Changes in soil structure following passage of a tracked heavy machine

Golf course construction with a tracked heavy machine (scrapedozer) involves soil treatment with a high risk of compaction, especially when the machine drives directly on subsoil. The aims of this study were i) to use a coupled physical and hydraulic approach to better evaluate the effect of soil deformation on soil structure, parameterized as bulk density (BD); penetration resistance (PR); pore size distribution (PSD), Brilliant Blue (BB) tracer distribution and infiltration capacity, following passage of the scrapedozer during golf course construction, ii) to evaluate the effect of initial soil conditions on changes in soil structure and iii) to provide comprehensive recommendations on the use of such heavy machines in golf construction operations. Special attention was paid to subsoil below 0.30 m since the topsoil layer is normally reconstructed after scraping. The compaction effect was more evident on wet trafficked plot, as clearly confirmed by the results of BD, PR and PSD (decrease of mesopores) while less pronounced effect was observed in moderately dry soil (MD) as shown by the PR and BB. The non-significant decrease in macropores on both plots between 0.30 and 0.40 m, on the one hand, and the discrepancy between BD and PR in indicating soil compaction for same soil layers on the other hand, can be attributed to the heterogeneity and/or to the cracking effect, depending on initial water content. In fact, soil cracking was observed in MD and may be attributed to the existence of microcracks visible at the soil surface which promote cracking at deeper levels. Although there was a notable increase in the PR in the topsoil at depths between 0 and 0.10 m for both trafficked plots, no significant increase was shown at this depth. This result may be attributed to the steel tracks that help to loosen the topsoil layer and consequently to diminish the effect of soil compaction. Based on the observed structural deterioration, the use of a lighter machine is recommended under wet soil conditions and also when the topsoil is scraped.