The Effect of Earthworm, Cow Manure and Its Biochar on Some Soil Biological Properties

Little is known about the effects of biochar on earthworms and their interactions on soil biological properties. The purpose of this study was to investigate the effects of earthworm and cow manure biochar (compared to cow manure) on some biological properties of soil. For this purpose, the soil was treated with cow manure or its biochar in 4 levels (0, 1, 2 and 5%) in the absence and presence of earthworm and incubated for 30 and 90 days. The results showed that the number of earthworm decreased in soil treated with cow manure biochar in 30 days of incubation. After 90 days of incubation, application of 1, 2 and 5% cow manure increased the number of earthworm by 26, 91 and 104%, respectively. Application of 1% biochar resulted no significant effect on the number of earthworm, but the 2 and 5% biochar decreased the number of earthworms by 43 and 48%, respectively. The results showed that the earthworm led to considerable increase on the basal respiration, substrate induced respiration and microbial biomass carbon in soils treated with cow manure compared to cow manure biochar. Also, application of both amendment improved the soil biological properties compared to the control. On the other hand, earthworm increased and decreased the metabolic quotient in 30 and 90 days incubation, respectively. The addition of cow manure and its biochar reduced the metabolic quotient in 90 days of incubation. In addition, the soil treated with 5% cow manure and earthworm (in 90 days) had the lowest metabolic quotient. Overall, cow manure improved soil biological quality better than cow manure biochar. However, application of 1% cow manure biochar in the soil which has no negative effect on earthworm, can be also beneficial to improve soil biological quality.