Biological Systems Engineering

 

Date of this Version

3-1989

Citation

SOIL RESOURCE MANAGEMENT E-1, Compaction Issued March 1989, 12,000

Comments

Copyright 1989 U.S. Department of Agriculture

Abstract

Nature has some built-in processes that reduce soil compaction. They include cycles of wetting and drying, and freezing and thawing.

In the last 20 to 30 years, farming practices have changed drastically. These farming changes have made it more difficult for nature to rejuvenate the soil environment to an optimum condition for crops. Performing field operations on wet soils, using multiple field operations to grow the same crop continuously, and eliminating meadow crops from crop rotations contribute to more extensive and deeper compaction.

Each farmer has the opportunity to make decisions that can keep soils from becoming compacted.

Adoption of management strategies to minimize soil compaction, such as controlled traffic, may require a bit of planning; staying off wet soils may require little planning. If you have soil compaction that is limiting production, measures such as deep tillage might be needed to help loosen and shatter the compact soil layer.

Management Strategies

Stay Off Wet Soils. Compaction of any soil is greatest when the three to six inch soil depth is near field capacity. Field capacity is only a guideline to identify optimum moisture conditions for compaction.

Clay content and organic matter content also influence the compactibility of each soil. The water content of a soil can be determined using the feel-and-appearance method (NebGuide 083-690).

You also may check the soil water content by digging up a portion of soil from the three- to six-inch depth. Mold the soil in your hand and drop the soil ball onto a hard surface. If it does not break or crack on impact it is too wet for field operations.

Perform field operations in your driest fields first. This allows more drying time for fields that tend to remain wet.

Some years field operations may have to be conducted when the soil is near field capacity to remain timely. Minimizing the axle load and increasing tire size will help reduce deep compaction in these situations. The larger tire will compact more of the soil surface, but the lower pressure will help reduce the depth to which the high compactive forces will penetrate.

Reduce Tillage. Tillage for many years contributed to the breakdown of soil structure. Each individual tillage operation using a disk, chisel, sweep, harrow, moldboard plow or combination of these tools breaks down soil structure by compressing and breaking soil aggregates. A soil aggregate is a mixture of clay, silt, sand and organic matter bound together to resemble a crumb. Soil aggregates are necessary for good air and water movement and root growth. Soils that have been tilled are more susceptible to compaction than are soils receiving little tillage.

Tillage systems with a reduced number of operations leave greater amounts of residue on the soil surface. This surface residue helps prevent surface sealing, a form of compaction, by intercepting raindrops before they hit the soil surface.