اثر تناوب زراعي بر تركيب ، تراكم و نحوه پراكنش گياهچه هاي علف هرز

The effect of crop rotation on composition, density and distribution of weed seedlings

To study the effect of crop rotation on composition, density and distribution of weed population, a field experiment was conducted at the collage Agricultural, of Ferdowsi University of Mashhad Experimental Station during spring 2003. Different rotations in three experimental parts of the field were: 1) corn silage-barley silage, 2) chickpea-barley silage and 3) cumin-barley silage. Weed species identification and weed density were measured in 0.5m x0.5m quadrates. Sumples were taken based on systematic methods by using grids of 12.5m x12.5m, 11.5m xi 1.5m and 5m x10m respectively, depending on the shape of each part. Sampling was done in two stages: a) before post emergence herbicide treatment and b) three weeks after application of herbicide. Weed density in barley silage was very low; however, there were highest and lowest densities in cumin-barley silage and corn silage-barley silage rotation, respectively. On the other hand, weeds in field had patchy distribution. The patchiness is the basic character for site-specific weed management. The results indicated that weed density and composition is influenced by crop species and management practices. Therefore, with proper crop rotation, and suitable weed management, we can overcome the weed problem by using minimum amount of herbicide.