Pretreatment of soil samples before NO3-N analysis

Soil samples (sand, loam, clay) were stored for either 2 or 3 days or for 2 months at varying temperatures ( 20 °C, + 4 °C, room temperature, 30-40 °C and 70 °C). As references field moist samples were used. Oven drying caused significant decreases in extractable N03-N for the three soils and for the short as well as for the long sto­ rage period. The other treatments ( 20 °C and + 4 °C) and drying at room tempe­ rature gave results that equalled those obtained on reference samples except for the samples at room temperature and at the 2-month storage period. In that case, a substantial increase in N03-N was measured, especially in the sandy soil with a relatively high organic matter content.