AgWatch


Pioneer Talks Crops: Herbicide And Potassium

Insights To Help Growers Increase Yields Through Better Crop Management

GREG PFEFFER

DEXTER, MO.
   Overall we have experienced a wet spring. Some areas have had more normal conditions, but it seems that planting windows have been pretty narrow in the delta. Weed control is more difficult in wet springs because it is not always easy to find days to make burndown applications. Therefore, herbicide applications may have to be made after planting in some situations.
   Once a stand is established, it will be important to evaluate additional herbicide needs. Weeds need to be controlled by the three- to five-week period after planting to prevent competition. This is when corn is in the V2/V3 growth stage (four to five leaves showing), or about six to eight inches tall. Severe weed pressure, especially from grasses, during that period can significantly impact corn yield potential.





   Excess or insufficient rainfall may raise concerns about the performance of fall-applied or early spring-applied herbicides. Scout cornfields regularly to determine if weeds are “breaking through” and beginning to grow normally. Usually, the most effective herbicide program across a wide range of conditions is a two-pass program of a pre-emergence herbicide followed by a post-emergence herbicide.
   Soybeans seem to be the big crop this year and there has been more interest in growing high-yield soybeans than ever before. To achieve high soybean yields, start with strong fertility. Soybeans need a significant amount of potassium. A 60 bu/acre soybean crop will utilize 320 pounds of nitrogen, 64 pounds of phosphorus, 142 pounds of potassium, 27 pounds of magnesium and 25 pounds of sulfur.  Some of this will return to the soil in the stover, but it is important to note that high yields require a lot of good plant food. 
   When potassium in the topsoil is deficient, soybean plants will try to obtain their potassium needs from the subsoil (only as adult plants). Potassium deficiency may occur when soil potassium levels are low, when the pH is very low, when root restriction occurs or when nematodes are a problem. Test soils to determine the proper amount of fertilizer to apply to achieve high soybean yields. For more information, contact your local Pioneer sales representative. ∆
   GREG PFEFFER: Agronomist for Pioneer, Dexter, Missouri

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