments, data was collected for pure rye termination early and at plant before corn experiment, and soy to facilitate comparison across research station and farmer-cooperator locations.
Corn Experiment: Rye biomass approximately doubled between early and late termination, except at the Rock Springs research station where the interval between early termination and planting was only 6 days instead of the 9-14 days at the other sites.
Soil moisture and temperature trends for the top 3 inches of the soil varied between sites. Both temperature and moisture were significantly lower in late-terminated plots at planting in Clinton County, but the difference diminished by early June. Lancaster County revealed no difference between treatments for either moisture or temperature. Rock Springs soil moisture was not different between treatments until late August, when the late-terminated treatment was significantly wetter than the early-terminated treatment (Figure 1); temperature was cooler in the late-terminated treatment at planting and the week after, and then not different until mid-August when the late-terminated treatment was wetter. The Southeast late-terminated treatment had moister and cooler soil for the whole growing season than the early-terminated treatment., All treatments at Rock Springs were about 15% drier than Landisville at planting, which led to shallower than optimal seed placement at that research station.
Slug populations were insufficient to draw strong conclusions in 2015, likely due to the dry spring. Populations were very low at the Clinton County, Lancaster County, and Southeast sites, with zero slugs found at 6/8, 3/5 and 10/13 sampling dates, respectively. Predation and predator insect populations were measured at Rock Springs only. This data requires further analysis, but preliminary results show greater predation along with higher predator populations in the late-terminated treatment compared to the early-terminated treatment.
Corn populations were 9% lower in the late-terminated treatment only at the Rock Springs site (Figure 2); likewise, grain yield was 12% lower in the late-terminated treatment at the Rock-Springs site (Figure 3). Corn yield was also significantly reduced at the Clinton County site, where manure was top-dressed before corn planting, but no side-dress N was applied, unlike the other sites in the study. The yield reduction without corn plant stand reduction may indicate nitrogen immobilization issues with the late-terminated rye, because the other sites without stand reduction that applied side-dress N did not have significant yield penalties for delaying rye termination timing. Additionally, dry soil resulted in shallower than desired corn planting depth at most sites, likely compounding stress and reducing yields.
Soy Experiment: Rye biomass increased by 49 to 126% from early- to late- termination between the four sites. Soil moisture and temperature in the top 3 inches behaved similarly between locations. At all sites, soil moisture was lower at soybean planting in the late-terminated treatment compared to the early-terminated treatment (Figure 4). This difference diminished by June at all sites; no difference in treatments was measured for the rest of the growing season at Clinton County and Rock Springs, though the early-terminated treatment was drier than the late-terminated treatment at one sampling date in late July at the Centre County and Landisville sites. Soil temperature was cooler in the late-terminated treatment at planting at Clinton County, Rock Springs, and Landisville; this difference diminished by the following sampling date at Clinton County, but was maintained at Rock Springs until mid-June and through early July at Landisville. No soil temperature difference was measured between treatments at Centre County.
Slug populations were insufficient to draw meaningful conclusions, likely due to the very dry spring. However, slug populations were reduced in the late-terminated treatment at the Centre County location.
Soybean population was reduced by an average of 8% at the Centre County, Rock Springs, and Southeast sites in the late-terminated treatment (Figure 5). However, soybean yields were no different between the early- and late-terminated treatments at any location (Figure 6).
Conclusion: Overall, soybeans responded better than corn to delayed rye termination in this very dry spring when planting was delayed due to lack of moisture. Planting green would not be recommended for corn in future dry years similar to this one. Additionally, we learned that managing nitrogen in corn is essential when rye termination time is delayed to obtain optimum yields.
Though farmers currently practicing planting green discouraged the practice this year due to lack of spring precipitation, feedback about this research from farmers at outreach events has been positive. Multiple enlightening discussions took place at field days regarding ideal rye seeding rate, planting and termination dates, corn and soy planting depths, and the difficulty of obtaining untreated seeds. For example, some farmers found that reducing rye seeding rate resulted in greater success when planting green. Some proposed that planting corn an inch or greater deeper in the soil than typically recommended has helped with their stand establishment. Several farmers mentioned the importance of additional nitrogen needs, and apply more in either the fall or the spring, often in manure form to reduce potential immobilization. Furthermore, we learned that several county extension agents in Pennsylvania already promote the practice with some reservations about the risk of N immobilization or allelopathy associated with excess rye or small grain cover crop biomass. Some farmers’ greater interest in soil health than in cash crop yields was notable as well. Several agronomists and agricultural industry workers personnel voiced interest in keeping updated with the findings of this project.
- Figure 1. Corn Experiment Soil Moisture at Research Station Sites
- Figure 2. Corn Population at All Sites
- Figure 3. Corn Yield At All Sites
- Figure 5. Soybean Population at All Sites
- Figure 4. Soybean Experiment Soil Moisture at Research Station Sites
- Figure 6. Soybean Yield at All Sites
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