Near-saturated hydraulic conductivity measured on a swelling silty clay loam for three integrated weed management based cropping systems

Equipe AgroSup (EA) Pôle ECOLDURInternational audienceIntegrated weed management (IWM)-based cropping systems included diversified agricultural practices (i.e., diversified crop rotations with diversified sowing dates, false seed-bed technique, delayed autumn sowing and mechanical weeding) to reduce the dependence to herbicide, some of these influencing soil hydraulic properties. The aim of our study was to assess the vertical and annual variability of the near-saturated hydraulic conductivity K(h) for IWM-based cropping systems. The three cropping systems considered were classified as no-till cropping system S2 and moderate to intensive tillage cropping systems S4 and S5. The soil of cropping systems was a well-structured silty clay loam soil with shrink-swell behavior. Soil was studied at three depths (10, 20 and 50 cm) and during two or three annual measurement campaigns. The tension disc infiltrometer device was used to measure steady state flows at −5, −3, −2 and −1 cm pressure heads for all the cropping systems, horizons and measurement campaigns. The steady state flows were used to derive K(h) at each pressure head applied as well as the effective macroporosity. No vertical variability was found on K(h) for any of the cropping systems due to well-developed porosity networks throughout the soil profiles, confirmed by comparable average effective macroporosity values between all soil horizons and with the presence of non-equilibrium flows and water repellency behaviors at all soil horizons. The consequences for modeling the water flow of well-structured clayey soil imply taking into account comparable values of K(h) for all soil horizons and considerably simplifies the work of modelers. The no-till cropping system S2 presented time-invariable K(h) under different θi, which was in agreement with the equally time-invariable macroporosity results. For cropping system S4, K(h) variability was found to be in agreement with θi variability, which was confirmed to be inversely correlated to K(h). As expected, the K(h) of cropping system S5 was found to be stable through time, in agreement with its comparable θi Moreover, our results allowed confirming the temporal stability of no-till cropping system S2 compared to superficially tilled cropping systems S4 and S5