Impact of three herbicides alone and in mixture on the soil microbial activity and community.

What is it about?

Herbicides and other pesticides are applied to increase crop yield and raw material quality. However, once in the soil, they may affect non-targeted organisms by reducing their population, changing community structure or metabolic activity. Soil microorganisms has key role on the degrade herbicides, affecting their persistence in the environment. The degradation of organic compounds can be by catabolism (metabolism), in which the microorganism obtains energy or carbon from organic compounds for its growth, or by co-metabolism, in which the microorganism does not obtain energy or benefit from degradation. While transformation processes by co-metabolism are usually mediated by appropriate non-specific enzymes that are able to transform a variety of compounds. As co-metabolism does not play a role as a source of energy or nutrients for microorganisms, the populations do not grow in response to the degradation process. An extra source of carbon is necessary to sustain microorganism growth. Several formulated mixtures of herbicides, fungicides and insecticides are available for crop protection in Brazil. In fact, herbicides, applied in mixtures or in sequential applications, are common practice in agricultural areas from Brazil. Pesticides may accumulate and affect the structure of soil microorganism populations in the soil. Consequently, the rate to which organic compounds are degraded by microorganisms in the soil may change. Thus we aimed to evaluate the effect of the application of three herbicides alone and in mixture on the soil microbial activity and bacterial community structure.

Featured Image

Photo by Alex Kondratiev on Unsplash

Photo by Alex Kondratiev on Unsplash

Why is it important?

Our results showed a strong effect of herbicide mixture on soil microbial respiration. The application of diuron alone promoted increase in detachment rate of 14C-CO2 after 42 days of incubation both clay and sandy soils. However, the strongest effect of the treatments was observed in the sandy soil, where there was lower emission of 14C-CO2 in the initial incubation periods (7, 28 days), suggesting that there was a deleterious effect on microbial activity. The soil type affected the microbial diversity, and in the clay soil the highest diversity indices were from the communities treated with hexazinone. While in sandy soil, the highest rates were for diuron and sulfometuron-methyl treated samples. The microbial community was structured in a complex way, with strong control separation in both soils and application alone or in mixture of herbicides.

Perspectives