Response of Soil Microbial Communities to Different Doses of Glyphosate and Sulfosulfuron in a Calcareous Soil
نویسندگان
1 Department of Crop Production and Plant Breeding, College of Agriculture, Shiraz University, Shiraz, Islamic Republic of Iran.
2 Queensland Alliance for Agriculture and Food Innovation and the School of Agriculture and Food Sciences, The University of Queensland, Gatton 4343, Queensland, Australia.
3 Department of Agrotechnology, Faculty of Agriculture, Ferdowsi University of Mashhad, Mashhad, Islamic Republic of Iran.
4 Weed Science, Queensland Alliance for Agriculture and Food Innovation, The University of Queensland, Queensland, Gatton 4343, Australia.
5 Department of Crop Production and Plant Breeding, College of Agriculture, Shiraz University, Shiraz, Islamic Republic of Iran.
6 Department of Crop Science, Faculty of Agriculture, Ferdowsi University of Mashhad, Mashhad, Islamic Republic of Iran.
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چکیده
To investigate the response of soil microbial populations to different doses of glyphosate and sulfosulfuron, a factorial experiment based on a complete block design was conducted at Shiraz University, Iran. The factors included different herbicides and dose rates (glyphosate at 0, 540, 1,080, and 4,320 g ae ha-1 and sulfosulfuron at 0, 12.5, 25, and 50 g ai ha-1), and time of measurements (4, 15, 45, and 65 days after herbicides spray). Microbial respiration, microbial biomass carbon, metabolic quotient, dehydrogenase activity, and aerobic heterotrophic bacteria were measured in soil samples. The results showed that microbial respiration, microbial biomass carbon and metabolic quotient were highest for glyphosate 1,080 g ae ha-1 at 4 days after herbicide application. Dehydrogenase activity had a decreasing trend in all herbicide treatments in comparison with the control treatment in all measuring times, except 4 days after spraying. There was no significant difference in dehydrogenase activity between herbicide treatments. The effect of sulfosulfuron on microbial respiration and metabolic quotient was not significant, whereas time and its interaction with herbicide dose rate affected these two variables significantly. Generally, all the measured indices for sulfosulfuron and glyphosate treatments decreased with time after herbicide application. Sulfosulfuron at 50 g ha-1 and glyphosate at 4,320 g ha-1 had the lowest amounts of aerobic heterotrophic bacteria after 65 days, decreased by 23.7 and 50%, respectively compared with the control. Our results demonstrate that the effects of herbicides on soil microbial communities are strongly related to the herbicide dose and the time after herbicide spray. In conclusions, the herbicides at doses more than the recommended doses showed inhibitory effects on soil microbial communities in the alkaline soil, where the inhibitory effect was more at 4,320 g ae ha-1 glyphosate.
