In agriculture, soil compaction can be a major issue that can prevent crops from developing properly. Compacted soil not only makes is harder for plant roots to grow and spread, but it also reduces the soil’s ability to absorb water, which can lead to runoff and increased soil erosion. There are several ways soils can become compacted, including from issues with water levels in the soil to heavy equipment or large animals moving over it.
What is Soil Compaction?
Regardless of the cause, soil compaction is generally defined as a reduction is pore space between soil particles, making the soil denser, with less large pores and an overall decrease in pore volume. When the soil becomes dense and less porous, water and air are less able to penetrate downwards through the soil, making it difficult for roots to grow. While dense, compacted soils are desirable for some engineering purposes (you wouldn’t want to build a house on top of loose, unstable soil), they are generally not desirable for agricultural purposes. In agriculture, growers usually experience soil compaction in 3 main areas: surface compaction, often caused by wheel tracks from large machinery, plow or tillage pans, which occur just below the plow depth, and deep, or subsoil compaction which is also caused by very large, heavy machinery moving over the surface soil.
What Causes Soil Compaction?
There are three main causes of soil compaction, and one of them is related to nature. The impact of evaporated rainwater on soil can cause the soil to crust at the uppermost layer, which makes seed emergence and establishment difficult. While the rain is essential for plant growth and development, the evaporation process can leave the surface soils hard and cracked. Another form of compaction, called consolidation, is also caused by water evaporation. As the water evaporates from the soil, it creates a suction effect that pulls the soil particles together, reducing the amount of space between the soil particles. Tillage operations can also cause soil compaction below the depth of the plow. Known as tillage pans, these areas of compacted soil are usually only around one to two inches thick and do not necessarily have a detrimental effect on crop production. This type of soil compaction can be treated by using varying depths of tillage over time, which helps to break up the compaction and reduce further compaction. Lastly, wheel traffic. Wheel traffic from large machinery like tractors and combines can greatly compact the soil. Often found in wheel tracks, this type of compaction can affect the first couple of feet of soil, depending on how large the moving equipment is.
How Does Soil Compaction Affect Plant Growth?
While it may seem that soil compaction only has negative effects on crop production, there can be some benefits as well. Soils that are slightly compacted can speed up the seed germination process as the compaction allows for better seed-to-soil contact, which can help increase crop yields as more seeds successfully germinate. This benefit decreases however as compaction increases. Corn planters are designed to provide a little compaction to the soil with planter-mounted packer wheels that apply moderate compaction after seed placement. This gives the seed more contact with the soil, increasing the chances of successful germination. The role weather plays in soil compaction and plant growth can also affect crop yields. In dry weather, soil compaction can lead to drought-stressed, stunted plants as the roots struggle to grow and spread. Alternatively, wet, compacted soil can also decrease crop yields as the excessive water decreases soil aeration while increasing soil denitrification. Excessive moisture levels in the soil can also create ideal conditions for certain crop diseases to develop.
Consequences of Soil Compaction on Crop Production
There is no doubt that very dense, compacted soils are difficult to grow crops in, so as one consequence of soil compaction, yields can be greatly reduced. In order to grow healthy crops, the soil needs to allow the plant roots to grow without too much resistance. When root growth is restricted, the plant has less ability to uptake both water and essential plant nutrient elements, which leads to stunted growth and poor yields.
How to Reduce Soil Compaction
As mentioned above, one of the most common causes of soil compaction is wheel traffic. As the weather is impossible to control and as the timing for seeding, spraying, and harvesting are important, farmers sometimes find themselves working in fields that are wet and muddy. When large equipment moves over the surface of wet soil, air is displaced and removed from the spaces between soil particles causing compaction. As the soil dries out, soil consolidation and crusting can happen as well. If possible, it’s better to wait for the soil to dry out until it is less susceptible to compaction. Keeping machinery tires properly inflated and reducing axle load can also help, as well as using the right equipment for the job. Taking a few extra precautions when working on wet soil can greatly improve the quality and yield of your crops.