关键词: 参考作物蒸散量, 参考作物蒸散量, Penman-Monteith公式, 趋势分析, Mann-Kendall突变检验, EOF分析

Abstract: Leaf lettuce and lettuce were used as materials, the effect of levulinic acid on leaf vegetables yield, chlorophyll and nitrate nitrogen were studied through foliar spraying different concentrations of levulinic acid. The results showed that levulinic acid had significant difference on leaf lettuce yield and had no significant difference on the yield of lettuce. Spraying the diluted 800 times levulinic acid was the most effective on leaf lettuce yield, and increased 6.46%. Spraying the diluted 600 times levulinic acid was the most effective on lettuce yield, and increased 3.33%. The order of chlorophyll content at different positions on leaf lettuce was leaf apex＞leaf middle＞leaf base. Chlorophyll content showed no significant difference on the same parts of leaf lettuce through spraying different concentrations of levulinic acid, but different parts of chlorophyll content all increased compared to the control group. And the same time, the leaf chlorophyll contents on leaf lettuce all increased compared to the control group through spraying different concentrations of levulinic acid. In addition, Spraying the diluted 600 times levulinic acid was the most effective on chlorophyll content on the leaf of lettuce, and increased 6.95%. Spraying levulinic acid could improve nitrate nitrogen concentration of leaf lettuce, and could reduce nitrate nitrogen concentration of lettuce.