Abstract:

This experiment mainly studies the effects of different fertilization treatments on the quality of Toona sinensis in lead-cadmium contaminated soil, aiming to provide a theoretical basis for further explore the cultivation technology of pollution-free vegetables. With Toona sinensis (A. Juss.) Roem. as the test material and the heavy metal lead-cadmium combined contaminated soil and background soil as the cultivation substrate, the effects of non-fertilization (CK), single application of inorganic fertilizer (NPK), single application of organic fertilizer (WM) and combination of organic and inorganic fertilizer (1/2NPK+1/2WM) on the nutritional quality and safety quality of Toona sinensis were studied. The top buds of Toona sinensis were collected before the leaves fell, and the contents of soluble sugar, soluble protein, vitamin C, trace elements, minerals, nitrate and heavy metals were measured by conventional methods. The results showed that the soluble protein content of NPK, WM and 1/2NPK+1/2WM treated with heavy metal lead and cadmium was 4.28, 4.59 and 5.40 mg/g, respectively, which were higher than that of CK of 3.56 mg/g with significant difference (P<0.05). Under background soil condition, the contents of soluble protein under four fertilization treatments in soil matrix were 3.23, 4.62, 5.38 and 5.85 mg/g, respectively, with significant differences (P<0.05). The Vc content of the three fertilization treatments under heavy metal lead and cadmium polluted substrate was 83.36, 117.57 and 112.33 mg/100 g, respectively, which were significantly higher than that of CK (P<0.05). The Vc content in the leaves under four fertilization treatments in the background soil matrix was 51.33, 56.06, 74.03 and 65.03 mg/100 g, respectively, and that of WM and 1/2NPK+1/2WM treatments were significantly higher than that of CK (P<0.05). Whether in the background soil or in the soil contaminated by heavy metals such as lead and cadmium, WM and 1/2NPK+1/2WM could significantly improve the soluble sugar content and the content of total Fe and total Mn in Toona sinensis leaves (P<0.05), while WM treatment could also significantly increase the content of total Cu and total Zn in Toona sinensis leaves (P<0.05). Among the treatments in the two different cultivation substrates, the Pb content of Toona sinensis leaves was the lowest in CK, and that of the other treatments were significantly higher (P<0.05), while the Cd content was the lowest in NPK. The following conclusions could be drawn from this experiment: in the two kinds of cultivation matrix, 1/2NPK+1/2WM could significantly improve the soluble protein, vitamin C, soluble sugar content, beneficial microelements of Toona sinensis leaves, to some extent, it could reduce nitrate and heavy metal lead and cadmium content, so as to improve the quality of the leaves. Under the same fertilizer treatment, soluble protein, soluble sugar content, total content of Fe, Mn, Cu in leaves were much lower in heavy metal lead-cadmium contaminated soil than that in background soil, but the vitamin C content, total zinc content and nitrate content were higher in leaves in polluted soil, indicating that heavy metal pollution could significantly reduce the quality of Toona sinensisleaves.

Key words: Toona sinensis, heavy metal lead and cadmium pollution, fertilization, nutritional quality, the quality of safety