The most effective marestail control program should start with fall treatments, especially in fields with a history of marestail problems or fields that we can see now with adult plants setting seed. A number of different herbicides can be applied in the fall for marestail control ahead of soybeans, such as 2,4-D, dicamba, Clarity, Sharpen, Canopy EX, Autumn Super, or Valor XLT. The addition of glyphosate helps control grasses and other broadleaf weeds, and can even help on glyphosate-resistant marestail.
Herbicide effectiveness on marestail depends largely on the stage of growth and size of the plants. Marestail generally is most susceptible to herbicides when it is small and still in the rosette stage of growth. Once marestail starts to bolt and exceed 4 to 6 inches tall, it becomes very difficult to kill with most herbicides. Since marestail can germinate throughout much of the year, a single herbicide application probably will not provide season-long control, particularly in no-till.
Fall applications can be effective even into December as long as applications are made to actively growing weeds during a stretch of mild temperatures. In fact, for fall applications, it may be better to wait until November to allow most of the fall-germinating winter annuals to emerge. A residual herbicide such as metribuzin-, Valor- or Classic-containing products (unless the marestail is ALS resistant) can be added to help control marestail through winter and early spring. But don’t expect a residual herbicide applied in the fall to provide good residual weed control through the spring and summer of the next year. If a fall treatment isn’t made, early spring treatments in March to early April should be applied to help control fall-germinated marestail.
I helped with the Harvey County tillage survey this week and saw evidence of insect damage across the county.
Be on the lookout for corn earworms Continue reading “On the Lookout for Corn, Milo and Soybean Insect Damage”
Compared to corn, wheat, and sorghum, soybeans remove significant amounts of nutrients per bushel of grain harvested. Nutrient uptake in soybeans early in the season is relatively small. However, as they grow and develop, the daily rate of nutrient uptake increases. Soybeans need an adequate nutrient supply at each developmental stage for optimum growth. High-yielding soybeans remove substantial nutrients from the soil. This should be taken into account in an overall nutrient management plan. A 40-bushel-per-acre soybean crop removes approximately 30 pounds of P2O5 and 50 pounds of K2O with the grain; in addition, approximately 10 pounds of P2O5 and 40 pounds of K2O can be removed with the stover. Continue reading “Fertilizing Soybeans”
When soybeans turn yellow at an early stage of growth, there are several possible explanations.
Nitrogen (N) deficiency. In fields that have been extremely wet or extremely dry, or under severe early heat stress, rhizobial nodule development can be delayed, resulting in N deficiency. As soil moisture levels return to more normal conditions (if a short-term stress), the nodule-forming bacteria will go to work and the deficiency symptoms will quickly disappear. With N deficiency, it is usually the lower leaves that are chlorotic or pale green. Within the plant, any available N from the soil or from N fixation goes to the new growth first. Continue reading “Yellow Soybeans”
Controlling glyphosate-resistant marestail in soybeans has been a big challenge for Kansas no-till producers in recent years. Because soybeans are generally planted later in the season, and marestail generally germinates in the fall or early spring, application timing and weed size are critical factors to successful control. Continue reading “Controlling Marestail in Soybeans”