Effects Of Giant Reed Biochar On Nitrogen Bioavailability In The Agricultural Soil

Biochar, which was produced by the pyrolysis of biomass under limited oxygencondition, was a carbon-enriched and porous material. It was always used as a soilamendment due to its high retention of water and nutrients. Biochar also plays asignificant role in the carbon cycle and global climate change.Agricultural non-point source pollution, which caused by application of largeamount of nitrogen fertilizer, is forming three-dimensional pollution pattern withsoil, water, atmosphere and biology, such as soil acidification, water eutrophication,intense emission of greenhouse gas. It has caused serious impact on the sustainabledevelopment of agricultural and ecological balance. Thus, it is critical to improve theefficiency of nitrogen fertilizer utilization and mitigate the related environmentalproblems for the coordinative development of economic, ecology and environment inChina.In this thesis, biochar was produced from giant reed (Arundo donax Linn) at500°C, soil column leaching experiment and pot experiment were conducted. Theobjects of this study were to study the effects of biochar on the soil nitrogen leachingand retention, estimate the nitrogen uptake by crops growing in soils amended withbiochar and distinguish the nitrogen distribution between rhizosphere andnon-rhizosphere soils with biochar addition.The main results are presented as the following: the biochar pyrolyzed at500°Ccontained73.38%C,2.71mmol·kg-1acid surface function group,2.96mmol·kg-1basic surface function group, less aliphatic groups and more aromatic groups.In two leaching experiments, application of biochar significantly increased thepH of the leachates and soils. The amount of NH4+leached from the soils added withNH4+-fertilizer was not effected by application of bochar, while the NO3-leachingwas significantly decreased by46.0%,50.0%and81.1%in1%,2%and5%treatment,respectively. Application of biochar significantly decreased the leaching of NO3-andNH4+from the soils added with NO3-fertilizer. These results indicated thatapplication of biohar may increase nitrogen retention in soils. In the pot experiment, the application of biochar significantly stimulated thegrowth of maize and cucumber. The dry biomass of maize and cucumber wasincreased by63%~80%and19%~23%respectively. The rhizosphere parameters ofcrops such as root length, volume, surface area and tips were significantly increasedin biochar treatments. However, the total nitrogen content in both of the crops was notaffected by biochar addition and the amount of biochar.In summary, the application of biochar in soil may reduce nitrogen leaching fromsoils and retain more nitrogen in soils. Additionally, the crops growth could bestimulated by biochar addition, caused more nitrogen uptake by the crops from thesoils. Thus, biochar may be a promise soil amendment for reducing nitrogen loss andimprove crop growth.