Effects of water and fertilizers on vitamin C content in tomato under alternate partial root-zone irrigation

The effects of irrigation amount and fertilizer rates of nitrogen(N),phosphorus(P) and potassium(K) fertilizers on the vitamin C(Vc) content in tomato fruits were investigated by pot experiment under alternate partial root-zone irrigation.Quadratic orthogonal regressive rotation design with four factors was used in this study.A regression model on water and fertilizers and Vc content in tomato was established.Single and coupling effects were analyzed.The results showed that if other factors were zero codes,the Vc content in tomato increased firstly but then decreased with irrigation amount or P fertilizer rate,while decreased firstly but then increased with K fertilizer rate.However,it was not affected by N fertilizer rate.The order of effects on Vc in tomato was irrigation(X1)P(X3)K(X4)N(X2).Interaction effects between irrigation amount and P fertilizer rate and between N and K fertilizer rates were presented significantly negatively.The application of medium irrigation amount with P fertilizer rate,low N or K fertilizer could enhance the Vc content in tomato fruits.The related results still remain farther test and verify.