Effect of soil type, soil humidity and spray parameters was studied. Four trials were conducted in pots under laboratory conditions during 1997 and 1998. The trials dealt with the effect of the humidity, spray volume, irrigation frequency and type of soil on the efficacy of oxadiazon herbicide at 750 g a.i / ha applied by using a wagon wears-boom under shelter. The physical characterization of the spray has been realized by the laser granulometry method and by the method of image analysis of water-sensitive papers. Results showed that physical parameters of the spray have been favourable for all the tested treatments (number of impacts / cm², coverage rate). Moreover, the oxadiazon efficacy was affected by soil humidity. It was also affected by irrigation frequency under the greenhouse conditions (high evapotranspiration). The effect of soil type was not significant. Finally, these trials have confirmed the possibility to reduce the water volume down to 123 l/ha.
