Reducing plastic mulch use by expanding adoption of cover-crop-based no-till systems for vegetable producers

At Rodale Institute Site

Cover crop biomass, % Carbon and % Nitrogen: Results showed that highest cover crop biomass was achieved in rolled rye+vetch treatment (13,000 lb/acre) and approximately similar to rye+vetch mowed mulch treatment. However, it was significantly different from treatment with rye cover crop either plowed with plastic, rolled, or mowed (6,000, 11,000, and 11,000 lb/acre respectively). The lowest cover crop biomass was in vetch cover crop treatment whether plowed, rolled, or mowed (4,000 lb/acre). All tested cover crops under plastic were plowed and terminated earlier than those rolled or mowed. Thus they had less time to grow and lower biomass. Consequently, the contribution of carbon of any cover crop treatment with plastic mulch was minimal (ranging from 1,500 to 2,500 lb C/acre).The highest carbon input was in treatment with rye alone (whether rolled or mowed) averaging 3,450 lb C/acre but was not significantly different from those with rye+vetch (either rolled or mowed ones) averaging 3,330 lb C/acre. However, the scenario was different for nitrogen contribution from these treatments. High cover crop N contribution was achieved in treatments that included hairy vetch whether singly or mixed with rye (averaging 152 lb N/acre and 161 lb N/acre, respectively). The lowest N contribution was in treatments that had rye alone (averaging 69 lb N/acre).

Soil Moisture and temperature: Across the three years, soil moisture was on average 26% in either mowed or rolled treatments and about 23% in plastic mulch treatments. Differences in soil temperature between black plastic and cover crop mulch treatments was greater early on and fairly minimal by the end of the season. Rolled or mowed cover mulches reduced soil temperature by 5.8^oF in June, 2.0^oF in September, and 0.5^oF in October. There was no difference in soil temperature based on cover crop type. The advantage of cover crop mulch is that it kept the soil temperature moderate (72-77^oF) in comparison to plastic mulch (81-84^oF) and reduced fluctuation over time.

Soil %C and %N: There was no significant difference in percent carbon or nitrogen in soil was observed across years. However, within the rye+vetch cover crop in 2012, percent carbon did increase in the course of the season in both the rolled (from 2.28% to 2.55%), and mowed (2.15% to 2.28%) in comparison to that in plastic (2.3% C) treatment.

Weed suppression: Across the cover crop types, vetch was the least effective at suppressing weed growth. Over the three years, there was a variation in weed biomass in all treatments, although the black plastic system was more consistent than the other two. While the black plastic more effectively suppressed weeds in 2011 and 2012, the rolled and mowed systems outperformed the black plastic in 2010. Rolling was generally more effective at suppressing weeds than mowing. The rye+vetch rolled system outperformed the rye or vetch alone rolled systems.

Photo 1 (see Attachment D1). A square-meter of rolled vetch plot, photographed 4 weeks after planting tomatoes. These plots had the most weed biomass 4 weeks after planting. The main weed trouble-makers shown here are marsh yellow cress and ragweed.

Photo 2 (see Attachment D2). A square meter of rolled rye, photographed 4 weeks after planting tomatoes. Rolled rye plots had the least amount of weed biomass after 4 weeks. The rye provided a much thicker mat than did the vetch.

Tomato Yield: In 2010, total tomato yield was higher (averaging 38,000 lb/acre) in either rolled or mowed system than in black plastic mulch (averaging 20,500 lb/acre). This trend did not translate in 2011, where total tomato yield was highest in black plastic system averaging 25,000 lb/acre in comparison to those rolled or mowed (12,500 lb/acre, 10,300 lb/acre, respectively). Unfortunately, in 2012 Phytophthora late blight dramatically reduced the tomato harvest, affecting total and marketable yields in all systems. It is important to note that marketable yields in both rolled or mowed systems were 70% higher in rye+vetch treatments than in plastic mulch. More research is needed to better understand the factors involving the annual variations in mulch performance.

Waste Production: When we look at the non-degradable waste produced by black plastic mulch we found that it was around 91.46 lb of waste versus none by either cover crop system. The only non-degradable waste that was produced in the organic mulch was the drip irrigation lines (28 lb/acre).

Profitability: The fixed cost per acre in all systems was $9,668 and the variable cost was highest in all systems for the rye cover crop followed by rye+vetch and hairy vetch (Table below). Fixing the price per pound of produce, the marketable yield, revenue and profit varied across systems and was highest in the rolled and mowed rye+vetch system and lowest in the rye alone system. More research is needed to improve the cover crop systems to outperform black plastic mulch in securing higher marketable and total yields (see attached profitability table, Attachment B).

At Farmers’ Sites- Case Studies

Genesis Farm: Mike Baki trialed RI’s rolled rye/vetch system side-by-side with his standard black plastic system. In 2011, Mike grew summer squash, tomatoes, and watermelon, and in 2012 he substituted peppers for watermelon. The tomatoes were more similar between the two systems, with the rolled rye/vetch plots producing about 75% of what the black plastic plots produced. However, the watermelon and summer squash both yielded about twice as much in Mike’s standard black plastic treatments as compared to the rolled rye/vetch. The rolled rye/vetch treatment cost the farm $202.50 for 300 ft, less than half of the $506.80 cost of the black plastic treatment. Mike is continuing to experiment with the rolled rye/vetch system and hopes to find an effective way to put it to work at Genesis Farm.

Swallow Hill Farm: The Randolphs compared RI’s rolled rye/vetch system to a variation of their own technique: rye and crimson clover, rolled instead of cultipacked, with occasional applications of post-emergence herbicide. They planted butternut squash as their test crop with a no-till seeder. In both 2011 and 2012, the squash yield was greater by 27% in the rye and crimson clover system. The Randolphs have demonstrated that crimson clover is a viable alternative to hairy vetch in rolled cover crop systems, providing it is grown in an appropriate climate (hardiness zone 6b). Compared to their former method of cover crop termination using the cultipacker, the roller-crimper provided a more effective crimping of stems, reducing the chances of cover crop regrowth. As a result, there was much less of a need for post-emergence herbicide when using the roller-crimper. Since participating in this study, the Randolphs have switched to using a roller-crimper instead of a cultipacker to terminate their rye or rye and crimson clover cover crop, reducing the use of herbicide on their farm by 40-50%.

Meadow View Farm: James Weaver trialed his standard black plastic management alongside RI’s rolled rye/vetch. James’s standard system uses black plastic mulch in combination with hand weeding, vinegar sprays (which cause the tops of plants to die back), and occasional pesticide applications on tougher perennial weeds. James grew two varieties of tomatoes in the test plots in 2011 and tomatoes and cabbage in 2012.

Although the black plastic plots produced 32% more total yield, James reports that the quality of the tomatoes in the rolled rye/vetch was much better due to a good deal of splitting in the black plastic tomatoes. As a result, the actual marketable yields and profit from each treatment were very similar.

James says it was a bad year for the cabbages in both treatments, though the black plastic plots had higher yields by about 65%. He would like to transition more of his production to a rolled cover crop mulch system. “Especially as I get older,” James says, “I would be happy to not have to deal with plastic removal and disposal.”

Quiet Creek Farm: John and Aimee Good trialed RI’s rolled rye/vetch alongside their own organic weed management approach, which involves tillage and cultivation without black plastic. They used butternut squash as their test crop and did not perform any weeding in either of the years.

Weed pressure in John and Aimee’s test plots varied between 2011 and 2012. In the first year, weed biomass was higher in the rolled rye/vetch treatments by about fourfold. In 2012, however, the Goods’ standard bare-soil treatment had twice as much weed pressure as the rolled rye/vetch. The average yields of the two systems ended up being very similar. The rolled rye/vetch brought 13,503 lb/acre, while John and Aimee’s standard management brought 14,249 lb/acre, a difference of about 5%.

Since their participation in this study, John and Aimee have started to incorporate cover crops into the system. They now plant rye grass and clover in the paths between black plastic rows, adding organic matter to their soil and reducing the erosion that would otherwise occur due to the increased runoff from the plastic. In addition, John reports that this technique creates a much more pleasant space to work in between the rows, especially when the ground is wet.

Milestone 1 (Introductory article):

(Completed in 2010) More than 1,500 people viewed the introductory project article for an average of almost 4 minutes. Most viewers who responded to the survey posted with the article indicated an interest in finding alternatives to black plastic and a need for more information (n=10). Some had tried conservative experimentation with cover crops already, and were eager to find plastic alternatives, but were concerned about weed control and lack of equipment.

Milestone 2 (iButton installation/sampling):

RI technicians installed three temperature data loggers in each RI plot (n=88) and in all the farmer collaborator’s (FC’s) plots in early June 2012 (n=54). IButtons were successfully removed in October to collect soil temperature readings throughout the season. Average full-season soil temperatures (June through October) showed no significant differences at the RI site in the nine different treatments (as in 2010 and 2011), ranging in from 59°F in the rolled vetch plots in early June to 98°F in the black plastic rye plots in early July. However, when daily soil temperature highs and lows were separated by month, distinct differences emerged among the treatments, with the rye and rye/vetch black plastic plots showing the highest daytime temperatures in June and July (around 82°F) and the rye rolled and mowed plots showing the lowest daytime temperature in July (around 72°F). The month of June showed the greatest differences between daytime and nighttime temperatures for all the treatments, with a change of at least 10°F between the time readings. The swing between daytime and nighttime temperatures decreased over the course of the growing season, as did the daytime temperature differences between the treatments, particularly in August, when daytime soil temperatures showed the smallest difference between the treatments.

Soil samples were taken at different points throughout the growing season at the RI site to determine gravimetric soil moisture. Data for April and June have been tabulated and an analysis of the later season readings is on-going. For these two months, average percent soil moisture ranged from 24.2% for rye/vetch in black plastic to 30.6% for mowed vetch, a range similar to those seen in the last two seasons. Though the treatments including vetch appear to hold more moisture in April, differences among the treatments become negligible by June (to be confirmed by statistical analysis in January). This growing season brought fairly consistent rainfall, and as such, coming analysis of the remaining soil moisture data should clarify whether and how the treatments impacted soil moisture later in the season, given “normal” moisture conditions. Soil moisture was not measured at the FC locations.

Cover crop biomass was collected for analysis of biomass production, percent N, and percent C. Once again, vetch biomass production at RI was even greater this year than last year, reaching nearly 5,000 lb/acre (compared to 4,000 lb/acre in 2011 and 2,200 lb/acre in 2010). Rye biomass reached 10,000 lb/acre, on par with 2011 (and much higher than the 4,700 lb/acre in 2010), but the rye/vetch treatments produced less biomass, reaching a maximum of about 7,800 lb/acre compared to 11,500 lb/acre in 2011. What is also interesting to note is that the rye biomass nearly doubled from the time of plow termination for black plastic (April 14th) to the time of rolling and mowing (June 5th), while the rye/vetch biomass did not increase as much over that time period. The vetch biomass also did not increase much between the plowing and rolling/mowing dates this year, but this is due to the fact that plowing and rolling/mowing for this treatment happened only three weeks apart (May 22nd to June 5th). Unlike last year, which brought an extremely wet spring, April and May were relatively dry in this area in 2012, which may have hindered vetch growth as much as the excess moisture in 2011.

Cover crop biomass at the FC sites, consisting primarily of the rye/vetch mix, ranged from 4,900 lb/acre on April 27th (plow/black plastic at Baki’s) to 12,300 lb/acre on June 1st (rolled at Randolph’s), a range very similar to 2012. Again, Baki’s cover crops showed excellent growth between the plowed and rolled terminations dates (late April to late May) but growth at the Good’s plot (which is located at the RI site) was quite minimal over the same time period. Weaver’s cover crop biomass also only increased from 7,800 lb/acre to 10,000 lb/acre from April 12th to May 30th, indicating that a dry spring may have slowed cover crop growth a bit in the area near RI.

Nitrogen concentrations were greatest in the vetch and mixed rye/vetch treatments (200 lb N/acre) and lowest in the rye treatments (70 lb N/acre), which is consistent with what the rye/vetch and rye cover crops produced last year (the vetch alone produced around 70 lb/acre more N in 2012 than in 2011). However, again, the vetch and rye/vetch cover crops showed little or no increase in N content between mid-April and early June, even though the biomass increased. Carbon inputs ranged from 2,200 lb/acre for the vetch (at all termination dates) to 4,500 lb/acre for the rye/vetch mix at the roll/mow termination date, which is right in line with data from 2011.

At the FC plots, N concentrations were unusually low this year, ranging from 28 lb/acre in Baki’s plowed/black plastic plots that were terminated on April 27th to 134 lb/acre for Randolph’s plots that were rolled on June 1st. Carbon inputs, however, were excellent in these plots, ranging from 2,200 lb/acre to 5,500 lb/acre on these same plots, which was exactly the same as 2012. We are not certain how to explain the low N concentration in these cover crops, but it is possible that the vetch simply didn’t grow as well over the 2012 winter as it did in 2011, even though the rye grew normally.

Milestone 3 (Data collection-weed density, diversity and OM inputs):

After adjusting our weed data collection in 2011 to only assess weed biomass, based on the determination that the weed species data was not of sufficient value, we then adjusted our weed data collection again in 2012. In this year, we only collected weed biomass at four weeks after planting, and after that point, we instead measured the amount of time that was required to control the weeds in the plots. Weed biomass was assessed at 4 weeks, both at RI and the FC locations.

At 4 weeks after planting at RI, the rolled and mowed treatments showed similar weed suppression, and in some cases showed statistically similar weed suppression to that of the black plastic (the black plastic serves as a control in this portion of the research, and the weeds collected were those that fell beyond the reach of the plastic, between rows). The mowed rye showed the greatest weed suppression of the non-plastic treatments, amassing less than 4,000 kg/ha of weed biomass, while the mowed rye/vetch amassed almost 2,000 kg/ha of weeds, and the mowed vetch and mowed rye allowed over 6,000 kg/ha of weeds at that date. Despite the fact that the 2012 RI plots produced just as much cover crop biomass as the 2011 plots, they appeared to be less effective at deterring weed growth. In 2011 data, after 4 weeks, the rolled rye/vetch treatments had only 500 lb/acre of weeds, the rolled vetch treatments had 2,100 lb/acre of weeds, and the mowed vetch and rye had about 3,800 lb/acre of weeds. It is possible that the steady supply of moisture throughout the 2012 growing season allowed for greater weed growth, relative to the dry 2011 mid-summer season.

After week 4 weed biomass cut, weeds at the RI site were managed with an in-row hand weeding, followed by occasional mowing between the plots. Week 4 weed pressure at the FC plots was extremely low, ranging from 78 lb/acre in the Good’s plowed fields to 1,450 lb/acre in Weaver’s rolled fields (most of the FC plots had weed pressure of less than 500 lb/acre). These weed pressure data are lower than those of 2011, where data ranged between 900-1,500 lb/acre, with a high of 3,000 lb/acre at Weaver’s. Time and methods for weed control after 4 weeks at the FC sites is still being tabulated. The highest pressure in Weaver’s rolled plots (though it still isn’t very high) may again be due to the fact that he planted on raised beds and used the project’s new raised-bed roller to terminate the cover crop. The roller again appeared to give good kill of the cover crop, and the cover crop biomass was comparable with the other sites, but it is possible that the orientation of the raised-bed roller’s angled drums may have moved the crushed cover crop mat in a way that allowed for weed emergence. Since these data are similar between 2011 and 2012, they suggest that the raised bed roller may need some adjustments before being recommended for large scale use.

Milestone 4 (collect and weigh marketable yield):

Total tomato yield was collected and weighed twice or three times weekly at the RI site from August 13th until September 6th. The harvest season started at a reasonable date, due to the normal weather patterns, but ended very early due to an outbreak of Phytophthora late blight that struck in late August (only at the RI site). Both total and marketable yields were assessed, and as in previous years, to avoid flooding the market and displacing local tomato farmers, project tomatoes were donated to the Berks County Food Bank.

Because of the blight, marketable yields ranged from 2,500 lb/acre in the mowed vetch treatment (total yield for that treatment was 18,000 lb/acre) to 21,000 lb/acre (50,000 lb/acre total yield) in the rye black plastic plots, totaling over 3,000 lb of tomatoes picked throughout the season. To compare, in 2011 total yields ranged from 15,000 lb/acre in the mowed rye treatment up to 84,000 lb/acre in the rye-vetch black plastic treatment, and a total of around 6,500 lb of tomatoes were picked over the season. These yields are lower than the Pennsylvania 10-year commercial average of 10,500 to 22,000 lb/acre due to blight and the shortened picking season. While the black plastic plots generally yielded statistically more total tomatoes than the rolled or mowed treatments for all cover crop types, there were no statistical differences in marketable yields among the nine treatments. Though these data are rather different from those of 2010 and 2011, due to the impact of blight, they suggest, in their raw form, that the rye/vetch rolled and mowed treatments can produce comparable yields to those of the black plastic, as was seen in 2010. Statistical comparison of all three years’ data is on-going and should be complete by the end of January.

Harvest data from the FC is still being tabulated, but raw 2012 data on acorn squash from the Good’s and Randolph’s showed that yields in the rolled plots were higher than in their standard treatments. These data analyses will also be completed by late January.

Milestones 5, 11, 14 and 16 (field day/conference presentations):

2012 –

• RI’s July 2012 Field Day, “Showcasing the Value of Research in Organic Production,” hosted at RI on July 20, 2012, educated a total of 108 participants on cover crop use, supplemental weed control practices, and no-till practices.      
• In addition to the July field day, the second project farmer field day, “No-Till Vegetable Production and Farm Food Safety GAP Mock Audit Twilight Field Walk”, on August 10, 2012, gave 16 participants an up-close and focused opportunity to review the trial on an FC’s farm, learn about the FC’s experiences in implementing the production practices, and receive up-to-date trial data.
• A third outreach presentation entitled “Impacts of Plastic and Cover Crop Mulches on Weeds, Soil Quality, Yields, and Season Length for Tomatoes” was given at the University of Minnesota’s “Extending the Growing Season” Workshop held in April 2012 at their Southwest Research and Outreach Center in Lamberton, MN.
• Project presentations at RI’s June 8, 2012 field event hosted for PA Women in Agriculture (PA-WAgN), entitled “Annual Tour of Rodale Institute: What’s Happening on the Farm” reached over 40 participants, and field tours provided as part of custom group tours throughout the season reached over 600 more visitors of all ages, ranging from elementary and home-school groups to college students to farmer-extension groups.

2011 –

• Fifty-eight people attended RI’s July 22, 2011 Field Day, “Showcasing the Value of Research in Organic Production,” where the no-till vegetable trial was showcased.      
• Forty farmers, researchers and extension agents received information on project production methods and results via Christine Ziegler’s presentation “Organic Vegetable Production Using No-Till” at the 11^th Annual Iowa Organic Conference, held November 20-23 in Ames, IA.
• Fourteen farmers and other interested parties attended Rodale Institute’s “Cover Crop Alternatives to Black Plastic” Farmer Field Workshop held at RI in Kutztown, PA on August 4^th, 2011.
• Project presentations at RI’s June 3, 2011 field event hosted for PA Women in Agriculture (PA-WAgN) reached over 40 participants, and field tours provided as part of custom group tours throughout the season reached over 200 more visitors.

2010 –

• Sixty-seven people attended RI’s July 16, 2010 Field Day, “Emerging Technologies in Organic Agriculture”, where the no-till vegetable trial was showcased.

• About 20 farmers attended Alison Grantham’s “Alternatives to Black Plastic” presentation at the May 27, 2010 meeting of the Berks Agricultural Resource Network, a non-profit agency serving the Berks County agricultural community.
• Project presentations at RI’s June 4, 2010 field event hosted for PA Women in Agriculture (PA-WAgN) reached 42 participants, and RI’s June 9^th training session hosted for NRCS scientists and agents reached 59 people.

Milestone 6 (work with FC):

RI staff worked with the four collaborating farmers throughout each growing season to lay out field treatments; assist with cover crop incorporation, rolling, and crop planting; take cover crop and weed biomass cuts; deliver and plant cover crop seed; sample soil for percent moisture, rocks and fines, and active organic carbon; and answer any questions the farmers had about the project or the work involved. All the farmers were very willing and helpful collaborators throughout the seasons and a delight to work with.

The winter 2012 planning meeting provided a good opportunity for all to see each other again, discuss ideas and plans as a group, and make sensible changes for the coming growing season. While the farmers’ 2011 experiences with the rolled cover crop treatments were mixed, ranging from full success at the Good’s and Randolph’s to fairly serious failure at Baki’s and Weaver’s, all four farmers were excited to try the treatments again in 2012, making adjustments for weed pressure (allowing weeding after 4 weeks), and all carried through admirably.

Milestone 7 (process and analyze samples):

We have collected and analyzed the plant and soil samples, tabulated and prepared graphs that were published in the production manual.

Milestones 8, 9, 12 and 13 (FC, beneficiary meetings and article review):

The FC Winter Workshop in late February 2012 brought the stakeholders together to review the article that had been posted on the website in January and discuss work plans for the coming season. We calculated costs and savings in winter 2013 to encompass both full field seasons of the project.

Milestone 10, 15 (field day surveys):

The on-line field day participant survey was sent to participants of the 2010 and 2011 events in mid-2012, and results from this survey are outlined in this report. Surveys were sent to participants of the 2012 Field Day in early January, and results from that mailing were tabulated in late February 2013.

In December of 2013, we sent an electronic survey to our e-newsletter subscribers. We had a total of 198 respondents, 71.7% were farmers who have tried incorporating more cover crops into their farming production system. The most common cover crops tried were rye, crimson clover, oats, and hairy vetch. Also, 76.2% of the respondents were willing to use cover crops again in their farming system and 14.6% of the respondents tried rolling/crimping the cover crops. About 13.6% of the respondents were willing to test this technique in the coming seasons. About 24.2% of the respondents were non-growers (some educators were also farmers) who recommended cover crops to farmers. At least 5.5% of the farmers have implemented the use of the roller/crimper in their farming production system.

Milestones 17, 18 and 19 (production manual, final article, journal publication):

Due to the time needed to finish processing and analyzing the 2012 data and correlate it with data from the previous years, work on the production manual and final project articles started in January 2013 throughout December 2013. A journal publication will be available in draft form by December 2014.

• Profitability Table
• Rolled Rye
• Rolled Vetch
• Final Financial
• Survey Summary