Hebei Messi Biology Co., Ltd. stated that magnesium is a forgotten nutrient element in China and many other countries. Europe has a history of more than 80 years of magnesium fertilizer application, and the application amount of magnesium fertilizer in Europe has reached one million tons (in terms of magnesium sulfate), which is the highest in the world. The magnesium deficiency in China’s soil is also quite serious. Statistics from the agricultural department show that there are 210 million mu of soil with moderate magnesium deficiency and 140 million mu of land with severe magnesium deficiency in the country.
The Institute of Magnesium (IMI), established before September 2016, focuses on plant magnesium nutrition and the interaction between magnesium and other trace elements and other nutrients. It proposes three combined positionings – the combination of industry, agriculture, business and academia, the combination of basic and applied research on plant nutrition, and the combination of theory and practice. Faced with the current situation of severe magnesium deficiency in China’s land, the Institute of Magnesium, based in China and radiating to the world, undoubtedly caters to the new needs of the Chinese market.
With the increase in the degree of intensive agricultural production, the problem of crop magnesium deficiency has become increasingly prominent, and the demand for the application of magnesium fertilizers has become increasingly urgent. In the early 1960s, the application of magnesium fertilizer on acidic red soil in southern my country could significantly increase the yield of rice and soybean. In the 1970s, rubber trees on Hainan Island showed large-scale magnesium deficiency and yellow leaves, and crops such as peanuts, rapeseed, potatoes, beets, and corn also showed a good response to the application of magnesium fertilizer. After the 1980s, with the increase in multiple cropping index, the increase in crop yield, the large-scale application of high-concentration compound fertilizers, and the continuous reduction in the use of farmyard manure, the phenomenon of crop magnesium deficiency has become increasingly serious, and the yield-increasing effect of applying magnesium fertilizer has become more and more obvious.
The magnesium content in soil gradually decreases from north to south and from west to east
The magnesium content in my country’s soil has a trend of gradually decreasing from north to south and from west to east. The magnesium content (MgO) in the northern soil is generally 5-20g/kg, with an average of about 10g/kg. The chestnut calcium soil and brown calcium soil in the northwest contain more than 50g/kg of magnesium, while the magnesium content in the southern soil is 0.6-19.5g/kg, with an average of about 5g/kg.
The exchangeable magnesium content of soil (extracted with 1.0 mol/L NH4OAc at pH 7.0) can better reflect the magnesium supply status of the soil and can be used as a diagnostic indicator of effective magnesium in the soil. For many plants, 60 mg/kg is the critical value for magnesium deficiency, and the magnesium supply status of the soil is also affected by other cations. The exchangeable magnesium saturation of the soil (%) is also an indicator to measure the magnesium supply capacity of the soil. When the saturation of exchangeable magnesium is lower than 10%, there is a possibility of magnesium deficiency. Its value varies depending on the crop’s demand for magnesium:
The exchangeable magnesium saturation of forage grasses that require more magnesium is between 12% and 15%, while the demand of most crops is 6% to 10%, the value of leguminous crops is not less than 6%, and general crops cannot be less than 4%. In addition, the soil Ca/Mg ratio is generally required to be between 12-17. When the exchangeable Ca/Mg ratio is greater than 20, magnesium deficiency is prone to occur. The exchangeable K/Mg ratio is required to be between 0.4 and 0.5. When the soil K/Mg ratio is higher than 1.0, it is deficient. Therefore, excessive application of potassium fertilizer and lime will induce magnesium deficiency in crops. The form of nitrogen fertilizer applied will also affect the effect of magnesium fertilizer. NH4+ has an antagonistic effect on the absorption of Mg2+, while NO3- can promote the absorption of Mg2+ by crops. The degree of adverse effects of different types of nitrogen fertilizers on magnesium absorption is: ammonium sulfate> urea> ammonium nitrate> calcium nitrate. Therefore, the appropriate amount of nitrogen, phosphorus and potassium fertilizers, combined with organic fertilizers or nitrate nitrogen fertilizers, is conducive to the effect of magnesium fertilizers.
The results of the soil testing and fertilization formula test of the Ministry of Agriculture showed that 44% of the soil in my country has an exchangeable magnesium content of less than 50mg/kg, and the proportion of cultivated land below 25mg/kg is as high as 36%. The results of Xu Minggang’s magnesium application test on 22 crops showed that the application of magnesium fertilizer when the soil exchangeable magnesium content was less than 50mg/kg showed an increase in yield, and when it was less than 25mg/kg, the average increase in yield was more than 10%.
Fujian, Jiangxi, Guangxi and Hainan provinces in the tropical and subtropical humid areas of southern my country are the areas with the most serious magnesium deficiency. Different crops have different requirements for magnesium. Generally, fruit trees, leguminous crops, root and tuber crops, tobacco, beets, etc. require more magnesium than cereal crops; fruit and vegetable crops and root vegetables require more magnesium than leafy crops. Magnesium has a good yield-increasing effect on crops such as citrus, grapes, vegetables, potatoes, sugarcane, tobacco, oil palm, beets, perennial forage, rubber and olives, and attention should be paid to the application of magnesium fertilizer on these crops.
Consider the acidity and alkalinity of the soil when applying magnesium fertilizer
1. Slow-release magnesium fertilizers such as magnesium oxide, magnesium hydroxide, magnesium carbonate, dolomite powder, and calcium magnesium phosphate fertilizer are suitable for strong acidic soils. They have a good effect as base fertilizers, which can increase solubility and improve the effectiveness of magnesium, and neutralize soil acidity and eliminate H+, Al3+, and Mn2+ poisoning.
2. Magnesium sulfate and kainite are suitable for weakly acidic and neutral soils. Magnesium fertilizer can be used as base fertilizer, topdressing and foliar topdressing.
3. Water-soluble magnesium fertilizer is suitable for topdressing, while slightly water-soluble magnesium fertilizer is suitable for base fertilizer. Using 2% to 5% MgSO4·7H2O solution to spray on the leaves to correct magnesium deficiency symptoms is effective quickly. Spray once every 7-10 days and spray continuously for 2-3 times.
The effect of magnesium fertilizer is also related to the application amount. For example, when too much magnesium fertilizer is applied to rubber, the magnesium content of leaves and latex will be too high, causing early coagulation of latex, increasing rubber discharge obstacles, and being unfavorable for rubber production. It is reported that the application amount of magnesium fertilizer (MgO) for grain crops is 25 to 45 kg·hm-2; the application amount of magnesium fertilizer (MgO) for economic crops is 40 to 60 kg·hm-2; the application amount of magnesium fertilizer (MgO) for fruit trees and vegetables is 50 to 90 kg·hm-2.