Effects of spacing treatments on production of Poplar and alfalfa in intercropping method

Poplar species are usually cultivated for their wood production in most areas of Iran. They are traditionally planted with low spacing which does not render thick trees. Moreover, for different reasons, increasing poplar spacing is not accepted by people and the farmers before accepting a new system, pay high importance for earning continuous income. Thus, addfitional income besides wood products is a vital factor to inrcease the public acceptance for poplar intercropping system. Therefore, intercropping poplar and fodder with increased spacing in order to increase under Randomized Compelete Block Design in 1998 with three replicates, using seedlings of P. nigra betulifolia, four spacing treatments (3×4, 3×6.66, 3×8 and 3×10m.), intercropped alfalfa and two monocultured control treatments of poplar and alfalfa. The trial continued to 2003. Each plot area was 1200 m2. Ten different growth parameters the poplar and alfalfa species were measured. The data were analyzed, using the univariate and the multivariate statistical methods. The results showed that the effect of treatments on poplar and alfalfa parameters were the greatest poplar height and volume amounts belonged to the spacing treatments of 3×4, 3×8 and 3×6.66m which were 1541, 141, 136 cm and 31.7, 20 and 19m3, respectively. The greatest production of alfalfa belonged to control, 3×10 and 3×8 m. spacing treatments which were 7507, 4788 and 4265 Kgha-1 biomass dry weight. The effects of the treatments on branch diameter and annual stem diameter growth rate were not significant, whereas the effects of time and interaction between time and treatments on some growth parameters were significant