[Effect of the melamine residue in soil on growth of Chinese cabbage]

Soil and foliar application of melamine (ME) treatments to 'Zaoshu 5' Chinese cabbage were investigated. The ME was degraded very slowly in soil treated with different dosages (40,160 and 800 mg x kg(-1)), and 90 days later the residuals of ME were 21.1%, 15.8% and 43.6% respectively. The Chinese cabbage could take in exogenously applied ME through its root and stem leaf and accumulate it to considerable levels with the increasing applied density. In soil application test, the maximum and minimum contents of ME were 105.7 and 8.0 mg x kg(-1) in root, and 139.9 and 7.1 mg x kg(-1) in stem leaf; the ME transport occurred from root to stem leaf. In foliar application test,the maximum and minimum contents of ME were 4.3 and 0.9 mg x kg(-1) in root, and 8.5 and 3.2 mg x kg(-1) in stem leaf. In soil application test,the low level of ME (40 mg x kg(-1)) increased the biomass yield by 9.8% and the high level of ME (800 mg x kg(-1)) decreased the biomass yield by 15.9%; the contents of chlorophyll and soluble sugar increased,but the content of Vitamin C decreased. Foliar application ME had no obvious significance on the growth of Chinese cabbage. The studies indicate that the residual time of ME in soil is long and the Chinese cabbage can absorb exogenously applied ME and ME can affect the growth of Chinese cabbage.