Hybrid Mulching Effects on Vegetable Crop Productivity, Weed Dynamics and Soil Quality

Final Report for LNE04-203

Project Type: Research and Education
Funds awarded in 2004: $131,302.00
Projected End Date: 12/31/2009
Matching Non-Federal Funds: $61,712.00
Region: Northeast
State: Maine
Project Leader:
Dr. Mark Hutton
University of Maine Coope
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Project Information


The hybrid mulch system is a grower developed combination of sustainable agricultural practices designed to address concerns of growers in the northeastern United States. It produces vegetables on fall established, plastic mulch covered, raised beds with a living mulch inter-bed of perennial ryegrass and white clover. The beds are left in place for up to three years, and the system aims to reduce waste plastic and the need for herbicides and tillage. An evaluation of the system and its impact on production and economic factors was carried out at Highmoor Farm, in Monmouth, Maine from 2004 to 2007 and on three participating farms in 2004 to 2006. The hybrid mulch system produced yields greater or equal to the traditional spring planted system in the first two years, but lower yields in the third year. Net returns were doubled with a tomato, cucumber, pumpkin rotation, while in the cucumber, tomato, pumpkin rotation, net returns remained stable in comparison to a traditional production system. Major cost differences between the two systems were due to mowing, increased time spent weeding and planting, and increased harvesting costs. An important factor in the success of this system appears to be in its ability to allow earlier planting dates, up to 14 days earlier. The ability to plant earlier is very important to growers in regions with short growing seasons or wet springs.

Performance Target:

1) On-farm and Experiment station research will demonstrate and develop refinements to the hybrid mulch production system tailoring it to Maine and other northern growing conditions.

This objective has been met. The hybrid mulch experiment was replicated two times at Highmoor farm 2004-2007 and 2005-2008. Our data indicate that this system can produce yields and economic returns equal to or greater than the “standard” spring tillage system.

2) Three hundred farmers will observe the hybrid mulch cropping system. Thirty-five farmers will use the hybrid mulch system in at least one of their fields resulting in: decreased tillage, improvements in soil health, decreased weed competition, and increased economic returns.

Information about the hybrid mulching system was presented to more than 475 vegetable growers in the period extending from 2004-2008. Eighty-five mixed vegetable growers observed the hybrid annual beds established in the fall of 2004 during meetings held at Highmoor Farm in September of 2005, July and September of 2006. Additionally, 125 growers learned about the project at the Maine Small Fruit and Vegetable Growers Association winter meeting held in January of 2005. During the 2006 growing season 85 mixed vegetable growers attended the Highmoor Farm summer tour and learned about the hybrid mulched beds and the crop rotation study. In 2007, a total of 75 growers visited the experiment site at Highmoor to learn about the research we are conducting with the hybrid mulching system. A 35 minute presentation was made to 70 vegetable growers at the 2008 Maine Vegetable and Fruit School describing the hybrid much system and its associated benefits and drawbacks. The hybrid much research was also presented to 35 organic farmers as part of the 2008 Farmer to Farmer conference.

We also presented results of this research at the 2008 annual meeting of the American Society for Horticultural Science.

We are short of our goal of having more than 35 growers adopting the hybrid mulch or fall made beds system. There are between 15-20 growers who carry over plastic mulched beds in any given year. Decisions to carry over plastic and replant are based on the condition of the plastic in the spring of the second year and weather conditions. Many growers are not removing all the plastic from fields in the fall and if the spring is very wet they are keeping the plastic in place and using these beds for the earliest planting. In the fall of 2008, five growers made inquiries about establishment of fall made beds.

3) An economic analysis will measure economic returns of each system.

Partial budget analysis has been done for the two crop rotations in the hybrid mulched beds and comparisons made to “standard” spring tillage. The hybrid mulch systems are more expensive to manage; however, they can result in higher economic returns. The increase in profit from this system seems to be mostly due to the earlier planting dates created by having planting beds already in place in the spring.


Click linked name(s) to expand
  • Andrew Files
  • Eric Gallandt
  • Charles Gill
  • Mark Guzzi
  • Rob Johansen
  • Eric Sideman


Materials and methods:

In fall 2004 a hybrid mulch system was established at the University of Maine Agricultural and Forest Experiment Station, Highmoor Farm, in Monmouth, ME. The field had been in sweet corn production the previous year. It was rototilled and treated with 50 yds3/acre of compost. Nine rows of raised beds were established using a bed former. One of three types of extended-life plastic mulch from Pliant Corporation was assigned to each of the nine rows. The mulches were 1.25 Mil and intended for use in the southern U.S. where two crops per year are common. Mulch 1, “micro,” was a micro embossed 18 month plastic, Mulch 2, “taffeta,” was a taffeta embossed 18 month plastic, and Mulch 3, “EL” was a 24-month, extended-life micro-embossed plastic.

Each row was subdivided into 60 ft beds. One of two cropping rotations was assigned to a bed in each row, with each rotation replicated three times on each of the three types of plastic for a total of 18 hybrid mulch beds. Rotation 1 (TCP) was tomatoes in 2005, followed by cucumbers in 2006 and pumpkins in 2007. Rotation 2 (CTP) was cucumbers, followed by tomatoes, followed by pumpkins. Finally, a living mulch of perennial ryegrass was planted in the inter-beds. By spring 2005 white clover had colonized the inter-beds throughout the field establishing a ryegrass and clover mix that persisted till the end of the experiment. Spring tillage and bed establishment was subsequently unnecessary in the hybrid mulch beds, although crop residues were removed from the plastic mulch each fall, holes in the plastic were weeded by hand as needed throughout the growing season, and the living mulch was managed by mowing as needed (five to six times per cropping season).

In the spring of 2005, 2006 and 2007 a block of traditional spring-made beds were established adjacent to the block of hybrid mulch beds using the “taffeta” black plastic mulch. Each spring, the beds were fertilized with 500 lbs/acre of 10N-10P-10K and planted with the same crops as the hybrid mulch beds. Weeds in the beds were managed by hand weeding and the bare ground inter-beds were managed by rototilling as needed (one to three times per cropping season).

Determinate, beefsteak tomato varieties were planted into the field as transplants. In 2005, ‘Fabulous’ transplants were grown in the greenhouse at Highmoor and in 2006 ‘Celebrity’ transplants were purchased from a local grower as the ‘Fabulous’ seeded in the greenhouse that year had poor germination rates. Plants were spaced 18 inches apart and received one cup of 8N-45P-14K fertilizer solution at transplanting. The tomatoes were pruned to one stem up to eight inches above the ground, staked and basket-woven for structural support.

‘Cross Country’ pickling cucumbers were direct-seeded at 18 inch in-row spacing. Each plant received one cup of 8N-45P-14K fertilizer solution 14-28 days after planting when true leaves were present.

‘Charisma’ jack-o-lantern pumpkins were direct seeded at 5 ft in-row spacing. Each plant received one cup of 8N-45P-14K fertilizer solution 14-28 days after planting when true leaves had formed.

Each spring all beds were planted once the danger of late spring frost was past and when the beds could be prepared, as would happen on a commercial farm, the timing of which varied between treatments. The hybrid mulch beds did not need to be tilled each spring and thus were planted when they dried out enough for foot traffic. The traditional beds had to be dry enough for tractor traffic before the beds could be formed and consequently, were planted later than hybrid mulch beds in two of the three years. Due to severe vertebrate predation all the pumpkins planted in 2007 had to be replanted three times until the final replanting using transplants on 11, July.

Data were collected on plastic deterioration, marketable yield, fruit quality, and cost and labor requirements. A qualitative assessment of the condition of the plastic in the hybrid mulch beds was carried out in the fall of 2007 based on methodology developed for use with biodegradable plastic mulch. The plastic was evaluated on a scale of 0-5 based on visual inspection of tears, holes, percentage of ground coverage and overall deterioration. A score of 0 meant no breakdown of the plastic with 100% ground cover; and a 5 meant the plastic mulch was largely deteriorated with less than 50% ground coverage. Data were analyzed as a RCBD with three replications.

Fruit yields were harvested, graded, counted and weighed. Tomatoes were graded “A” for premium or large fruit with few if any blemishes, “B” for marketable fruit which were smaller and/or blemished but still marketable, and “C” for culls or unmarketable fruit. Cucumbers were graded “A” for marketable fruit which were straight, 4-6 inches long and without blemishes and “C” for culls which were unmarketable due to curving, excessive size, and/or blemishing due to insect damage or disease. Pumpkins were also graded “A” for marketable which were mature fruit with few if any blemishes and “C” for culls which were unmarketable due to disease, immaturity, or vertebrate feeding damage. Notes were made for each bed on each harvest date on the types of problems that led to a grade of “C”. Yield data were analyzed as a CRD with three replications.

To compare the performance of the rotations over the three years of the project, the mean value of the treatments, in $/ha, were compared. Using this common unit allowed comparison of yields of the three different crops. Receipts and costs of production were based in part on data collected during the project and in part on price data from the New England Agricultural Statistics Service and cost data compiled for Agricultural Alternatives publications on tomato, cucumber and pumpkin production and enterprise budgets.
To calculate receipts, data on 2005 and 2006 vegetable prices in Maine were obtained from NASS. As, NASS does not keep statistics on the market value of pickling cucumbers, figures from slicing cucumbers were substituted. The 2007 prices were not yet published at the time of analysis so the average of 2005 and 2006 prices was used to calculate receipts for 2007 crops. The price data was multiplied by the actual average yields obtained per treatment in kg/3.7 row meters and then adjusted upwards to reflect the value of the yields in $/ha.

The production costs associated with hand weeding, planting, and mowing or rototilling the inter-beds were calculated based on labor costs of $10/hr for the actual number of hours spent on each task throughout the experiment, which were then adjusted upward to reflect their value in $/ha of production. Fuel requirements in gallons per field operation were estimated from farm fuel records and costs per gallon were based on the average price of fuel over the three years of the project. Production costs associated with plowing and bed preparation, and installing and removing irrigation and plastic mulch were obtained from Agricultural Alternatives estimated costs for commercial production. Harvesting costs were also based on estimates from Agricultural Alternatives with an adjustment made for cucumbers. This publication reported the costs for harvesting pickling cucumbers one time per season, but in the experiment cucumbers were harvested three times per week over the course of the season as would be more usual for a grower marketing direct to consumers. Therefore the figures for the once-over harvest were multiplied by the actual number of weeks each treatment was harvested. This adjustment allowed the enterprise and partial budgets to reflect the increased costs that would have been incurred by a grower when the hybrid mulch system extended the harvest season for cucumbers.

The receipt and cost data was then combined to create enterprise budgets for each rotation in both hybrid mulch and traditional systems. From these enterprise budgets, partial budgets were prepared for each rotation. Partial budgets show only the receipts and costs that differ between the two systems to facilitate analysis of any economic differences.

Research results and discussion:

Grower attitude to this project was mixed. The three farmers participating in the project were generally unimpressed with the use of fall made beds and hybrid mulching. Detailed presentations of their experiences are presented here. Other growers are finding this system useful but in a way we had not expected. Bill Spiller has found that carrying over plastic into a second year is working on his farm. He typically grows cucurbits in the first year and then follows with tomatoes in the second year. Bill says “I like being able to get my tomatoes in early and there is less vegetative growth on the plants.” Bill uses a non-selective herbicide over the plastic in the second year prior to transplanting and then adjusts the fertility by fertigation.

Excessively wet springs in 2007 and 2008 have encouraged other growers to look into carry over beds or fall made beds. In 2008, Rick Belanger planted peppers in to plastic that had cucumbers the previous year (2007) with acceptable results. Adoption of the practice is not happening the way in which we expected. Growers seem to be leaving some plastic in the fall and then depending on the condition of the plastic and weather conditions in the spring choosing to plant back into the beds or remove the plastic and follow standard tillage practices.

The following case studies were written on the basis of biweekly visits and conversations with the growers through 2005-2006.

Goranson Farms

Goranson Farm is a second generation family farm in Dresden, Maine. It is currently owned and operated by Jan Goranson and Rob Johanson. The operation began as a potato farm and evolved into a diversified organic farm producing maple syrup, potatoes, vegetables, berries, transplants and meat when the current generation assumed management. Goranson Farm markets their products directly through a CSA program, an on site farm stand and three weekly farmers markets. The farm is located on a peninsula in the Kennebec River and Rob, who acted as the primary contact for this project, believes good soil conditions are a major contributor to the farms’ success.

At the beginning of the experiment we asked Rob what he anticipated would be the biggest potential constraint of the system. He said “competition for nitrogen”. He anticipated signs of nitrogen deficiency in the first year, and anticipated nitrogen would become an especially big challenge in the second and third years if the treatments were left in place as the lack of tillage would make it impossible for him to incorporate fish meal as usual. He noted that while his soil is very good it is also very well drained and a little sandy meaning he has to keep a close eye on his nitrogen levels.

All three treatments were planted with transplants of several varieties of tomatoes over the last week of May and the first week of June. Both the mowed and straw treatments controlled weeds except for nut sedge and hairy vetch volunteers from the last years’ cover crop. The weeds in the hybrid mulch beds were managed by hand weeding twice over the season. The weeds in the spring treatments were managed by rototilling twice in July.

At transplanting, the field was covered with remay for insect control. Consequently it was not possible to mow the live mulch until the remay was taken off in the third week of June. At this point, the live mulch was about 2 feet tall which may have increased the ability of the live mulch plants to compete with the crop plants for water and nutrients. The stress associated with competition may explain why the tomatoes in the mowed treatment were smaller and flowered and fruited earlier than the straw treatment which in turn flowered and fruited earlier than the spring treatment. However, Rob felt he could not be sure at this stage that the differences were all due to nutrient and water competition and not due to differences in varieties.

In the first week of July, Rob began to notice that the tomato plants in the mowed treatment were showing signs of nutrient deficiency in the leaves compared to tomatoes in the other treatments. As it was a wet year no irrigation was needed, but Rob observed that in more average years he would need to irrigate at this point in the season and could fertilize the plants at the same time if necessary.

Unfortunately, fertilization would not have helped because early blight also began to appear in the field at the beginning of July and it proved to be a year with heavy early blight pressure in tomatoes across the region. Rob pruned and sprayed copper, but that did not stop the disease and most of the tomatoes were lost. A small amount was harvested from the mowed treatment before the disease killed the plants at the end of August. As the tomatoes in the straw and spring treatments were developmentally behind those in the mowed treatments, they were almost a total loss.

When asked what management challenges he saw with the hybrid mulch system, Rob observed that he couldn’t cover each row individually with remay or plastic as he normally does without tearing up the grass or straw inter-rows. When asked in early July which treatment he felt showed the most potential on his farm, Rob chose the straw treatment as the leaf color on those plants showed less nutrient deficiency than the mowed treatment, the straw showed good weed control, and it would add organic matter to the system over time. By early August, Rob said of the grass treatment “I wouldn’t try this again because of the competition for nutrients”. Between the signs of nutrient deficiency already visible in the first year and the organic regulations that prevent growers from leaving plastic in place for more than one season, Rob chose not to attempt to leave the treatments in place for a second year.

Kennebec Flower Farm and Nursery

Kennebec Flower Farm was established in 1992 by Chas and Linda Gill in Bowdoinham, Maine. The Gills primarily grow cut flowers using greenhouse, hoophouse and field production systems. They also produce flowers for sale as transplants, and some vegetables, primarily squash, melons, tomatoes, and onions. Nearly all their products are marketed direct to consumers primarily through two weekly farmers markets, and occasionally through contract work for weddings or special events. Chas and Linda designed their operation to combine elements of organic and conventional management systems, and strive to minimize the use of pesticides.

The perennial ryegrass planted in the inter-rows did not overwinter well, and clover was seeded in the last week of April to fill them in. At this time portions of the hybrid mulch beds were planted with perennial flowers. Although Chas was not convinced that early bed establishment would prove to be much of an advantage to him due to the danger of frost, he did note that “last year it was the second week of June before I could lay plastic. I’ve never lain plastic in April”.

Chas installed the spring beds when the soil dried out at the end of May. By this point the grass beds were fairly well filled in with rye and clover. The onions and melons were planted in all treatments in mid June. Chas noted “it might just be my soil but it seems very compacted [in the hybrid mulch beds] since it’s been settling all winter.” When asked which beds he felt would yield best, Chas chose the spring beds and said he expected little difference between the grass and straw beds. He also said that he loved the straw treatment because of its weed control, but he found lots of slugs under the straw and had to use slug bait to control them.

Most of the weeds in the hybrid mulch beds grew up through the hole in the plastic and along the edges of the beds, but overall the weed control was good throughout the first year. However, by early August it was clear from looking at them that the plants in the grass and straw beds were nutrient deficient compared to the spring beds, and that the plants on the grass beds were more deficient than those on the straw beds. The melons were harvested at the beginning of September and yields bore out that observation.
Despite lower yields in the hybrid mulch beds, Chas decided to keep the beds in place because he had perennials in some of them and wanted to see what would happen with them over time. He said, “I’m still convinced that compaction is my biggest issue. Getting on my beds early isn’t important for me because I’ve built my business around knowing I can’t get on early. But the covering over winter is interesting. I think I might need something like that.”

A visit the first week of May, 2007 showed that the perennials had overwintered well. Some deer damage was evident on the plastic, but otherwise it held up well. Severe deer damage was evident in some tulips planted just outside of the hybrid mulch beds which were surrounded by a battery operated electric fence.

By the middle of June, the soil had dried out sufficiently for Chas to install spring made beds. Chas noted “I would recommend against clover because it attracts deer.” Penetrometer readings taken at this time showed that Chas’s observation about increased compaction in the hybrid mulch beds compared to the spring beds was accurate.

By the middle of July it was clear that the straw was not controlling weeds as well in the second year as the first, but Chas was able to manage them by mowing. The clover grew fast and tended to creep up on to the plastic in the rows. He found he could gain some control of this problem by spraying roundup along the edges of the plastic.

“If I had it to do over, I’d make the rows narrower and use the straw. Or maybe bluegrass, I saw that at another farm and it stays short. The clover has to be mowed a lot and it attracts deer.” Chaz felt that the plastic held up pretty well and it “shouldn’t be too bad to pull up”. He top dressed the beds to try to address the fertility problems, and felt that this would work well enough that he wouldn’t need to worry about removing the N-fixing clover from the system.

At the end of July, Chaz observed that turkeys were moving the straw around and snapping turtles were laying eggs in the plastic. He said “I probably wouldn’t do it [hyrid mulch beds] again”. The fertility was a problem, but primarily, he found the spring made beds were just easier to manage.

In early September, Chaz indicated that he would probably hold on to the hybrid mulch beds for one more year as the flowers were still looking pretty good and top dressing with compost should help. He also noted that the straw wasn’t holding the weeds back in this second year like they did in the first and suggested replacing the straw every year. He was considering killing the current ryegrass and clover mix and reseeding a slower growing grass. When asked if he thought it would be beneficial to add fertigation to the hybrid mulch system, Chaz said that in his situation it wouldn’t be because his soil tends not to dry out.

Peacemeal Farm

Peacemeal Farm was purchased by Mark Guzzi in 2003 after he and two other partners had rented the farm and taken over management three years earlier. Located in Dixmont, Peacemeal is a certified organic farm. Peacemeal produces vegetables such as greens, lettuce, carrots, tomatoes, cucumbers, peas, beans, potatoes, and squash. Most of Peacemeal’s produce is marketed direct to consumers through 6 weekly farmers markets and a booth at Maine’s annual Common Ground Fair.

The soil at Peacemeal is heavy and fertile because the previous owners had for many years added organic matter in the form of manures. Mark said at the beginning of the experiment that one of his biggest challenges is dealing with weeds.

A visit to the farm the first week of May, 2006, showed that the ryegrass and clover inter-row planted the previous fall had not overwintered well. It was replanted and germinated well. Mark planted a variety of squashes in the hybrid mulch beds the last week of May and covered the crops with remay for insect control. The spring beds were planted with tomato transplants in the first week of June. When asked soon after planting what his major concerns were Mark said he wasn’t sure the black plastic would warm the soil adequately. “We usually use IRT, because our beds are colder, and that causes delays in germination”. We discussed the fact that some growers had found they could get on their fall made beds earlier than conventional beds, but Mark felt that would not be an advantage on his farm as his fields traditionally are dry enough to be worked as soon as the soil is warm enough to plant.

An early disadvantage that emerged with the fall made beds was the need to pick up the remay to mow and hand weeded the beds once before the remay was removed for the season in early July. During this early period the weed control was best in the mowed beds; the only major weeds were vetch. In both grass and straw beds the primary location of the weeds was where the inter-row had to be disturbed in order to lay the remay. The vetch in the straw beds was flowering while in the grass beds it was not, indicating the grass was competing with the vetch. The conventional beds seemed to have more weeds, but Mark was able to control them with cultivation.

In mid July Mark hosted a stop on a regional SARE tour and had the following observations. “Fertility is my least concern with this project. We hardly use any fertilizer here.” Mark told the tour visitors that the project had gotten him thinking about the paths between his beds and having something growing there. “I’m tempted to put oats in the paths”. When asked if he thought the system would provide assistance with weed control, Mark said “the weed I’m expecting at the end of this is rye and clover”.

By the end of July the squash vines had begun to run and had filled in the rows to the point that mowing was no longer possible. Meanwhile the vines had completely closed in the straw inter-rows. The weeds still seemed to be fairly well controlled in both treatments and the squash were flowering and looked healthy.

In early August discussions with Mark touched on the fact that the squash plants in the grass treatments were looking a little smaller than those in the straw beds, and Mark said he couldn’t tell yet if the differences were varietal or due to competition. However, by the end of August it did appear clear that the grass was competing with the squash. “The acorns aren’t doing too good – about one fruit per plant. We wouldn’t do it again if we only got one fruit per plant”.

The squash were harvested in mid September and Mark again mentioned his disappointment with the yields with the hybrid mulch system. He had originally thought he would put lettuce in second year as he tries not to plant squash in the same spot year after year, but he decided he couldn’t keep the beds in if they weren’t producing much. He did note the advantage of the straw treatment in that it would add organic matter when it was plowed in.

A variety of similar themes as well as suggestions and observations that will help identify avenues of future research emerged on the farms that participated in this project. All the growers noted yield reductions, two found logistical constraints when using remay, and all three showed interest in the straw mulch. Two growers suggested a change of live mulch inter-row species, one highlighted the need to adjust our thinking on weeds, and the experience of two of the growers illustrated the need for a closer look at the hybrid mulching system and how the organic regulations affect its potential.
Yields were reduced in the hybrid mulch system at all three locations. Simultaneous experiments at the University of Maine’s Research and Experiment Station Highmoor Farm showed that the hybrid mulch system allowed crops to be planted earlier in wet years which compensated for the yield reductions due to competition for water and nutrients. However, this advantage was not important to any of the three growers participating on farm, as they felt they had already adapted their businesses to the dates they could traditionally get on their fields.
Both organic farms use remay for insect control. Peacemeal found that laying the remay disturbed the grass and straw and led to weed control problems. Goranson’s found that laying the remay over multiple rows allowed them to leave the inter-rows undisturbed, but it also prevented mowing which helps control competition for water and nutrients.

All three growers liked the straw mulch treatments. The weed control, at least in the first year was good, and all three growers liked the idea of being able to incorporate the straw as an organic matter soil amendment.
Chas and Mark suggested changing the live mulch inter-row, indicating that they agreed with the idea that keeping the soil covered was worth exploring, but that they felt the ryegrass and clover mix was too fast growing and competitive. In Chas’s case the clover was also too attractive to deer. All three growers currently use cover crops, which may explain why they see advantages in keeping the soil covered. Chas felt he was able to deal with the nutrient competition problems by top dressing and he felt that the hybrid mulching system might be a good match with his perennials.

Mark’s observation that the weeds he expected at the end of the project were rye and clover was a good one. The hybrid mulch system may be more about identifying and managing the weeds growers are prepared to live with than it is about eliminating weeds.

Rob and Mark both noted that current organic regulations do not allow growers to leave plastic mulch in the ground for more than one season. If the system proves interesting for organic growers, this issue will need to be addressed.

Participation Summary


Educational approach:

Information about the hybrid mulching system was presented to more than 475 vegetable growers in the period extending from 2004-2008. Eighty-five mixed vegetable growers observed the hybrid annual beds established in the fall of 2004 during meetings held at Highmoor Farm in September of 2005, July and September of 2006. Additionally, 125 growers learned about the project at the Maine Small Fruit and Vegetable Growers Association winter meeting held in January of 2005. During the 2006 growing season 85 mixed vegetable growers attended the Highmoor Farm summer tour and learned about the hybrid mulched beds and the crop rotation study. In 2007, a total of 75 growers visited the experiment site at Highmoor to learn about the research we are conducting with the hybrid mulching system. A 35 minute presentation was made to 70 vegetable growers at the 2008 Maine Vegetable and Fruit School describing the hybrid much system and its associated benefits and drawbacks. The hybrid much research was also presented to 35 organic farmers as part of the 2008 Farmer to Farmer conference.

Heather Bryant has published the detailed findings of this research in her Master’s of Science thesis ‘Hybrid Mulch System: Effects on Crop Production, Economics, Weeds and Soil Quality’ submitted to the University of Maine, Department of Plant, Soil and Environmental Science. Heather also authored a poster presentation delivered to the 2008 annual meeting of the American Society of Horticultural Science with an abstract published in HortScience 43:4 p 1184.

We intend to put photos and a information regarding this project there.

Additional Project Outcomes

Project outcomes:

Impacts of Results/Outcomes

Plastic Durability

The three types of extended-life plastic mulch showed no differences in durability throughout the three cropping seasons of the experiment. The major causes of damage were holes created by small rodents, woodchucks, deer and turkey. Weed pressure increased as more holes were created. Some wind damage occurred the first year when wind blew across the rows creating a Bernoulli effect that lifted the plastic from where it had been buried into the soil. While the level of damage sustained over the three cropping seasons and subsequent weed pressure would preclude further use, all three types of plastic were equally effective in the hybrid mulch beds in terms of producing yields and maintaining integrity over time.

Marketable Yields

Marketable yield of tomatoes, cucumbers, and pumpkins were similar using the three different plastics. In the TCP rotation, tomatoes planted in hybrid mulch beds in 2005 produced greater yields of marketable fruit than tomatoes in traditional beds. Cucumbers in hybrid mulch and traditional beds yielded similarly in 2006, but in 2007, pumpkins in hybrid mulch beds yielded less than those in traditional beds. Somewhat different yield results were seen in the CTP rotation. In the first two years, hybrid mulch marketable yields of cucumbers and tomatoes were similar to yields of the traditional beds. Like TCP, in 2007, CTP pumpkins produced lower marketable yields in the hybrid mulch beds compared to traditional beds.

In both rotations the hybrid mulch beds were competitive with traditional beds during the first two years, that is, they produced the same or greater marketable yields of tomatoes and cucumbers. Due to wet springs, the hybrid mulch beds were planted 14-15 days earlier than traditional beds in 2005, and 14 days for tomatoes and 9 days for cucumbers in 2006.

The difference in planting dates is likely the primary reason for the competitive yield results seen in the hybrid mulch beds in the first two years. The summer of 2005 was drier than the summer of 2006 which could explain why the earlier planted hybrid mulch tomatoes showed greater yields in 2005 but not in 2006. The drier summer 2005 weather may not have given tomatoes in the traditional beds a chance to “catch up” to hybrid mulch tomatoes. Another potential factor is that the tomato transplants that were planted in the traditional beds in both 2005 and 2006 spent two weeks longer in the greenhouse and may have become physiologically stressed. This stress could have been further intensified in 2005 by the drier summer.
In comparison to the first two years, the spring of 2007 was dry and the hybrid mulch beds were only planted one day before the traditional beds. This meant the hybrid mulch pumpkins had no early planting advantage over traditional. Subsequently, the summer of 2007 was also dry and likely led to competition for water between the crops and the living mulch of the hybrid mulch beds. Data collected from this experiment but not discussed here showed slightly greater losses of nitrogen over three years in the CTP hybrid mulch beds compared to spring beds, but no greater losses of phosphorus or potassium between. The loss of the advantage of earlier planting plus competition for water and possibly nitrogen likely combined to cause the yield reductions seen in the 2007 hybrid mulch beds, but it is not possible to separate the relative impacts of these factors with the data collected. The conclusion is that yields from the hybrid mulch system will be most competitive with traditional in years with wet springs and summers with adequate rainfall.

Fruit Quality and Earliness

In addition to being planted 15 days earlier, in 2005 the Rotation 1 – TCP hybrid mulch tomatoes were harvested 15 days earlier than the traditional. Overall the hybrid mulch beds produced higher yields of marketable fruit than the traditional beds. Looking at the fruit quality classes individually, the hybrid mulch beds produced higher yields of premium quality fruit and cull fruit than the traditional beds and lower yields of marketable fruit. It is not possible to tell from the data collected if the quality differences are due to earliness or biological differences of the two systems.
In 2006, the cucumbers in the hybrid mulch beds in the TCP rotation were planted 9 days earlier than traditional and harvesting began 5 days earlier. Overall, the yields of marketable fruit were similar in the two systems. As with the tomatoes the hybrid mulch beds produced greater yields of culled cucumbers than traditional beds. Poor pollination leading to fruit deformity was the most common quality problem for the hybrid mulch cucumbers and other common problems were belly rot and slug and insect damage.

In the TCP rotation, the hybrid mulch pumpkins in 2007 were planted and harvested at the same time as the traditional pumpkins. While the traditional beds did produce greater yields of pumpkins than the hybrid mulch beds both treatments produced minor and similar yields of culls.

In Rotation 2 – CTP, the hybrid mulch cucumbers in 2005 were planted 14 days earlier than the traditional cucumbers and harvesting began 12 days earlier on 29, July. Both hybrid mulch and traditional cucumbers produced similar yields of marketable fruit and continued producing till the end of August. Towards the end of the season the fruit quality in the hybrid mulch beds had diminished. In fact the hybrid mulch beds produced higher yields of culls than traditional. Poor pollination resulting in curved fruit was the primary quality problem noted in the hybrid mulch beds. Other more minor problems included belly rot, and slug and insect damage.

In 2006, the tomatoes in the CTP rotation were planted 14 days earlier in the hybrid mulch beds than the traditional beds, but the harvest only began 7 days earlier. While the overall yield of fruit (premium + marketable) was the same across treatments, when that yield is broken down by quality category, some differences emerge. The yield of premium fruit was greater in the hybrid mulch beds than in the traditional beds and the yield of marketable fruit was similar across treatments. The yield of culls was also lower in the hybrid mulch beds than in the traditional.
In the CTP rotation, the hybrid mulch pumpkins in 2007 were planted and harvested at the same time as the traditional pumpkins. While the traditional beds produced greater yields of pumpkins than the hybrid mulch beds both treatments produced similar and minor yields of culls.

Impacts were seen on the earliness of harvesting the tomatoes and cucumbers in both rotations. In 2005 planting 14-15 days earlier led to harvesting 12-15 days earlier (TCP tomatoes and CTP cucumbers). In 2006 planting TCP cucumbers 9 days earlier led to harvesting them 5 days earlier while planting CTP tomatoes 14 days earlier only resulted in harvesting 7 days earlier. Meanwhile, no impacts on earliness were seen in 2007 when the pumpkins in both rotations were planted and harvested at the same time. It is not possible to determine from the data collected whether it was the planting dates alone or planting dates plus the biology of the hybrid mulch system which impacted the earliness of the harvest. However, the evidence does seem to suggest that the hybrid mulch system has value as a season extension tool.

Overall the hybrid mulch system impacted fruit quality differently for different crops. Pumpkins appeared to maintain high levels fruit quality in both systems, but tomatoes had a more variable response. In both rotations the yields of premium tomatoes increased in the hybrid mulch system, but in the TCP rotation the yield of culls also increased. It is not possible to tell from the data collected if these results are related to the earlier planting and harvesting allowed by the hybrid mulch system or something more specific to the biology of the system. Some clear loss of fruit quality was evident in the form of increased yields of culled cucumbers which was seen in both rotations. Poor pollination was the primary cucumber quality problem, followed by belly rot, and slug and insect damage. Crew observations indicated that moving the cucumber vines onto the plastic was a possible management strategy to minimize belly rot and slug damage, suggesting a connection between cucumber quality and the damp environment of the living mulch. Moisture fluctuation during the growing season is known to cause fruit deformity in cucumbers. Future research could look at whether or not the living mulch of the hybrid mulch system impacts the water availability to cucumbers or impacts pollination by confusing pollinators or providing them with more appealing options than the crop plant.

Economic Analysis

Detailed economic analysis was conducted on the Highmoor Farm hybrid mulch system. Measured in $/ha over the three year period, hybrid mulch TCP (tomato, cucumber, pumpkin rotation) beds showed greater economic yields than traditional beds with the same crops. Receipts of $295,972 for the hybrid mulched beds TCP rotation compared to $168,418 for the same crop sequence in traditionally made beds. For the CTP (cucumber, tomato, pumpkin) rotation, however, yields of the hybrid mulch and traditional beds were similar $224,932 and $214,338 respectively.

Partial budgets were used to investigate the differences in performance of the two rotations. Tomatoes had the highest value of the three crops used in these experiments. In 2005, yields of tomatoes in hybrid mulch TCP beds were more than double traditional yields. Consequently the hybrid mulch TCP rotation gained a large advantage in terms of receipts and returns. While traditional beds yielded more than double what the hybrid mulch pumpkins did in both rotations in 2007, the differences did not greatly impact receipts because pumpkins had the lowest value of the three crops.

In the CTP rotation tomato and cucumber yields were similar between hybrid mulch and traditional beds, and therefore, the receipts were very similar. Notably, in the CTP rotation, tomatoes were again the source of increased receipts. This highlights the importance of whichever crop in the rotation has the highest value or sells for the highest price.

In both rotations, the costs of managing the hybrid mulch system were higher than the costs of managing the traditional system. Major cost increases were due to the differing costs of fertilizer types, mowing, increased time spent on weeding, planting, and harvesting cucumbers. The compost used in the hybrid mulch beds was nearly 5 times more expensive than the granular fertilizer used in the traditional beds. The hybrid mulch inter-beds needed to be mowed more often than the traditional inter-beds need to be rototilled increasing those costs. Over time the plastic in the hybrid mulch beds began to degrade allowing weeds to germinate in the beds, increasing the amount of hand weeding needed in the system. The time spent weeding the beds in preparation for spring planting in 2007 was particularly high. Likewise as the plastic degraded, the time needed to plant increased as workers need to assess when to reuse old holes and when to make new ones. Increased costs of harvesting hybrid mulch beds occurred in the cucumbers which were harvested three times a week until the plants stopped producing. In 2005 the hybrid mulch cucumbers in the CTP rotation reached maturity 12 days earlier and had a longer harvest period compared to traditionally grown cucumbers. Again in 2006, the hybrid mulch cucumbers in the TCP rotation reached maturity five days earlier than the traditional cucumbers and kept producing until the same end date.

Decreased costs with the hybrid mulch system resulted from 2nd and 3rd year elimination of spring tillage, and the need to remove and install new plastic and drip irrigation lines, but these decreases did not cancel out the cost increases. While the plastic mulch did perform well over the course of the experiment, it required more effort to remove after three and a half years in the field than plastic that had only been in the ground a year or less, and therefore the costs were adjusted to reflect the extra time spent on the task. Mechanical plastic mulch removal would be a good solution to this challenge.

The three year costs of managing the TCP and CTP rotations in the hybrid mulch system were respectively $12,455 and $14,184/ha ($5,044 and $5,745/acre) higher than the costs of managing those rotations in the traditional system, but increased receipts in the first two years offset those increased costs in the TCP rotation and partially offset the increased costs in the CTP rotation. The hybrid mulch TCP rotation showed a substantial increase in net returns over traditional of $115,101/ha ($46,616/acre) and the hybrid mulch CTP showed a slight decrease in net returns of $3,590 ($1,454/acre) over traditional.

The application of an herbicide in the third year or the elimination of the third year from the system are two possible avenues for increasing the profitability of the hybrid mulch system. Data on the effectiveness of herbicides was not collected, but the economic data was re-analyzed assuming that each rotation lasted only two years (“TC” and “CT”) and that cucumber harvests were stopped one week early in the CT rotation when the marketable yields dropped below cull yields. In this scenario, marketable yields in $/ha were again greater in the hybrid mulch TC rotation than the traditional TC rotation, and similar between systems in the CT rotation. Compared to their traditional counterparts, the net returns in the hybrid mulch TC rotation increased by $132,197/ha and $11,177/ha in the hybrid mulch CT rotation. Thus both hybrid mulch rotations remained economically competitive with their traditional counterparts for the first two years.

Farmer Adoption

We hear that more farmers “carrying over plastic” into a second year and we estimate about 15-20 growers using this practice. This is being done on a small scale and dependent on the condition of the plastic and spring weather conditions. The primary benefit growers’ mention is the ability to plant earlier in the spring. Fewer farmers are being proactive in establishing beds made specifically in the fall for early spring production often citing that there is too much other work in the fall or not field space available. There were more calls (5) in the fall of 2008 asking about establishment of fall made beds. This is perhaps and indication that more growers are now aware of the advantages of having some fall made beds.

Assessment of Project Approach and Areas of Further Study:

Areas needing additional study

We have identified several factors critical to the success of hybrid mulched beds that need further investigation: irrigation/ fertigation, ability to rapidly and easily mow the living mulch, selection of slow growing species for living mulch, and the possible use of herbicides

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.