CC342 Soil Compaction... Fact and Fiction Common Questions and their Answers

. What causes soil compaction? Compaction occurs when soil particles move closer together because of external forces exerted by humans, animals, equipment and water droplets. It can be found on the soil surface and at almost any depth. Compacting soils leads to conditions that are less than optimum for crop growth, soil water management and efficient use of agricultural chemicals. 2. How does soil compaction develop? Soil compaction can be influenced by several factors, but tillage of wet soils is the most common practice that causes compaction. The amount of water in the soil has more effect on compaction than any other factor. Research findings indicate that 80 percent of soil compaction from wheel traffic occurs on the first pass. This is why it is important to avoid any field operations when soil is wet. 3. How much compaction is there in Nebraska? Compaction has been found from Falls City to Ainsworth and from McCook to Blair. In general, about 40 percent of the fields surveyed showed compaction in the top 12 inches of soil. Of the fields with compaction, about 10 percent would be expected to cause yield reductions. 4. I thought freezing over the winter got rid of compaction? Freezing and thawing will help to reduce compaction in the surface. soil. It will be most noticeable when there are several freeze-thaw cycles during the cold months. Below about 5 inches, the soil only freezes and thaws once during the year. This is not enough to break up deeper compaction. 5. My soils dry and crack in the summer. Does that help compaction? Most definitely. Those cracks penetrate compacted layers and provide channels for roots and water movement into soil. 6. I farm some steep land. Will compaction promote erosion? Erosion and runoff are likely to occur faster on compacted soils than on noncompacted soils. Water will infiltrate the compacted zone slower than the noncompacted area. As a result, the soil above the compacted zone will become saturated more rapidly and additional water will run off sooner. Erosion may be accelerated if crops are planted up and down the hill and water is channeled into compacted furrows. 7. Does compaction affect water quality? Water quality may be affected indirectly by compaction. Compaction can increase runoff and erosion resulting in more sediment in our streams, lakes and drainage ditches. Moving into these waterways with the soil will be nitrates, phosphorus and other agricultural chemicals that lower our water quality. 8. Compaction doesn't affect my crop production on irrigated ground, does it? You bet it can ... an early symptom of compaction is slow infiltration of irrigation water. This might be seen as ponding of water on level ground or accelerated runoff on steep ground with sprinkler irrigation or extremely rapid movement of water along furrows with little infiltration. These two situations may lower irrigation efficiency and prevent the crop from receiving enough water to grow top yields. Also, if you schedule your irrigations with moisture blocks and the blocks are in or beneath a compacted zone you may get readings which are higher than the soil water environment seen by the crop. 9. My neighbor has duals on the tractor. Will that prevent compaction? Dual wheels or large flotation tires help minimize surface compaction, but have little influence on subsoil compaction. Axle weight is the major factor in deep compaction. When adding duals, the tractor weight increases by at least 1/ 2 ton for tires and hubs ... you're going in the wrong direction. By increasing the tire effective width you actually compact about twice the soil volume as compared to singles. The greatest danger with duals is the temptation to use the added flotation to work soil when it is wet. 10. When should I graze livestock to minimize compaction problems? Livestock cause compaction when they traffic soil that is fairly wet and not frozen. One good management technique is to keep livestock off fields after fall rains and until the soil becomes frozen. In the spring, keep them off when the soil begins to thaw and until the surface soil is fairly dry. 11. How does compaction affect crop production? Compaction can influence all stages of crop growth. Planting into compacted soils may decrease stand emergence which will affect yield potential. Root growth may be limited to the soil zone above the compacted layer. Water and nutrient uptake may be decreased and can result in nutrient deficiencies