James B. Stordahl, Alan G. Dexter and Allan Cattanach
Sugarbeet Research Associate, Extension Sugarbeet Specialist, and
Extension Sugarbeet Specialist
North Dakota State University-University of Minnesota
Fargo, ND
Sugarbeets can be successfully produced utilizing living cover crops with or without spring tillage. However, early control of the cover crop is imperative for successful sugarbeet production. Previous research has shown that when Roundup is applied soon before or after a tillage operation, cover crop control was reduced. Therefore, the objective of this study was to characterize the Roundup by tillage interaction.
A field experiment was conducted at Casselton ND on a Bearden loam soil. The soil pH, exchangeable P, and exchangeable K were approximately 7.9, 55 lbs/A, and 475 lbs/A, respectively. Nitrogen was added to increase residual soil nitrogen levels to 120 lbs/A in September of 1989. Musketeer winter rye plots were established at a seeding rate of 30 lbs per acre on September 7, 1989 in 6 diagonal rows. The experimental design was a randomized complete block with a split-block restriction. Time of herbicide application comprised the main plot, while tillage (tillage or no tillage) comprised the sub-blocks with four replications. Beta 1745 sugarbeet was planted at 1.25 inches deep in 22 inch rows and later thinned back to a population of 125 plants per 100 feet of row. Roundup, at 1 pt/A and 2 qts/A, ammonium sulfate at 2.5 lbs/A and X77 at 0.5% v/v were applied to the center four rows of six-row plots in 8.5 gpa of water at 40 psi through 8001 nozzles. The timing of applications were 7, 3, 1, 0 days before (DB) and 0, 1, and 3 days after (DA) tillage. An Alloway RTS tilled the sub-blocks on May 9, 1990 at approximate 2.5 inch depth with ground speed of approximately 6 to 7 mph. Winter rye control was evaluated May 23 and June 14, 1990.
Figure 1 illustrates winter rye control in 1990. The ''8O-TILL" column represents the average winter rye control in the no-till sub-block; treatments were similar in the no-tilled sub-blocks, thus these values were averaged for illustrative purposes. In 1990, Roundup application on the day of, 1 day after, or 3 days after tillage significantly reduced winter rye control, regardless of the 1 pt/A or 2 qts/A herbicide rate. At the 1 pt rate, a nonsignificant reduction in control occurred with Roundup applied one day before tillage.
Roundup, at both rates tested, provided excellent winter rye control unless a tillage operation occurred on the day of or up to 3 days after Roundup application. However, further research is needed to ensure repeatability, determine the interactive effects beyond 3 days after tillage, and to establish management guidelines.
1990 Sugarbeet Research and Extension Reports. Volume 21, pages 216-217.
