A model for agricultural soil compaction

The compactness of agricultural soil may vary greatly during a crop season due to tillage and other machine operations that apply forces to the soil. Thus, an adequate model for agricultural soil compaction must be capable of predicting soil density over a wide range of compactness, from a very loose state to a very compacted state. The traditional logarithmic model does not adequately predict soil density at low levels of compactness and low stress levels. A three-parameter multiplicative model of soil compaction is proposed. This model satisfies certain boundary conditions for natural volumetric strain at low and high stress levels which are not satisfied by the traditional model. The model was fitted to hydrostatic compression test data for two agricultural soils, a sandy loam and a clay. The model was capable of predicting soil density at low stress levels with less error than the traditional model. Data from three levels of moisture content of the clay showed that all three coefficients of the proposed model were influenced by moisture content.