Results were presented and discussed with approximately 614 growers, extension personnel, and agricultural and industry professionals from Pennsylvania at six outreach events. All third and final year field data has been collected and is being analyzed; some sample processing and laboratory analysis is still in progress. The third year provided further evidence of some conclusions from the previous two years: i. in a wet spring, stand establishment can be improved by planting green as long as biomass remains standing until planting; ii. planting green cools soil all growing season and can dry soil early in the season and conserve soil moisture later in the growing season; and iii. soybeans are highly elastic and adaptable to planting green management. In soybeans, planting green in 2017 did not increase slug feeding on soybeans, but neither did it reduce slug feeding as highlighted in 2016. We again found that planted green soybeans maintained yields similar to early-cover crop termination at 4 of 5 sites. Contrary to 2016 results when planting corn green increased slug damage, the opposite was true for 2017; however, planted green corn still had 5% lower yields at 2 of 4 sites, likely due to nitrogen deficiency at one site and lower corn population at the other. Lastly, similar to 2016, instances of increased slug activity-density with planting green did not coincide with increased slug feeding on cash crops. One final meeting date with all project investigators and farmer-cooperators is being planned for March.
No-till cover crop systems (NTCCS) provide multiple benefits to agroecosystems. Fortunately, their adoption has been increasing in the Northeast and Mid-Atlantic regions, presenting unique agronomic and pest management challenges. In particular, cover crops (CCs) terminated in spring prior to planting of the cash crop create covercrop residue that: i) conserves soil moisture often leading to poor seed placement and coverage, ii) provides ideal habitat for slugs, the dominant invertebrate pest in no-till systems, and iii) interferes with planting equipment; all contributing to reduced establishment and yield of the cash crop. We have observed these problems in our Sustainable Dairy Cropping Systems project and farmers frequently request advice about controlling slugs, which annually damage about 20% of Mid-Atlantic not-till acreage. Addressing these spring cover crop termination challenges has the potential to significantly enhance the productivity, sustainability and adoption of NTCCS in the Northeast. The experience of some PA No-till Alliance farmers and our NTCCS research indicates that terminating cover crops at or close to planting the cash crop (i.e., “planting green”) can: i) reduce soil moisture and improve soil conditions for seed placement; and ii) reduce slug herbivory and weed establishment; thereby enhancing crop establishment and yields. Planting green can also protect soil, improve soil health, and reduce costs associated with early cover crop termination. In this project, we will compare planting green to terminating cover crops at 14 days or more prior to planting corn and soybean on two research farms and three commercial farms that routinely plant green. We will assess soil moisture and temperature; seed depth and coverage; CC residue or live biomass and C:N ratio; slug, insects (pest and beneficial), and weed populations; slug damage to CCs and cash crops; and cash crop populations and yields to evaluate the potential benefits of planting green. Working with our cooperating farmers, who are members of the Pennsylvania No-Till Alliance (our target audience), we will present the results of this research at field days hosted at all five farm locations and the NESARE Sustainable Dairy Cropping System project, as well as through extension meetings, conferences, and workshops; an educational website, and scientific meetings.
As a result of these activities, on over 10,000 acres, 50 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.
The 2017 growing season presented the opportunity to evaluate planting green under different weather conditions for the third year in succession (Figure 1). April brought typical rainfall but unusually warm average temperatures (1.5-3.9°C warmer than 2016 at Landisville and Rock Springs, respectively). Then, May was uncharacteristically cold and wet across locations, with Rock Springs accumulating a profuse 17.8 cm of rainfall during the month. Timely rainfall for the remainder of the summer resulted in little drought stress at any study site, perhaps diminishing moisture conservation benefits seen when planting green in previous years.
After a discussion at the 2017 advisory panel meeting, we decided to attempt to kill the early-killed cover crop treatment sooner in both the corn and soybean experiments with the intention of also planting cash crops earlier. The goal of this change was to more accurately reflect what a “typical” farmer would do, while maintaining a significant biomass difference between the early-killed cover crops and those killed at planting (planted green). The warm and wet April resulted in more rye growth than desired, despite these efforts. Then, a brief break in the rain allowed us to plant both corn and soybeans at Rock Springs and Landisville on May 1 and 3, respectively. Unfortunately, continued rainfall and unseasonably cool temperatures in May resulted in delayed and uniformly low cash crop emergence at Rock Springs. With better restraint, our cooperators waited until the second and third week in May to plant both cash crops, though early termination was done between April 22-28 at all three cooperator locations. The following paragraphs outline 2017 results in further detail.
Corn experiment–Rye only, all sites
Though both research center locations had additional cover crop and nitrogen rate treatments, the following results specifically discuss rye cover crops terminated early or at corn planting (planted green), in order to facilitate comparison across research stations and farmer-cooperator locations. Rye biomass increased by 155-293% with a 16-27 day delay between early termination and planting at 4 of 5 sites, but did not increase at the P<0.05 level at Rock Springs, with the shortest (11 days) delay between early termination and planting for 2017 (Figure 2). Similar delays in 2015-2016 did result in significant increases in rye biomass. The lack of difference in 2017 may have been due to lower solar radiation (increased cloudiness) compared to 2015 and 2016. The higher biomass at the cooperator farms reflected the necessity of delaying their cash crop planting (longer intervals between early-kill and planting), while the lower biomass at Landisville compared to the 2015 and 2016 experiments was due to late rye seeding in 2016 (November 3, compared to September 10, 2014 and September 21, 2015) and a competitive but low-in-biomass downy brome infestation.
Soil moisture was influenced less by rye termination timing in 2017 than in prior years. A significant soil drying benefit from planting green was only measured at Clinton and Lancaster County cooperator sites, which had the largest differences in rye biomass between the two treatments, stressing the connection between biomass and soil moisture. Further, moisture conservation later in the growing season was only significant at Lancaster County, with only marginally higher soil moisture in the planted green treatment Clinton County and Landisville. Soil moisture was not significantly influenced by rye termination timing at Rock Springs, likely due to the small difference in biomass between early termination and planting green, and also because of the regular rainfall during the 2017 growing season, which permitted little opportunity for soil drying between rainfall events. Soil temperature (0-8 cm) behaved similarly to 2015 and 2016, with significantly cooler soils when corn was planted green than when rye was killed early. Again, greater temperature differences between treatments were seen at sites with larger differences in biomass between early termination and planting green.
Cool temperatures and wet conditions early in the 2017 season provided welcoming conditions for high slug populations, similar to 2016. Slug activity-density trended higher in the planted green treatment at Clinton County, Lancaster County, and Landisville, while no clear trend was evident at Rock Springs. However, despite generally higher activity density, slug damage to plants was 50% and 25% lower in the planted green treatment at Clinton County and Lancaster County, respectively (P<0.02), 13% lower at Rock Springs (P=0.0553) and not different between treatments, but lower than any other site (average of 4% of plants damaged) at Landisville (Figure 3). These results are contrary to 2016, when planting green increased slug feeding on corn two to nearly threefold. In addition to higher slug pressure in 2017, fall armyworm damage reached the economic threshold of 25% of plants displaying feeding damage at the Clinton County cooperator site and at Rock Springs, so a rescue spray of Intrepid 2F insecticide, a selective growth regulator that targets lepidopteran pests, was used. We specifically chose this pesticide to protect our beneficial insects, as we also did not apply neonicotinoid seed treatments to any of our seed in any year of the study.
Corn populations were not different between early-termination and planted green at Clinton County or at Rock Springs, but Rock Springs had very low (about half) the target population overall. Corn population trended higher when planted green at Landisville, but at the Lancaster County cooperator site, planting green reduced population by 20% (Figure 4). The Lancaster County cooperator site experienced a corresponding 5% yield reduction when corn was planted green (Figure 5). Despite good populations and lower slug and armyworm damage when planted green at the Clinton County cooperator site, corn yield also trended lower (by about 7%) when planted green compared to when rye was killed early (P=0.062). This may have been due to slower nitrogen cycling in cooler planted green soils, though the Clinton County site received manure in the fall and the spring, so nitrogen as a yield limiting factor was not expected. Perhaps the combination of cooler soil when planted green, slowed N mineralization and the high rainfall experienced in 2017 leached plant-available nitrogen out of the soil profile as it was mineralized, and with no side-dress application of nitrogen at the Clinton County site, the planted green corn was unable to achieve the same yields as corn planted into early-killed rye and warmer soils. Yield at Landisville trended higher when planted green, possibly due to higher corn populations, and was not different between early-kill and planted green at Rock Springs (Figure 6).
Corn experiment–Nitrogen rate and different cover crops at PSU research stations
We hypothesized that corn planted green would be more nitrogen limited than corn planted into early-killed rye (i.e., late killed rye would cause more N immobilization due to higher C:N ratio of the tissues plus slowed N cycling due to cooler temperatures), and that planted green corn would therefore benefit more from the high nitrogen treatment than corn planted into dead rye residue. Therefore, the corn experiment Rock Springs and Landisville research stations was comprised of additional nitrogen rate and cover crop treatments. Either 0 kg/ha (low) or 78 kg/ha (high) nitrogen was applied to early-killed and living, green rye at planting; then side-dress nitrogen was applied based on a combination of pre-sidedress nitrate test results and Penn State Agronomy Guide recommendations, due to PSNT results in 2016 that we suspected were not accurate. At Landisville in 2017, the low and high N treatments received 168 and 112 kg/ha N at side-dress, respectively; at Rock Springs, both treatments received 168 kg/ha N. As previously mentioned, termination timing did not significantly affect corn grain yield at either location–surprisingly, neither did nitrogen rateIn addition to rye, crimson clover (clover) and a crimson clover + rye mixture (mix) were either terminated early or at corn planting (PG). Clover and the mix had significantly higher biomass than rye at Landisville, likely because they were planted over a month earlier than pure rye in 2016; further, both covers accumulated significantly more biomass when termination was delayed until planting. The opposite was true at Rock Springs, where clover had the lowest biomass, and rye the most, with the mix intermediate, and no significant termination timing effect. At Landisville, corn population did not differ between cover crops. At Rock Springs, clover had the highest corn populations, and populations were not different between early termination and planted green.
Slug and other insect damage was very low at Landisville, and not different between covers or termination timings. At Rock Springs, corn planted into clover was more damaged by slugs, but less damaged by armyworms than the mix or pure rye, and termination timing did not influence damage. However, slug activity density was not significantly influenced by cover crop, and there was no clear trend of termination timing influence in the clover or mix over the growing season at either site. The top 8 cm of the soil profile was driest in clover regardless of termination timing; this effect was especially apparent at Rock Springs, where soil was an average of 15% drier (29% compared to 34% volumetric soil content) under crimson clover than rye. Soil temperature was highly dependent upon biomass. For example, at Rock Springs where clover had the lowest biomass, soil temperature was higher on average compared to rye or the mix. Conversely, at Landisville where clover had the highest biomass, soil was generally cooler than under the rye. Finally, corn planted into clover had the highest yields out of any cover, though corn yield was reduced by 15% when planted into green clover compared to early-killed. Similarly, corn planted into clover or the mix yielded 11% higher than when planted into pure rye at Rock Springs. The yield benefit from crimson clover could have been due to: i. nitrogen provision by the legume cover crop, with faster nitrogen cycling due to warmer soils possible at Rock Springs; ii. reduced armyworm damage compared to rye at Rock Springs; and/or iii. a soil drying benefit, though in 2015 and 2016 soil drying could have been detrimental, it was likely a benefit in this extremely wet spring.
Soybean experiment–all sites
In this section, only results for the 67 kg/ha seeding rate and 34 kg/ha nitrogen rate are presented for the research stations, as they were most similar to what our cooperators would suggest. Rye biomass increased significantly at all sites, from 60% at Rock Springs to almost five-fold at Clinton County between early termination and soybean planting (Figure 7). The low biomass accumulation at the Centre County cooperator site was due to late (November 1) rye seeding, followed by a several week period with no rainfall. The cooperator was not satisfied with the biomass accumulation or ground cover at the early-kill date (771 kg/ha), and had to take care to control winter annual weeds that had established in the sparse stand.
Significant soil drying (0-8 cm) by planting green was only evident at Landisville, however Rock Springs soil trended drier planting into green rye than into early-killed, dead rye residue. Soil moisture holding fostered by planting green was significant at the Lancaster County cooperator site, Landisville, and Rock Springs, with the difference between early-termination and planted green lasting through July and diminishing in August. Soil moisture was not significantly influenced by treatment at the Centre or Clinton County cooperator sites. Planting green did significantly cool the top 8 cm of the soil profile at all five sites for the majority of the summer, with the cooling effect ranging from up to 0.6°C at the Centre County cooperator site to 3.3°C at Landisville. The magnitude of the cooling effect was dependent on the difference in biomass between the early-killed and planted green treatments, with a larger difference resulting in more cooling.
As in the corn experiment, slug activity-density was most dependent upon the sampling date. Slug activity density trended higher in the planted green treatment at Lancaster County and Rock Springs, perhaps due to the increased soil moisture at those sites, mentioned in the preceding paragraph. Conversely, the termination timing effect varied depending on the week, with no apparent trends, at Centre County, Clinton County, and Landisville. Slug feeding was elevated across the state in 2017, and at our worse-hit sites 94%, 93%, and 55% of soybean plants soybeans suffered slug feeding at Clinton County, Lancaster County, and Rock Springs, respectively (Figure 8). The Clinton County cooperator had to replant several soybean fields, excluding the research site. However, there was no difference between slug feeding on soybeans planted into early-killed rye or planted green at any location. Centre County and Landisville escaped with 7% and 16% feeding damage, respectively–however, both fields have historically had low slug populations. These results are contrary to 2016, when we saw significant reduction in slug feeding on soybeans in the planted green treatment. However, these results do support our conclusion from 2016 and from the 2017 corn experiment that slug activity or presence doesn’t necessarily correlate with slug feeding damage.
Soybean populations were: i. not different between treatments at the Centre County cooperator site, Landisville, or Rock Springs, ii. 53% higher when planted green at the Lancaster County cooperator site, and iii. reduced by 32% when planted green at the Clinton County cooperator site (Figure 9). Population was quite low overall at the Lancaster County cooperator site (average of 147,563 plants/ha), perhaps due to slug feeding on seeds before they emerged, as high slug activity-density was recorded at the site. Poor stand establishment at the Clinton County cooperator site was caused by compounding circumstances: first, delayed soybean planting and “late” rye termination due to weather resulted in taller-than desired rye; then, the tall rye was blown down in a severe wind storm, unfortunately causing the cooperator to lose much of his rye silage crop since it was unharvestable. Finally, the cooperator used a no-till drill for soybeans instead of a planter, which struggled to slice through the downed rye residue and provide the desired seed-soil contact that we’ve achieved using a planter.
Similar to previous years, soybean yield was either no different or 8% higher when planted green than when planted into early-killed rye, with the Lancaster County cooperator site presumably showing a yield benefit associated with the large increase in population (Figure 10). The exception to this was Landisville, which had a 5% (p=0.01) yield reduction despite the slightly higher population when planted green (Figure 11).
Soybean experiment–Rye seeding rate and top-dress nitrogen rates at PSU research stations
The soybean study at Rock Springs and Landisville research stations was a fully crossed factorial experiment comprised of varying rye seeding rates (34, 67, or 134 kg/ha) and top-dress nitrogen rates (34 or 67 kg/ha) either early-killed or planted green (rye killed at planting). In addition to more biomass accumulation with delayed rye termination, higher rye seeding rate increased biomass accumulation at Landisville, with increased growth at the 67 kg/ha seeding level when the higher N rate was applied, but no N-rate effect at 34 or 134 kg/ha rye seeding rates. At Rock Springs, increasing rye seeding rate from 34 or 67 to 134 kg/ha increased rye biomass by about 10%, but N rate had no effect on rye biomass. The lack of N-rate effect on rye growth at Rock Springs was surprising, as there were 17 days between top-dress and early termination at that site, compared to only 11 days delay at Landisville.
The only treatment that significantly influenced soybean population in 2017 was termination timing, and that was only at Landisville, where planting soybeans into green rye increased soybean populations by 6%. Populations were not different among any treatment combinations at Rock Springs. Similar to the corn experiment, slug activity-density followed no clear patterns, and was more influenced by date than any treatments we imposed. Further, soil moisture and temperature were not significantly influenced by any treatment except termination timing at Rock Springs. At Landisville, planting green dried soil at planting but conserved soil moisture later in the growing season across seeding rates, and, contrary to what we expected, soil moisture significantly increased with increased rye seeding rate all growing season. Soil temperature was warmer on average under the 34 kg/ha seeding rate than the 67 or 134 kg/ha rates and in the early-kill treatment than planted green, with a larger average difference between early-kill and planted green temperature at the 67 kg/ha seeding rate than the 34 or 134 kg/ha rates.
A termination timing by nitrogen rate interaction influenced soybean yield at Landisville–soybeans yielded significantly but only slightly better (4%) when planted into early-killed rye regardless of N-rate compared to planted green, while soybeans planted green did get a small but significant 3% yield benefit from higher N-rates applied to rye. At Rock Springs, yields were not different among treatment combinations.
Project members shared these results at several outreach events (Figure 12), in addition to two scientific meetings (Agronomy Crops and Soil Science Societies of America, and Northeast Cover Crop Conference). As in 2015 and 2016, soils were cooler when planting green, slowing cash crop emergence and likely nitrogen cycling. Despite some soil drying around planting and moisture conservation later in the season associated with planting green, in a very wet year like 2017, these benefits of the practice were limited by the frequency of rainfall events. While in 2016 planting green increased slug feeding on corn and reduced slug feeding on soybeans, in 2017 the opposite was true for corn, and soybeans saw no slug feeding suppression from planting green. This could imply that in some situations, slug activity-density may be too high for planting green to cause a significant reduction in feeding by providing alternative forage for slugs and habitat for slug predators. Despite persistent cold and wet conditions across the state around planting, high slug pressure and armyworm outbreaks, planting green maintained the same or higher yields than killing cover crops early at 2 of 4 and 4 of 5 of sites in corn and soybeans, respectively. This supports our conclusions from 2015 and 2016, that soybeans are highly adaptable to planting green, but planting corn green successfully requires additional, precise management and is more vulnerable to yield losses attributable to either reduced crop populations, increased pest pressure, nitrogen limitations, or a combination thereof.
Farmers in Pennsylvania learn about the benefits of terminating cover crops and “planting green” through presentations and educational handouts at our two research farm field days, and at Penn State pest management field days, the Diagnostic Clinic, and winter extension meetings.
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.
In winter 2016, results were presented and discussed with growers, extension personnel, agricultural industry professionals, and agricultural educators from Pennsylvania. Events included: Pennsylvania Agronomic Education Conference (January 22), attended by 110 agricultural educators; Potter County Crops Day (January 29), attended by 85 growers and extension personnel; Conewago and Chiques Watersheds Winter Farmers Meeting (February 25), attended by 60 farmers and technical service providers
Farmers contact members of our project team to gather more information and adopt planting green. They share their experience with members of our project team and other farmers through PSU and No-Till Alliance field days and meetings in summer 2016 and winter 2017.
Farmers learn about the benefits of planting green at project field days at the three cooperating farm and two research farms, at the NESARE Sustainable Dairy Cropping System field day; as well as winter meetings, state-wide conferences, regional and county crops days, and summer educational events described in milestone one, and Penn State’s Ag Progress Days.
In summer 2016, results were presented and discussed with growers, extension personnel, agricultural industry professionals, agricultural educators, and legislators from Pennsylvania. Events included: Penn State Crop Diagnostic Clinic (July 21-22), attended by 115 farmers and ag industry professionals; Penn State Ag Progress Days Manure Hauler Training (August 18), attended by 46 commercial manure haulers; and Penn State Ag Council Research Tour (September 22), attended by 120 legislators and extension personnel.
Additional farmers adopt planting green, consult with project members and obtain technical assistance. Farmers share their experiences at field days and meetings in summer 2017 and winter 2018.
Farmers learn about the benefits of planting green through field days, newsletters and farming news articles, fact sheets and the educational events described in milestone 3.
In 2017, results were presented and discussed with growers, extension personnel, agency and agricultural industry professionals from Pennsylvania at six outreach events. Events included: Improving Soil Health with Cover Crops and Planting Green Field Day (June 22), attended by 81 farmers, agency, industry, extension, and non-profit personnel; Penn State Crop Management Extension Group Field Day (June 27), attended by 23 extension personnel; Farming For Success Field Day (June 29), attended by 230 farmers, agency, industry, and extension personnel; Pennsylvania No-Till Alliance Summer Field Day (July 27), attended by 240 farmers, agency, industry, extension, and non-profit personnel; Kanagy Field Day (August 10), attended by 40 farmers, agency, and industry personnel; and Soil and Water Conservation Society Keystone Chapter Annual Meeting (August 16), attended by 15 agency personnel.
Farmers describe the multiple benefits of planting green in our follow-up
Additional farmers adopt planting green, for a total of 50 farmers.