Although this paper was published in the year 2016, there are many contradictory and convincing statements, research articles on Glyphosate from two decades. Some of them are from The German Federal Institute for Risk Assessment (2013) World Health Organization (2015) and European Food Safety Authority (2015) as they are not safe as assumed and having lethal factors to humans, environment and the ecosystem. There are no Environmental Quality Standards (EQS) particularly for the Glyphosate and its formulations. Some countries have proposed various EQS values for Glyphosate. There is an increase in global market of pesticides from $61.8 billion in 2014 to $83.7 billion in 2019.
Glyphosate is a broad spectrum herbicide to kill weeds and grasses which competes with the main crop. The herbicide Glyphosate is reported as environmental friendly by the manufacturing companies and their advertisements but they also have hazardous effects on non-target biota which is still a topic of concern among soil ecologists, microbiologists and researchers. In the research paper titled “Glyphosate effects on soil rhizosphere – associated bacterial communities” author was very much concerned about microorganisms which are located in the soil rhizosphere and the effect of interaction between the plants, soil and microbial groups with glyphosate. The biogeochemical process among the plant microbe interaction leads to high impact on plant growth and development. The results in the paper show that there are shifts in the microbial populations due to long-term glyphosate effect.
Albeit, there is extensive research on response to glyphosate for a short term the author is interested to investigate the long term effect of glyphosate on soil and microbes in the soil. Glyphosate has been found harmless to soil microbes in some research papers but they are not clear about the time period or concentrations of the glyphosate formulations. However some or no effects of glyphosate were also recorded on soil microbial properties in the research done earlier. Author gives a hint to the experimental hypothesis that effect of glyphosate may be masked by different species in the ecosystem where the soil properties are unaffected but a change in microbial community composition. As glyphosate inhibits protein synthesis by acting on 5-enolpyruvyl-3phosphte synthase which is present in both plants and microbes by which authors statements gives a relation that toxic effects of glyphosate can also found in microbes and also has a long-term effects on soil fertility.
Author used Greenhouse as experimental study site with the help of rhizoboxes where the soil used was Blount silt loam which is collected from the farm undergoing organic management, it could have made more sense if he would have done the research using small area of plots with different types of soils, as microbial diversity varies with the type of soil, pH and availability of nutrients. He was interested in glyphosate tolerant corn and soybean for the experiment and used non tolerant plants as control but there are no specific reasons why he chooses them. The mentioned growth periods for three years and the fertilizer solution composition prepared was unclear and the growth period does not relate with the sample collection for results. The molecular biology techniques were well used for easy identification of microbial community using DNA sequencing and library construction to identify different species.
The data analysis was done using different sequences and pipelines like PANDAseq, QIIME pipeline v1.5.0 and two sample t tests with Carlo Permutations. But the produced results are not elaborative to understand the sequences. As the analysis and results make the readers more familiar he could have explained Bioinformatics terminology for understanding results. Author showed some bias on identifying bacterial community leaving some contradictory aspects like types of soil and fertilizer composition and growth period. Figure 2 was very clear and understandable which depicts the differences between control and treatments, different species of microbial population but I am not sure whether he differentiated the microbial communities using the resulted sequences or not. But after keen observation to Figure 2 and the results stated only about Proteobacteria, Acidobacteria and Actinobacteria without considering other species of microbial community. Among which the largest shifts observed in proteobacteria (gamma proteobacteria) and Acidobacteria, now my question is how the author identified and distinguished the proteobacteria as alpha, beta,gamma and delta bacteria and Acidobacteria and there was a decrease of abundance in Actinobacteria. Based on the results author has mentioned to have corn-soybean crop rotation but the justification statements were not found.
Furthermore several statements made me think more about the hypothesis and the results produced, as he says “although effects of glyphosate on specific bacterial taxonomic groups was observed ,there was no bacterial overall effect of glyphosate on bacterial community diversity”. Anyhow author clearly mentioned that the results vary depending on the soil types, glyphosate absorption and its components in formulations. The high clay content in the soil used was also the reason for the absorption capacity whereas soil pH is not favorable.
Finally the paper in the end of discussion says increase in use of huge number of herbicides and its dosages results in the shifts of microbial populations as well as subpopulations due to long-term Glyphosate tolerant cropping. Without any subtle conclusion for the research author says the research justifies the gap between earlier research and research further which means earlier research was conducted only on some specific bacteria but not the bacterial community as a whole.
Author in the end can conclude with the contrasting points as he came to know that glyphosate has its effect on soil microbes in the rhizosphere but not specific microbes such as plant growth promoting rhizobacteria species, Nitrogen fixers and effect on other rhizosphere organisms like earthworms, protozoa, amphibians etc.