بررسي تداخل جمعيت طبيعي علف هاي هرز در زراعت گندم در استان مازندران

A Survey of natural weed population interference in wheat crop in Mazandran Provience

To study the extent of yield loss that weeds may cause, and the most suitable index for estimating the reduction of wheat yield a survey bas been conducted in Ghaemshahr in 1998-1999. For this purpose 27 plots in a farm with dimensions of 5x5 were identified, and in different stages the density of weeds were counted and recorded. At the end of growing season, every single species in each plot was measured, seperately. For calculation and comparison of coefficient of damage in species, indices such as dry weight , plant equivalent ratio, and also average dry weight of a single weed plant was measured. The results shown that the ratio of weeds biomass to their number, provided a better index for estimating of wheet reduction in wheat yield. Yeild equation was developed using multivariate regression, in which the effect of weeds in wheat crop is divided in two different groups; the first inhibiting and the second as possitive effect. lntra specific competition of wheat plants was more than the inter specific competition.Two species (Rapistrum reugosum) and (Avena fatua) had the most effect on reducing wheat yield in this study. However Veronica persica and Artemisia sp. had the least effect on wheat yield reduction. ln the next survey conducted, we found the positive effect of some species of weeds in inhibiting of those species with the of high competitive ability in wheat crop.