The effects of soil chemical characteristics on weed species diversity in eastern Mashhad region wheat (Triticum aestivum L.) fields

In order to investigate the effects of soil chemical characteristics on weed species diversity in eastern Mashhad region wheat (Triticum aestivum L.) fields, an investigation was held in the year 2009. Wheat fields were classified based on the acreage from 3-5, 5-10 and higher than 10 ha. Five random soil samples were taken using a 5 cm diameter auger from the soil of each experimental field and were analyzed in the laboratory to measure carbon, nitrogen, phosphorus, potassium and pH levels. The results indicated that there is a significant correlation between carbon, organic matter, nitrogen, phosphorus, potassium and pH with field area. With increasing field area decreased soil carbon, nitrogen, phosphorus and potassium levels and increased soil pH. A significant negative correlation was found between C/N ratio and field area (a decreased C/N ratio correlated with increased area and vice versa). A significant correlation was found between increasing soil carbon, nitrogen, phosphorus, potassium levels, decreasing soil pH and an increasing shannon index of weeds. The shannon index for weeds was increased with increasing soil carbon, nitrogen, phosphorus and potassium and a decreasing soil pH. Significant correlation was found between increased soil carbon and nitrogen levels and increased weed species richness.