Strip-tillage in California’s Central Valley
click image to zoomJeff MitchellFigure 1. Strip-tilling into barley cover crop before cotton planting, Riverdale, California, 2001. Strip-tillage is a form of conservation tillage that clears crop residues in a narrow zone of soil and loosens subsoil layers prior to planting. This tillage zone is typically 8 to 12 inches wide and 2 to 14 inches deep, depending on the implement that is used (fig. 1). Strip-tillage decreases both the volume of soil that is disturbed and the amount of dust that is typically generated in intercrop tillage, and it also reduces fuel, labor, and equipment costs when compared with traditional broadcast tillage. It also provides opportunities for band application of surface-incorporated herbicides and fertilizers at different depths prior to seeding. Because only a relatively small volume of soil is tilled using strip-tillage, it is often also called “zone” or “vertical” tillage. This tillage system requires a strip-tillage implement as well as several other key changes in an overall cropping system to be successful.
Strip-tillage systems were developed several decades ago and are now widely used in the coastal plains region of the southeastern United States for crops such as cotton, corn, and peanuts as a means to break up the naturally settling and consolidating subsoil layers that are routinely formed in this area. In these systems, the objective of strip-tillage is to loosen compacted subsoil zones while leaving the soil surface and crop residues relatively undisturbed (fig. 2). Strip-tillage also is used in irrigated row crop production systems in eastern Colorado and western Nebraska (Smith and Pearson 2004), for sweet corn and bean production in western Oregon (Luna and Staben 2003), rainfed corn and soybean production in the Midwest, and for a variety of row crops in Texas.
click image to zoomJeff MitchellFigure 3. Basic components of early prototype strip-till implement used in California, including residue-cutting coulter, subsoiler shank, and clod-busting rolling basket, Five Points, California, 1996. Strip-tillage was first introduced in California for melon production in 1998, for processing tomato production in cover crop surface mulches in 2001 (Mitchell et al. 2004) (fig. 3), and for cotton under clean-till conditions. Initially, PTO-powered rototiller-type implements were used with success for both direct-seeded melons and corn and for transplanted tomatoes in a number of research station and farmer field evaluations. Subsequently, ground-driven strip tillers were introduced for processing tomato production in both cover cropped and organic fields (Madden et al. 2004). More refinements and variations on the strip-till tomato theme with both rotary-powered and ground-driven strip-tillage equipment have been made in recent years.