INFLUENCE OF PRECIPITATION UPON DRAINAGE DISCHARGE IN TWO DIFFERENT CLIMATIC REGIONS

The goal of three-year investigations was to determine the influence of precipitation upon the drainage discharge in two different climatic regions (Croatia and Lithuania) at two different pipe drainage spacing in each region (first region with 15 m and 20 m drainage spacing and second region with 12 m and 24 m drainage spacing), to calculate the soil water balance according Thornthwaite's method and compare the measured drainage discharge and the calculated surplus of water in soil. Investigations were carried out at the experimental amelioration sites in the central Sava River Valley (Croatia) on hydroameliorated Gleyic Podzoluvisol soil and in Middle part of Lithuania on hydroameliorated Hypogleyic Luvisol soil in the period 2009 - 2011. The research results showed that the drainage discharge and its duration depended on the amount and distribution of the precipitation during the study period. There isn't difference in the total drainage discharge between the tested drainpipe spacing in each investigation year, but there are differences in the duration of the drainage discharge both on an annual scale and depending on drainpipe spacing. In each year, the duration of drainage discharge was smaller at the 12-15 m drainpipe spacing than at the 18-20 m drainpipe spacing. The calculated surplus of water followed the monthly amounts of precipitation, but in all years was higher than the drainage discharge. The 12 to 15 m pipe spacing is more efficient for draining the surplus water from drained soils, since the surplus of water from soil is drained in a shorter period of time and better water-air relationships in soil are created faster, which is a prerequisite for timely application of agricultural management practices on hydroameliorated arable areas.