COMPACTION

One of the myths about zero tillage is that it leads to an increase in soil compaction since there is no tilling of the soil to loosen it. In fact, the opposite appears to be true. Once a field is established in zero till, there is a noticeable improvement in filth. The undisturbed surface mulch and root network of a no-till field better support field equipment.

The freezing and thawing of soils in the northern Great Plains helps but isn't as effective as once thought in breaking up soil compaction. It can take several freeze-thaw cycles to off-set the compaction effects of a single season's traffic.

It is important to remember that not all soil compaction is harmful. For example, firming the soil over the seed row promotes good seedsoil contact for fast germination. The firm soil promotes root branching and formation of secondary roots and results in increased uptake of non-mobile nutrients such as phosphorous. Ideally, crop producing soils should be about 50% pore space with the space shared equally by water and air. This ideal is lost when the soil particles are squeezed together by an outside force such as tractor wheels.

With today's large equipment, there is more field work being done when soils are wet. Since wet soil is most susceptible to soil compaction, problems (under either zero tillage or conventional tillage) can be reduced by avoiding field activity when the soil is wet. This a tough decision to make when the costs of delays are considered. One of the advantages of zero tillage in the spring is reduction of that time pressure since not as many field operations are required. It stands to reason as well that with fewer passes across the field - compaction will be less.

Over the course of time in a no-till field, normal forces will break down any compaction to allow the crop greater access to the moisture and nutrients deeper in the soil.

The wheels of modern agriculture are the major cause of excessive soil compaction - the more passes with equipment, the more the soil packs.

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