LEACHING OF NITRATE FROM MONOLITH LYSIMETERS OF DIFFERENT TYPES OF AGRICULTURAL SOILS

Nitrate leaching was measured in field lysimeters containing undisturbed soils of different texture and organic matter content. Spring barley (Hordeum distichum L.) was sown on each lysimeter and fertilized with 100 kg N ha-1. Each soil type received supplementary watering to simulate either "average" or 'worst-case" precipitation. The largest leaching losses of NO3-, ca. 65 kg N ha-1 yr-1, occurred in a sandy soil that contained little organic matter and in a peat soil. Two loamy soils lost between 25 and 40 kg N ha-1 yr-1. Smallest leaching losses, ca. 20 kg N ha-1 yr-1 or less, occurred in a clay soil and another sandy soil rich in organic matter. With the exception of the clay and peat soils, the watering treatment did not significantly affect the amounts of NO3- leached, although the temporal distribution of leaching was clearly influenced by weather conditions. The difference in leaching between the two sandy soils was explained by differences in crop growth, whereas leaching differences between soil types were mainly considered to be due to different textural and structural properties. The results show that to make a thorough comparison of NO3- leaching between different soil types they have to be tested simultaneously at the same site.