Peter Kenagy’s rotation provides regular windows of opportunity to grow cover crops, which he has used for twenty years to build soil and control weeds on his farm. Kenagy raises processing vegetables, small grains, cover crop seed, and native grass forbs and seeds on 320 tillable and 130 riparian acres in Oregon’s fertile Willamette Valley.
The period following green beans, which are in the ground just seventy days and come off in July or August, is a perfect time, Kenagy says, to plant a summer cover crop like sudan grass, which will grow up to 5 feet tall before winter-killing with the first frost. The thick grass mulch continues to provide a good ground cover when he plants corn into it in the spring. Sometimes he plants sudan grass as a bridge crop between beans and a fall-planted grass crop.
Maintaining weed-free fields is especially crucial for Kenagy’s intensive production of native grass forbs and seeds, which are destined for wetlands mitigation and other restoration projects.
Kenagy also uses cover crops to capture excess nutrients and silt and prevent them from flowing into the adjacent Willamette River during perennial flooding episodes on his low-lying fields. “The more cover crop vegetation you have there, the more silt you catch,” he says. Besides sudan grass, he often relies on fall-planted oats—he uses the variety “Saia,” planted at 30 pounds an acre—to produce abundant aboveground biomass.“I have a huge gap between one crop and the next,” says Kenagy. “I have to control weeds during that period, which is just one of a number of things a cover crop does so well.” Maintaining weed-free fields is especially crucial for Kenagy’s intensive production of native grass forbs and seeds, which are destined for wetlands mitigation and other restoration projects.
He has experimented with many different covers, modifying his use of cover crops to fit changes in his cash crop rotation. In addition, practical concerns or experiences inform his choices of which cover crops to use. For example, he no longer plants dwarf essex rape because it could cause unwanted cross-pollination with other brassicas. He favors using oats rather than triticale because he’s found the former are more readily and cheaply available and cause fewer disease problems when followed by a wheat crop.
Though Kenagy typically plants common vetch to fix nitrogen, he’s searching for another legume that will provide solid cover and boost N levels in the late summer before fall planting of grass crops.
Phaecelia, which overwinters in the Willamette Valley, has become one of Kenagy’s preferred covers in recent years. He plants this small-seeded cover crop at a rate of 2 to 4 pounds per acre. He says, “You don’t have to plant the seed too deep, and with a little moisture, [phaecelia] grows like gangbusters” and is highly effective at suppressing weeds. “It’s easy to kill, pretty much using any method you want. Its biggest attribute is that it breaks down really fast. Barely any effort is required to get rid of it.”
“One of the most abusive things farmers do to the soil is till it, and most do it repeatedly,” Kenagy says. “Strip till does less abuse to the soil, and keeping the residue on top is a much more natural way for it to be handled.”
“Part of what’s driving this is logistics,” he says, describing a field of perennial ryegrass that he recently left to break down in the field for a year after it was killed with an herbicide. “The [ryegrass] crowns left good cover while they rotted; this was a good alternative to plowing the residue in right away,” he says, noting that as a result “there will be less kick-up of sod bunnies into my [mechanical] bean picker.”Reducing the effort required to manage any crop is a hallmark feature of Kenagy’s operation. “I plan my rotation by looking at what I’m coming out of and figure out the easiest thing to rotate in, so that I don’t have to do so much,” he says. “ I don’t want to be stuck trying to till wheat stubble in the fall.” Through his careful choice and timing of specific crops, Kenagy is able to till less, save money on fuel, and improve soil quality.
Kenagy’s commitment to building good soil goes beyond planting cover crops. Whenever possible, he uses no-till methods to plant and manage his cash and cover crops. For certain crops, such as sweet corn, he uses strip-tillage to cut through vegetative residue, which disturbs just 6 inches of soil—a mere one-fifth of the soil surface that is typically plowed with conventional tillage. (For information about strip tillage, see chapter 16.)
“One of the most abusive things farmers do to the soil is till it, and most do it repeatedly,” Kenagy says. “Strip till does less abuse to the soil, and keeping the residue on top is a much more natural way for it to be handled,” as it is thus mimicking a more natural system. Grassland and forests, he points out, undergo perpetual cycles of accumulating new residue and undergoing decomposition by soil fauna.
“As a society, we’ve made much too big a footprint on the land,” Kenagy once told the Oregon Statesman Journal. “I think it’s time to make it smaller.”—UPDATED BY AMY KREMEN
Table of Contents
- About the Authors
- Healthy Soils
- Organic Matter: What It Is and Why It's So Important
- Amount of Organic Matter in Soils
- The Living Soil
- Soil Particles, Water, and Air
- Soil Degradation: Erosion, Compaction, and Contamination
- Nutrient Cycles and Flows
- Soil Health, Plant Health, and Pests
- Managing for High Quality Soils: Organic Matter, Soil Physical Condition, Nutrient Availability
- Cover Crops
- Crop Rotations
- Animal Manures for Increasing Organic Matter and Supplying Nutrients
- Making and Using Composts
- Reducing Erosion and Runoff
- Preventing and Lessening Compaction
- Reducing Tillage
- Managing Water: Irrigation and Drainage
- Nutrient Management: An Introduction
- Management of Nitrogen and Phosphorus
- Other Fertility Issues: Nutrients, CEC, Acidity, and Alkalinity
- Getting the Most From Routine Soil Tests
- Taking Soil Samples
- Accuracy of Recommendations Based on Soil Tests
- Sources of Confusion About Soil Tests
- Soil Testing for Nitrogen
- Soil Testing for P
- Testing Soils for Organic Matter
- Interpreting Soil Test Results
- Adjusting a Soil Test Recommendation
- Making Adjustments to Fertilizer Application Rates
- Managing Field Nutrient Variability
- The Basic Cation Saturation Ratio System
- Summary and Sources
- How Good Are Your Soils? Field and Laboratory Evaluation of Soil Health
- Putting It All Together