Tillage for Sunflower Control and for Annual Canarygrass and Fieldbean Production1

Abstract

AbstractSunflower (Helianthus annuusL.) is a major weed in crops that follow sunflower. This research measured the population density of volunteer sunflower and performance of annual canarygrass (Phalaris canariensisL.) and fieldbean (Phaseolus vulgarisL.) following tillage treatments of moldboard plowing, chisel plowing, rototilling, or zero tillage repeated on the same plots for 5 yr. Tillage plots, on Typic Hapludoll soil at Rosemount, MN, were divided into subplots of annual canarygrass planted between 26 March and 30 April and fieldbean planted between 21 and 25 May. Less than 1% of the volunteer sunflower achenes survived more than 1 yr in the soil, but tillage and planting date determined whether sunflower remained an important weed for 0,1, 2, or 3 yr. Sunflower was a major weed the first year after sunflower; however, the problem could be avoided by planting after mid‐June in soil not tilled in the fall. Moldboard plowing, which buried 82% of the achenes over 10 cm deep, gave the best but not adequate control the first year. Zero tillage or chisel plowing in the spring eliminated sunflower as an important weed after 1 yr, regardless of planting date. Chisel plowing in the fall or moldboard plowing in the spring tended to prolong the sunflower problem beyond 2 yr. Weed control in both crops was poorest following zero tillage. Moldboard or chisel plowing in the spring resulted in highest average yields of fieldbean. Highest yields of canarygrass followed moldboard plowing.