Originally published in Purdue Pest Management & Crop Production Newsletter (17 May 1996)

Soil Management Issues in a Wet Planting Season

Gary Steinhardt, Agronomy Dept., Purdue Univ., W. Lafayette, IN 47907-1150

1. Has excessive moisture impacted the soil?

Yes. Ponding from excess water may be particularly troubling in terms of soil properties. Ponding creates a set of layers in the soil that appear very much like compaction in the soil and early root growth often follows the weaker path between these layers. The plants can have many of the problems that we associate with compaction from tillage or traffic. Seep spots in the field are another difficulty that we associate with excessive moisture. These areas cause problems nearly every year but seem particularly troubling when time is so short as is the case this year. These seeps are most often associated with the changes in soil parent material that is so common in Indiana. The loess(silt) that covers the northern two thirds of the State provides us with fertile soils that store considerable amounts of plant available water but also leads to seep spots on side hills. These areas should be avoided if severe. This makes planting less efficient but these areas can be so wet that no good will come of trying to go through.

2. Are we facing more water erosion than we have had in recent years?

Yes. This answer must be tempered with the fact that there has been a revolution in the way that farmers farm. Far more residue covers the land than has been true since the days of sod rotation. This residue has the capacity to protect the soil under most conditions. We may have exceeded those conditions in many places and find that the residue itself has been rearranged into rows that follow drain ways in the field. These clumps of residue may cause difficulty in planting and those that have residue moving attachments for the planter may find them useful in these situations.

3. How quick can I get into my fields to plant?

Drying of the soil will depend on a number of factors. The natural drainage of the soil and the texture are two major considerations in making an estimate. We would expect well drained soils to dry more quickly because they will normally have less water in the soil profile. This is not always the case, in the spring many well drained soils will have a saturated profile but just not for as long a period as the less well drained soils. Sandy soils will commonly dry more quickly because they can not hold as much water as the finer textured soils. Sandy soils can be poorly drained if no outlet is available for the water. There is to my knowledge no means to estimate how long this process of drying will take on a given landscape. Frequent observation is the only real method and that is to a degree subjective.

4. How do I decide that it is dry enough to plant without causing additional problems?

Decisions that a soil is dry enough are made based on a number of criteria. The feel of the soil is usually part of this but it is difficult even under the best of circumstances. The problem is that field capacity (the soil moisture after gravitational water has been removed) is exactly the point at which you can drive onto the field without getting stuck and it is exactly the soil moisture content when the soil will be compacted to the highest density. It is probably not practical to wait for ideal conditions. This would most likely take too long. Farmers may have to look at this as a matter of relative risk. If the planter is operating correctly and doing a decent job of planting they may have to accept some risk of compaction and the damage that it may or may not do to yields. This is not an easy question. Weather as we know from our research plays a great part in determining the impact of soil compaction. If we are lucky it is minimal if not then there can be a measurable effect. If crop difficulties develop after planting under these moist conditions then soil compaction must be considered in an analysis of the possible problems. There are simply no easy answers and no " magic bullet." The effects of compaction as we have documented can last for more than one season so we must be prepared to examine soils for these problems in the future even if we avoid damage in this difficult period.

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