Effects of different fertilization on soil nitrogen and microbial community and function in Camellia oleifera forest

【Objectives】Transformation, absorption and utilization of nitrogen are key elements for the growth and high yield of Camellia oleifera. The effects of differentfertilizer treatments on soil nitrogen content, number of microorganism and biological intensity in Camellia oleifera forest are studied, to reveal internal relationship between soil nutrient cycling and soil microbial communities, and to provide theoretical basis and scientific guidance for reasonable fertilization of Camellia oleifera. 【Methods】Using Ganwu clone of Camellia oleifera Abel grown in Haihui town, Lushan area of Jiujiang City, Jiangxi province as experimental material, this experiment was set to 4 different fertilizer treatments, Camellia specialty fertilizer (ZYF), bio-organic fertilizer(YJF), compound fertilizer(FHF) and no fertilizer (CK), 3 replicates per treatment. 【Results】Under different fertilizer treatments, the contents of soil total nitrogen, ammonium and nitrate vary largely, and the annual average contents of soil total nitrogen are in order of ZYFFHFYJFCK. For all the treatments,soil total nitrogen increases from spring to autumn with the maximum in autumn. The annual average contents of soil ammonium are in order of ZYFYJFFHFCK, and those of soil nitrate are ZYFFHFYJFCK. The seasonal variations of the contents of ammonium and nitrate are not consistent in different fertilizer treatments. Under different fertilizer treatments, the numbers of ammonifier and nitrite bacteriavary greatly, and the annual average numbers of ammonifier and nitrite bacteria are in order: YJFZYFFHFCK. The numbers of ammonifier have distinct and consistent changes in relation to seasonal variations, reaching the highest in autumn and the lowest in winter. The numbers of nitrite bacteria do not change obviously in relation to seasonal variations. The average annual levels of ammonification and nitrification intensities are in: YJFZYFFHFCK. The changes of ammonification intensity of all the treatments begin to increase from spring and reach the maximum in autumn, and then start to decline, while the changes of nitrification intensity are complicated in four seasons. The content of soil ammonium is significantly correlated with the number of ammonifer and ammonification intensity (P0.01). There are significant correlations between the content of soil nitrate, the number of nitrite bacteria and nitrification intensity (P0.01). Compared with CK, the average yields of per plant of Camellia oleifera are increased by 27.55%, 76.10% and 77.57% respectively under FHF, YJF and ZYF treatments.【Conclusions】The application of Camellia specialty fertilizer(ZYF), bio-organic fertilizer(YJF), compound fertilizer(FHF) can improve soil nitrogen contents, microbial communities and their biological intensity and the yield of Camellia oleifera. Especially the bio-organic fertilizer with rich organic matter and beneficial bacteria and Camellia specialty fertilizer with comprehensive nutrients are better for Camellia oleifera Abel. Therefore, in the practice of production, we should apply the conventional compound fertilizer as well as the application of Camellia specialty fertilizer and bio-organic fertilizer according to actual situation and local conditions.