Effects of chemical pesticides on weeds population dynamics, species richness and biodiversity and yield of winter wheat

Document Type : Research Article


1 Ferdowsi University of mashhad

2 Ferodwsi University of Mashhad


IntroductionCompetition between wheat (Triticum aestivum L.) and weed is one of the most important restrictions of global production of this plant and Human solutions for management of pests and weeds have destroyed the biodiversity in agroecosystems (Bushong et al., 2011; Lemerle et al., 2001). The function of natural and agricultural ecosystems is based on biodiversity. Destruction of biodiversity is a serious threat to the sustainability of agricultural ecosystems and  finally food security in the world. Use of pesticides and chemical fertilizers  is one of the most important methods of intensive management in agriculturethat damaged biodiversity (Marshal et al., 2003).Materials and Methods A factorial experiment based on randomized complete block design with three replications in two years of 2012-13 and 2013-14. The test factors included pesticides at three levels (Non insecticide, Deltamethrin as a general insecticide and Phyenrythion as a specific insecticide) and Herbicide on four levels (Non herbicide, two herbicides 2,4.D , Topic and the combination of them) was carried out. Weeds was sampled 5 times during the growing season and Weed species were identified and counted. Sampling was performed before and after the treatment. Relative density and relative frequency of weeds, weed Species, Shannone diversity index, Species reachness and wheat yield were studied.Results and Discussion Data analysis showed that in both years the effect of herbicides on the weed density and dry weight of broad-leaf weeds and total weed dry weight were significant. However, the effects of pesticide treatments on density and dry weight of weeds were not significant. in both crop years, Use of two herbicide mixture had the greatest effect on reducing the density and dry weight of broadleaved weeds and total weed dry weight. The highest Shanone diversity index was observed in non-herbicide treatments in the 2012-13, which had a significant difference with other treatments. The highest Shannon diversity index were observed in the control plots and the lowest Shannon diversity index were observed in the combined treatments of both herbicides in the 2013-14 crop year. It seems that the combination of both herbicides in addition to dry weight and density has the greatest impact on weed species diversity. The species observed in both years were similar to each other. The main weed species of the field included Convolvulus arvensis L.، Descurainia sophia Webb ex Prantl ، Avena ludoviciana Durieu  and Secale cereale L. The contribution of grass species to the total density were 30% and The share of broad-leave weed was measured at 70%, Therefore, the frequency of broadleaved species was higher than grass weed in the field. Herbicides changed the demographic structure of weeds societies and reduced the weeds biodiversity index.In both years, different treatments of pesticides did not have a significant effect on the changes in weed density.The effect of herbicide in both years and the effect of pesticides only in the 2013-2014 on the yield of wheat were significant. Application of pesticides significantly increased economic yield of wheat. However, Increase density and dry weight of weed decreased wheat economic yield. Wheat economic yield decreased with increase in weed density and weed dry weightConclusionHerbicides have changed Population structure of weeds and Reduced the biodiversity index of weeds. Negative and significant correlations were observed between wheat yield and species richness and shannon diversity index in both years. In general, Intensive management, specialy herbicides usage in wheat agroecosystem changed the composition of the plant communities and reduced the biodiversity , weed species richness. The result of the reduction in diversity in this ecosystem is a greater dependence on chemical inputs Which causes environmental pollution and a threat to agricultural sustainability.


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Articles in Press, Accepted Manuscript
Available Online from 01 January 2024
  • Receive Date: 01 February 2019
  • Accept Date: 06 March 2019
  • First Publish Date: 27 November 2020