关键词: 线性趋势, 线性趋势

Abstract: 3-year field experiments were conducted on two yellowish red earth tea plantations in Xuancheng and Xiuning, which were mechanical plucking tea garden and artificial plucking tea garden respectively, to study the dynamic of fluoride content in the fresh tea leaves under different nitrogen levels in tea gardens located on the yellowish red earth. The results showed that, the content of fluoride in fresh tea leaves decreased year by year, and decreased with the increase of nitrogen rates in both mechanical plucking tea garden and artificial plucking tea garden. The regulation equations of Xuancheng tea garden and Xiuning tea garden were y=2.7072x²-36.641x+305.73 (R²=0.9827) and y=-0.4235x²-6.7592x+118.48 (R²=0.9815), respectively. The fluorine content in one bud with three leaves shoot increased rapidly with the delay of plucking time, but it began to decline in August. Applying nitrogen in tea garden had some regulatory effects on the fluoride content in fresh leaves of spring tea, summer tea and autumn tea. The fluoride contents decreased in the following order: summer tea＞autumn tea＞spring tea, and decreased by 27.75%, 15.41% and 12.37%, respectively, comparing to that under the control treatment. The nitrogen application benefit results showed that N180 was the best nitrogen level to reduce fluoride content in tea leaves in Xiuning and Xuancheng. The fluorine content in fresh tea leaves decreased by 1.73% and 0.45% with per kilogram N application, comparing to the control treatment. Therefore, long-term rational application of nitrogen fertilizer in tea garden can effectively reduce the fluoride content in fresh tea leaves.