| Potassium-magnesium sulfate is a kind of compound fertilizer with a highly efficient and high-quality source of potassium, magnesium and sulfur that crops needed, is a high-quality natural mineral fertilizer, known as the "golden partner" of crop fertilization. The potassium-magnesium sulfate fertilizer application on rice, cotton, rapeseed and other field crops have a very good effect, it can also increase crop yield, quality and economic traits, enhance the ability of drought resistance, cold resistance and resistance to the pesticides poisoning when applying on ornamental fruits, tea, flowers and some other economic crops. As the production of potassium-magnesium sulfate fertilizer in the market of China is relatively new, its effectiveness, the application of conditions such as social cognition is still very low, the applying effect of the related application research on vegetables is less. In order to understand the fertilizer efficiency of potassium-magnesium sulfate on growth, quality and nutrient absorption of pakchoi and the efficiency on soil, so as to determine the optimal fertilization scheme for pakchoi and potassium-magnesium sulfate fertilization reference for the popularization and application on vegetables. This study is based on the brown soil in quaternary red clay development as the research object of pot experiment, which set up five fertilization treatments on the basis of applying a certain amount of nitrogen, phosphate, respectively NP (CK), NP+Potassium sulfate, NP+Potassium-magnesium sulfate, NP+Potassium sulfate+Magnesium sulfate, NP+Magnesium sulfate. Each processing has six K2O concentration respectively0.05-0.50g/kg soil, The results showed that:(1) The output of the pakchoi had increased significantly by using potassium-magnesium sulfate (K2) compared with the control and other treatments. With the increase of soil K2O content, the processing of pakchoi production related index increased, and showed a trend of increase first, then slow down as a whole. Under the treatments of potassium sulfate treatment (K1), potassium-magnesium sulfate(K2), potassium sulfate and magnesium sulfate mixed (KIM) with different soil K2O concentrations, pakchoi fresh weight increased by14.7%～81.0%,52.2%～69.5%, and12.9%～54.2%respectively controlled with the CK, the biggest production appeared in the K2O concentration of0.20g/kg,0.20g/kg,0.30g/kg, the growth of pakchoi is restrained under the treatment of magnesium sulfate (M) with no potassium. According to the production equation of potash fertilizer effect, the processing of potassium sulfate treatment (K1), potassium-magnesium sulfate (K2), potassium sulfate and magnesium sulfate mixed (KIM) achieve maximum yields respectively in the soil K2O concentration of0.237g/kg,0.283g/kg,0.587g/kg. Under each level of K2O application of potassium-magnesium sulphate processing, the unit nutrient output of the pakchoi is higher, and showed an advantage of high yield with low K2O content in soil compared to potassium sulfate, with the increment of the concentration of soil K2O, the growth of the pakchoi changes a little under the potassium-magnesium sulphate processing compared with potassium magnesium compost, and showed a stable effect under high K2O content. Potassium-magnesium sulfate fertilizer (K2) lead more increasing effect and output profit in equivalent conditions and showed better appearance quality.(2) K fertilizer can significantly promote the pakchoi plants on the accumulation of soluble sugar, soluble protein and Vc. The soluble sugar content under K1, K2treatment is higher when the concentration of soil K2O is less than0.30g/kg, and showed no significant differences with KIM, with the increment of soil K2O, the soluble sugar content of Kl, K2treatment decreased gradually while KIM continues to rise, the soluble sugar content of KIM was significantly higher than K2, K1processing. In addition, the application of potassium-magnesium sulfate can make the soluble sugar more accumulation in leaf in the body of pakchoi plants. The application of magnesium can improve the content of soluble protein and Vc to a certain extent in experimental conditions. The content of soluble protein of pakchoi plants increased with the concentration of the soil K2O and is always KIM> K2>K1> M under the same concentration. The Vc content of pakchoi plants of K1, K2processing which decreased with the increasing of the concentration of the soil K2O and showed no significant difference with each other is significantly higher than that of KIM processing. The content of soluble sugar, soluble protein and Vc were higher than that of control36.46%～70.83%,10.06%～52.59%and70.83%～10.06%respectively and achieved maximum when the concentration of the soil K2O is0.20g/kg by using potassium-magnesium sulfate. The research also showed that the content of soluble sugar, soluble protein and Vc along with the change of concentration of soil K2O under the treatment of K2is minimal compared with Kl, K1M and M.(3) The concentration of soil K2O has little effect on the accumulation of nitrate of pakchoi plant of different treatments, but the accumulation of nitrate is strongly influenced by the different element type of fertilizer under the test condition. The applying of potassium fertilizer can significantly reduce the nitrate content of the pakchoi compared with the CK, while the presence of magnesium in a certain extent can promote the accumulation of nitrate instead, the nitrate accumulation showed in large deposit situation especially under the condition of potassium magnesium coexist(4) Potassium-magnesium sulfate fertilizer (K2) has significant effect on the absorption of K, Ca, Mg of soil and promoting the accumulation of mineral nutrients of pakchoi plant, and the effect between Kl and KIM. It can not only maintain the normal growth and accumulate high potassium in pakchoi, but also coordinate the plant for the activation and absorption of calcium, magnesium of soil when the concentration of K2O is low, maintaining a relatively balanced plant nutrition. |
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