Effect of soil properties and soil management on the EUF-N fractions in different soils under uniform climatic conditions

Summary

The influence of soil properties and soil management on the EUF-N fractions in different soils under uniform climatic conditions is described. The results of the investigations are as follows:

• 1. A close correlation was found to exist between EUF-NO₃ extracted at 20°C and N_min contents. These EUF-NO₃ contents were about 0.4–0.8 mg N/100 g higher than the N_min contents (Table 2).

• 2. No correlation was observed between EUF-NO₃ extracted at 80°C and N_min contents. These EUF-NO₃ contents, however, showed a certain dependence on the humus and the N_Kjeldahl contents (Table 3). They reflect, therefore, soil properties which are not influenced by seasonal changes in weather conditions and by soil management.

• 3. Application of slurry increases mainly the contents of EUF-NO₃ extracted at 20°C and does not affect the values of EUF-NO₃ extracted at 80°C (Table 2).

• 4. The EUF-extractable total N fractions (without NO₃) showed a certain correlation with the humus contents as well as with N_Kjeldahl values. These total N fractions were smaller in the Anthropic Regosols which are poor in humus than in the other soils rich in humus. The EUF-N fractions (without NO₃) were not influenced by slurry dressings (Table 4).

• 5. Large amounts of sewage sludge which had been applied to an Orthic Luvisol over a period of ten years considerably increased the EUF-NO₃ (20°C) values as well as the EUF-extractable (20°C) N values (without NO₃). Compared with these values, the increases in N_Kjeldahl values were rather small. The EUF-NO₃ (80°C) values were found to be less influenced by additions of sewage sludge than were the EUF-NO₃ (20°C) values (Table 5).