The 2011 ASHS Annual Conference

Reduced tillage, including strip tillage (ST) which limits tillage to the crop rows, may lower fuel, labor, and maintenance costs while maintaining or improving soil quality and crop growth relative to conventional tillage (CT).  Integrating cover crops into ST systems may offer additional benefits related to soil fertility and weed management.  By experimentally separating tillage and cover cropping effects, this research seeks to understand how weed emergence in and between crop rows and cabbage (Brassica oleracea var capitata) growth and yield are affected in ST fields with a cover crop.  Between the crop rows (BR), we hypothesized that fewer weeds would emerge in ST compared to CT due to the lack of germination-inducing tillage, with surface cover crop residue acting as a mulch and leading to stronger suppression.  Incorporated residues in CT and in crop rows (IR) in ST were hypothesized to reduce emergence to a lesser extent.  In the absence of weed competition, cabbage yields were expected to improve with cover crops because of improved soil moisture and fertility benefits (though early nitrogen immobilization was expected); higher yields in ST were also expected due to higher soil moisture in the BR areas that cabbage could utilize.  A fully-factorial field trial was established with tillage (ST or CT) and cover cropping (spring oat (Avena sativa) or none).  Soil temperature and moisture were measured IR and BR as these influence weed seedling emergence.  Quadrats of Powell amaranth (Amaranthus powellii) seeds were established both in IR and BR locations immediately following tillage and again nine days later following cabbage planting; emerged seedlings were counted and pulled daily.  After tillage, soil temperature was lower under a surface cover crop residue (ST BR); surface and incorporated residues also increased soil moisture.  In 2010, Powell amaranth emergence immediately following tillage was 68% lower in ST plots compared to CT, but no significant cover crop effect was detected.  In contrast, and counter to our hypothesis, emergence of Powell amaranth sown at the time of cabbage transplanting (9 days after tillage) was higher with oat residue compared to no cover crop, especially in ST treatments.  When grown with a fixed amount of weed competition, mid-season cabbage plant biomass was higher with cover crops than without, though total cabbage plant biomass at maturity was similar in all treatments.  Final cabbage yield was not affected by treatment, suggesting that yields can be maintained with adoption of soil-improving practices.