Integrated Vegetable Production Systems: Using Strip-tillage and Cover Crops

John Luna and Mary Staben

Extensive tillage is used to prepare land for vegetable crop production with 4-8 separate operations across the field. While tillage can have a beneficial effect of loosening soil compaction, killing unwanted vegetation, and aerating the soil, tillage can damage soil structure and create soil compaction. Tillage has also been shown to increase the rate of microbial oxidation of soil organic matter, reducing organic matter content in the soil. Minimum tillage systems (particularly no-till) have been used extensively in the mid-west and the eastern United States for field corn and soybean production. However, success in vegetable production has been limited. The strip-tillage system developed in this project for vegetable crops offers a compromise between tilled and no-till systems, and is specifically adapted for vegetable production in western Oregon.

This project focuses on developing and evaluating strip-tillage vegetable production systems that integrate winter-annual cover crops. Project goals include increasing farm income and enhancing soil and water quality. A participatory, on-farm research project was conducted with six vegetable producers in western Oregon from 1997 through 1999. A strip-till system was compared to "grower tillage" practices in 9 large-scale, on-farm comparison trials for sweet corn production in 1997-98. The cooperating growers planted winter-annual cover crops in the fall prior to the year of the trial. These cover crops were killed with glyphosate prior to spring tillage. Each on-farm trial consisted of two tillage treatments: "grower tillage" and strip-tillage. Standard tillage practices varied among the cooperating farms and fields within farms depending on soil conditions, ranging from 4-6 tillage operations per field. The strip-tillage treatment consisted of a single pass of the 6-row strip-till machine. Plot sizes for the tillage treatments varied among farms, but were all at least three acres. Sweet corn was planted using the collaborating growers’ standard 6-row planting equipment. Most growers applied fertilizer alongside the row at planting. Sweet corn fertilization also included a side-dress nitrogen application when the corn was approximately 12"-14" tall. Weed control programs varied among the collaborating farms, ranging from broadcast residual herbicide applications with no cultivation to banded herbicides applied in a 10" band over the tilled row combined with cultivation between the rows.

In 1997-98, the strip-till system increased average corn yields by approximately one half ton per acre and average net return by $34 per acre; however, a few fields experienced a yield decline. There was a 75% probability of increasing economic return (not including savings in tillage costs) by $68 per acre and a 25% probability of decreasing economic return by $40 per acre. In 1999, strip-till increased average yields by 0.4 ton per acre and economic return by $29 per acre. Again, not all trials showed strip-tillage to give an economic advantage. Of the 7 fields in the trial, there was a 57% probability of increasing economic return by $84 per acre and a 43% probability of decreasing economic return by $44 per acre.

Tillage savings by strip-till were calculated from 5 fields in 1997-98 where the participating growers kept accurate records of tillage machinery and time of operation in both strip-till and grower tillage treatments. These data show average savings of $13 per acre by the strip-till system. Data on tillage costs from three fields show average savings of $15 per acre using strip-till.

The integrated vegetable production system developed here offers the potential to enhance soil quality through conservation of soil organic matter and biological diversity, and improve water quality through reduction of leaching and surface runoff. Reduced tillage dramatically reduces weed germination and cover crop mulches help suppress weed growth. Integrated with band-applied herbicides and high-residue cultivation, these systems offer the potential to reduce herbicide inputs. Fertilizer inputs can be dramatically reduced by the use of legume cover crops and from the enhanced nutrient capture and recycling from cereal cover crops.

The potential of strip-till to increase net profit has also been demonstrated. However, a better understanding of specific field conditions that cause strip-tillage to reduce yields will be required before widespread adoption of this practice will occur. However, growers collaborating on this project intend to expand the acreage planted to strip-till in 2000, and on-farm research projects will continue to evaluate agroecological and economic performance of this system.

John Luna and Mary Staben
Dept. of Horticulture
Oregon State University
4017 Ag & Life Sciences Bldg
Corvallis, Oregon 97331
Tel: (541) 737-5430

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