氮肥深施及间种白三叶草对茶园N2O排放的影响

N2O Emissions from a Tea Field with Deep Application of Nitrogen Fertilizer and Intercropping with White Clover

近年来我国茶园面积不断扩大,茶园施氮(N)量大、N2O排放量高,是重要的N2O排放源,开展茶园的N2O减排研究十分有必要.本研究在位于我国亚热带丘陵区的典型茶园,通过设置常规施肥、氮肥深施和间种白三叶草这3种处理,观测不同施肥及管理措施下茶园土壤N2O排放及其相关土壤环境因子动态,旨在明确不同措施对茶园N2O排放的减排效果,并解析相关影响因子.通过3a的田间试验表明,亚热带丘陵茶园具有较高的N2O排放,N2O-N年累积排放量高达5.1~10.1kg·hm^-2.N2O排放主要发生在春夏季,当土壤温度低于15℃,其排放主要与土壤温度呈正相关;当温度高于15℃,则主要与土壤含水量、土壤NH4^+-N和NO3^--N含量呈正相关.三年间茶园间种白三叶草较常规施肥未显著影响N2O排放,肥料深施在降雨量较高年份增加了茶园N2O排放,间种白三叶草和肥料深施未显著影响茶叶产量.本研究表明,亚热带茶园间种白三叶草减排N2O的效果不显著,不减少氮肥用量下氮肥深施未能降低N2O排放,今后有必要研究肥料深施配合氮肥减量来减排N2O.

In recent years,the area of tea fields in China has expanded.The application rate of nitrogen fertilizer is usually high in tea fields,which causes high N2O emissions.Tea fields are important sources of N2O emissions;thus,it is necessary to research N2O emission reduction in tea fields.A three-year field study was conducted to investigate soil N2O emissions and influencing factors under different fertilization measurements in a typical tea field in a subtropical hilly region of China.Three treatments-conventional fertilization,deep application of nitrogen fertilizer,and intercropping with clover-were studied to measure the soil N2O fluxes and the related soil and environmental properties.The results showed that the subtropical hilly tea field had high N2O emissions,and the cumulative annual emissions of N2O-N were as high as 5.1-10.1 kg·hm^-2.The N2O emissions occurred mainly in spring and summer. When the soil temperature was lower than 15℃,the N2O flux shown mainly a positive correlation with the soil temperature.However, when the soil temperature was higher than 15℃,the positive correlation was mainly with the soil water,soil NH4^+-N,and NO3^--N contents.Compared with conventional fertilization,the intercropping of white clover did not significantly reduce N2O emissions, although deep application of fertilizer increased annual N2O emissions when the rainfall was high.Neither intercropping of white clover or deep application of fertilizer affected the tea yield or the yield-scaled N2O emissions compared with conventional fertilization.Our study indicates that both intercropping of white clover and deep application of fertilization without reducing the nitrogen application rate did not reduce the soil N2O emissions in subtropical tea fields.Further studies are needed to determine the effects of deep fertilization application combined with a reduction in the nitrogen application rate on N2O emissions from tea fields.