Résumé :
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Soil water potential and nitrate content in soil solution were measured simultaneously, using Tensionic tensiometers, in farmers' fields at three different sites for assessing nitrate leaching. The above measurements were made every 10 days at two depths below the rooting zone, for three different cropping systems; namely, grassland, field crops, vineyard in 1994 and 1995, and under field-grown and greenhouse-grown salads during the winter 1996-1997. A nitrate leaching risk indicator was calculated by using the soil water potential gradient and the nitrate concentration of the soil solution below the rooting zone. This approach can be used to analyse nitrate leaching under different management practices for a range of cropping systems. It was also possible to diagnose the contribution of groundwater containing a relatively high level of nitrate to nitrogen and water supply to crops.
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