Spacial variability and agro-pedological determinisms of an herbicide fate in the surface horizon - an application to isoproturon in an agricultural catchment of the "Beauce chartraine" region, France

Julien Moeys
Abstract : Diffuse pollution of groundwater bodies by pesticides is a critical environmental issue. Approaches designed to spatially modulate the applied pesticide dose, as a function of pesticide leaching risks down the soil, seem to be appealing solutions. In a research context, such approaches require a mapping of soil hydropedologic properties and of pesticides adsorption and degradation properties, in order to be able to model molecules fate in soils. The PhD work presented here deals with the first step of such approach: the characterisation of soils properties and an herbicide molecule - isoproturon - fate properties in soil at the scale of a 2600 ha agricultural area in the Beauce chartraine region. The PhD objectives hold in 3 parts: [i] characterising the spatial variability of soils pedological, physico-chemical and hydraulic properties (water retention, hydraulic conductivity KSAT, immobile water fraction fIMM), as well as isoproturon adsorption (KD) and degradation (DT50) properties in the topsoil of the studied area; [ii] Identify the agronomical and/or pedological determinisms of properties that are important for pesticides fate in soils; [iii] Calibrate and test pedotransfer classes or functions in order to predict important properties using simpler agronomical and/or pedological properties. Soils in the studied area have intermediate thickness and are derived from an aeolian loess that stands on a frost cracked and cryoturbed limestone. The topsoil of 34 sites has been characterised, with a systematic measurement of the seedbed properties, and a partial measurement of the rest of the cultivated layer. Among the 50 layers / samples that were characterised, one-third holds in no-tillage fields. With the exception of bulk density, soil physico-chemical properties are moderately variable (notably clay and CaCO3 contents). If the water holding properties and isoproturon KD are moderately contrasted too, soil fIMM, and KSAT, as well as isoproturon DT50 are highly variable. An important
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Julien Moeys. Spacial variability and agro-pedological determinisms of an herbicide fate in the surface horizon - an application to isoproturon in an agricultural catchment of the "Beauce chartraine" region, France. Sciences of the Universe [physics]. AgroParisTech, 2007. English. ⟨NNT : 2007AGPT0063⟩. ⟨pastel-00004448⟩

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