Effect Of Potash Fertilizer On Cabbage-Growing Soil Polluted By Lead And Cadmium

Vegetables are main sources for human to absorb necessary vitamins, minerals, other organic and inorganic nutrients in daily life. Acidic purple soil is Chinese unique resources with the most concentrated distribution in Sichuan basin. Recently acidic purple soil in Chongqing has been greatly polluted, and the growth and quality of vegetable in such soil has been a highlight in research. This paper firstly studied the effect of different varieties and amounts of potash on the heavy metals concentration in foliage plant in field experiment with the combination of field and pot experiment and chemical analysis. Then the effect of potash on the absorption and accumulation of heavy metal, physiological characteristics of Chinese cabbage and nutrition indicators was further studied through pot experiment, with aim to find the appropriate usage of potash to reduce heavy metal pollution in Chinese cabbage and provide theory support for scientific application of potash in healthy vegetable production. Results showed that:1. In lead-polluted soil it could significantly decrease available lead content after six varieties of application of potash fertilizer along with the training time. The decreasing effect is as follows: KH2PO4>K2SO4>K2CO3>KNO3>KCl>HA-K. The available lead content is decreased by32.6%and33.4%in low-lead and high-lead soil, respectively. Compared with non-potassium, in cadmium-polluted soil the available cadmium content could increase in the beginning and then descend. KCl enhances available cadmium content in soil. The other five potassium fertilizer could decrease soil available cadmium content under the condition of CdLKL,CdLKH,CdHKL with no significant difference with control group.2. In lead-polluted soil, fresh weight aboveground in the K2SO4,KCl,KNO3treatment could be significantly increased. When increased by400mg/kg, the optimum fresh weight could be obtained. In low-cadmium-polluted soil, the cabbage biomass aboveground could be increased in six treatments, compared with control group and by1.8%～36.2%and1.9～68.9%in low-potassium and high-potassium treatments, respectively. In high-cadmium-polluted soil, the cabbage biomass aboveground could be significantly decreased in six treatments. compared with control group and by70.9%-77.1%, because possibly the cadmium concentration (10mg/kg) have far exceeded the biological critical value and highly impeded the cabbage growth.3. It could promote cabbage growth to increase application of potash fertilizer in cadmium or lead polluted soil, for the content of chlorophyll increased. In the soil with same lead stress, the chlorophyll content is lower in high-potassium application than in low-potassium application. In cadmium-polluted soil, though compared with CKL,CKH, chlorophyll content could be enhanced partly, it was still lower than in CK0. Therefore, potassium application could impede the toxic effect of cadmium on chlorophyll biosynthesis to some extent, but limited and could not get rid of the effect of cadmium stress completely. 4. In cadmium or lead polluted soil the activity of POD in cabbage decreased while the activity of CAT and SOD in cabbage increased, compared with CK0.Under lead stress the activity of POD and CAT in cabbage in all kinds of potash fertilizer treatments could be significantly decreased, and the activity of POD is higher under low-lead stress than under high-lead stress. K2SO4, KNO3and KH2PO4could improve the activity of SOD in cabbage. K2SO4, K2CO3and HA-K could increase the activity of POD and SOD in cabbage in cadmium polluted soil, however all kinds of potash fertilizers could improve CAT activity, and CAT activity in the same potash fertilizer treatments could be increased gradually with the increasing of potassium application.5. In lead-polluted soil, the lead content of the cabbage in the six kinds of potash fertilizer treatments free amino acid could be significantly decreased. Reducing sugar content in cabbage could be increased by KCl and K2CO3treatment. Vitamin C content could be increased by KCl, K2SO4,KNO3and K2CO3treatment. In cadium-polluted soil, reducing sugar content in cabbage could be decreased and vitamin C could be increased by enhancing potash-fertilization. Free amino acid content in cabbage could be increased by increasing potash-fertilization in low-cadium stress and could be reduced by potash fertilization in high-cadium stress.6.In lead-polluted soil, the lead content of the cabbage in the six kinds of potash fertilizer treatments except for KCl could be significantly decreased. The decreasing effect is as follows:HA-K> KH2PO4>K2SO4>KNO3>K2CO3>KCl,and the lead content is lower in high-potassium application than in low-potassium application. The lead content of the cabbage in the six kinds of potash fertilizer treatments except for KCl(CdHKH) could be significantly decreased by8.6%～40.5%. So it is concluded that application of potash fertilizer in cadmium-polluted soil could decrease the content of cadmium in cabbage.7. The nitrate content in cabbage is significantly increased under the stress of lead and cadmium, compared with CKo. When the six kinds of potash fertilizer was applied, KNO3could significantly promote the cabbage nitrate content compared with control group and the other five treatments could significantly lower cabbage nitrate content. In all treatments the nitrate content in cabbage is within the limits of food safety.