Compaction that occurs below the soil surface is even more important than surface crusting. It is hard to diagnose and can cause serious yield losses if not corrected. Soil compaction can occur throughout the growing season and can cause poor crop growth.
• If the soils are wet, tillage implements can cause soil compaction just below the depth of the operation.
• Large farm equipment like tractors, manure spreaders, trucks, planters and combines can cause compaction within the root- zone, especially, when the soils are wet.
• If tillage operations are always performed at the same depth, a hardpan can develop just below the depth of tillage operation. Weight of the tillage machines can cause compression of the soil particles causing compaction.
• Wet soils, especially those with higher clay content are more likely to develop a hardpan. The depth of the compacted layer can be determined by slowly digging and moving the soil with a shovel and exposing the top of the compacted layer.
• If the roots of the plants start growing horizontally rather than vertically, it indicates that the roots are having problems in penetrating the soil because of a hardpan.
• The hardpan may be 2 to 3 inches thick. Natural cycles of wetting and drying plus freezing and thawing can help in breaking down this type of compacted layers, but if they persist, some tillage operations may be needed.
• Tillage operations for breaking the hardpan should be done in the fall when soils are dry. You may want to use a heavy-duty cultivator with spikes to penetrate below the hardpan but deep-ripping equipment is not recommended for this type of compaction.
• Try to maintain the residue on the soil surface to prevent erosion. Minimum tillage and use of cover crops that include Tillage-radishes should be helpful in reducing this type of compaction.