Distribution of Cheat Grass (Bromus tectorum L.) and Other Poaceae Weeds in Wheat (Triticum aestivum L.) Farms in West and Northeast of Iran

Undoubtedly, planning and providing appropriate management strategies for weed management requires accurate understanding of plant growth. In fact, by identifying plant growth flora and determining the abundance and distribution of weed species, we can obtain important background information for designing weed management plans. Usually the composition and density of weed flora reflect the system of production and agronomic operations. In fact, by identifying the weed flora and determining the abundance and distribution of weed species, we can provide important background information for designing weed management plans. In this case, Cheat grass is problematic weed in winter crops like wheat and barley.
Material and The distribution of this weed as random sampling method in 2012 was surveyed in 40 irrigated wheat farms in Khorramabad, 27 farms in Mashhad and 28 farms in Neyshaboor. Factors related to relative abundance, species richness, density and relative uniformity as well as variability and dominance indices were measured. Sampling in each farm was a W pattern. At almost all fields monitored, sampling was done in the post-stemming phase of the wheat before filling the seeds. Also, using the GIS technique, the distribution map of grass plots was drawn in these areas.
Results showed that sixteen weed species from poaceae family other than cheat grass were observed. Relative frequency of hirsotum ecotype of cheat grass (with 8.76%) was higher than tectorum ecotypes (with 4.76%) in Khorramabad. The Animated animated oat with 19.65% and then Wild barley with 13.52% in mean of 5 samples had the highest relative frequency. In Mashhad relative frequency of tectorum ecotype with 12.44% was higher than of hirsotum ecotype with 7.25%. Common wild oat with 13.99 and then Wild barley with 12.95% had the highest frequency. In wheat farms of Neyshaboor, two ecotypes had similar relative frequency with 10.75%. Common wild oat with 14.52 and then Secale with 12.29% had the highest frequency. In this case only Johnson grass and Bermuda grass were perennial and other weed species were annual. The properties of annual plants are capable of retrieval and rapid reproduction after the destruction occurring in the environment. Therefore, the abundance of more than one year in agricultural lands that are associated with continuous degradation is not unexpected. Additionally, most of the crops are annual, and it is normal that annual crop rotations that have the same growing needs as a crop are more abundant than perennial weeds Similar results were also obtained in thi sstudy. Furthermore, it was shown that the latitude had no large effect on density of grasses and cheat grass ecotypes. Shannon-Weiner diversity index in Khorramabad 2.24, in Mashhad 2.16, in Neyshaboor 2.29, Simpson's diversity index 1.04, in Mashhad 1.31 and in Neyshabour 1.16 and Simpson dominance index in khorramabad 0.960, in Mashhad 0.764 and in neyshaboor 0.862 was calculated. Also using GIS techniques distribution map of cheat grass were drawn in these areas.
The characteristics of annual plants such as grasshopper can be recovered and are capable of rapid replication after the destruction occurring in the environment. Therefore, the abundance of more than one year in agricultural lands that are associated with continuous degradation is not unexpected. In addition to theaccording to the findings of this research, the difference in the indices of species diversity and dominance were associated with the level and type of management practices on farms.
In general, farms with a higher diversity can be said to be managed with weaker management practices that minimize the use of agricultural machinery and the inadequacy of chemical inputs such as pesticides and fertilizers.