Influence of fungicides, carbendazim and metalaxyl on soil enzymatic activity and microbial population under laboratory conditions

Abstract EN

Laboratory experiment was conducted to investigate the impact of different dosage$ of two fungicides, Carbendazim and Metalaxyl on the activity of soil enzymes dehydrogenase, urease, acid invertase and rhodanese as well as total counting of bacteria and fungi in sandy c،ay loam soil.

The fungicides were applied at 1, 5 and 10 mg ai kg'1 dry soil.

The soil sample was submitted to an ^ ysis at 0, 7, 14, 28, 35, 42, 49, 56 and 63 day $ after the fungicides treatments.

The investigations showed severe inhibitory effect of these fungicides on dehydrogenase activity.

While the activity of urease enzyme was fluctuated form decrease to increase during all the periods of the experiment.

Application of all doses of tested fungicides significantly decreased the activity of acid invertase enzyme once added to soil and the inhibition was reversible over time at low doses of the fungicides particularly Carbendazim.

Carbendazim and Metalaxyl at 1 mg kg'1 significantly enhanced the rhodanese activity once added to soil and this effect continued until the end of the experiment with percentages activation 11.23° / o and 9.66 %, respectively.

All dosages of Carbendazim and Metalaxyl significantly decreased the total number of fungi throughout all the ex^rimental periods except the low dose lmg kg'1 of Carbendazim which gave some increase at zero, 35 days and 42 days after treatment.

As mean of all periods of the experiment, Metalaxyl ranked the first ؛ decreasing the total number of fimgi.

The effects of the Carbendazim and Metalaxyl at low doses vuere converted since these doses gave a highly significant increase in the total number of bacteria throughout all the incubation periods of the experiment.

As a collective mean of all incubation periods of the experiment, Metalaxyl and Carbendazim at I mg kg gave 107.

72 % and 47.28 % increase of total numher of soil bacteria, respectively.