Degradation of chlorpyrifos using different biostimulants/biofertilizers: Effects on soil biochemical properties and microbial community

• Chlorpyrifos insecticide caused a negative effect on soil biological properties.
• The application of biostimulants/biofertilizers decreased the toxic action of chlorpyrifos.
• The low molecular weight protein of wastes increased the degradation of insecticide.

In this manuscript we conducted a laboratory investigation over a 120-day period studying the effect of three biostimulants/biofertilizers (BS), in a Calcaric Regosol soil, polluted with chlorpyrifos insecticide at a rate of 5 L ha−1 (manufactures rate recommended). The BS were manufactured by the pH-stat method, from two different types of chicken feathers (CF1 and CF2) and from sewage sludge (SS). We determined their effects on enzymatic activities and the structure of the soil microbial community by analyzing phospholipid fatty acids (PLFAs). The BS that contained higher amounts of proteins and a higher proportion of peptides, under 0.3 kDa, exerted a greater stimulation on the dehydrogenase, β-glucosidase, phosphate and arylsulfatase activities, possibly because low molecular weight proteins can be easily assimilated by soil microorganisms. The soil urease activity was not stimulated because these chemical compounds were rich in low molecular weight proteins. Soil biological parameters decreased in insecticide-polluted soil. The application of the BS in chlorpyrifos-polluted soils decreased the inhibition of the soil enzymatic activities and biodiversity, principally at 10 days into the experiment. However, this inhibition decrease was higher when CF2 was applied to soil, followed by SS and CF1, respectively. This suggested that the application of BS with higher amounts of proteins and a higher proportion of peptides under 0.3 kDa is more beneficial for remediation of soils polluted with chlorpyrifos.