Effects of nutrient solution on organics migrating from drip irrigating plastic pipes for agricultural soilless culture

It is critical to insure agricultural environment safety for human health. The effect of nutrient solution on High-Density Polyethylene (HDPE) pipes was researched to evaluate the security of agricultural plastic pipes better. 3 nutrient solutions with 3 different pH (4, 5 and 6), distilled and prepared water, were as water tested to investigate the single and interactive effect of factors on Total Organic Carbon (TOC), as an organics index, migration during 12 days by static experiment. The results demonstrated that the TOC migration patterns with time in the nutrient solutions were different from distilled and prepared water. However, the pipe brand had much effect on the TOC migrating, and r2 of relationship between total TOC migration in the first two periods (TOC0-6) and in 12 days (TOC0-12) arrived 0.781 (P < 0.001, N = 15), when only water composition was considered. Experiments of 3 factors with 3 levels were designed for brand and nutrient solution characters including formula and pH, and TOC0-12 was dependent variably. Three factors all influenced TOC migration very significantly, and the main effect of the brand was the greatest. There were very significant interactions among all factors, and the one between the brand and pH was the strongest. Considering the effect of nutrient solution contents, the ratio of N, P and K fertilizers (N/P/K) and the concentration of calcium (Ca) strongly correlated with TOC0-12.