Spatial optimization of fertilizer application by a centrifugal spreader

[Departement_IRSTEA]EA [TR1_IRSTEA]TESAD / TECHPROPREFertilisation practice using centrifugal spreaders generally consists in the mass flow rate regulation thanks to the simple mathematicl relation D=Q.L.V/600 where Q is the prescribed fertilization rate, L the working width and V the tractor speed. Modern machines equipped with DPAE device can thereby continuously control the mass flow rate with respect to the working width that is in most cases considered as constant during spreading. When computing the previous equation, one reasons as if fertilizer was homogeneously distributed by the machine onto a rectangular area which length is equal to the wished working width. This practice gives satisfying results with regularly spaced parallel travel direction but is very inefficient when geometrical singularities are met in the field (pointed end of field, irregularly spaced parallel travel path, bends, start and end of spreading) and then can produce some local application errors. Indeed, the broadcasted amount of fertilizer is often higher than the local crop requirements. In some cases, it can be lower and then results in smaller crop productions. Thus, spreading process is more and more considered as a source of pollution of groundwater and watercourses