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The effect on corn yield of interplanting two different cover crops, Trifolium repens, and Lolium perens into sweet corn, Zea mays, at 4 different times from corn planting was examined. Sweet corn was planted in 30 inch rows, and the cover crop was planted 0, 7, 14, and 21 days afterwards. The study was designed as a complete randomized block experiment with 4 replications. Weed management practices included pre-emergent herbicides and cultivation only treatments.
No significant yield differences in corn yields were detected (alpha=.05). Most of the plots had very little weed competition, including those with no herbicide treatment. Earlier planted cover crops were better established at time of corn harvest. Additional work is needed to examine this practice in conditions of greater weed competion.
Two strip tillage systems for sweet corn production were compared to conventional tillage systems in western Oregon. A power take-off rotary tiller configured to till six rows per pass was used in 1997 and 1998; a shank/coulter strip tillage machine was used in 1999 and 2000. A paired t test experimental design was used in field-scale, on-farm research with eight replications in 1997-98 and 12 replications in 1999-2000. Sweet corn was harvested using the participating growers' corn pickers and yield was determined. A subset of the participating growers recorded types of machinery and labor for tillage operations and total costs were computed for each tillage system. The rotary strip tillage system produced 900 kg·ha-1 greater corn yields (P = 0.11) than conventional tillage. The shank/coulter strip tillage system produced yields comparable to conventional tillage (P = 0.95). The rotary strip tillage system reduced total tillage costs by an average of $38.50/ha compared to conventional tillage (P = 0.03) and reduced machinery operating time by 0.59 h·ha-1 (P = 0.01). The shank/coulter strip tillage system reduced tillage costs by $36.50/ha compared to conventional tillage (P = 0.003) and reduced machinery operating time by 0.47 h·ha-1(P = 0.001). Slugs damaged corn in several strip tillage fields requiring the use of slug bait to prevent economic damage. Herbicides used in conventional tillage systems were generally effective in the strip tillage systems. Mechanical cultivation with standard cultivating equipment was more difficult in some of the strip tillage fields with heavy cover crop residue.
Five on-farm trials were conducted in the Willamette Valley of western Oregon in 1996 to evaluate the potential for integrating winter-annual cover crops and rotary strip-tillage in vegetable productions systems. Two kinds of rotary strip tillers were used to till strips into killed winter cover crops or wheat stubble. Strip-tillage systems were compared to the “standard tillage” practices of the participating growers. In two sweet corn trials, yield of sweet corn was reduced ≈1 MT/ha in the strip-tillage treatments, compared to the standard tillage practices used by the growers. In these trials, the number of tillage operations was reduced by four to five passes with the strip-tillage system. In two other sweet corn trials, corn yield was reduced by ≈4.5 to 5.6 MT/ha in the strip-till treatments compared to the standard tillage treatments. In a transplanted broccoli trial, the strip-tillage and standard tillage treatments produced comparable yields. Possible factors reducing crop yield in the strip till systems include reduced soil temperature at planting and during early growth, soil moisture depletion in the undisturbed cover crop areas, soil compaction, nitrogen immobilization by the cover crop, weed competition, and possible glyphosate/microbiological interactions. Although an economic analysis of this project has not yet been completed, a rough estimate of tillage costs at $25/40 per pass per ha suggests that, in the field with only a 1 MT/ha yield reduction, the reduction in tillage costs would offset the yield reduction in corn (valued at about $88/MT). If yield reducing factors can be understood and a predictable, manageable system of strip-till vegetable production developed, there is a potential to dramatically reduce tillage costs and enhance soil quality through conservation of soil organic matter and biological diversity.
A project was initiated in which a collaborative and mutual learning process was emphasized to (1) improve farmer designed research and to facilitate learning among farmers, research and extension, agribusiness and government agencies; (2) to enhance vegetable production systems by improving farm profitability, protecting water quality, and enhancing long-term soil productivity. The poster displays mutual learning that occurred during each step of the following process:
A participatory, on-farm research project was initiated in 1992 in an effort to enhance mutual learning, knowledge, and experience of integrating cover crops into western Oregon vegetable production systems. A major goal of the project was to include growers, agribusiness representatives, governmental agency, Extension and university researchers in a collaborative learning process, emphasizing grower participation in the design and implementation of on-farm research and demonstration projects. To facilitate this participation from the planning stage forward, four “focus sessions” were hosted by lead farmers in different areas of the Willamette Valley to define growers' needs and interests relating to on-farm research and demonstration trials.
Based on individual growers' specific experimental objectives, cover crop evaluation trials were established on ten farms. Typically on each farm, 5 to 10 cover crop species or mixtures (grain and legume) were planted in large plot strips. Twenty five different cover crop species, varieties, and mixtures were planted. Seasonal cover crop biomass and nitrogen accumulation rates were determined, with cover crop impacts on crop yields and economic returns evaluated at selected sites.