A MODEL FOR ESTIMATING CROP YIELD LOSSES CAUSED BY SOIL COMPACTION

A computerized empirical model for estimating the crop yield losses caused by machinery-induced soil compaction and the value of various countermeasures is presented, along with some examples of estimations made with it. The model is based mainly on results of Swedish field trials, and predicts the effects of compaction in a tillage system that includes mouldboard ploughing. It is designed for use at farm level and predicts four categories of effects: (1) Effects of recompaction after ploughing. The calculations are based on the wheel track distribution in the field and the relationship between "degree of compactness" of the plough layer and crop yield. (2) Effects of plough layer compaction persisting after ploughing. Crop yield losses are estimated from traffic intensity in Mgkm ha-1 (Mgkm = the product of the weight of a machine and the distance driven), soil moisture content, tyre inflation pressure and clay content. (3) Effects of subsoil compaction. The calculations are similar to those presented under point (2), but only vehicles with high axle load are considered. These effects are the most persistent. (4) Effects of traffic in ley crops. The estimations are based on wheel track distribution, soil moisture content and several other factors.