Cilj rada je bio istraživanjem utvrditi na četiri različita razmaka cijevi podzemne odvodnje od 15 m, 20 m, 25 m i 30 m u hidromelioriranom pseudoglej-glejnom tlu ukupno drenažno istjecanje i njegovo trajanje, koncentraciju nitrata u drenažnoj vodi, ukupnu količinu ispiranja nitrata i prinos uljane repice. Istraživanja su se provodila na melioracijskom pokusnom polju “Jelenščak” u blizini Popovače, u vremenu od 1. rujna 2009. do 31. kolovoza 2010. Na pokusnom polju uzgajana je industrijska biljka uljana repica, a pri uzgoju bile su primjenjivane jednake agrotehničke mjere na svim razmacima cijevi. Ukupna količina primijenjenog dušika u gnojidbi bila je 175, 5 kg ha-1.. Rezultati istraživanja ukazuju da se drenažno istjecanje kretalo od 320 mm (pri razmaku cijevi od 30 m) do 350 mm (pri razmaku cijevi od 15 m), a dužina trajanja drenažnog istjecanja bila je od 123 dana (15 m) do 145 dana (30 m). Maksimalna koncentracija nitrata u drenažnoj vodi pri svakom razmaku cijevi bila je viša od MDK (10 mg l-1 N03 - N) i kretala se od 43,53 mg l-1 N03 – N pri razmaku cijevi od 30 m do 50,13 mg l-1 N03 – N pri razmaku cijevi od 20 m. Količina ispranih nitrata kretala se od 65,2 kg ha-1 (30 m) do 76,4 kg ha-1 (15 m). Prinos uljane repice kretao se od 2,38 t ha-1 (30 m) do 3,30 t ha-1 (15 m).. U istraživanom razdoblju palo je 1159,5 mm oborina te su manji razmaci cijevi bili učinkovitiji u odvodnji suvišne vode iz tla, što je prouzročilo veće ispiranje nitrata, ali i veći prinos uljane repice u odnosu na veće razmake cijevi..; The aim of the paper was determining the total drain outflow and its duration, nitrate concentration in drainage water, total nitrate flush as well as rapeseed yield by investigating four different spacings of subsurface drainage pipes of 15 m, 20 m, 25 m and 30 m in hydroameliorated pseudogley - gley soil. Investigations were carried out in the amelioration test field “Jelenščak” near Popovača in the period from 1 September 2009 to 31 August 2010, where industrial rapeseed plant was cultivated. In the course of cultivation, the same agrotechnical measures were applied to all pipe spacings. The total quantity of nitrogen used during fertilization equalled 175.5 kg ha-1.. The research results indicate that the drain outflow ranged from 320 mm (at pipe spacing of 30 m) to 350 mm (at pipe spacing of 15 m), while the duration of the drain outflow lasted from 123 days (15 m) to 145 days (30 m). The maximum nitrate concentration in drainage water at each pipe spacing was higher than the MAC (10 mg l-1 N03 - N), and ranged from 43.53 mg l-1 N03 – N at pipe spacing of 30 m to 50.13 mg l-1 N03 – N at pipe spacing of 20 m. The quantity of flushed nitrates ranged from 65.2 kg ha-1 (30 m) to 76.4 kg ha-1 (15 m). The rapeseed yield ranged from 2.38 t ha-1 (30 m) to 3.30 t ha-1 (15 m).. In the research period, the precipitation was 1159.5 mm, so smaller pipe spacings were more efficient in draining excess water from the soil which in turn caused higher nitrate flush, but also higher rapeseed yield in view of larger pipe spacings.