Effects of several chemicals on yield, nitrate content and nutritive quality of lettuce

The orthogonal design, L₈(2⁷), was adopted to study the effects of gibberellin (GA), ammonium molybdate (Mo) and dicyandiumide (DCD) on the yield, nitrate content and nutritive quality of lettuce. The results indicate that the yields of lettuce are increased by 10.7%～41.6% by three chemicals combined treatments with the following sequence, Mo＞GA＞DCD. The nitrate contents in stem and leaf are decreased by 21.8%～54.5% and 4.3%～40.2%, respectively, with the following sequence, GA＞DCD＞Mo. Compared with CK, the contents of Vc and amino acid in stem are reduced while the water content increases according to the yield of lettuce with different fertilization. The contents of Vc and amino acid in leaf are improved but the water content does not change obviously. The spraying of ammonium molybdate can lead to the accumulation of Mo in lettuce, but it does not exceed the safe limit. According to the yield, nutritive content and healthy quality of lettuce, the optimum treatment is A₁B₁C₁ (GA 25mg/L+Mo 150mg/L+DCD 12.5mg/pot).