Effect of Biochar, Green Compost, and Vermicompost on the Quality of a Calcareous Soil

Abstract

Purpose: Biochar addition has been recognized as a potential way to improve soil quality. However, questions remain regarding the influence of biochar on soil biological activity. In order to mitigate the possible negative effects of biochar on soil biological activities, it can be enriched by amendments such as compost. Since there is no unanimity on the advantages of biochar when mixed with amendments, it is important to ascertain how the impacts of biochar on soil biological activity could be changed by the addition of compost.Materials and methods: A 360-d aerobic incubation was carried out of a soil treated with biochar, green compost, vermicompost, biochar+green compost and biochar+vermicompost. The biochar was produced from pruning residues of fruit trees by slow pyrolysis at 550 °C. The green compost was taken to the CERMEC facility (Massa Carrara, Italy) and the vermicompost was produced mainly from farmyard manure and green waste by the Centro di Lombricoltura Toscano (Pisa, Italy). The pH, total and dissolved organic C, microbial biomass, dehydrogenase and alkaline phosphatase were monitored. The metabolic quotient, specific enzyme activities and the metabolic potential were calculated.Results and discussion: After 360-d incubation the green compost and vermicompost significantly lowered the alkaline soil pH by about one unit, increased total and dissolved organic C, microbial biomass, microbial quotient, alkaline phosphatase and specific alkaline phosphatase, dehydrogenase and specific dehydrogenase, and metabolic potential. The improvement in the biological activity was more notable and permanent with vermicompost than green compost. The biochar lowered soil pH by about one unit, showed the lowest loss of the total organic C (3.9%), did not change the amounts of dissolved organic C and microbial biomass, induced scarce effects on biological activities. When mixed with biochar, composts significantly induced higher C mineralization, dissolved organic C, microbial biomass, dehydrogenase, and did not change the metabolic quotient, specific alkaline phosphatase and specific dehydrogenase activities. The metabolic potential of control was more than halved by the green compost (2.89) and was not changed by the vermicompost.Conclusions: The mixing of green compost, and especially vermicompost with biochar increased some biological parameters in the used calcareous soil compared with the biochar-only treatment.Biochar could have benefits for carbon sequestration. The specific enzyme activities (alkaline phosphatase and dehydrogenase) were more suitable indicators than the respective absolute activities and metabolic potential for detecting the effects of amendments on soil microbial activity.

Potential short-term negative versus positive effects of olive mill-derived biochar on nutrient availability in a calcareous loamy sandy soil

“…OMSW-derived BC treatments of 1% and 3% (w/w) increased soil pH from 7.85 to 8.05 and 8.28 for BC300, 8.15 and 8.31 for BC500, and 8.11 and 8.32 for BC700 (Table 4), mainly because of the alkalinity induced by BCs as a result of the basic oxides and carbonates produced during the pyrolytic process. Previous studies have also indicated the application effects of BCs on increasing soil pH [39–41]. However, in contrast to our results, other studies have found that alkaline soil pH decreased with biochar addition [14, 18].…”

“…The increases in soil pH could have occurred because of the increase in the level of soil exchangeable base cations with BC addition. In a study conducted on calcareous soil, Cardelli et al [39] suggested that the alkalizing effects of BC on soil pH could be explained by the poor buffering capacity of soil induced by the low levels of soil organic matter.…”

Differential Effects of Organic Amendments on Maize Biomass and Nutrient Availability in Upland Calcareous Soil

“…Organic amendments in the amount of a billion tons are added to calcareous soils into the agricultural ecosystem [7] have been reported to increase N soil organic carbon (SOC) to maintain soil fertility and carbon stocks [8]. Compost, vermicompost and biochar incorporation in calcareous soil has positive effects on the biological activity, as reported earlier [9]. Organic amendments, including farmyard manure, green manure [10], humic acid fertilizer and vermicompost improve the physicochemical properties of soil [11].…”

Potential short-term negative versus positive effects of olive mill-derived biochar on nutrient availability in a calcareous loamy sand soil

“…The occurred increases in soil pH, due to BC application, are mainly because of the alkalinity induced by BCs as a result of the basic oxides and carbonates produced during the pyrolytic process. Previous studies have also indicated the application effects of BCs on increasing soil pH [ 36 – 38 ]. However, in contrast to our results, other studies have found that alkaline soil pH decreased with biochar addition [ 14 ].…”

“…The increases in soil pH could have occurred because of the increase in the level of soil exchangeable base cations with BC addition. In a study conducted on calcareous soil, Cardelli et al [36] suggested that the alkalizing effects of BC on soil pH could be explained by the poor buffering capacity of soil induced by the low levels of soil organic matter. In this study, the EC values for control soils were 2.03 dS m -1 (CK) and 2.08 dS m -1 (CK +NPK) (Table 4).…”