Growers have found their No-til soybeans this year growing slower and staying yellower longer than normal as compared to their conventionally tilled soybeans.The fieldshot above shows
exactly what many growers have been experiencing.Part of this can be explained by the wetter and cooler spring that we've experienced.The extra 4-5 ton per acre of corn residue from last years bumper corn crop has not helped matters as it is contributing to keeping soils much more moist and cool.Soil bacterial populations are also tying up N as they break down the extra Carbon that has been added to the soil from last years bumper yields.The C/N ratio of corn stover is roughly 60:1 and the soil microbes job is to keep the soils C:N ratio at 10:1.The unfortunate part of this is that to break down this extra carbon load the soil micobes are tying up in their bodies most of the mineralized N that is in the soil.Though the soybean plant in the early part of its life depends on a bunch of this same mineralized N to keep it green and growing it is experiencing some serious competition from the soil microbes for N thereby leaving the soybean crop short of its needs and looking much yellower than normal.Because soil N mineralization has been very slow this year the plant is having a difficult time coming up with sufficient N to stay a healthy green until its nodules are formed.Once nodule formation occurs and kicks in gear the plant will be able to produce all of its own Nitrogen needs and turn a deep dark green.It takes roughly 8 lbs of N to produce 1 bu of soybeans.It remains to be determined whether an additional 30-40 pounds of N this year would have helped soybeans overcome this early N deficient period and produce more beans come harvest.There are a few locations that have tried broadcasting an additional 30-40 lb of N to their crop to see if this will have any beneficial result.Though this is not something that is normally recomended we will have to wait and see if under the circumstances of 2009 it has any value.
Conventionally tilled soybeans like those shown above have had the advantage of a slightly warmer seedbed this spring.This has helped the crop in two ways.First the warmer soil temperatures have allowed bacterial populations to mineralize N at a faster rate which has helped make the crop greener.Also the warmer soil tempeatures have helped improve the speed of Nodule formation so the plant can begin fixing its own N sooner.
We wouldn't normally expect to see No-til soybeans like those shown here staying dramatically yellower than conventionally tilled soybeans for such a long period of time.A factor that could be contributing to their extended yellowness is their slower growth rate.If soybeans are sprayed with Glyphosate,the Glyphosate/Enzyme complex moves to the plants meristematic tissue.With slower growth this higher concentration of Glyphosate-enzyme complex will cause plants to yellow flash.The only resolve to this dilemma is to hope that we receive some Warmer 80*F+ temperatures to move crop growth along.