Integrating Compost Into an Intensive Plasticulture Production System for Vegetables
During the summer of 2004, the Cornell University Cooperative Extension staff in Washington County worked in partnership with three Washington County businessmen, Jim Stannard, a vegetable farmer, and two commercial compost makers, Bob Wilmot and Kevin Booth. The project received funding from the Northeast Region SARE (Sustainable Agriculture Research and Education Program) Partnership grant program. The project looked into the possibility of integrating compost into an intensive plasticulture production system for vegetables.
The objectives of the project were two fold. First, we wanted to address some problems inherent to large scale plasticulture vegetable production. Nearly two dozen vegetable farmers grow high value, direct market crops on over 700 Washington County acres. Some of this ground tends to be gravelly loam that is fertile, but low in organic matter. Studies have shown the benefit of incorporating compost into vegetable soil, but for those growers using plastic mulch and trickle irrigation, this can be difficult to do. Plastic mulch systems, while offering significant benefits like soil moisture retention, weed control within the row, and soil warming, are still challenged by weed pressure between the rows if herbicides are not used. When pre-emergent herbicides are used, the use of cover crops can be limited. The question posed was: Can compost applied as mulch between rows of plastic adequately suppress weed growth without the use of herbicides and what would the effect on crop production be?
Our second question involved the performance of two different composts. For the trial we examined paper -based and manure-based compost. Cow manure based composts have been well accepted by local vegetable farmers who use the material in seed starting mixes, as well as a way to increase soil organic matter and fertility primarily in non-plasticulture systems. The analysis of the manure based compost showed 15.2% OM and .56% total nitrogen. These values are somewhat lower than normally expected from a manure based compost, but are probably due to high mineral content of starting materials, which are sawdust from cow stalls, manure, sand. This compost was ~4 months old. The physical properties of the material made it very easy to work with and it was well screened.
Paper based composts are more recently available to food producers as NYS DEC works to approve these materials. Most growers assume that the advantage to using a manure based compost is increased nitrogen, but the total nitrogen available was .95% and organic matter was 33.9%, higher than the manure based compost. This compost was ~ 7 months old and the starting materials were paper sludge and yard waste. The paper-based compost had not been screened so was difficult to use. It has excellent water retention properties and was quite moist when applied which also made hand application more challenging.
Jim Stannard fit the field as he normally does for cantaloupes, which were chosen as our study crop due to their high value and tight harvest window. The intensive plasticulture system is defined as slightly raised beds, fertilizer, machine laid plastic and trickle irrigation with a soluble 20-20-20 delivered throughout the season. Seedlings were transplanted through the plastic on June 9th. Four treatments were tested. Treatment one was a control of no herbicide and no compost between the plastic beds. Treatment two had post-emergent herbicide applied and no compost. Treatment three had no herbicide and a three-inch layer of manure-based-compost between plastic beds. Treatment four received no herbicide and a three-inch layer of paper fiber-based compost between plastic beds. There were three replicates of all treatments. Plots were 20 feet long with 5 feet of an unplanted buffer between plots. Cantaloupes were planted in the middle row of the three rows.
In addition to cantaloupe yield and quality, measurements were taken on the types and quantity of weeds. Crop vigor was observed. Tissue samples were taken from each plot to monitor the nutrient status of the crop in each treatment. Soil moisture levels were visually monitored. The trial was evaluated three times a week during harvest and pest problems were recorded.
An extremely wet summer encouraged disease and weed pressure. By July 6th, both the control and the post-emergent herbicide treatments had over 75% of the between row test area covered with weeds while only one of the compost replications reached that level of weed pressure a month later. On August 5th, all of the control reps were at 100% weed pressure and the weeds were very mature. None of the treatments received any hand weeding and the herbicide treatment had an application failure. By August 13th, the compost treatments had reached at least 80% weed infestation and at that point most of the weed seeds had germinated. It seemed that weed species were consistent throughout the trial – most of the weeds had germinated below the mulch.
The heavy weed population and high moisture resulted in a major disease problem. Alternaria spp. were isolated, but the most profound vine loss was caused by powdery mildew. Despite alternate sprays with Quadris and Bravo and occasional sprays of Oxidate, by August 5th all of the Control and Herbicide reps had experienced 100% infection, while the compost treatments were between 5 and 35% infection and no vine death. On August 23rd, over 95% of the vines had died on all of the control plots (including the ineffective herbicide reps). 40% of the vines had died on the manure based compost and just over 60% of the vines were dead on the paper based compost. 93% of the compost treatment vines were infected.
Yield on all plots was discouraged by disease pressure. The season yield totals are listed in Table 1.
Table 1. Seasonal yield data totals
Treatment # Fruit Total Wt. Avg. Wt.
Control 36 103.75 2.88
Herbicide 29 83.25 2.87
Manure Compost 50 216.25 4.33
Paper Compost 39 174 4.46
The control and herbicide plots set fruit and ripened earlier than both compost trials by 5-7 days. The average individual fruit weight was significantly greater for melons grown with paper compost between the alleys with manure based compost yield close behind. The greatest overall yield came from the manure based compost treatment.
Leaf analysis results show some difference in the plants grown with compost between rows. Paper based compost may have resulted in higher levels of Molybdenum, Boron and Magnesium with lower Manganese levels; Manure based compost showed slightly higher levels of Sodium, Boron and Magnesium. Leaf edges on both compost treatments were chlorotic in mid-August.
In early-August we held a twilight meeting that looked at the progress of the trial. At that point the harvest had just barely begun, but growers were able to look at weed pressure and very obvious disease control in the compost plots. More outreach will be underway this winter at the Empire Expo, a vegetable growers meeting held in Syracuse in February.
Impacts and Contributions/Outcomes
Using compost in a plasticulture vegetable production system may result in slightly delayed yield, but weed control is enhanced. Overall yield was respectable, but comparison is difficult due to vine death from disease. The fact that the compost treatments did not succumb to the same disease pressure is noteworthy. Perhaps early season weed control helped maintain good air movement in the compost treatments and reduced infection caused by soil splashing.