EFFECTS OF TILLAGE AND STUBBLE MANAGEMENT ON THE STRUCTURE OF A SWELLING SOIL

Abstract

Summary A method, described previously, is used to quantify the macrostructure within the surface layers of swelling soil. Dissimilarity coefficients are defined and used to quantify soil structural differences resulting from different treatments. Structural differences over small increments in depth are resolved. Effects resulting from different tillage and stubble management practices are distinguished. Differences resulting from burning or retention of stubble had at least as great an effect as tillage practice on the void and aggregate size distributions. However, tillage increased the macro‐porosity. The structures of two mechanically‐prepared seed beds are compared with the structure of soil on tillage and stubble management trials where seed beds had not been prepared. It is shown in Appendix I that the structures measured on the two sections through each impregnated soil sample are essentially independent. A method is presented in Appendix II for converting the structural transition probabilities at unit spacing ( e.g. 0.5 mm) to transition probabilities at double spacing ( e.g. 1.0 mm). This enables results from different sources, which have been measured on the two scales, to be compared.