Farmer/Scientist Partnership for Integrated Cropping Systems

Farmer/Scientist Partnership for Integrated Cropping Systems

Summary

The goal is to develop and promote an integrated vegetable system for Oregon’s Willamette Valley. Studies at on-farm and station sites are focused on integrating cover crops, strip-till planting, predator refuges, and IPM to improve soil quality and reduce pesticides; and whether earthworms are critical for the success of an integrated system. Cover cropping and strip-till has caused a rapid response in the soil biology (microorganisms, some soil arthropods and earthworms) but soil physical properties are not improving with less disturbance of strip-till planting after 2 years, which may be affecting crop productivity.

Objectives/Performance Targets

The goal 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 of 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 preliminary results there is evidence that incorporation of the cover crop has the greatest effect in developing a more diverse 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
1. To fully integrate farmer/scientist contributions to research, evaluation, and dissemination 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 do 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?

ON-FARM RESEARCH AND EXTENSION
The goal 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 of 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

ON-FARM RESEARCH

Soil Quality Measurements: The soil quality test kit (USDA, ARS, NRCS, SQI kit) was used to continue soil quality monitoring at all on-farm research sites. Based on results from last year’s work, analyses included falling-head infiltration with a 12-inch infiltration ring, soil slaking, water stable aggregation, and earthworm midden abundance. Sample processing and data analysis for this year’s soil slaking and water stable aggregation is currently underway. Results from the infiltration test indicate an increase in infiltration with cover cropping. This trend is seen in all but one of the farm sites.

This year we are testing whether midden counts can be useful indexes of earthworm abundance. From our on-farm and station research we found that midden counts were significantly higher with cover cropping (Fig. 1). Data analysis is in progress to establish whether midden counts are closely correlated with hand sorting and field counts of earthworms.

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 soilborne 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.

The focus of this years study was 12 spot beetle, the primary insect pest of green beans in Oregon’s Willamette Valley. The 12 spot beetle (Diabrotica undecimpunctata) feeds on the developing bean pods causing distortion and scaring of the harvested product. Processors tolerate approximately two percent (2%) damage before rejecting a load. Yellow sticky traps were established and maintained at six cooperating farms plus the OSU Vegetable Experiment Station in Corvallis, Oregon. At harvest, beans were rated for beetle damage.

Beetle pressure varies from time to time during the growing season and from year to year. Beetle pressure was significantly higher than average during the 2003 growing season. As expected, there are three activity periods reflected in the regional and local trap counts. Early beetle activity is mostly female beetles emerging from over winter refuge and laying eggs in emerging corn and other host plants. This was followed by a period of low densities above ground during the month of June. During this period, the population is mostly below ground. The sharp rise in beetle counts in July corresponds to the emergence of the first summer generation. The above ground activity in September corresponds to the emergence of the second annual generation. It is this second generation that over winters and becomes active again the following spring.

Beans in the Corvallis trial began to bloom and form pin-size pods in mid July. This corresponded to the peak in above ground beetle activity. Past experience suggests that when beetle counts approach two per trap per day, significant pod damage can be expected. This trial was unsprayed with insecticide that would normally be applied during the blossom period. Damage to pods at harvest ranged from about six to twelve percent of the pods (Fig. 2). The damage was significantly (P value = 0.05) less in the winter fallow conventional tillage treatment, however, the level of damage in the best treatment was above what the processors would accept. Less crop residue and fewer weeds in the conventional tillage system is correlated with the presence of fewer beetles in this treatment. Further experimentation would be required to prove that this relationship is the cause of fewer beetles in the conventional treatment. It is possible that an earlier bean planting date in a lower pressure year would produce less beetle damage by avoiding the high pressure period during July. Planting dates, however, are governed by processor planting schedules and weather during the wet spring.

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 complement the on-farm activities. This research is being done under the controlled environment of the research station toward 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 planted in the fall of 2001 were a combination of oats and vetch, 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 seasonal soil samplings in 2002 (see 2002 annual report for details), and a third soil sampling in 2003 in the spring (prior to cover crop incorporation), approximately 30 days after the snap beans were planted and at bean harvest. 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.

Earthworm Enclosures: To enable closely controlled studies of earthworms, mini-plot enclosure were established and this year new design was put in place. For the plots excluding earthworms, reduction was again achieved by electroshocking, and inoculated plots were augmented with earthworms in early summer. Reduction and inoculation of earthworms will continue throughout the year to insure decreased and increased earthworm populations, respectively. Because enclosures were re-established this year, results from soil sampling are inconclusive. Next field season should provide interesting data, as the enclosures and earthworm populations will have been established for a year.

Cropping Systems Treatment Results: Soil samples were collected just prior to cover-crop incorporation and again 30-days post-planting of bush beans. Analyses performed included microbial biomass (carbon), enzyme activity, earthworm midden abundance, earthworm extractions, water stable aggregation, bulk density, and falling-head infiltration. Aggregate size distribution analysis is currently underway. B-glucosidase enzyme activity continues to be a sensitive indicator of soil quality as it is able to detect differences in treatments in a relatively short amount of time (Fig. 3). Additionally, earthworm midden abundance and earthworm extractions both showed differences in treatments (Fig. 4). Bulk density was significantly higher in the no-till systems.

The soil microbial community profiles were determined using FAME analysis. Although data analysis is still in progress, preliminary results indicate that the first sampling just before cover crop plow down in spring 2003 had no significant differences in community structure between cover-cropped and winter fallow soils. At the second sampling date after cover crop incorporation and crop establishment there was a shift in community structure due to cover cropping. 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.

Results from 2003 confirm, once again, that soil arthropod species richness in these annually cultivated fields is extremely low year-round. In general, less than 2 dozen species are encountered with predictable frequency (under the best of possible management scenarios). Species richness is lower at harvest time than during spring planting. Overall arthropod density in these farm soils is very low year round, as compared with any native ecosystem. Density is higher at planting than at harvest (densities range from 500 to 20,000 /m2 at planting, 1,500-2500 / m2 at harvest).

At planting, tillage reduces total arthropod density, all functional groups of arthropods, and nearly all individual taxa. Tillage following fallow reduces total arthropod density even further (Isotoma springtails and endeostigmatid mites are especially reduced). By harvest time all conventionally tilled plots have lower arthropod densities than strip-tilled plots; this holds true for most species, but not Diabrotica cucumber-beetles, Onychiurus springtails and Micryphantid spiders. Some species still show further reduced densities as a legacy of the fallow treatment in addition (particularly gamasid predaceous mites, Folsomia and Entomobrya springtails, total predaceous mites, and total springtails).

The former results are based on the OSU Vegetable Experiment Station trial; the on-farm results are less conclusive. At planting, the 3 farms sampled were characterized by extremely low densities of arthropods; densities were so low that meaningful comparisons of densities between treatments are not feasible. At harvest time, the Kenagy farm samples were very definitive. Nearly all individual species and all component functional groups were greater in soils that had been cover-cropped previously (only Onychiurus springtails, Diabrotica beetles, Aphodius dung-beetles, and earthworms were more abundant in the fallow treatment). Results at the Sweeney and Hendricks farms were not clearly defined. However, at the Hendricks farm predaceous arthropods and detritivorous millipedes were clearly denser in the previously cover-cropped treatment.

Accomplishments/Milestones

The goal 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 of 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. Extension activities using the soil quality kit have been done.

Objectives
1. To fully integrate farmer/scientist contributions to research, evaluation, and dissemination 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 do 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?

Impacts and Contributions/Outcomes

Because this is the second season of results and we have not fully analyzed all the data 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 are 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. We have evidence that cover cropping and strip tillage causes a rapid response in the soil biology (microorganisms, some soil arthropods, and earthworms) but soil physical properties are not improving with less disturbance of strip tillage planting of summer vegetable crops. It will be important to continue this experiment for some years to determine whether soil structure properties will ultimately improve with strip till management.

Collaborators: