Appreciate Dry Soil Conditions to Avoid Compaction and Correct Its Effects

The "up side" of dry soil.
Appreciate Dry Soil Conditions to Avoid Compaction and Correct Its Effects - Articles

Updated: August 8, 2017

Appreciate Dry Soil Conditions to Avoid Compaction and Correct Its Effects

Fall is one of my favorite times of the year, and we are enjoying a truly nice one so far. The beautiful sunny days, mild temperatures, and lack of rain in many parts of Pennsylvania have also caused the soil to become quite dry. This is very beneficial for the farmers who are in the field harvesting corn silage, forages, corn grain, and soybeans. Manure spreading can proceed without delay. The heavy machinery, trucks, and wagons that are used to harvest the crops and spread manure are not likely to cause significant compaction if the soil is below the plastic limit. The plastic limit is that moisture content when a soil can be molded into shapes. At that moisture content, clay platelets are lubricated and slide over each other under pressure, causing the soil to compact. Without this lubrication effect the clay particles bind together with organic matter into aggregates, which remain intact, causing pore space to be preserved. Usually we see the surface soil being compacted after harvest, but if the soil is dry only that near the surface is affected.

When you dig down with a shovel, we would expect to see that the soil beneath will be in great shape if you used practices to preserve aggregation. Additionally, very soon after you will see soil organisms like earthworms poking holes through the surface and depositing their casts on the surface.

The dry soil conditions also allow a great opportunity to alleviate surface and subsoil compaction:

First, immediately after harvest, a good compaction alleviation tool is to plant a cover crop. There is no danger of mudding the cover crops in and once a rain shower arrives to moisten the soil the cover crop will start healing the compaction that was caused, particularly at the surface. The cover crop helps sequester atmospheric carbon, the foundation of the soil food web. Thereafter, fine roots will enmesh the soil particles, root exudates will act as glues, mycorrhizae will start populating the roots and exude glomalin, and bacteria, and protozoa will multiply in the rhizosphere on the root surfaces.

Second, the dry soil also allows subsoiling to proceed if there are evidences of severe compaction in the subsoil. The best way to check this is to use a shovel and dig some 2 feet down. Study the soil profile to determine if the soil is well aggregated, and if there is evidence of compacted layers recognizable by lack of previous root growth, platy or massive structure, and lack of pore space. There can be an old plow or disk pan just below the depth of tillage or a dense layer because of heavy equipment traffic when soil moisture was plentiful. Our research has shown that without severe compaction there is no benefit of running a subsoiler through the field, so it is important to diagnose the soil to determine the need for subsoiling. Then, after subsoiling, it is important to start building the soil structure back up.

Remember that tillage never creates soil structure - it merely busts up compacted soil after which we need to use biological means to build aggregates and to avoid the soil from recompacting. The best means to do this is to plant a (cover) crop so that the roots can grow into the voids created by the subsoiling operation.

Instructors

no-tillage cover crops soil compaction soil health soil erosion soil conservation nitrogen fixation

More by Sjoerd Willem Duiker, Ph.D., CCA