Air May 31, 2000

Thank you Mark, and good morning everyone. The rain the end of last week was at least a temporary life saver. I’m afraid we may need live savers about every ten days through the summer at this rate though. The good news is that the rain probably saved 2 to 4 pounds per bushel test weight and 5 to 8 bushels per acre in a lot of fields. We are seeing an increasing amount of chinch bug activity so keep an eye on your milo fields.

I put about 750 miles on my car this weekend up through northeast Kansas and southeast Nebraska. I saw a lot of seedling soybeans that were sure happy for the rain. But I also saw a lot of weeds coming right along with those soybeans. I’m going to assume that these were roundup ready soybeans. The advent of the roundup ready technology has brought us back around to some new old thinking on soybean weed control. Soybeans, more so than any of our other crops, are very sensitive to early season weed competition. Give corn, milo or wheat some early season weed competition and it will outgrow or compensate later on. Not so with soybeans. As the soybean crop was becoming a standard crop in the first half of this century, we used things like rotary hoes and cultivators to deal with those small early season weeds. For the last 30 or 40 years, we didn’t worry too much about that because we had our pre-emergent herbicide applied. We were more concerned with getting that plant up and canopy developed so we wouldn’t have to worry about late season weeds. Now, we’ve come back around to where we aren’t using a pre-plant or pre-emerge herbicide. We’re going to come in over the top, and spray our roundup. But we often want to keep the herbicide cost to a minimum so we delay as long as possible before we apply the first roundup application. This may be hurting us and is why I still recommend a low end pre-emerge herbicide treatment. If you have a lot of weeds coming on in your roundup ready beans, and with last week’s rain you probably do, I’d get ready to spray those as soon as possible. And then next year, give some thought to a preplant treatment so that you do have a little extra time margin before that first roundup treatment. In the meantime, monitor those weeds very closely. A little competition may be good, but for soybeans, it needs to be darn little!

This is Chuck Otte, Geary County Extension Agent, with Ag Outlook 2000.

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