Vertical and lateral variations of soil immobile water fraction in two tillage systems
Résumé
A better understanding of water and solute movement in soils is crucial to limit the environmental impact of agricultural practices. Th e objective of this study was to compare preferential fl ow in soil due to mobile-immobile water partitioning at various depths in two tillage systems. Since 2000, an agricultural fi eld has been divided into two plots cultivated using two tillage systems: conventional tillage with moldboard plowing (CT) and conservation tillage with disk harrowing (MT). Th e hydraulic conductivity at −1-cm matric head, K−1, and the immobile water content of diff erent soil compartments identifi ed with a morphological description in each tillage system were measured using tension disk infi ltrometers and a Br− tracer. Measurements were performed in 2005. A higher spatial variability of K−1 was observed in the CT plot than in the MT plot. Th e immobile water fraction at -1-cm matric head under CT ranged from 0.039 to 0.947 with a mean of 0.524 (CV = 55%). Under MT, the immobile water fraction ranged from 0.216 to 0.882 with a mean of 0.631 (CV = 30%). Soil structure variation due to plowing was found to signifi cantly infl uence the soil immobile water fraction under CT, while it was more uniform under MT at the 1-m observation scale.