Influences of Farmyard Manure and its Biochars Prepared at Different Temperatures on Soil Properties and Soil Enzymes and CO2 Emission from Soil Under Irrigation Conditions with Treated Wastewater

While irrigation with treated wastewater and using farmyard manure are important in the effective use of resources, this dual considers a more economical strategy by improving the soil properties thus increasing the yield. However, soil-sourced CO2 production that may occur in this case reveals the risks of both global warming and infertility of the soils with carbon loss from the soil. In this case, biochar, an organic improver, provides carbon sequestration, reducing emissions and maintaining soil fertility. However, the emission-reducing and soil-improving effects of the biochar, which is prepared by the pyrolysis of organic-raw-material at different temperatures, are not clear depend on the pyrolysis temperatures. In this study, the emission-reducing and improving physical-chemical properties and enzyme activity of soil by mixing farmyard manure and its biochars prepared at different temperatures into the soil irrigated with treated wastewater were investigated. The results showed that the biochar prepared at low pyrolysis temperatures had a higher improvement effect on the porosity, wet aggregate stability, organic matter/carbon, total N and cation exchange capacity of soil, and biochar prepared at high temperatures increased the EC and pH of the soil more, while the application of biochar prepared at low temperatures to the soil resulted in a decrease in bulk density of the soil. In addition, while the highest enzyme activities were obtained from farmyard manure, the biochar prepared at low temperatures increased the enzyme activity of the soil more than high temperatures. The improvement in soil properties was higher in irrigation with treated wastewater according to fresh water but it caused 42.7% more CO2 production from soil. While 20.6% to about 2 times more soil CO2 production was obtained from farmyard manure according to soil and biochar treatments, its biochars significantly reduced CO2 emissions and the emission-reduction effect of biochars with increasing pyrolysis temperature was further increased. Considering that biochar prepared at low temperatures supports the improvement in soil properties but causes higher CO2 production, in the irrigation conditions with treated wastewater, the use of farmyard manure biochar prepared at high temperatures was found to be advisable to improve agricultural and environmental sustainability.

Automated summary

Irrigation with treated wastewater and using farmyard manure are important for resource utilization. However, soil-sourced CO2 production may pose risks of global warming and soil infertility. Biochar prepared at different temperatures can sequester carbon, reduce emissions, and maintain soil fertility. This study investigates the effects of biochar prepared at different temperatures on soil properties and enzyme activity when mixed with farmyard manure and irrigated with treated wastewater.