Prevention and treatment of magnesium deficiency in Citrus

In recent years, due to the transfer of a large number of rural labor force to cities and towns, the amount of livestock raised by farmers is decreasing, and the source of organic fertilizer is significantly reduced. Coupled with the depressed fruit prices for many years, the amount of organic fertilizer used by fruit farmers in fruit production has been greatly reduced, or even not used. As a result, the phenomenon of element deficiency in orchards has been increasing in recent years. Especially for the medium element magnesium, the demand of fruit trees is large, and the supply of magnesium in soil is insufficient. The loss of magnesium in Rain Water soil in southern red and yellow soil is serious, resulting in more and more serious symptoms of magnesium deficiency in orchards. In the production, the correction of magnesium deficiency in citrus is mainly solved by the application of magnesium fertilizer, but in recent years, fruit growers generally reflect that the correction effect is not obvious after magnesium application. According to the summary of experiments on different application methods of magnesium fertilizer carried out by the author in recent years, the key to the correction of magnesium deficiency in citrus lies in the application method. At the beginning of magnesium deficiency in citrus, the leaves were yellowed, and the green area at the base of the leaves was inverted "V". As a result, the more plants were yellowed, the more serious the yellowing was, and then the main and lateral veins were swollen and corked like boron deficiency. The whole leaf may become bronzed and fall off early, which seriously affected the yield and quality of the local citrus. The correction of magnesium deficiency is in the red and yellow soil in the south, and the soil pH value is 4.5-6. Generally, magnesium fertilizers such as magnesium oxide, magnesium lime, calcium magnesium phosphate fertilizer and so on can be applied to supplement magnesium in the soil. The effect of these magnesium-containing fertilizers is slow, and it is suitable to be used as a mixed ditch with mature pig and cow manure, cake fertilizer and other organic fertilizers near the crown dripping line, mainly for the prevention of magnesium deficiency or orchards with mild disease. The application amount per mu is 20kg magnesium oxide and 50kg magnesium lime or calcium magnesium phosphate fertilizer. For orchards with symptoms of magnesium deficiency, the effect of applying magnesium fertilizer once a year is not obvious. The key is to apply quick-acting magnesium sulfate and magnesium nitrate fertilizer 3-4 times a year for correction, and after continuous application for two years, the yellowing symptoms will be alleviated and the effect will be significant. Citrus fruit trees can be combined with winter base fertilizer, pre-anthesis or post-anthesis fertilizer from February to March, fruit protection fertilizer in May and shoot-promoting and strong fruit fertilizer in July. The annual application amount of soil is 50-60 kg per mu. In order to increase the correction effect, foliar fertilization can be carried out every 10-15 days after the spring shoot leaves are unfoliated and sprayed with 1% magnesium nitrate or magnesium sulfate solution for 3 times. After magnesium deficiency is alleviated, organic fertilizer, slow-acting and quick-acting magnesium fertilizer should be applied every year to ensure a uniform supply of magnesium in order to get a more thorough correction.