Strip-tillage in California’s Central Valley
Strategies that reduce or avoid the risk of soil compaction will be required for successful long-term conservation tillage dairy forage systems. By reducing the number of tractor traffic trips across a field, less compaction will occur. In addition, avoiding harvesting when the soil is wet, and subsoiling, or breaking up compacted subsoil layers by ripping, may reduce the risk of compaction.
Dairy Manure Application and Strip-Tillage
When strip-tillage is used in San Joaquin Valley dairies following winter forage chopping and before summer corn seeding, dairymen typically apply solid manure materials before seeding corn. Experience suggests that applying composted manure ahead of strip-tilling seems to be better than applying raw manure. Composted manure is lighter and more uniform in nitrogen content, is less odiferous, has less viable weed seed, and will be mixed more efficaciously into the surface soil with the strip-tiller. Spreading raw manure can leave large clumps on the soil surface that can present problems for seeding, in addition to adding large amounts of weed seed. Local air quality regulations governing manure applications may also apply.
A variety of strip-tillage implements have been developed and are now used for different cropping systems in California. These implements tend to be either PTO-powered rotary tillers that have been used primarily in processing tomato fields or ground-driven coulter or subsoiling shank implements that have been most commonly and widely used in corn forage systems. Rotary strip-tillers are essentially modified rototillers that till only the areas into which seeding or transplanting is done (fig. 9). Herbicide and starter fertilizers also have been applied and incorporated with these rotary strip-tillers. Strip-tillage implements that are used in California dairy cropping systems for corn planting generally include a residue-cutting coulter or blade, a subsoiling shank, and a tool or mechanism for breaking up soil clods and creating smooth seedbed conditions (fig. 10).
click image to zoomJeff MitchellFigure 10. Bigham Brothers Terratill strip-tiller implement, showing residue-cutting coulters, subsoiling shanks, and clod-busting baskets. While there are variations in the types of strip-tillers that are currently available in terms of the draught energy that is required to pull them, in general, about 30 horsepower is needed for each row unit or subsoiling shank. This horsepower requirement, however, depends on the design, weight, and other features of the strip-tiller, as well as on the desired depth of tillage. Soil water content is also a factor: more energy is needed in dry soil.
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