Effects of biochar amendment on sorption, dissipation, and uptake of fenamiphos and cadusafos nematicides in sandy soil.

BACKGROUND

The application of biochar to soil is supposed to alter its adsorption/desorption potential toward pesticides, thereby affecting their bioavailability and efficacy. This is particularly relevant in the case of nematicides because these pesticides are directly applied to soil.

RESULTS

Biochar was produced from date palm (PB) and eucalyptus (EB) waste at 450 °C and added at a rate of 1% to a sandy soil. The half-life (t ) of fenamiphos was increased from 2.7 to 18.3 and 18.6 days in PB- and EB-amended soils, respectively. By contrast, the half-life of cadusafos was unaffected. Freundlich K values increased from 1.22 and 0.39 (μg g mL ) to 4.49 and 6.84 in 1% PB-amended soil, and to 3.49 and 4.62 in 1% EB-amended soil for cadusafos and fenamiphos, respectively. Plant uptake of both nematicides in tomato seedlings was reduced by approximately 97% (cadusafos) and 85% (fenamiphos). Although nematicide efficacy against Meloidogyne incognita was not altered at the recommended dosage, it was negatively affected at a half-dose rate. Under these conditions, it decreased from 43.1% in unamended sandy soil to only 18.3% in 1% PB-amended soil.

CONCLUSIONS

Biochar addition increased the sorption capacity of soil. This resulted in a decrease of nematicide bioavailability, together with a reduction of both the dissipation rate and uptake by tomato plants. © 2018 Society of Chemical Industry.