不同农田施肥方式下土壤碳氮变化特征及其环境意义

为了明确不同农田施肥方式对土壤碳氮变化及其对环境的影响，通过长期定位试验研究了不同施肥方式下土壤碳氮变化特征。结果表明：土壤有机碳、全氮在土壤剖面中呈上高下低趋势，秸秆还田作用主要发生在0~10 cm处的耕层；单施化肥和化肥配施秸秆均能增加土壤有机碳、全氮含量，长期无肥处理的土壤有机碳、全氮含量明显下降，单施化肥对农田土壤有机碳、全氮含量影响不显著，长期化肥配施秸秆显著增加土壤有机碳、全氮含量，4年内增幅分别达到35.8%和17.3%；土壤有机碳和全氮含量呈极显著正相关(R2=0.78, P<0.01)，两者含量变化趋势相同；太湖地区土壤C/N比呈下降趋势，现阶段土壤C/N比主要集中在10.0左右，化肥配施秸秆可以增加土壤C/N比，促进土壤碳氮循环。化肥配施秸秆能够改善农田土壤理化性状，提高农田生产力，是一种值得推广的施肥方式。

The Variation Characteristics of Soil Organic Carbon and Total Nitrogen in Paddy Field and Its Environmental Effect Under Different Fertilization Patterns

In order to identify the variation characteristics of soil organic carbon and total nitrogen in paddy field and its impact on the environment under different fertilization patterns, an investigation was carried out to study the changes in soil organic carbon （SOC） and total nitrogen （TN） as affected by long-term fertilizations of zero fertilizer, NPK fertilizer alone and NPK with straw incorporation in flee-wheat cropping system in paddy soil in Taihu Region. The results showed that the SOC and TN over the soil profile were characterized by a gradual decrease from the top to bottom, and the effect of straw-returning was mainly in the top 0-10 cm soil layer. Both the contents of SOC and TN increased in treatment of NPK fertilizer alone and NPK with straw incorporation, and decreased significantly in zero fertilizer treatment. The increasing of SOC and TN wasn＇t significant in NPK fertilizer treatment, but SOC and TN increased significantly in treatment of NPK with straw, being 35.8% and 17.3% respectively during four years. SOC and TN had the same variation trend, which was a significant positive correlation （R2=0.78, P〈0.01）. The C/N ratio of soils was around 10.0 in Taihu Region, which declined in the past 20 years. Treatment of NPK with straw incorporation could increase the C/N ratio of soil and promote the soil carbon-nitrogen cycling. These results indicated that pattem of NPK with straw incorporation could improve the soil physical chemistry property to enhance the farmland productivity and be worth extrapolating.