Effect of fertilization on nitrate and nutrient forms of lettuce in acid garden soils

Effects of different nitrogen, phosphorus and potassium ratios combination with complex nitrification inhibitors on the yield, nitrate content and nutrient forms of lettuce(Lactuca saliva L. ) were studied in three acid garden soils under field experiment condition. The results indicated that the yield of lettuce was in the order of little acid soil > acid soil > strong acid soil. In acid and strong acid soil, the yield of lettuce was significant increased by 6.2%-18.2% , but decreased in little acid soil. The nitrate contents of lettuce stem and leaf were decreased by 25.1%-76.3% and 3.1%-27.7% (except in little acid soil) in HNK treatment (high rate of N and K fertilizers) combination with complex nitrification inhibitors. The effect was stem > leaf and the HNK + C2 (complex nitrification inhibitor No. 2) treatment was best. The nitrate content of lettuce leaf in three soils was acid soil>little acid soil>strong acid soil, and nitrate content of lettuce stem was highest in acid soil. The nutrient forms of N, P, and K in lettuce leaf were mainly protein N, non - protein P and non - protein K. The ratio of protein N to total N, protein P to total P, protein K to total K was increased in HNK + C1 (complex nitrification inhibitor No. 1) and HNK + C2 treatments. There were significant negative correlations between nitrate content and total N, protein N, total P, protein P, protein K of lettuce leaf.