Variability of Biochar Performance Among Soil Amendments and Enzymes Activity

Abstract

In a randomized complete block design, a field experiment was established with fourteen soil treatments: no mulch control (NM native soil), sewage sludge (SS), horse manure (HM), chicken manure (CM), vermicompost (Vermi), commercial organic fertilizer (Org), inorganic fertilizer (Inorg), and biochar added to NM, SS, HM, CM, Vermi, Org, and Inorg. The main objective was to assess the impact of various soil amendments (SA) and biochar added to SA on soil urease, invertase, acid and alkaline phosphatase activity involved in N, C, and P cycles, respectively. The addition of biochar to Vermi amended soil increased urease and invertase activity by 54 and 50%, respectively compared to soil mixed with Vermi alone (not amended with biochar). CM amended with biochar did not increase alkaline phosphatase activity compared to CM alone. Acid phosphatases activity decreased by about 21% after the addition of biochar to Vermi amended soil. Biochar added to HM and NM soil reduced soil alkaline phosphatase activity by 49 and 41%, respectively. The effect of soil amendments before and after the addition of biochar on soil pH, electrical conductivity (EC), nitrates (NO3-), and ammonia (NH4+) concentration was also investigated. No significant differences were found among soil treatments in soil pH values. Whereas Vermi mixed with biochar (VermiBio) significantly increased EC values indicating an increase in soil total ions compared to all other amendments tested. Addition of CM to native soil increased (NH4+) ions by 7.8 times compared to the control treatment. Whereas biochar added to CM (CMBio) increased (NO3-) ions by 2.7 times. We concluded that the duality in biochar impact on soil enzymes activity and amendments tested in this investigation requires prior testing for reconsidering the use of biochar in agricultural systems.