The Effects Of Adding Peanut Shell Biochar On Nitrification In Acidic Soil In Northern China

Biochar, referred to as a carbon-riched material, produced from biomass under a low or zero oxygen environment with the intent for soil amendment and carbon sequestration. Due to special physicochemical properties (e.g., surface oxygen-containing functional group, pore structure and cation exchange capacity), biochar plays a significant role in soil fertility, the storage of atmosphere carbon, and the envrionmental remediation. For this reason, applying biochar into soil received extensive attention. In this thesis, biochars produced from peanut shell at different temperatures were used to study the intrinsic relationship between the pyrolysis temperature and the different physicochemical properties of biochars. Soil acidification, intensified nitrification and reduction of N bioavailability were three substantial issues which prevent the healthy and sustainable development of agriculture in north China. An incubation experiments were carried out to study the effects of different amount of biochar on soil physiochemical property and soil microbial diversity, nitrification, rape gowth and N bioavailability in acidic soil. Furthermore, the mechanisms of biochar on nitrification were discussed. The outcomes of this research may provide a reference for the application of biochar in agriculture.The main results as follow:(1) With increasing temperatures, C content increased, while H and O content decreased. Ash content, pH and specific surface area aslo increased, whereas cation exchange capacity decreased.(2) Applying biochars to soils is suggested as an effective way for improving soil quality. The effect of biochar on acidic soil physical and chemical properties were investigated using incubation experiments in greenhouse. Results showed that biochar additon to acidic soil could effectively increase the soil pH value, cation exchange capacity and soil organic matter content, and With increasing of biochar application rates, soil pH, cation exchange capacity and soil organic matter content clearly increased. Biochar increased acidic soil pH depended on not only the ash of the biochar but also on other effect.(3) Applying biochar treatments increased the total microbial activity. In the view of applying biochar proportion,3%BC treatment showed the highest total microbial activity, followed by 1%BC treatment, and 5%BC treatment showed the lowest total microbial activity. Both 3%BC and 1%BC treatment increased the AWCD, species richness index, evenness index and dominance index.3%BC treatment were higher than 1%BC treatment. while the 5%BC treatment decreased the AWCD, evenness index and dominance index.(4) Adding biochar into soils has potential to manipulate the nitrification process due to its impacts on nitrogen (N) cycling. However, the exact mechanisms underlying alteration of nitrification process resulted from biochar addition into soils are still not clear. The effects of peanut shell biochar on nitrification process in an acid soil were tested. Results showed that the nitrification was suppressed by peanut shell biochar addition due to decreased NH4+-N content and reduced ammonia-oxidizing bacteria (AOB) abundance in biochar-amended soils. The AOB population size was decreased by two to four orders of magnitude following the peanut shell biochar addition. Removal of phenolic compounds (PHCs) from peanut shell biochar resulted in increase of the abundance by more than three orders of magnitude. Denaturing gradient gel electrophoresis (DGGE) fingerprint profiles showed that PBC-PH treatment had an increase in the diversity of the AOB community compared to the peanut shell biochar treatment. While, there was no significant difference in the abundance of AOB between the raw biochar treatment and no polycyclic aromatic hydrocarbons biochar treatment.(5) The low N bioavailability constraints of crop production for sustainable development. A pot experiment was conducted to clarify the effects of biochar on rape growth, root distribution, N bioavailability and rhizospheric environment. Results showed that biochar applied in soil could stimulate the rape growth, including the increase of biomass and the parameters of root morphology. 3%BC treatment was significantly higher than 1% BC treament and 5%BC treament. Applying biochar treatments decreased N AE (N accumulation efficiency) by 19.8-41.2%, but increased the NUE (N utilization efficiency) by 11.3-15.0%, indicating that biochar addition may improve N bioavailability in acid soil. By adding into biochar, the Total N,organic matter and the CEC of rhizosphere soils increased and pH decreased.The rhizosphere soil organic matter and CEC were higher than that in non-rhizosphere soil, total N was lower than the non rhizosphere soil. The effect of biochar on AOB was more than that of rhizosphere.