Title : Effects of Soil Compaction
Visit Count : 2030 Time(s)
Upload Date : 8/4/2016 - 4 Year(s) ago
Category : agricultural technical notes
Thursday, August 4, 2016
Visit Count : 2030 Time(s)
Upload Date : 8/4/2016 - 4 Year(s) ago
Category : agricultural technical notes
Most are already aware that compaction effects on yields can be severe. Studies done in Indiana and Wisconsin prove as much. On Wisconsin silty clay soil, corn yields were reduced as much as 51 bushels per acre on compacted soil. In Indiana, yields were decreased by 48 bushels per acre in moderately compacted soil. The question more commonly asked is "why does compaction effect yeild". The answers can be found when we consider restricted water movement, limited aeration, and inhibited root development in a compacted soil profile.
1. Water Movement through the soil profile
"Heavily compacted soils contain few large pores and have a reduced rate of both water infiltration and drainage from the compacted layer. This occurs because large pores are the most effective in moving water through the soil when it is saturated. Studies done on Hoytville soil in northwest Ohio showed that normal water movement through the soil profile of 4.8 to 14.4 inches per day was reduced to just 1.4 inches per day in compacted soils due to tillage and traffic.2 When soil is compacted, water movement through the soil profile is slowed. This often causes excess water to be present, which means more water on the surface, more runoff, increased erosion, and longer drying times. This will lead to delayed planting and harvesting resulting in a decrease in crop harvesting.
2. Aeration in compacted Soils
The presence of excess water within the soil profile also can cause aeration problems. The excess water will fill pore space that would normally be filled with oxygen necessary for good seed germination and plant growth. Water need not always be present for aeration problems to occur. Simply compacting the porous space between soil particles is enough to slow down the exchange of gasses within the soil and cause aeration-related problems.
3. Root Development in compacted soils
Root development can be restricted simply because soil strength, or "the ability of soil to resist being moved by an applied force". Roots systems in a compacted soil profile must exert more force to break through compaction. Shallow root systems and malformed roots develop due to the excess effort needed to grow in compacted soils. Roots often will go down to a compacted soil layer and then spread horizontally, instead of breaking through the compaction and continuing down through the soil structure. The root is prohibited from using the moisture and nutrients that are below the compacted layer. Dense soils will not provide adequate moisture and nutrients for plant roots to grow well. With crops that are grown underground, such as potatoes, tuber size can be reduced."In Minnesota, potato yields were reduced 35 percent becuase of wheel traffic compaction restricting the development of tubers".
4. Other Problems found in compacted soils
In addition to the problems caused directly by compaction, other problems are heightened by the presence of compaction within a soil structure. Disease and low nutrient supply due to reduced root distribution are two challenges that producers will face more often with compacted layers in their fields. When compaction causes excess water to appear in a field, denitrification also occurs from the loss of stored nutrients within the soil.
• causes soil pore spaces to become smaller
• reduces water infiltration rate into soil
• decreases the rate that water will penetrate into the soil root zone and subsoil
• increases the potential for surface water ponding, water runoff, surface soil waterlogging and soil erosion
• reduces the ability of a soil to hold water and air, which are necessary for plant root growth and function
• reduces crop emergence as a result of soil crusting
• impedes root growth and limits the volume of soil explored by roots
• limits soil exploration by roots and decreases the ability of crops to take up nutrients and water efficiently from soil
• reduces crop yield potential
Compacted soil will restrict root growth and penetration into subsoil. This situation can lead to stunted, drought-stressed plants as a result of restricted water and nutrient uptake, which results in reduced crop yields. In wetter than normal years, soil compaction can decrease soil aeration and lead to the increased loss of nitrate nitrogen by denitrification, which is the conversion of plant available nitrate-nitrogen into gaseous nitrogen forms that are lost to the atmosphere. This process occurs when soils are in an anaerobic condition and soil pores are mostly filled with water. Reduced soil aeration can affect root growth and function, and lead to increased risk of crop disease. All these factors result in increased crop stress and yield loss.
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