Last week as I traveled from Mankato to Thief River Falls, it was impossible to miss the consequence of heavy rains that had covered most of the state. This week Minnesota is still in the news as the river systems swell while removing that rainfall through our State’s waterways. Field low spots are also draining at variable rates and this raises the question; what to do with that field area? I’m not going to focus on crop loss or insurance at this point, but on the field itself. For most of the field low spots I have observed, the drying process has been slow and we have rain forecast for the later part of the week at this writing. The option to replant any area is quickly diminishing if not already past. University of Minnesota Extension reports that when planting soybeans on July 1, yield potential is reduced by approximately 50% compared to soybeans planted early. The slow drainage compounded by more possible rainfall begins to suggest that by the time those field areas are dry enough to be planted, the loss of yield potential precludes that as a profitable option this year. In light of that, there are several other considerations to keep in mind for those field low spots.
As the crop surrounding those low areas continues to develop, access to them may become more limited by the risk of traffic damage to the remaining crop. In the desire to do something in those flooded out field areas, it is important not to enter them too early after they drain down because although crop size may still allow access through the field, the risk of compaction in those saturated soils remains very high. Driving equipment on saturated soils can create compaction damage down 20 plus inches creating a whole new caveat of trouble for future growing seasons. Waiting to do something can be frustrating but can also yield dividends in soil structure in future crop years. University of Minnesota Extension Specialist Jodi DeJong-Hughes has an excellent article on soil compaction that I recommend as a read prior to entering into previously flooded low spots where the soil may be unable to handle equipment traffic.
On the other hand, doing nothing with those low spots through the remaining growing season is also not a good option. Why? For one thing, weeds. You know they (weed seeds) don’t mind germinating in those wet soils for some reason and the open areas of drowned out crop fields are a perfect habitat for weeds to thrive. This is all the more important if you have any herbicide resistant weed problems on your fields. Any weeds allowed to go to seed in this season will only add to the control issues you may encounter for next year. It will remain important to manage the weed population in those open areas where crop shading and competition will not reduce their presence. Those areas that are in center of fields may create both access problems for mid to late-season control but can also fall prey to the “out of sight” mentality where we would just as soon forget about the frustration of their existence until fall tillage. An option along with a solid weed control practice is to plant a cover crop; again as long as the soil is dry enough to avoid compaction issues and the crop allows access without further damage by the time you can get enter the field again. Late last June, University of Extension Specialist Liz Stahl wrote an article about Fallow Syndrome in light of the prevent plant acres in Minnesota).
Dr. John Sawyer, Extension Professor at Iowa State University also has an article concerning Flooded Soil Syndrome (here). Fallow syndrome and flooded soil syndrome are essentially the same thing identified by reduced crop performance on those soils the next year where land has been idle for a growing season. Typical reported cause for that poor crop performance is decreased beneficial soil fungi (arbuscular mycorrhizae) that thrive on healthy root systems and are reduced phosphorus availability. Management recommendations include planting a cover crop to continue a plant cycle in those field areas to compete against weeds and maintain soil productivity.
Now is a good time to finalize plans for those flooded out areas of your operation so that when the soil is dry enough to manage the land you are prepared to go. Make sure your plan includes how you will access the area if crops become too large for normal field equipment by the time its dry enough, avoiding entrance too early to reduce soil compaction potential, season long weed remediation, and some sort of cover crop to maintain soil health and fertility for the next year. As you consider your fields and flooded out areas this summer, don’t lament the rainfall you can’t control, implement plans for those flooded low areas to prepare for next year’s crop there, and of course, read as much as you can.