Microbial Diversity and P Content Changes after the Application of Sewage Sludge and Glyphosate to Soil

How do glyphosate and AMPA alter the microbial community structure and phosphorus cycle in rice-crayfish systems?

Glyphosate, a commonly used organophosphorus herbicide in rice-crayfish cropping regions, may alter regional phosphorus cycle processes while affecting the structure of microbial communities. However, the effects of glyphosate residues on rice-crayfish systems remain unclear. In this study, we assessed the spatial and temporal distribution characteristics of glyphosate and its primary degradation products, as well as the impact mechanisms of glyphosate on microbial communities and the phosphorus cycle in rice-crayfish systems such as paddy fields, breeding ditches and recharge rivers. The detection rates of glyphosate and aminomethylphosphonic acid (AMPA) were 100% in rice-crayfish systems. Concentrations of glyphosate in the water phase and soil/sediment were as high as 0.012 μg/L and 7.480 μg/kg, respectively, and concentrations of AMPA were as high as 17.435 μg/L and 13.200 μg/kg, respectively. Glyphosate concentrations were not affected by rainfall or sampling site, but concentrations of AMPA in the water phase of recharge rivers were affected by rainfall. The glyphosate concentration was significantly and positively correlated with RBG-16-58-14 abundance, and the AMPA concentration was significantly and positively correlated with Actinobacteria and Lysobacter abundance, and negatively correlated with Cyanobacteria abundance (P < 0.05). The highest abundances of phoD, phnK, and ppx genes were found in all soils/sediments. Glyphosate concentration in soil/sediment was significantly and positively correlated with the abundance of phoD gene encoding an organophosphorus-degrading enzyme and ppx gene encoding poly inorganic phosphate (Pi) hydrolase (P < 0.05). In addition, the glyphosate concentration was significantly and positively correlated with the Ca-bonded Pi content (P < 0.05). This implies that glyphosate may promote the production of stable Pi in rice-crayfish systems by increasing the abundance of phoD and ppx genes. The results of this study reveal the impact mechanism of glyphosate on the phosphorus cycle in rice-crayfish systems and provide a basis for the risk assessment of glyphosate.

Biomonitoring of Soil Contaminated with Herbicides

The state of environmental pollution is of random character, and it depends on climatic conditions, landforms, development and industrialization. It is estimated that in the last decade as many pollutants have been released into the environment as in the previous 70 years, and the pollution rate still increases. Many scientific reports indicate that, in addition to metals, pesticides are the most commonly detected compounds in the environment. This situation is mainly due to the irrational use of these chemicals by humans. Mostly, soil environment changes caused by the influence of pesticides can be determined by various chemical analyses, which require the use of sophisticated and expensive equipment. However, biological methods, such as those using microbiological activity and an abundance of microorganisms, e.g., organisms responsible for the cycle of organic matter and nutrients, tend to be neglected. For this reason, the aim of the present study is not only to assess the validity of other research studies that were performed based on the available literature but to compile methods and compare them, which allows for an in depth understanding of the complexity of soil processes following herbicide application by conducting comprehensive soil biomonitoring.