Effects of application rates of N,P fertilizer on yield and nitrate accumulation in lettuce

An experiment was carried out on field to investigate the relationship between the yield,nitrate accumulation and N,P fertilization level in lettuce.The yield of lettuce increased 32.4%,when the rates of N and P were reduced to 46.4% of that in high fertilizer groups.N and P,applied in proper combinations,are important factors for high yield of lettuce.The optimal level of nitrogen for high lettuce yield was 180～270 kg·hm-2,and that of phosphorus was 125～190 kg·hm-2.The content of nitrate in lettuce increased with the increasing of nitrogen levels of fertilizers.Appropriate phosphorus levels could restrain nitrate accumulation of lettuce.Proper N,P combinations could improve the quality of lettuce and increase yield.