Don Robison doesn't have to guess how much soil compaction costs on their farm. The no-tiller has a perfect example to watch. A utility company put a waterline through their property four years ago. The effects were still very evident this year.
Not only did the corn look shorter and suffer more during the drought, he has photographic proof of where the line was installed. Beck's Hybrids offers an aerial service that takes images of fields for diagnostic reasons in late summer. The image shot of this field clearly shows the area over the water line as brown and yellow colors in a ribbon cast against a green background of crops that were doing well in their cover crop plots. After harvest, he estimates the area over the line made between 50% and 10% of the average of the field.
Gary Steinhardt, Purdue University Extension soils specialist, one of the first to study the effects of soil compaction in the early 1980s, says that the effects of deep compaction can last for a long time – years in certain situations. The effects are more pronounced on crop growth in a poor growing season with heat and drought stress. If soil compaction was going to show up four years after the fact, the summer weather conditions made sure that conditions were right for the area to express the effects of soil compaction.
The compaction problem is usually worse in corn than soybeans. You can see the effects in soybeans if the soil compaction is severe, but the yield effect is usually much greater in corn.
You may be dealing with compaction that's less severe, but still bothersome. Some fields were planted on the tacky side last spring. This could have created sidewall compaction that held back root growth. In conventional tilled fields there could be plow layer compaction.
What to do about it is the bigger issue. There is anecdotal evidence the deep ripping helps, but Steinhardt and his co-workers or anyone else in academia have not been able to prove a benefit of deep ripping in a scientific plot. Freezing and thawing helps. Obviously, however, if the compaction is deep, it will take a long time for natural processes to restore the land to its original condition.