Update from the Field: Maximize Yields, Reduce Compaction
Posted by Dave Dyson, Agronomist on March 12, 2020
As the days get longer and spring approaches, the itch to get out in the field becomes more overpowering. According to the NOAA, the outlook through April calls for temperatures near or slightly above normal with precipitation above normal (Figure 1). Excessive rainfall and an itchy trigger finger on spring fieldwork, due to a late and wet fall, spells trouble for the health of your soil.
Figure 1: Maps from the NOAA predicting warmer and wetter weather conditions heading into April.
Let’s talk about soil compaction and why we are so worried about the health of our soil. Soil compaction is most likely to occur when soil moisture is at or near field capacity, when soil pores are filled with equal amounts of air and water. Under these conditions, aggregates can be "lubricated" by water and readily reposition themselves through the air spaces under heavy traffic and farm equipment.
Several factors can indicate soil compaction, including stunted plants, slow infiltration, ponds of water, high surface runoff, soil erosion under normal or light rainfall, and evidence of poor root system establishment. This poor root development can cause a crop to have a nutrient deficiency, and compaction can result in reduced potassium uptake. According to Iowa State University, the impact on yield has been reported to be as much as 10 to 20 percent. Changes in the soil's physical properties alter the ratio of water to air in the soil. Plant roots require air as well as water to develop a healthy root system.
The most devastating and longest lasting compaction is deep sub-soil compaction. The chief reason for sub-soil compaction is high axle loads driven over saturated soils. The definition of an axle load is the total load supported by one axle, usually expressed in tons or pounds. Farm equipment with high axle loads will cause deep compaction. Deep sub-soil compaction can only partially be alleviated with sub-soil tillage, and at considerable cost. Freezing/thawing and drying/wetting cycles have been shown not to improve soil compaction at this depth. Research from Penn State University shows yields can be reduced by up to 15% with this type of compaction and will last up to 12 years. Sub-soil compaction should be avoided at all cost. Soils that are near or at their water holding capacity will act like a hydraulic ram and will drastically increase the chances of both surface and sub-soil compaction.
In conclusion, compaction, no matter how slight, can cause a yield reduction and should be avoided. Keeping loads in the field as light as possible and driving on travel lanes will help in the majority of cases. Keeping axle loads under seven tons will help prevent sub-soil compaction (Figure 2). Driving on saturated soils can lead to long term damage and yield reduction, so remember to stay off the soil during wet conditions. Deep soil compaction now will restrict the plant’s roots from absorbing water and nutrients in future years.
Figure 2: Research from Penn State University indicates axle loads of 10 tons or more have a significant increase in sub-soil compaction.
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Dave Dyson is a regional agronomist for The Andersons’ Farm Centers which are located throughout Ohio, Michigan, and Indiana. He is an Indiana native and grew up on a dairy farm in Miami County. A graduate of Purdue University with a degree in Crop & Soil Science, Dave has a deep knowledge of various agronomic topics and is committed to helping growers improve their crops. If you have any questions, Dave can be reached at david_dyson@andersonsinc.com.
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