Study of density and predominance of weeds in vineyards of Miandoab city and its effect on grape yield

Grapes with the scientific name (vitis vinifera L) have a prominent position among the country's fruit trees as from the entire level of gardens in the country,  about 306 thousand hectares, equivalent to 11.4% , belongs to small fruits and about 96.2% of which is related to the grape surface. West Azerbaijan province is one of the most important regions of Iran for planting vines and the area under grape cultivation is close to 21808 hectares. Subsequently its production amount is reported more than 265 thousand tons which is important in the prosperity of the region's economy in terms of currency. According to the importance of grapes and raisins and its position in the country's economy and region and due to the lack of basic information about the weed status of this product at the national level and especially in the state of West Azerbaijan (which has an important share in the production of grapes), with identifying weed cover and determining the abundance status and distribution of weed species, it can be achieved to the substructure information for designing weed management programs in this important crop.

 Miandoab city (has a semi-arid climate with hot and dry summer and semi-humid winter) has 2694 square kilometers area with geographical longitude 46 degrees and 6 minutes east of the Greenwich meridian and 36 degrees and 58 minutes north From the equator. It is located in the middle of the plains leading to Lake Urmia with a height of 1314 meters above sea level. In order to identify and determine the density and dominance of weeds in the vineyards of Miandoab city 25 vineyards in 25 areas of the Miandoab city were investigated in late May 2016. Frequency, uniformity, density, mean density and dominance index of different weed species were calculated in each garden. Then experiment to investigate the effect of weeds on grape yield is done in mid-September. For this Weed biomass from 25 rural areas were collected in 4 replications. At the same time as sampling weeds, also characteristics of grape were evaluated in 4 replications. These characteristics include fruit weight, volume, length, density and number of berries per grape cluster. After calculating the Shannon-Wiener index of different regions, Ward's cluster analysis with SPSS software was used to compare and group regions. After these steps, the desired map was prepared using Google earth software.

In total, 61 species of weeds from 24 plant families were identified in the vineyards of Miandoab city. 21 species were present in more than three regions. In terms of density, Sogli Tappeh, Mullah Shahabuddin and Shabilo villages had the highest weed density with 49.6, 49.5 and 46 plants per square meter, respectively. From the 61 identified species, 32 species (46%) belonged to 4 families: Gramineae, Asteraceae, Fabaceae and Brassicaceae. These 4 families with 11, 10, 7 and 4 species had the highest diversity in the city, respectively. In terms of weed abundance index (AI) Glycyrrhiza glabra, Sorghum halepense and Convolvulus arvensis were recognized as the dominant weeds in the city, respectively. Gara Tappeh, Gog Tappeh and Mameh Del villages with 26, 24 and 22 species, respectively, with the highest variety And Islamabad, Hyderabad and Hosseinabad villages had the least variety with 10, 10 and 11 species, respectively. Results of comparing the means of different traits of grapes (volume, weight, length and density of fruit and number of berries per spike) indicate a significant difference in the level of 5% probability between villages. The results showed that there was a positive and significant correlation between weight, length, volume and fruit density at the level of 1% probability. Thus, it is clear that increasing any of the above parameters causes the weight of the berry to increase.

In general, according to the knowledge of density, dispersion and species of weed ‎‎in the studied vineyards and using the right management methods the amount of interference of problematic species can be reduced and also the entry of weeds, especially problematic species, from one area to another susceptible area can be prevented. In addition by studying the climatic conditions, climate and soil of the region and also, by having information about the common management methods in the region, it is possible to understand the reasons for the presence and changes in the density of some species in some areas and used this information in integrated weed management.