肥际氮素浓度下添加不同碳源对水稻土微生物特性的影响

研究肥际氮素浓度下添加不同碳源后微生物的变化特征,对于了解不同活性碳源对肥际养分浓度下氮素转化和调控作用以及提高氮素利用率等具有重要意义。采集我国亚热带地区典型的水稻土,模拟肥际氮素浓度,设置不同硫铵用量和葡萄糖、纤维素或木质素碳源添加处理,进行室内培养试验,研究了各处理土壤微生物生物量碳氮、矿化及微生物群落功能多样性的变化。结果表明,在培养7天和35天,高氮素用量下与不添加碳源处理相比,添加葡萄糖、纤维素和木质素各处理土壤微生物生物量碳分别增加5.0%～126.8%、17.5%～210.9%和14.7%～210.0%,微生物生物量氮分别增加-5.4%～109.3%、32.0%～173.1%和-14.2%～194.8%(负数表示减少)。而中等和常量氮素条件下添加这3种碳源,土壤微生物生物量碳氮也呈增加趋势。肥际氮素各浓度下添加葡萄糖处理CO2释放量最多,其次是添加纤维素,最后是添加木质素。BIOLOG分析显示,高、中氮素用量下,平均吸光值(AWCD)、Shannon、Simpson和McIntosh指数都较低,添加3种碳源处理后均有提高,而单独添加不同碳源及添加常量氮素和碳源处理,AWCD值和微生物功能多样性指数水平较高。较高的肥际氮素浓度下添加葡萄糖、纤维素或木质素可提高土壤微生物活性。在当前大量施无机氮肥的条件下,注重有机物的配合施用,有利于减小氮素损失的风险。

Effects of addition of carbon on microbial properties as affected by source of carbon and N concentration at Fertisphere in paddy soil

The study on changes in microbial properties as affected by addition of carbons of different sources and N concentration at the fertisphere is of great significance to understanding of effects of carbons of different sources regulating nitrogen transformation in fertispheres different in concentration and improving nitrogen use efficiency. Samples of paddy soils typical of the subtropical region of China were collected and treated with ammonium sulphate at different rates and carbons of different sources, separately to simulate different fertispheric nitrogen concentrations. The treated soil samples were then incubated in lab and analyzed for changes in biomass carbon and nitrogen of the soil microbes, nitrogen mineralization and functions of the microbial communities. It was found that after 7 or 35 days of incubation, in treatments high in N application rate, addition of glucose, cellulose and lignin separately increased microbial biomass carbon by 5.0%~126.8%, 17.5%~210.9% and 14.7%~210.0%, respectively, and microbial biomass nitrogen by -15.4%~109.3%, 32.0%~173.1% and -34.2%~194.8%, respectively, and in treatments, medium or low in N application rate addition of any of the three types of carbon also stimulated somewhat increase of microbial biomass carbon and nitrogen. Regardless of fertispheric N concentrations, the treatments with glucose were the highest in CO2 emission, those with cellulose came the next and those with lignin the last. BIOLOG analysis shows that AWCD value and Shannon, Simpson and McIntosh indices were all quite low in treatments either high or medium in N application rate, and they were increased after addition of carbon. In treatments with carbon added alone or treatments with carbon and N fertilizer added at a normal rate, AWCD value, Shannon, Simpson and McIntosh indices were all relatively high. In treatments high in fertispheric N concentration, addition of any of the three, glucose, cellulose or lignin increased soil microbial activity. So, in the current condition of using large volumes of inorganic N fertilizer, it is advisable to use organic manual in addition, which helps reduce the risk of nitrogen loss.