| Vegetables are indispensable food, as they offer necessary vitamins, protein, amino acids, sugars, minerals, other organic and inorganic nutrients in daily life for human. China is the biggest country of vegetables production all over the world, and vegetable production has become important pillar of economic development. Acidic purple soil is China’s 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. Compared with the control, it could generally increase cabbage yield to increase application of potash fertilizer in Chongqing acid soil. When the usage of potash fertilizer was same, potassium chloride could bring higher cabbage yield than potassium sulfate. It was best for moderate amount of potassium sulfate to reduce nitrate and heavy metal content. Applying potash (potassium sulfate) and high-quality organic fertilizer (peat) at the same time, the potential of yield increase of these two fertilizers could be fully utilized. It could increase cabbage yield above 10%and reduce content of nitrate and heavy metal (except mercury).2. Compared with non-potassium, it could significantly increase fresh weight aboveground after increasing application of potash fertilizer in cadmium contaminated soil with an increase of 7.3%～37.3%. Fresh weight underground decreased obviously under cadmium pollution. The effect of increasing of application of potash fertilizer on root growth was not consistent, but the tendency is promotion. When fresh weight of cabbage aboveground reached the peak under low cadmium pollution, the concentration of potash fertilizer was 400 mg·kg-1. The concentration was 600 mg·kg-1 under high cadmium pollution. Compared with non-potassium, it could significantly increase fresh weight of cabbage aboveground after increasing application of potash fertilizer in lead contaminated soil with an increase of 7.8%～30.3%. When the concentration of applied potash fertilizer was 100 mg·kg-1 and 400 mg-kg-1 under low lead pollution, the effect of increasing fresh weight of cabbage aboveground was best, with increase of 25.3%and 25.7%respectively.When the concentration of applied potash fertilizer was 400 mg·kg-1 and 600 mg·kg-1 under high lead pollution, the effect of increasing fresh weight of cabbage aboveground was best, with increase of 31.6% and 31.9% respectively.3. It could promote cabbage growth to increase application of potash fertilizer in cadmium or lead polluted soil, for the content of chlorophyll increased and the activity of antioxidant system was enhanced. Compared with the control, chlorophyll content of cabbage increased 2.6%～8.9% after increase application of potash fertilizer under low cadmium pollution. Chlorophyll-a,b concentration decreased under high cadmium pollution disposals and leaves seem more yellow compared with other disposals which obviously indicates toxic symptom. Chlorophyll a/b was stable at 3:1 and the leaves was green without obvious toxic symptom after increasing the application of potash fertilizer. All the activity of antioxidant system enzyme(Catalase CAT, Peroxidase POD, Superoxide dismutase SOD) in cabbage increased under low cadmium pollution without obvious toxic symptom by cadmium.At the same time, all the activity of antioxidant system enzyme in cabbage decreased under high cadmium pollution with apparent toxic symptom by cadmium.The activity of antioxidant system enzyme in cabbage increased at different degree after increasing application of potash fertilizer(200～400 mg·kg-1)under two different concentration of cadmium pollution. Compared with the control, chlorophyll content of cabbage increased 2.0%～18.0% and the activity of antioxidant system enzyme in cabbage significantly increase after increase application of potash fertilizer under low lead pollution, chlorophyll a.b content of cabbage decreased a little without apparent toxic effect under high lead pollution, it could greatly inhibit the toxic effect from lead to increase the application of potash fertilizer.4. Compared with the control, it could increase the content of vitamin C and reducing sugar content in cabbage, while reduce the content of free amino acids to apply potash fertilizer in cadmium or lead polluted soil.The effect on nutrition quality of cabbage was same applying potash fertilizer in the two heavy metal polluted soils. Under low cadmium or lead pollution, nutrition quality of cabbage was best when concentration of applied potash fertilizer was 200～400 mg·kg-1. Under high cadmium or lead pollution, nutrition quality of cabbage was best when concentration of applied potash fertilizer was 400-600 mg·kg-1.5. Due to the imbalance absorption of nitrogen, phosphorus and potassium in cabbage in heavy metal polluted soil, the deficiency symptom appears in cabbage growth. It could regulate the absorption in the three elements of cabbage and promote the growth of cabbage to apply potash fertilizer. When the concentration of applied potash fertilizer in low cadmium polluted soil was below 400 mg·kg-1 the content of total potassium was proportional to the usage of potash fertilizer, but when the usage of potash fertilizer reached 600 mg·kg-1, the total potassium decreased. When the usage of potash fertilizer under low cadmium was 100～200 mg·kg-1,the crude protein and total phosphorous was highest. Under high cadmium, the optimal usage of potash fertilizer was 400～600 mg-kg-1.It was different with cadmium pollution that when the usage of potash fertilizer increased in lead polluted soil, the content of potassium significantly increased.It was reverse with cadmium pollution that when high amount of potash fertilizer(400 mg·kg-1) under low lead pollution was applied, the content of crude protein and total phosphorous was highest and when low amount of potash fertilizer (200 mg·kg-1) under high lead pollution was applied, the content of crude protein and total phosphorous was highest.6. It was mainly decrease the absorption of trace elements in cabbage to increase application of potash fertilizer in cadmium polluted soil. When high usage of potash fertilizer was applied, the antagonism between cadmium and trace elements was reduced. It could significantly improve the absorption of trace elements in cabbage to increase application of potash fertilizer in lead polluted soil, when the usage was 400 mg·kg-1 under low lead pollution and 200 mg·kg-1 under high lead pollution, the content of trace elements in cabbage was highest.7. Under low lead pollution, nitrate content sharply decreased with the increase of potassium concentration, the decline was 7.0%～27.1%. The effect of potash fertilizer on nitrate content was not consistent. When the usage of potash fertilizer was low, nitrate content in cabbage increased, but when the usage was 400 mg·kg-1 nitrate content decreased, under low lead pollution, nitrate content sharply decreased with the increase of potassium concentration, the decline was 6.2%-24.2%. under high lead pollution, nitrate content decreased 1.4%～20.6%by increasing application of potash fertilizer. Compared with non-potassium, decrease was the main tendency for the content of heavy metal (chromium, lead, mercury, arsenic, cadmium) in cabbage after increasing application of potash fertilizer. |
PDF Full Text Request