Spatial dynamic of weeds in a field with Canola-Fallow-Wheat crop rotation history

In order to evaluate the spatial dynamic of weeds during growing session an experiment was conducted at Astane Ghodse Razavi experimental field. One hectare size with canola-fallow-wheat rotation was selected. Sampling was carried out by discrete systematic method in which the samples were taken from plots of 7m×7m, using 0.5m×0.5m quadrates in three stages, pre chemical control, post chemical control and pre harvesting, and species and their densities were determined. Fifteen species were observed from 196 sampling points. Total weed density in the field during the first, second and third sampling stages were 44.42, 12.16 and 3.93 plant per square meter respectively. It seems that this downward trend was as a result of control operations efficiency. Goldbachia laevigata and Chorispora tenella were most important weeds in the filed during first sampling stage. While Fumaria vaillantii and Polygonum aviculare became important at during the second stage of sampling. Also P. aviculare was the most important weed in the filed during the third sampling stage and the importance of F. vaillantii was decreased. To describe the dynamics of weeds, the geostatistic method was used and variogram functions of weeds in each three sampling stages were calculated which had spherical and exponential models. Maximum and minimum of nugget effect were 0.13 and 0.45 respectively. The ranges were also between 2.8 and 196.6m. The spatial distribution maps of weeds were drawn applying variogram parameter in Kriging interpolation that showed patchy and plow directed distribution. The results showed that presence of canola in crop rotation and corresponding control operations was effective on type and spatial distribution of weeds of studied species. In fact crop rotation with the effects on weed communities can be as an option in integrated weed management effect on weeds.