Strip tillage for high-residue irrigated cropping systems
click image to zoomO. Steve NorbergFigure 1. Corn planted using a strip tillage field near Jamieson, Oregon, under a center pivot. Strip tillage is a conservation tillage system that was developed for row crops grown in heavy, poorly drained cool soils in the northern corn belt states, but which some Pacific Northwest farmers are adapting to their local conditions. Strip tillage is designed for row crops in which only a 9- to 12-inch wide strip is tilled and planted, and the ground between the rows is left undisturbed (figure 1). The depth of tillage varies with producer and equipment but can be up to 14 inches deep. Growers are currently adapting strip tillage technology to a variety of row crop production systems in the Pacific Northwest.
Strip tillage, also referred to as zone or vertical tillage, offers many environmental and economic advantages to growers over conventional tillage, including the following:
• Increased profit per acre by eliminating several tillage operations.
º Decreased fuel costs.
º Decreased labor costs.
º Decreased machine maintenance costs.
º Decreased time per acre, allowing more acres to be farmed or allowing more personal time.
• Ability to deep band during the strip tillage operation, reducing phosphorus and potassium losses via surface water runoff.
• Benefits of less soil movement (soil stirring).
º Increases water infiltration rates, which decreases runoff due to greater aggregation of soil particles and increased number of large water flow paths created by roots and worms.
º Increases organic matter levels of the soil (improving soil tilth) by incorporating less oxygen in the soil and slowing microbial breakdown of organic matter.
• Benefits of increased residue on surface of the soil (percent residue cover).
º Residues decrease soil sealing caused by energy of raindrop impacts tearing soil particles apart.
º Creates irrigation water savings by decreasing soil water evaporation by residue reflecting sunlight, thereby cooling the soil and slowing air movement over the soil surface.
º Reduces plant loss by blowing sand (wind erosion).
Strip tillage is a relatively new farming system, especially in the Pacific Northwest. Local research conducted on a farm in 2009 near Jamieson, Oregon, by Jensen and Norberg showed that yields of corn grown under strip tillage planted into wheat residue matched conventional yields and that six separate field operations, including two diskings, one field cultivation, fertilizer application, and a dammer-diker, were replaced with a flailing and a strip tillage operation (table 1). In Minnesota, research showed that strip tillage in a continuous corn rotation slightly reduced corn grain yield by 4 bu/a compared to conventional tillage and increased grain yield by 7 bu/a compared to no tillage (table 2; Vetsch and Randall 2002). After soybeans, corn yields grown under strip tillage matched conventional and no-tillage yields.