Temporal variability of the physico-mechanical properties of a volcanic ash soil under conventional tillage

Abstract

In order to determine the effect of soil tillage and natural processes of re-structuration that occur in a Andisol during a wheat growing season, this study evaluated the temporal variability of the physico-mechanical properties of a Andisol under wheat crop. The assesment was carried out using both laboratory and in situ measurements to compare the registered values with those described in the literature as critical values for correct plant grow. The laboratory measurements (precompression stress, cohesion, air conductivity and bulk density) required undisturbed samples which were collected in 110 cm3 cylinders, at 5 cm depth, 10 times during the crop development. For the field measurements, the evolution of the moisture content and penetration resistance of the soil, as well as rainfall and soil temperature were recorded.
The soil tillage and the wetting and drying cycles that occurred during the study generated temporal changes in soil structure, which were expressed in the evaluated properties. Soil tillage, caused a decrease in the values of mechanical strength and bulk density, and increased the air conductivity and air capacity. After the traffic of the roller, the opposite effect was observed but without reaching the values of the initial state of the soil. Those values were reached during some events in the summer period, after several wetting and drying cycles. After grazing, no changes in the studied properties were observed. Only air conductivity exceeded the critical values described in the literature, however, due to the dynamic nature of soil structure, the soil was able to recuperate their functional attributes due to the high resilience of soils derived from volcanic ashes.