This article was authored collaboratively by Ron Gelderman, former Professor & SDSU Extension Soils Specialist, and Ruth Beck.
The single most limiting factor to crop yields in central SD is moisture. This could be especially true this year after coming off a dry summer, fall and most of the winter. Luckily we have had some recent snows. While no-till is extremely important in saving additional soil moisture, it is not the only management practice that can be used to save water.
While setting up a plot area near Pierre recently, we ran across two side by side no-till wheat stubble fields. One was harvested with a stripper header with an average stubble height of 32 to 36 inches. The other field had stubble of about 8 inches tall with perhaps half of the stubble laying flat. Soil sampling each area showed moisture depth of about 30 inches in the tall stubble and only 22 inches of moist soil under the short stubble. The average moisture content was 22% under the tall stubble and 22.9% (by weight) under the short stubble. Making some assumptions on bulk density, this works out to 6.0 and 7.9 inches of water in these profiles for the short and tall stubble, respectively. Of course not all this moisture is plant available, but there should be at least 1.2 inches of extra plant available moisture under the higher stubble. Higher stubble heights can save more moisture by limiting evaporation and by trapping additional snow. Since there was little moisture after wheat harvest, evaporation was probably limited at this site. The increased depth of soil moisture is most likely to be primarily attributed to snow catch. Snow measured at Pierre between Oct. 1 and April 30, 2013 was 55.5 inches (incidentally this is the 5th highest amount of snow measured in Pierre in recorded history). This is the equivalent of approximately 5.7 inches of precipitation for the 2012 – 2013 winter months.
The additional soil water observed under the tall stubble is not unusual. Many other observations and research has shown similar results. The additional moisture here could increase corn yields from 4-6 bu/a over the short stubble field. In addition, less evaporation under the tall stubble as the season progresses could increase effective water and yields even more.