A two-year experiment was designed to determine a)the efficacy of no-till vegetable production utilizing high-biomass cover crops for Virginia vegetable production operations; and b)the effects of a farmscape on managing insect pest pressure. In the first year of this study adoption of the novel production system did not have a significant affect on crop yield. In the second year, significant weed pressure in the brassica crop resulted in lower yields. More desirable results could have been obtained in this study with more careful management of the cover crop and the farmscape system.
A wholesale market, the Shenandoah Valley Produce Auction, began in 2005 and as a result the Valley, especially Rockingham and Augusta Counties, have seen significant increases in the number of vegetable and produce operations. However, current production practices often fail to provide for beneficial insect habitat, degrade soil organic matter and soil quality, encourage soil erosion and nutrient runoff, and may not be sustainable in the long run.
The majority of commercial vegetable production operations in the valley do not incorporate or provide any form of beneficial insect habitat. Most operations rely heavily on commercial pesticides, and do not utilize cover crops or refuge areas. Almost all of the produce operations in the valley rely heavily on tillage, do not leave any surface residue, and do not utilize cover crops. As a result, soil quality, particularly soil structure, aggregate stability, soil organic matter, and inherent soil nutrient cycling capabilities decline rapidly. Furthermore, the majority of our valley farms are on moderate to severely sloping land, and the heavy reliance on tillage encourages both soil sediment loss and nutrient runoff. Many of our streams are currently listed as impaired waters, and thus runoff and sediment loss must be minimized.
Currently, the majority of commercial vegetable production in the valley takes place on plastic mulch, and relies heavily on tillage and commercial pesticides and fertilizer inputs. Adoption of a reduced tillage vegetable production system that relies heavily on cover crops and insect refuges could both significantly decrease input costs and increase sustainability of these operations.
In order to determine the effectiveness of a no-till, low input vegetable production system, I will compare these production practices to a conventional plasticulture production system side by side on my farm. Working with local Virginia Cooperative Extension agents, I will measure the differences in these production systems in terms of soil, crop and pest management outcomes. I will also develop detailed economic analyses between the two systems in order to validate economic savings.
Brian Jones and Maria Ignosh from Virginia Cooperative Extension will assist in developing the outreach and dissemination for this project. A field day will be held at my farm in the summer of 2008 to present the results of the project and demonstrate the methods and techniques involved in a low input no-till vegetable production system. This project will also be highlighted in a field day to occur in the summer of 2007 on my farm for another unrelated project.
In order to meet the goals of this project, I will establish a field scale replicated split-strip trial on my operation. A vegetable rotation consisting of sweet corn and broccoli will be established, with each component of the rotation beginning each of the two years of the study, in order to have both spatial and temporal replication. Main effect treatments will be either conventional vegetable production under plastic mulch, or a low input, no-till vegetable production system that utilizes high biomass cover crops. Within the low input system, cover crops will be established and managed in a “never fallow” system, where the soil surface is never left bare. Sub-treatments will be two levels, a high and low, of fertilizer applied through a drip irrigation system. This will allow us to determine if the low input system is providing adequate fertility needs from the inherent soil nutrient cycling process.
Overall goals of this project are to examine the effects of increasing beneficial insect habitat, building soil quality, and decreasing input costs for a two year vegetable crop rotation on my operation. The specific objectives of this project are to:
1. increase beneficial insect habitat by utilizing farmscaping, establishing refuge areas, using cover crops and reducing pesticide applications for a two year vegetable rotation;
2. increase soil quality and soil organic matter by utilizing high biomass cover crops, eliminating tillage, and minimizing pesticide applications;
3. decrease input costs by promoting pest predators, minimizing weed infestations, and reducing fertilizer costs by enhancing soil nutrient cycling dynamics;
4. quantify economic differences between cropping systems
The majority of commercial vegetable production in the Shenandoah Valley region of Virginia takes place on plastic mulch and relies heavily on tillage and commercial pesticide and fertilizer inputs. Recent research from Virginia Tech and other universities indicate that adoption of a reduced tillage vegetable production system that relies on cover crops and insect refuges instead of tillage and pesticides may be effective at maintaining or increasing yields, reducing input costs and building soil quality.
The overall goal of this project was to compare side-by-side conventional production practices involving tillage and plasti-culture to no-till vegetable production practices relying heavily on cover crops and beneficial insect habitat. Specific objectives were to: a)increase beneficial insect habitat by utilizing farmscaping, cover crops and reducing pesticide applications for a two-year vegetable rotation; b)increase soil quality and soil organic matter by utilizing high-biomass cover crops and eliminating tillage; and c)decrease input costs by promoting pest predators, minimizing weed infestations and reducing fertilizer costs.
Replicated strip trials were established in the spring of 2007 and 2008 on a Frederick/Lodi silt loam soil in Rockingham County Virginia. Plots were arranged in a split-strip plot design with two treatments and three replications. Each strip was 16’ wide x 100’ long. Treatments were designated as either “Conventional” or “Novel”. Conventional treatments consisted of typical production practices, including tillage and plasti-culture. Novel treatments utilized high-biomass cover crops and no tillage. A brassica-sweet corn crop rotation was selected for this study, both for the ease of establishment and maintenance and the fact that this is a very common vegetable rotation in the area. In order to better understand the temporal as well as spatial dynamics of the main effects, the split-strips were designed so that each component of the cropping system was present in each year of the study (Figure 1).
Cabbage (variety Ramada) was planted on 24 April 2007. In the conventional treatments land was prepared by chisel plowing and discing followed by one pass with a field harrow. In this treatment plastic mulch and drip-tape irrigation were installed by a local producer, and plants were set with a mechanical transplanter. In the novel treatments, the strips were sprayed with a burndown herbicide (glyphosate), drip-tape irrigation was installed and plants were transplanted with a modified no-till transplanter (Figure 2). Due to a mistake in ordering the transplants, in 2008 broccoli (variety Captain) was planted on 26 April in 2008 instead of cabbage. All other land preparations were the same between years. Sweet corn (variety BC 0805) was planted on 30 May and 16 June in 2007 and 2008 respectively. Conventional treatments were plowed as described above, but plasti-culture was not utilized as this is not typical of sweet corn production. In the novel sweet corn treatments, the strips were prepared as described above with application of a burndown herbicide. In both treatments, a residual corn herbicide (atrazine) was also applied for longer season broadleaf weed control. Corn was planted in both years with a modified two-row corn planter. In the fall of 2007, crimson clover was planted as a cover crop at a rate of 20 lb acre-1 in both crop rotations of the “novel” treatments. The cover crop was killed with a burndown herbicide approximately two weeks prior to planting in 2008.
The farmscape component of this project was established in May of 2007 in two 100’ long strips that bordered the long edges of the project site. The strips were roto-tilled, fertilized, and the seed mix was broadcast and packed. The farmscape consisted of a diverse mix of flowers, herbs and crop species including white dill, boneset, sensation, proa yarrow, bronze fennel, anise hyssop, calendula, cilantro, California bluebell, andover, dwarf sunflower and buckwheat. This mix was selected with the intent to offer beneficial insect habitat throughout the growing season.
Fertilizer was applied to both crop rotations according to the 2007 Commercial Vegetable Production Recommendations guide. Fertilization was applied through the drip tape irrigation system for both corn and brassica crops as needed. Pre-season soil tests and in-season plant tissue tests were taken from each treatment to determine fertilizer needs. Herbicides and insecticides were applied on an as-needed basis. Weekly scouting was performed to ascertain the need for pesticide applications.
At maturity, the brassicas and sweet corn were hand harvested. Yield was determined by weighing each treatment strip individually. Anecdotal notations of quality were also made at the time of harvest. Differences in yield between treatments were determined by the ANOVA procedure in CropStat, an agricultural statistical software analysis tool.
Neither cabbage nor sweet corn yields were significantly affected by production practice treatments in 2007 (Table 1). However, in 2008 broccoli yielded approximately twice as much in the conventional production system as in the novel production system. Unfortunately in 2008 severe herbivore damage to our sweet corn plots resulted in no yield being measured in these treatments.
Due to constraints in the grant start dates, cover crops were not able to be established prior to the start of this project. Therefore, both the conventional and novel production practices were planted into essentially bare ground. Because of the lack of cover crop biomass, weed pressure in the novel cabbage and sweet corn treatments in 2007 was significantly greater than the conventional treatments. The plastic mulch in the conventional treatments provided excellent season long weed control. Because of the nature of our study, we were attempting to delay herbicide application for as long as possible, and in 2007 we may have waited too long. In 2008 we had a tremendous stand of crimson clover cover crop that we killed and planted into. Data from Virginia Tech has indicated that weed biomass can assist in holding back weeds and in many cases may eliminate the need for herbicide. Unfortunately we did not find this to be the case with our cover crop program of crimson clover. While providing a significant source of nitrogen for our crops, the weed control characteristics were not as desirable as we hoped for. It is likely that most of the yield loss in the broccoli in 2008 can be attributed to competition from weeds.
In this study the farmscape had little impact on controlling insect pests in the vegetable crops. Scouting revealed economic threshold levels of cabbage looper, harlequin bugs and imported cabbageworm in both 2007 and 2008. This was understandable in 2007 particularly early in the season because the farmscape was not yet fully developed into a beneficial insect habitat. However in 2008 the farmscape was well established and significant numbers of pest insects were still observed. After discussing these results with Virginia Tech entomologists, it would appear that there may have been too large a distance between the host vegetable crops and the farmscape. However, even in those crops that bordered directly on the farmscape significant numbers of pests were observed. Rather than lose the crop, it was deemed necessary to treat the brassicas with insecticide.
While results from weed control with use of the cover crops were somewhat less than desirable, the crimson clover did supply a significant source of nitrogen to both the sweet corn and broccoli in 2008. Plant tissue testing indicated that less nitrogen fertilizer was required during the season, particularly in the sweet corn, and thus significant cost savings were realized. Some issues were encountered in getting a desirable stand of sweet corn in the crimson clover residue, but since we weren’t able to measure final yield it is unknown how much of an impact this made. Planter modifications will need to be made to plant through this level of residue in the future.
We will definitely be utilizing the methods in the novel cropping system on our farm in the future. We believe that even with slightly lower yields, this system is more economical, requires less input and equipment costs, and will in the long-term build and sustain soil quality.
Educational & Outreach Activities
A field day was held at my farm in April of 2008. Over 100 participants toured these and other experiments taking place on my farm. Results of this trial have been presented at several extension meetings around the area. Furthermore, this report will be published to a local extension web site.