How do morphological characteristics of hillslope control water movement in the saturated and unsaturated zone

Prediction of vegetation effect on soil moisture is a central feature of soil vegetation models. At hillslope scale, soil moisture is controlled by land use, soil characteristics, topography, stream and groundwater proximity etc. This paper aims to evaluate the importance of morphological characteristics on spatial soil water storage variation and their effect on water movement at hillslope scale. Five hillslopes were selected according to a set of morphological characteristics i.e. hillslope length, slope, drainage area, degree of convexity and concavity, convergence criteria, stream order. Soil characteristics and moisture were measured. Morphological characteristics were extracted from high resolution LIDAR. A physically-based, finite element model using Richards equation for variably saturated flow was implemented. Simulations were carried out for five hillslopes to evaluate the effect of morphological characteristics. Model sensitivity to soil hydrodynamic properties as well as hillslope morphology criteria was analyzed. Results obtained show that a spatial organization trend of morphological characteristics, especially soil thickness and porosity varies with topography and defines soil water capacity which seems to be a major factor on water availability for root uptake. The relationship between soil characteristics, hillslope morphology and water storage variation is a key to understand groundwater recharge amount control. Our results suggests a new perspective for the main morphological characteristics to consider for water movement modeling

Retour d’expériences sur le semis-direct sous couvert sans glyphosate

National audienceCet article présente les travaux menés dans le cadre du projet ENGAGED. Ce projet a été initié en 2016 à la demande d'agriculteurs normands qui pratiquent le Semis Direct sous Couvert Permanent de légumineuses pérenne (luzerne, trèfle) dans des rotations avec colza, blé, orge. Il vise à construire des systèmes de cultures basés sur la couverture permanente avec des Indicateurs de Fréquence de Traitements (IFT) herbicide inférieur à 1 sans avoir recours à l’utilisation du glyphosate. La faisabilité technique et les performances économiques des systèmes de cultures seront évaluées. La première phase de ce projet consiste à identifier les leviers existants pour gérer les adventices sous un couvert permanent et les pistes innovantes à approfondir. Des essais en plein champs sont mis en place pour acquérir des connaissances sur la dynamique des adventices qui se développent en concurrence avec un couvert permanent. Toutes ces informations sont ensuite mobilisées lors d'ateliers de co-conception à destination de conseillers et d'agriculteurs avec deux objectifs : communiquer les résultats du projet et les mobiliser pour d'autres situations de production. This article presents the project ENGAGED, initiated in 2016 at the request of Norman farmers who practice direct seeding under permanent cover of perennial legumes (alfalfa, clover) in rotations with rapeseed, wheat, barley. It aims to build systems of cultures based on permanent coverage with a small amount of herbicide (IFT herbicide <1) without the use of glyphosate The technical feasibility and economic performance of cropping systems will be evaluated. The first phase of this project consists of identifying the existing levers to manage weeds under a permanent cover and innovative ways to deepen Field trials are also being set up to gain knowledge of the dynamics of weeds that develop in competition with permanent cover. All this information is then mobilized during co-design workshops for advisers and farmers with two objectives: to communicate the results of the project and to mobilize them for other production situations