Farmer/Scientist Partnership for Integrated Cropping Systems

Farmer/Scientist Partnership for Integrated Cropping Systems

Summary

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 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. The results are showing evidence that incorporation of the cover crop and less disturbance with strip tillage is causing a more diverse microbial and soil fauna community and improving soil quality. This is being done on-farm and at the research station. 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 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 effects 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?

Accomplishments/Milestones

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 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) was used to continue soil quality monitoring at all on-farm research sites. Analyses included falling-head infiltration with a 12-inch infiltration ring, soil slaking, and aggregate stability. Sample processing and data analysis for this year’s soil slaking is currently underway. Results from the infiltration test indicate a significant increase in infiltration rate with cover cropping (Figure 1). However, farms with adequate site comparisons have diminished to two during the final year of sampling due to problems with follow-through on tillage commitments. Soil slake ratings from 2003 indicate a decrease in soil slaking with the addition of cover crop (Figure 2). Although less pronounced, a similar trend was found in the 2003 aggregate stability data, with the addition of cover crop yielding an increase in water-stable aggregates (Figure 3). Given this trend, I would not recommend continuing with the water-stable aggregate test as described in the soil quality test kit (SQTK) because of difficulty in repeatability.

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, 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 seasonal soil samplings in 2002, 2003 (see 2002 and 2003 annual report for details), and a fourth soil sampling in 2004 in the spring (prior to cover crop incorporation), approximately 30 days after the sweet corn was planted and at 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.

Results
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: Earthworm reduction was conducted by electroshocking, and inoculation with Lumbricus terrestris occurred in spring and again in early summer. Challenges continued with the enclosure design, including thick cover crop establishment that resulted in over-ground paths for earthworm migration. Additionally, it was not possible to electroshock during winter and spring months as planned, due to the thick cover crop concealing earthworms as they rise to the surface. Soil samples were collected in spring and summer and are currently being analyzed.

Cropping Systems Treatment Results: Soil samples were collected just prior to cover-crop incorporation and again 30 days post-planting of corn. Analyses performed included microbial biomass (carbon), enzyme activity, earthworm midden abundance, water-stable aggregation, bulk density, soil fauna counts, and falling-head infiltration.
For 2004 there were 4 samplings to determine soil faunal dynamics. In the spring, at plowdown, prior to planting, there was again a very significant decrease of total arthropods (especially springtails and macropredators) in the fallow treatment (90% decrease). By planting time, total densities remained rather similar (~10,000/m2), but for most functional groups of arthropods a significant difference between the strip-tilled (higher densities) and conventionally tilled treatments was apparent; the strength of this tillage difference was now stronger than the fallow difference. Several weeks later at canopy closure, total densities had dropped about 33% in all treatments and the only treatment difference that was significant was a higher density in the strip-tilled plots (true for total arthropods as well as nearly all component groups). Finally, at harvest-time total density of arthropods had decreased about another 75% and any previous treatment differences were obscured (density ~650/m2).
At the microbial level 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. Also there was a constant increase in enzyme activity in strip-tilled plots. This suggests that a combination of a reduction in soil disturbance and additional soil carbon from cover crops leads to continual increases in soil biological activity. Reflecting a similar trend, the microbial biomass data showed a rapid increase in soil biology in the strip-tilled plots, which remained significantly greater than both conventionally tilled plots. Additionally, earthworm midden abundance seems to correlate with treatment, and this was especially evident during the 2004 sampling.
Constant-head infiltration shows the same trend in 2003 as 2004, with the conventionally tilled winter fallow plots yielding the slowest infiltration rate (Figure 7). The infiltration data from the OSU Vegetable Research plots and the on-farm sites showed that that cover cropping affected the rate of water infiltration more than tillage. Infiltration rates were very low between rows in the strip-tilled plots, which suggest that this soil is compacted.

Impacts and Contributions/Outcomes

We continued to interact with our cooperating farmers with our on-farm research. We are getting valuable insights into their perceptions of managing soils to improve soil quality. We are finding that their approach will continue to be more qualitative than quantitative. We have used the portable soil quality kit on their farms and we find it can be useful in detecting change. However, we do not believe it is realistic to expect farmers to use this kit on a regular basis. Informal discussions suggest they would use this kit for diagnostic situations and likely would be willing to pay for this service. At the same time they have interest in being able to verify that their soils have been managed for environmental quality and sustainability. Again there may be incentives to pay for services to assess soil quality if it can be linked to a marketing advantage for the produce.

June 24, 2004, we held a field day that was attended by farmers and university personel. This was done at the OSU Vegegable Research Farm where we toured the SARE research plots. At the same time we had a series of simple posters that provided the results we have found for both on-farm and station research. We also, demonstrated the soil quality kit. Approximately 35 people attended the meeting.

This year provided the third set of research data. Our results are following previous years’ data. Soil biology improves first as one converts to integrated systems that have more C inputs. The lower disturbance of strip till combined with winter cover crops continues to stimulate soil microorganisms, some soil arthropods, and earthworms. However, soil physical properties are lagging in strip-tillage planting of summer vegetable crops. There is a higher level of compaction between the rows with strip till than with conventional till. We believe that in part this is due to the silty nature of the soils in western Oregon that over the winter rainy season disperse in soils and fill pores. We are encouraged by evidence that there is greater earthworm activity with less disturbance and cover cropping, but this apparently is not enough (after 3 years) to offset compaction under the type of strip-till system we are using. We have not fully analyzed the yield data from last year but believe there was a slight decrease in yield with strip till. Some growers have adopted a strip-till system that is deeper, and this may overcome this problem. Nonetheless our biological data suggest these integrated systems are improving soil quality and, given enough time, we would expect this to be true of physical properties as well.
We have made considerable progress in identifying soil quality indicators. Soil enzyme activity and key soil fauna are sensitive to management effects. Also this year we found counting of earthworm middens to be a simple and reliable method for determining earthworm numbers and activity. It also was sensitive in picking up soil management effects.

Collaborators: