Waterhemp control programs in soybean

摘要

This study was designed to identify effective programs for consistent control of waterhemp. The study was conducted on a Weir silt loam with 1.9 percent organic matter and pH 7.1 at the Belleville Research Center. Fertilizer applied was 50 and 150 lb/A P_2O_5 and K_2O, respectively, to an area that had been cropped to soybean in 2001. Asgrow brand 'AG 4602 RR' glyphosate-resistant soybean was planted 1.0 inch deep at 75 lb/A into a reduced-till seedbed on June 4. Plots consisted of four rows with 30 inch row spacing, 25 ft long arranged in a randomized complete block design with 3 replications. The herbicides were broadcast applied with a CO_2 pressurized sprayer using 8003 flat fan tips at 40 PSI in either 10 or 20 GPA water (see table). Application timings were preemergence (PRE), 4 to 6 inch weeds POST only in 10 or 20 GPA (4-6"W-1A and 4-6"W-1B, respectively), 6 to 8 inch weeds (6-8"W), 8 to 10 inch weeds (8-10"W), 10 to 12 inch weeds (10-12"W) and 4 to 6 inch weeds following a PRE application (4-6"W-2). Monthly rainfall in inches was 4.9, 6.6, 1.7, 3.7 and 3.6 in April, May, June, July and August, respectively. Common waterhemp population was 67 per 0.25 m~2 in the nontreated plots, mid-season.