Strip-tillage in California’s Central Valley
click image to zoomDennis BryantFigure 4. Ground-driven modified Orthman 1-tRIPr strip-tiller implement tilling in cover crop in center of tomato beds and sweeping out furrows for irrigation, Davis, California, 2006. Several thousand acres of both fresh market and processing tomatoes have been produced in recent years in western Fresno County using strip-tillage following triticale and barley cover crops. In these systems, cover crops break up tomato monocultures and are seeded and irrigated up generally in late October or early November, and terminated using glyphosate (a broad-spectrum postemergence herbicide) in February and March to avoid problems that can result from very high biomass cover crop surface residues. A variation on the ground-driven coulter or subsoiling shank strip-tillers that are used in California dairy cropping systems is a 3-row 60-inch strip-tiller used for sweeping furrows clean before transplanting processing tomatoes in a chopped cover crop (fig. 4).
BenefIts of Strip-Tillage
A range of economic and natural resource conservation benefits may result from strip-tillage systems. Because strip-tillage uses fewer intercrop tillage passes or operations strip-till than do traditional tillage systems, actual tillage, or “land preparation,” costs strip-till are lower. In a 2002 farm evaluation of strip-tillage forage corn production near Modesto, California, which was the first documented experience with strip-till corn in California, costs for strip-tillage corn establishment were about 54 percent lower than costs of traditional preplant soil preparation. Not only are seedbed preparation costs lower with strip-tillage, but the actual requirements for farm labor and the time required for tillage between crops may also be lower, too. The success of strip-tilled corn to date, however, has relied on the use of Roundup Ready (RR) corn, which would include at least one application of glyphosate early in the season, sometimes followed by a second application midseason depending on weed pressure.
The growing attractiveness of strip-tillage systems for California dairymen rests on the ability of these systems to cut production costs and reduce the time between successive forage crops, allowing more opportunities for triple-cropping, the sequential production of three crops within a given calendar year. Reduced tillage between winter forage and corn has also provided more time after corn for spreading and incorporation of manure prior to planting winter forage, or for fall tillage prior to spring-planted crops such as cotton or tomatoes.