The Factors Affecting Soil Compaction & Water Content

Soil Compaction

• According to the University of Minnesota Extension, "Soil compaction occurs when soil particles are pressed together, reducing pore space between them." The size of pores in between soil particles plays a critical role in the health of the plants growing in the soil; more porous soil drains water more quickly and thus is more susceptible to lose nutrients to leaching and drainage. Gas exchanges between soil particles is also slowed down in more compacted soils, leading to more problems associated with a lack of soil aeration.

Causes of Soil Compaction

• Several different factors, both natural and man-made, affect how compacted a soil is. In agricultural settings, soil tends to become compacted when heavy agricultural equipment moves over the top of the soil. Wet soils appear to be more susceptible to compaction than dryer soils. Several natural environmental phenomena also contribute to soil compaction, including temperature and rate of rainfall over the soil. A failure to rotate crops sufficiently from one soil to another can also contribute to soil compaction problems.

Compaction and Water

• Probably the most significant effects of soil compaction in terms of plant growth have to do with water. Water moves in the areas in between soil particles called "pores." The density of each soil particle determines the size of these pores, and soil pore size plays a decisive role in the amount of water a certain soil can hold onto. Pore size also affects a soil's ability to take on new water from rainfall or irrigation. More compacted soils, then, show a slower rate of water drainage and of water filtration from above.

Other Considerations

• Since home gardeners typically don't drive over their gardens with tractors and other massive equipment, soil compaction is rarely a serious issue for home gardeners. Even those home soils that become compacted due to natural phenomena and cultural practices can typically be resolved by tillage (though tillage is not an effective solution for agricultural settings). Some effects of soil compaction can actually be positive; seeds are sometimes more easily germinated in compacted soils, for instance, because compacted soils increase physical contact between seeds and soil particles.