Effect of application of biogas slurry on nitrate content and nutrition quality of lettuce and romaine lettuce

A pot experiment was conducted to study effect of application of biogas slurry on nitrate content and nutrition quality in romaine lettuce and lettuce. The results show that the application of biogas slurry increased plant height and yield of the crops, which had lower nitrate contents but higher water and amino acid contents (in lettuce) and higher vitamin C content (in romaine lettuce). On the basis of N,P,K fertilization (N∶P∶K=120∶80∶100 mg·kg ^-1 ), additional application of biogas slurry at 500 ml·pot ^-1 improved nutrition quality of the vegetables by decreasing nitrate content in the leaves of lettuce and romaine lettuce by 53.5% and 45.5% respectively, and also increased yield by 51.0% and 56.7% , respectively.Under this experiment conditions, the fertilization recommendation is the best for the two crops.