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Fluid Journal : Fluid Journal 1999-2001
3 Fluid Journal Winter 2001 Tire slippage. Pulling large implements with too small a tractor can create tire slippage. As drive tires slip, the weight of the tractor plus the shearing force of the tires can drive compaction deep into the subsoil. Extra trips. Many fertilizer programs are designed so that a separate operation is used to apply each nutrient. Whenever possible, combine fertilizer application with tillage operation when you apply other crop protection products. Low organic matter. Organic matter promotes coarser and stronger soil aggregates. At lower moisture levels, aggregates stick together to maintain larger pores than if broken down into individual particles. Organic matter is also much less dense than the mineral components of the soil. Prairie soils with five to eight percent organic matter are less likely to compact than soils with only one to four percent organic matter. The costs The costs osts The costs The costs Impeded root growth. Generally, roots cannot grow into a soil with a strength above 270 lbs/in2. Minnesota data in Table 1 show various soils strengths under different tillage methods. On plowed ground, soil strength is not high enough to restrict root growth. But look what happens when tillage is reduced. It approaches a level that can restrict root growth. Under spring disk at 4 inches, where soil strength is 280 lbs/in2, a hard pan develops that is strong enough to restrict root growth. Under no-till, it develops high soil strength all the way down. Reduced fertilizer efficiency. In Iowa State University tests, compaction reduced nitrogen uptake 30 percent, potassium uptake 70 percent, magnesium uptake 20 percent, and calcium uptake 10 percent. Compaction reduces oxygen levels in the soil causing denitrification. Nitrogen is lost by conversion into gaseous forms that are released into the atmosphere. Decreased soil porosity. Water infiltration into the soil is limited. Reduced yield. In Purdue In Purdue n urdue InPud In Purdue University University U i rsity nive s ty University tests (Figure 3), the corn plot yielded 200 bu/A where there was no compaction. Where the crop was subjected to severely compacted soil during the first year, yield dropped to less than half, raising the cost per bushel. Freeze and thaw cycles eased the severity in subsequent years. Preventing Preventing Preventing Preventing Preventing Don't use disk. Since disk blades create a hard pan, field cultivators or combination tillage tools are preferable. Another advantage of these tools is that they can be operated at faster speeds, thus reducing compaction. Use lighter equipment. This includes avoiding giant harvesting equipment that can cause compaction in a wet fall. Use wider tires such as flotation or dual tires that spread compaction out horizontally at a shallower depth. Subsoil. Such a practice is effective if done when soil is dry enough to shatter the layer. It must be deeper than the compacted layer. Ban livestock from unfrozen fields. They can compact fields into a concrete mass. Build organic matter to bind aggregates together to promote good soil structure, which prevents soil compaction. Such aggregates are not easily broken down by secondary tillage or traffic.
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