Managing soil moisture

One of the most limiting factors in western Kansas dryland cropping systems is moisture. It is critical that we do everything we can to capture and store as much water in the soil as possible. One of the key elements of doing this is to keep the soil covered with crop residue and crop canopy as much as possible. Not an easy task to accomplish in a semi-arid environment where sometimes we struggle to just grow a decent crop.

In wheat-row crop-fallow rotations, which are common in western Kansas, wheat stubble height can also help in storing more soil moisture. Tall stubble decreases the wind speeds at the soil surface which slows the water evaporation rate at the soil surface. Less evaporation means more moisture is stored in the soil profile that can be used by the next crop.

Tall wheat stubble also provides more “snow catch” when we have winters with snow. During a heavy snow event, with wind, a tall wheat stubble field will be filled with snow to the top of the stubble. Depending on the year this can be twice as much as a field that has a low stubble height.

I know the tendency for most farmers and custom cutters is to have the header cutter bar low enough so every last “sucker head” goes through the combine. In reality most of these heads have very little grain and it’s generally has a lower test weight. Research completed by Kansas State University shows that if you run the header cutter bar just 10” below the top of the majority of wheat heads the amount of heads not harvested is less than one half of a percent. So in a sixty bushel wheat crop you would lose about 0.3 bushels of wheat.

So it would only stand to reason that the more moisture we capture and store in the moisture profile the higher the yields would be in the next crop. Several years of Kansas State University research shows corn yields on an average can be increased by around 10 percent. Grain sorghum yields weren’t quite as dramatic but still increased by three to five percent. Most of the yield increase was due to the increased of amount of kernels per ear or head and increased kernel size. On tall wheat stubble plots the wheat after corn also showed a three to five bushel increase.

An added bonus to the tall stubble height is that it provides excellent habitat for upland game birds. Research completed several years ago by Kansas Wildlife and Parks shows that increasing stubble height from about 8 inches to around 18 inches more than doubled the amount of pheasants the field.

On our farm we started using a stripper header, which just removes the kernels out of the head and leaves everything else in place, to harvest our wheat, basically for all of the benefits mentioned above. One thing that I have observed is in the stripper straw the moisture at the soil surface doesn’t seem to dry out near as fast as it did when we were harvesting with a regular header. This should be a benefit, especially in a dry spring. It also works well in lodged wheat. Since it uses fingers attached to a high speed rotor the header actually lifts and stands the wheat stubble up again nearly to the height that it originally was.

For more information about this or other soil health practices you can contact me at [email protected] or any local NRCS office.