Air July 14, 2004

Thank you Gary, and good morning everyone.

Well, still it rains! All this rain started when I came back from vacation in mid-June. Maybe I need to leave for awhile to get a few days of dry weather! The good news is that even though you may still be seeing chinch bugs and grasshoppers, it appears that the rainy weather is starting to have the desired effect and numbers are starting to dwindle. Assume nothing though and keep an eye on alfalfa regrowth, and small double crop beans.

With the additional rain we are still seeing soybean fields with lots of yellow areas. Let's talk about why that happens and especially in such a patchy fashion. Surprisingly this is an area that hasn't been heavily studied and part of the following is basically Chuck's observations and personal studies over the past 23 growing seasons. We know that soybeans are a legume and they will produce a lot of their own nitrogen requirement with nitrogen fixing bacteria. However, legumes aren't crazy and if there is lots of free nitrogen available in the soil, they will use that first. Don't ask me how, they just do. If you fertilize a bean field heavily with nitrogen and monitor the roots of the plants, you will find very few nodules on the roots. At least not until the free available nitrogen is used up. Now, let's switch to waterlogged warm soils. A situation we've seen a lot of lately. Funny chemical reactions involving nitrogen occur when we develop these anerobic soil conditions, and it happens fast. Mainly, because of changes in the nitrogen and the roots of the plants (loss of root hairs that would be taking up nitrogen) nitrogen deficiency can occur in just a few days. Under these same waterlogged conditions, the nitrogen fixing bacteria are not adversely affected nearly as quick. I have seen some dramatic evidence of this in fields where manure has been spread or where cattle grazed last winter. Where there was noticeable manure, the plants are yellow and have little if any nodulation. The plants that are greener have nice nodulation occurring. Now, if the saturated conditions continue, everything starts to die, but with warmer and drier weather, the yellow should disappear and yield will not be affected.

This is Chuck Otte, Geary County Extension Agent, with Ag Outlook 2004.

Return to Radio Home Page

Return to Ag Home Page