Effects of integrated weed management based cropping systems on the water retention of a silty clay loam soil

• Soil water retention was studied for 5 cropping systems after 12 years of differentiation.
• Differences in water retention were found between cropping systems.
• Results for repacked soil samples were related to clay and organic C variability.
• Results for undisturbed soil samples were related to IWM practices.
• Intensive superficial tillage increased water retention.

Integrated weed management (IWM) based cropping systems employ a combination of agricultural techniques to manage weed communities. However, the effect of such a combination of agricultural techniques on soil hydraulic properties has received little attention. Main objective of our work was to evaluate the soil water retention of the superficial layer (3–15 cm depth) of 5 cropping systems of which 4 were based on IWM principles. Firstly, the effects of natural variability of soil properties on soil water retention were first evaluated for the 5 plots of the experimental site and then the effects of agricultural practices were investigated. To isolate the effects of soil properties from the effects of soil structure induced by agricultural practices on water retention, two different sample treatments (repacked and undisturbed samples) were set up. Significant differences between cropping systems in soil water retention were found for each soil sample treatment. For the repacked soil samples, significant differences were related to the slight spatial variability of clay content and the initial organic C gradient existing between cropping systems, whereas for undisturbed soil samples the significant differences observed were related to the combined effects of agricultural practices and higher clay and organic C contents. The highest water retention of undisturbed soil samples was found for the IWM-based cropping system without any herbicide and with a high frequency of shallow agricultural operations per year while the lowest values were found for the conventionally tilled cropping system. For the no-tillage cropping system low water retention values were found close to saturation, while high water retention values were found at the dry-end of the water retention curve. In conclusion, our work shows that, in the case of silty clay loam soil with shrinkage/swelling behavior, high clay and organic C contents and very frequent superficial tillage increased soil water retention.