Effect of different irrigation intervals on superior poplar clones yield

Various poplar varieties have different needs and requirements and different water supply and intervals can change their growth conditions, significantly. Due to limited water resources at most parts of Iran, irrigation interval is more important than irrigation volume in conventional and industrial poplar plantation systems. The aim of the study was to investigate the quantitative and qualitative growth characteristics of different poplar varieties at various irrigation regimes and identify the best irrigation interval. For this reason a trial was conducted in Karaj City of Iran under experimental design of split plots at three replicates. The main plots consisted of three irrigation intervals (4, 8 and 12 days) and the subplots consisted of nine poplar clones. The water supply at each irrigation interval was equal and there were nine seedlings at each subplot at 3 X 3 m. spacing. Irrigation regime for all treatments at first year of trial was similar. The irrigation treatments were supplied at the second year of the trial and an equal water supply was applied to all irrigation treatments, using flume model W.S.C. type3 at each water supply resource and measuring water dimension and time pass of each flume and application of standard curves. The measured poplar growth characteristics consisted of dbh, total height, stem height, crown diameter, stem volume, morphology and phenology. The results showed that there was only significant difference between the both 4 and 8 and the 12 day irrigation intervals in respect to growth parameters. Although there was not significant difference between the 4 and 8 day intervals in respect of growth parameters, but water consumption at the 4 day interval was 7500 m3 more than that of the 8 day interval. All the poplar clones had intensive growth reduction at the 12 day interval irrigation regime and it might be concluded that this irrigation interval is not appropriate for poplar wood production. The poplar clones of P. n. 62/154, P. e. 561/41 and P.e. vernirubensis had the best growth performance at the 4 and 8 day irrigation intervals