Do we need to think about conserving soil moisture prior to planting?

It most certainly has been a strange winter with very little moisture. This fact, combined with a multi-year drought has people concerned for spring planting. Most farmers I have talked to this winter have shared concerns about not only the lack of precipitation, but the lack of soil moisture. And while we had outstanding yields in some places in 2023 even with drought conditions, I would point out there is one major difference shaping up so far for 2024. That difference is in 2023, there was adequate water in the soil profile to sustain us for many weeks, but a large part of Iowa does not have that luxury going into the 2024 growing season.  See map generated by LIS NASA SPoRT and this quick primer on how soil moisture is derived.  

Spring Tillage

It is difficult to wrap our thoughts around the fact we may need to consider how to conserve soil moisture going into planting season when usually we are concerned about too much soil moisture this time of year. Work done in Nebraska showed that tilling a soil can result in a 0.5 to 0.75 inch loss of soil moisture for each tillage pass. When soils are already dry, additional loss of moisture can lead to non-uniform germination and emergence. A joint research project completed by University of Minnesota and North Dakota State University shows different soil moisture contents under different tillage practices. Here are a few points to consider as we slide into planting season.

1. If you did fall tillage and left a rough surface, then yes, you should do spring tillage to provide an adequate seedbed for planting. Tillage should be as shallow as possible to obtain a good seedbed and should be done as close to planting as possible.
2. If you did fall tillage and left an adequate soil surface and seedbed, you may not need to do any spring tillage. You can easily plant into existing conditions by adjusting your planters to manage residue. Leaving residue in place will reduce evaporation from the soil and reduce soil particle detachment when we do receive rain, thereby, reducing soil crusting, and allowing for more water infiltration. 
3. If you didn’t do any fall tillage, you can plant directly into existing residue, allowing the existing residue to reduce evaporation from the soil by acting as a mulch.  This may require adaptation of your planter to manage the residue.  See the ICM blog, Considerations for No-Till and High Residue Fields in a Predicted Dry Season.

Early Cover Crop Termination

Another consideration for soil moisture management is early cover crop termination. Cereal rye and other over-wintering cover crops have broken dormancy early this year due to favorable temperatures. This means they are actively growing and pulling up soil water.  You may want to consider terminating cover crops earlier than originally planned to conserve soil water.  One terminated, the decaying cover crop will serve as a mulch or barrier and reduce soil evaporation.  For more information on terminating cover crops, visit the ICM blog, Cover Crop Termination Review for 2023.