A compartmental model to simulate temporal changes in soil structure undertwo cropping systems with annual mouldboard ploughing in a silt loam

A practical model of the soil structure dynamics in ploughed fields can be a powerful aid to farmers attempting to optimise their management practices . This paper describes a compartmental model that simulates the changes ove r several years in an indicator of the effects of cropping systems on soil structure. This indicator, the proportion of severely compacted clods in th e ploughed layer, was measured in two plots at the INRA Experimental Centre at Grignon (Yvelines, France), where two cropping systems produced very di fferent compaction conditions in a silt loam. The ploughed layer was consid ered to be a set of elementary compartments delimited by the wheel tracks a nd actions of tillage tools. The percentage of severely compacted clods in each elementary volume changed with time due to transfer between compartmen ts during mouldboard ploughing, compaction and fragmentation. The proportio n of severely compacted clods changed exponentially until it reached a plat eau, after about 8 years. The equilibrium values of the indicator were very similar to those measured in the experimental plots. The model was very se nsitive to the rate at which severely compacted clods were lost, probably b ecause the vertical distribution of these clods in the soil profile was not taken into account in this compartmental model. The model in its present s tate can be used to compare the effects on soil structure of various techni cal changes. (C) 2000 Elsevier Science B.V. All rights reserved.