The investigation goal was to point the efficiency of pipe drainage set up on vertic amphigley of the trial field Oborovo. To obtain the relevant indicators, detailed hydropedological investigations were carried out at the trial field Oborovo during 1991 and 1992. Dynamics of effective soil moisture in the rhizosphere layer, fluctuations of groundwater level, and frequency and intensity of drainage discharge were continually followed in the long-term period from 1991 to 1995.
Only one systemic soil unit was determined at the trial field : amphigley, mineral, vertic, hydroameliorated.
During five-year investigations of moisture in the rhizosphere soil layer for maize in its growing period (May - October), dominance of the wet soil phase was determined. The wet soil phase prevailed outside the growing period while no dry was recorded.
Measured from the mean absolute ground elevation (98,63 m a.s.l.), groundwater levels fluctuated from 98,03 m a.s.l. to 96,21 m a.s.l., and 0,60 m to 2,42 m below the soil surface.
Drainage discharge was recorded in 26 of the 54 months of the investigation period. The mean drainage discharge intensity was 0,259 l/s/ha, whereby discharge values ranged from the minimum 0,010 l/s/ha to the maximum 0,760 l/s/ha.
Occurrence of drainage discharge was confirmed in 100 % cases, when the groundwater level reached 97,70 m a.s.l., or 0,80 m below the mean ground level.
On average, no drainage discharge was recorded for 15 of 27 drain pipes monitored, which indicates a 44 % system functionality.
The results confirm the fact that drainage of veric amphigley-epigley soils used for conventional agricultural production in the Central Sava River Valley basin cannot be efficiently solved by the traditional system of pipe drainage.

Pipe drainage; functionality; groundwater level; drainage discharge; soil; excess

Published by University of Zagreb, Faculty of Agriculture, Zagreb, CROATIA
Sponsored by Ministry Science and Education of the Republic of Croatia