Farmer/Scientist Partnership for Integrated Cropping Systems

Farmer/Scientist Partnership for Integrated Cropping Systems

Summary

The goal of this part of the project is to promote, in collaboration with farmers, adoption of more integrated vegetable cropping systems in Oregon’s Willamette Valley. The project is investigating integration of four practices at both on-farm and station sites: the use winter cover crops, reduced-tillage planting systems, pesticide refuges, and integrated pest management to conserve natural resources and reduce pesticide applications. A holistic study of soil biology (with particular emphasis on earthworms), beneficial insects, and soil quality is being conducted. From the first year’s results there is evidence that incorporation of the cover crop has the greatest effect in developing a more divers microbial and soil fauna community and improving soil quality. The latter being most evident in water infiltration tests. Extension activities using the soil quality kit have been done.

Objectives/Performance Targets

Objectives
1. To fully integrate farmer/scientist contributions to research, evaluation, and disseminate of findings related to the use of cover crops, reduced tillage, establishment of tillage and pesticide refuges and the use of more integrated pest management tactics on vegetable production farms.
2. To establish a network of on-farm research and demonstration sites where large-scale, long-term studies compare conventional and integrated vegetable production systems.
3. To track changes and validate the utility of soil and biological indicators of agroecosystem integrity we have identified in our past research efforts.
4. Disseminate findings to promote integrated vegetable systems to farmers and agricultural professionals.

Questions this research will address include:
1. Can the combination of cover crops, reduced tillage planting systems, tillage and pesticide refuges, and integrated pest management significantly reduce the cost of vegetable production and maintain competitive yields while protecting the environment?
2. How important are earthworms in promoting soil structure and soil drainage? Do tillage and pesticides affect the survival and functionality of earthworms? Should crop management promote earthworms and what are the benefits?
3. Can we combine conservation biology with IPM into a practical and effective pest control program at the farm scale?
4. What effect does strip-till/cover systems have on soil microbial and soil faunal communities in relation to soil physical properties?
5. How effective are soil and biological indicators for guiding sustainable crop management?

Accomplishments/Milestones

ON-FARM RESEARCH AND EXTENSION
The goal of this part of the project is to promote, in collaboration with farmers, adoption of more integrated vegetable cropping systems in Oregon’s Willamette Valley. We believe that a significant and realistic improvement in the current vegetable cropping systems would involve the integration of four practices: the use winter cover crops, reduced-tillage planting systems, tillage and pesticide refuges, and integrated pest management to conserve natural resources and reduce pesticide applications. The project is a collaboration between farmers and scientists, by on-farm research and demonstration.

Field Activities and Procedures
Farm scale research is being conducted on 5 family-owned vegetable farms that range in size from 400 to 2000 acres. Each cooperating farmer chose two fields that are similar or split one large field with a tillage or cover crop split a standard cropping system (no winter cover crop, aggressive tillage and prophylactic insecticide applications) and a farmer designed integrated system (winter cover crops or reduced till planting). The target crops are sweet corn, snap beans, and Cole crops grown for processing. Each farm serves as a block in a randomized complete block design. At each participating farm, two 150 X 50 ft. plots were measured to establish a cover-crop and fallow split-plot field design.
Selected tests from the soil quality test kit (USDA, ARS, NRCS, SQI kit, August 1999) were performed at the on-farm sites. These include aggregate stability, soil slaking, infiltration and soil respiration tests. The soil quality test kit and Soil Scorecard were also demonstrated in the field to growers involved in a short course at Chemeketa Community College. The kit and card proved to be an excellent teaching tool to create “learning moments” about soils and managing soil to improve soil quality.

Outcomes – Soil Quality
Results from the soil quality test kit’s soil respiration and infiltration tests did not indicate differences between treatments and showed high variability in the results. Aggregate stability and soil slaking preliminarily show a trend toward increased soil stability in reduced tillage systems, with soil slake test results pointing towards significant differences between tillage treatments (Fig. 1). This is encouraging as a potential monitoring tool for growers to assess the success of their management practices since the soil quality test kit is easily available for their use. These data also show potential for using these selected tests as a demonstrative tool during field days and for general presentation of the soil quality test kit.

Based on results from the soil quality test kit, soil respiration will not be included next season, as it has not proven to be a sensitive indicator of soil health between treatments. Infiltration measurements will be conducted using a larger infiltration ring to decrease the variability in the results; aggregate stability and soil slake tests will be repeated. In addition, earthworm middens will be counted on a monthly basis beginning in January and continued through crop establishment, and a Dickey-John soil penetrometer will be used to quantify soil compaction near the date of crop establishment.

Outcomes – Integrated Pest Management
Among the goals of our project are to enhance natural enemies of soil surface dwelling insect pests and to reduce soil applied insecticides that may contaminate surface and ground waters. Toward that end, we established pest monitoring stations on cooperating farms and established paired comparisons of sweet corn grown with and without insecticides applied at planting. The question of interest was, “are there times when pest pressure is low and insecticides are not needed?”

In the Oregon’s Willamette Valley, there are four soil borne insect pests that have a significant negative impact on sweet corn establishment: seed corn maggot, symphylans, black cutworm (Agrotis ipsilon) and 12 spot beetle larvae (Diabrotica undecimpunctata). Most sweet corn seed is treated with insecticide to control this seed pest. Symphylans are a chronic pest associated with certain soil types and crop rotations. Most growers are aware of which of their fields have a history of symphylan problems and treat these fields prior to or at planting.

During the 2002 growing season, black cutworm and 12 spot beetle monitoring stations were established on the five farms as well as the vegetable experiment station where the long-term tillage and cover crop comparison is in place (described below). Compared to the seven-year average, 2002 was a normal year in terms of black cutworm pressure (Fig. 2). Compared to the four year Willamette Valley average, the 12 spot beetle population was normal overall and below average during the sweet corn planting periods. In five trials on each of two farms (Table 1), there was no detectible damage to corn seed by seed corn maggot, or corn seedlings by cutworm or 12 spot beetle larvae. Corn seedling stand-counts were similar regardless of whether they were treated with insecticide or managed as conventional or reduced tillage planting systems. These results suggest that with careful field choice, avoiding fields with a history of symphylan problems, insecticide treated seed may be planted without soil applied insecticides if pest populations are low. The combination of reduced tillage and reduced insecticide costs may be of practical significance to growers.

INTEGRATED TILLAGE/COVER CROP SYSTEMS RESEARCH
The goal of this part of the project is to address component research questions raised by vegetable producers to compliment the on on-farm activities. This research is being done under the controlled environment of the research station towards the development of practical and credible integrated management systems to reduce external inputs and improve soil quality. Producers report that reduced till vegetables (strip till planting) have given mixed results in terms of yields. We hypothesize that for Western Oregon and its soils, strip till affects the soil biology and physical properties in some manner that ultimately is controlling crop productivity. In addition, we wanted to investigate whether earthworms could function as “soil engineers” in improving soil quality of strip till planted soils in systems that included winter cover crops.

Research Methods
The experiment is a statistically valid (4 reps) design with the following three treatments: (1) strip-till vegetable planting with winter cover crop; (2) conventionally tilled and planted vegetable with cover crop; and (3) conventionally tilled and planted vegetable with winter clean fallow. The cover cropped treatments were planted in the Fall of 2001 which were a combination of oats and vetch, which were planted in the autumn, then killed with systemic herbicide the following spring (2002). Cover crops were subsequently flailed and incorporated by disk in the conventionally tilled treatments, and remained as flailed surface residue in the strip-tilled treatments. Earthworm enclosures were constructed to provide a microplot of earthworm reduction and a corresponding enclosure of increased earthworm activity via inoculation. Reduction was achieved with an electroshocking device built to deliver 0.04V of electric current into the soil in order to bring any existing earthworms to the surface for collection. Inoculations consisted of hand spreading 30 individuals of the geophagous earthworm, Aporrectodea trapezoids, and 29 individuals of the endogeic species, Lumbricus terrestris onto the surface of each enclosure.

Baseline soil samples were collected prior to treatment implementation, followed by a second soil sampling just prior to cover crop burn (winter 2002), and a third soil sampling approximately 30 days after the crop of broccoli was transplanted (summer 2002). Soil cores were collected to a depth of 10 cm, with a separation of 0-5 and 5-10 cm cores in the strip-tilled plots. Approximately 15 cores were sampled (both interrow and intrarow) and pooled in three different locations within each plot as well as in each earthworm enclosure. All soil collected was passed through a 2mm sieve and a portion was retained at field moist conditions to measure microbial biomass. The remaining sieved soil was air-dried and stored at 4oC. Baseline measurements of total C and N, texture, and pH were done prior to initiation of the study.

Microbial biomass carbon (incubation fumigation) was measured on all field moist soil samples immediately following sample collection. Enzyme assays were determined on air-dried samples and reflect the ability of the soil to perform functions related to decomposition and nutrient mineralization, and to reflect changes in the microbial community. Physical properties were measured to provide information about aggregation/pore space which are important for root health and growth and as habitat for microbial and soil faunal community members. To study the microbial diversity we used fatty acid methyl ester profile technique (FAME). Fatty acids are used as biomarkers to identify certain species or functional groups in soils. Fatty acid extraction was done by direct saponification under mild temperature and alkalinity conditions (as described by Schutter and Dick, 2000) and then submitted to gas chromatography (GC) analysis. Fatty acids were identified by comparing the retention times of peaks in samples and those in standard mixtures.

Outcomes – Soil Physical Properties
Aggregate size distribution measurements were performed on all baseline and summer 2002 samples. An analysis of water stable aggregates was performed on all soil samples. Although significance has not yet been shown between treatments, a trend in the percent of water stable aggregates indicates that both cover-cropping and reduced tillage support greater aggregate stability. Figure 3 shows infiltration data, which is an integrative physical measure of soils. Higher rates of infiltration indicates the soil is better aggregated and has greater porosity that should reduce water runoff, increase water holding capacity and be higher quality soil. Interestingly, these results, taken during the prime growth period of the vegetable crop in late June suggest, that incorporation of the cover crop is more important than reducing the disturbance from tillage in increasing water infiltration. However, it should be remembered that this was only the first year of the study – longer periods of strip till might change these results. But on the other hand it is not possible for vegetable growers to do long-term strip till because most growers have required rotation crops that do not lend themselves to strip tilling and must have tilled seed beds. These results may provide preliminary evidence for why strip till has had mixed results in terms of crop productivity in farmers’ fields.

Outcomes – Microbial Activity and Community Structure
A trend in the microbial biomass data indicates an increase in microbial biomass with cover-cropping and strip tillage. b-glucosidase and arylsulfatase enzyme levels (Fig. 4) showed significant differences between the conventionally tilled soils with and without cover crops. This supports the idea that soil enzyme levels can be used as an early indicator of soil treatment effects and to potentially gauge soil health.

The soil microbial community profiles were determined using FAME analysis. The first sampling was done 187 days after cover crop establishment (just before cover crop plow down in spring 2002) and was about 30 days after vegetable planting (4th week of June).

For the first sampling prior to cover crop plow down, there was no significant differences in community structure between cover cropped and winter fallow soils (data not shown). At the second sampling date plots under the cover crop treatments tended to group together, regardless of the tillage treatment (Fig. 5). Fallow plots are concentrated at the bottom of the axis 2, while cover cropped plots are placed in the top of this same axis. These results indicate that it is the incorporation of the cover crop residue that is important in causing a shift in community structure – not the presence of the cover crop in the winter, at least on the bulk soil we sampled. The plot also shows that there is some separation of communities between conventional tilled and strip tilled soils.

Table 2 depicts the Pearson correlation (r) between FAMES and axis 2 (only FAMEs with r>0.500 were listed). An important finding is that FAME 16:1ù5c, an indicator of arbuscular mycorrhizal fungi, and other predominantly eukaryotic FAMEs (fungal markers) had a positive correlation with axis 2, indicating these groups dominated in cover cropped soils over winter fallow soils.

These results are preliminary and detailed analyses on microbial communities are in progress and these investigations will be repeated in 2003.

Outcomes – Soil Fauna
Soil-dwelling arthropods were sampled twice during the 2002 field season, once just before planting (June 20) and once the day before harvesting. At both times of year the principal arthropod taxa both by count and biomass were 4 species of fungivorous springtails (Isotoma 2 spp., Entomobrya, Onychiurus), one pestiferous fungivorous/omnivorous mite (Tyrophagus), two root-feeding beetles (Diabrotica, Phyllotreta), one introduced predaceous centipede (Lithobius), several species of immature predaceous ground-beetles and rove-beetles, and two common species of predaceous gamasid mites. A total of approximately 10,000 specimens were collected at each sampling time.

The sample at planting showed a treatment effect trend of depressed total population density in the fallow (cover/conventionally till=1556/m2; cover/strip till=878/m2; conventionally till/winter fallow =164/m2 – not significant P<0.05). The lack of significance may be due to the heavy cover-crop kill by symphylans in one rep of cover crop plots. Densities of approximately 1000 arthropods/m2 are typical of June planting dates in this locality. A total of 43 species were collected; the means of the different treatments were not different (FF=8/650 cm2; CC=9/650 cm2; CS=12/650 cm2). In neither respect were the samples significantly different in the simple fallow/cover-crop comparison. Samples taken at harvest revealed higher diversity of fauna and less difference between treatments. Species richness at harvest time was 12-13 species/650 cm2 in all three treatments. In addition to the total density of arthropods and their species richness, we examined the functional guilds, which comprise the community. In particular, we have found that the ratio of predaceous (potential biocontrol) species to total species is a useful metric to compare different management techniques in agricultural systems. We found no differences in the ratio of predators to treatment at either time of year. The worm studies were unsuccessful. There was an unexplained high level of mortality. The worms we used for inoculation were locally field-collected (presumably adapted), but were nearly all immature. Perhaps a combination of immaturity, transplant shock, thiocyanate and organophosphate application (unlikely) was responsible. As a result we measured no treatment effects in soil physical properties, soil biology or soil fauna. We will be repeating this experiment next year but will move the micro worm enclosures outside the large experimental plots (but with identical tillage/cover crop/fallow treatments) and will use commercially reared adults for the inoculation treatments and eliminate most pesticide inputs.

Impacts and Contributions/Outcomes

Since this is the first season of results we can only speculate what the potential impacts will be. We continue to learn new ways to conduct meaningful on-farm research. The project should refine and improve methods for doing on-farm research and our interactions with growers is having impacts on other farmers in the areas where we are doing collaborative on-farm research. Preliminary results would suggest we might be able to make recommendations on the limitations strip till may impose on crop productivity. Fundamental information on soil biology and beneficial insects will provide important information on the development of more sustainable vegetable systems.

Since this is the first season of results we can only speculate what the potential impacts will be. We continue to learn new ways to conduct meaningful on-farm research. The project should refine and improve methods for doing on-farm research and our interactions with growers is having impacts on other farmers in the areas where we are doing collaborative on-farm research. Preliminary results would suggest we might be able to make recommendations on the limitations that strip till may impose on crop productivity. Fundamental information on soil biology and beneficial insects will provide important information to guide development of more sustainable vegetable systems.

Collaborators: