Abstract:

Lettuce with rich nutrients is broadly cultivated around the whole years in both north and south of China. Among the three nutrient factors (N, P, K), the most amount absorbed for lettuce was K, then N and the least P. The nutrient limiting factors for lettuce growth was N and K.As a quality nutrient, the proper use of potassium fertilizer was beneficial to promote its growth, yield and quality. A field experiment was carried out to study the effect of different potassium fertilizer amount (K1, K2, K3, K4) on yield and quality of lettuce.The results indicated that there were significant differences between the yields of lettuce. The yield of lettuce was increased by 2.0%～18.5％ and the effect was in the order of K2＞K1＞K3＞K4 and the increase efficiency of yield by potassium fertilizer in the order of K1＞K2＞K3＞K4.Comapred to CK1,the nitrate concentration in lettuce leaf and stem were increased by 12.9%～140%,but application potassium fertilizer reduced the nitrate concentration in lettuce stem and leaf by 12.2%～43.8% and 20.6%～35.0%.The relationship of nitrate concentration in lettuce stem , leaf and potassium fertilizer could be well described with quadratic regression equations.Comapred to CK1,different treatments mainly had negative effects on Vc and soluble sugar in lettuce stem ,but the contrary effect were showed in leaf .The K1 and K2 treatments had positive effects on Vc and soluble sugar of lettuce.The amino acid concentration in lettuce leaf and stem were mainly decreased under different treatments。K2 treatment （K2O 150kg/km2）was best treatment for higher yield and quality of lettuce.