[en] It had long been considered that intensive agriculture was the only source of groundwater and river pollution. This study is about an area with low intensity agriculture. It is based on field measurements of several soil profiles in a small watershed. The soil profiles show that important nitrogen losses (up to 100 kg N/ha) occur during winter, mainly in maize and potato fields. This paper also draws the attention to soil and water pollution resulting from large quantities of poorly used manure.