Wet Harvest Conditions

There were some places in the county that received over four inches of rain last week within 2 days, thus causing some very wet field conditions making it difficult for harvest. I heard that there were some minimal soybean losses and some dryland corn also down, but for the most part it sounds like we dodged the bullet and things could have been much worse. With all of the rainfall and some damaged crops, producers are most likely anxious to get back in the field. There are a few things one should consider however to determine if it’s worth harvesting while soil conditions are still wet. This week I’ve chosen to use some excerpts from an article, extension engineer Paul Jasa shared in a previous CropWatch article for farmers to consider.

As I write this, it will most likely be atleast a week before some fields dry up enough. Remember that if you leave ruts on the soil surface; compaction occurs below them and that compaction can impede the crop’s roots next season and increase runoff because of reduced infiltration. Compaction is the loss of pore space between soil particles and occurs when that space is squeezed out of the soil and reappears somewhere else, such as in the form of a rut. If a rut wasn’t formed, there was enough soil structure present to support the weight without causing additional compaction.

Jasa discusses the importance of controlling traffic and compaction and says that eighty to 85 percent of soil compaction damage is done with the first pass of the tires. If additional passes are made on the same traffic lanes, little additional compaction occurs. Because once a traffic lane has been driven on and the soil has been firmed up, subsequent passes have little effect on the amount of compaction. By using the same traffic lanes year after year, the soil structure and water infiltration in the untrafficked areas greatly improve.

Controlled traffic lanes improves traction, soil load bearing, and timeliness of planting and harvesting operations while minimizing potential yield reduction from compaction. Compaction is managed, not eliminated, and the area subjected to compaction is minimized. The concept is to separate traffic zones from root zones. Controlled traffic keeps compaction where it is less detrimental to root development and uptake of nutrients and water. Fertilizer placement and furrow irrigation practices can be modified as these traffic zones are established and the traffic lanes are known.

To minimize wheel compaction at harvest time, grain carts should be following the same tracks as the combine. A lot of grain cart drivers think they should move over a few rows and spread out compaction, but this will only compact more of the field. Likewise, grain trucks shouldn’t be driven in the field as the axle loads and tire pressures are not suitable for soils.

If ruts are cut at harvest, wait until the soil is dry to smooth them out to avoid causing additional compaction. This smoothing operation may be a light tillage operation next spring before planting. Deeper tillage in the spring will usually cause more compaction as the soil is wet and the tillage will break up soil structure.

To fracture the compaction in the ruts from this year’s harvest, a producer may have to wait until next fall before the soil is dry enough. However, often the compaction in the bottom of the ruts extends deeper into the soil than most producers will be able to till. This is a case where prevention is far more effective than the cure. It’s best to build soil structure and not drive on wet soils if possible. Controlled traffic, no tillage, and cover crops will all help build soil structure and reduce compaction concerns

(Source: Jasa, Paul. Avoiding Compaction at Harvest, October 13, 2006)

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