2021 Weed Control Trials Overview

Caleb Dalley

Hettinger Research Extension Center

The 2021 cropping season brought many opportunities and challenges for weed control research.  The spring started out dry, with almost no stored soil moisture due to the dry winter of 2020-21. Under these dry conditions, spring wheat, oat, flax, dry pea, lentil, and chickpea trials were all planted into dry soil with hopes of rainfall. Few if any weeds had emerged at planting due to these dry conditions. Spring wheat was planted on April 26-28. Dry pea were planted on April 28. Lentil were planted on April 29. Oats were planted on April 30. Chickpea were planted on May 3. Flax was planted on May 5. Safflower were planted on May 6 (varietal response to sulfentrazone) and May 15 (preemergence herbicide trial). Canola was planted on May 12. Crop seed was drilled using a John Deere 1590 no-till drill. All field have been farmed under continuous no-till for 20+ years.

Following planting, rainfall during the month of May was above normal with a recorded 4.77 inches of rain (normal or average rainfall for May is 2.46 inches in Hettinger). Many of the trials included evaluation of preemergence applied herbicides. This above normal rainfall provided good conditions for evaluating crop tolerance to these herbicides as well as efficacy for weed control. However, results will differ in years when less rainfall occurs, but it is especially important to know how crops will respond to these herbicides in years when above average rainfall occurs. This wetter than normal month of May was followed by a hotter than normal and dryer than normal June and July. In the months of June and July, only 1.7 inches of rain was recorded (normal or average rainfall for June and July is 5.5 inches at Hettinger) and temperatures were frequently above 90 F and occasionally greater than 100 F; reaching 104 F on July 3, 100 F on July 22, and 105 F on July 27. The average maximum temperature for June and July ranges from 72 to 87 F at Hettinger.  These hot and dry conditions resulted in drought conditions which stunted the growth of both crops and weeds. These conditions made weed control with postemergence herbicide more difficult herbicides work best when weeds are actively growing and not stress by drought. The drought conditions resulted in high variability in crop yields making efforts to draw conclusions on crop responses to herbicides more difficult. In most cases, no significant differences in yield could be detected even when there were large differences because of the high amounts of variability. Many of these experiments conducted in 2021 will be repeated in 2022 to evaluated results under different environmental conditions.