BROMUS TOMENTELLUS اثر چراي كوتاه مدت بر برخي از خصوصيات فيزيكي و شيميايي خاك در چراگاه

Effects of Short-term Grazing on Some Soil Physical and Chemical Characteristics in a Bromus tomentellus Pasture

The effects of sheep trampling on organic matter, nitrogen, phosphorus and potasium of soil in a Bromus tomntellus pasture at the end of grazing season were studied in 2000. The place of study located on a high plain with elvetion of 1960 m from sea level which was surrounded by mountains in 70 km northeast of Tehran (Homand Abesard Research Station). Two treatments of continuous and rotation systems and four treatments of no grazing, light, medium and heavy grazing intensities were applied. Grazers were Sangesary sheep which remained on the pasture throughout the experiment period. The pasture was divided into two parts according to the grazing systems and each of them divided into four patches due to grzing intensities. In each treatment 12 hours and then the elements of N, P, K and organic matter measured. The measured parameters were compared by t-test method for all treatments. The results showed that the grazing but the differences were not significant. So the amount of accumulated organic matter decreased while the grazing intensity increased. Also there were not differences between grazing systems statistically (P=0.24) but the amount of organic matter in the continuous grazing system was more than rotation one. Soil nitrogen decreased a little while the grazing intensity increased. The reduction of N in rotation system was more than continuous one. But there was not meaningful difference between them (P=0.51). Totally, the grazing systems had a considerable effects on the meaningfull (P=0.07). The soil phosphorus in continuous system was more than no rotation system in comparison with control (P=0.04). The soil potasium was less than but the rotation system reduced it more than continuous one (P=0.14).