Every autumn and winter, citrus is more seriously diammonium phosphate fertilizer deficient in magnesium, and the old leaves fall off in the later stage, and even some of the bottom branches are dry, and it is possible to reach the most serious time of magnesium deficiency, it is possible that when you spray it recently, add magnesium fertilizer, especially citrus of the rootstock of the citrus shell head, it is easier to lack hormones. Calcium spray all the time Magnesium does not need to worry, but only calcium spray, you need to pay attention to replenishment. Magnesium is easily moved in citrus, preferential transfer to the growth point, and the magnesium extracted from the new leaves will be transferred from the old leaves to the new leaves, so that the old leaves are magnesium-deficient; More magnesium is required for seed formation, and the magnesium of the leaves in the late stages of fruit expansion is transferred to the seed . This can lead to magnesium deficiency in leaves close to the fruit. Therefore, citrus magnesium deficiency first manifests itself in the lower old leaves and leaves near the fruit. Magnesium deficiency, from June fruit into the expansion period after the decline of the largest amplitude, and there is no effective supplement in the middle, or the amount is not enough, the entire expansion period (June-October) needs a huge amount of magnesium, after the expansion period, almost consume all the magnesium of the old leaves, naturally now will be very serious.
The greater the demand for magnesium, due to the large dap diammonium phosphate demand, so our magnesium supplement is generally supplemented in advance to prevent magnesium deficiency, and once citrus has symptoms of magnesium deficiency, if you want to recover, it is not a fertilizer that can be made up immediately. Now entering September, calcium and magnesium can be supplemented. What happens when the orchard is seriously deficient in magnesium?
1. Deliberately pursue low cost, digging trenches have not been dug, every time fertilization is sprinkled with compound fertilizer, no organic fertilizer, no trace elements, or compound fertilizer is not used, urea + calcium superphosphate + potassium sulfate (because of the serious lack of magnesium in the two wide areas, so most of the compound fertilizer has calcium and magnesium).
2. Some mountainous land, or just planted Mono Ammonium Phosphate MAP on thin soil, this kind of soil is not in the original soil, so it is more likely to be missing than the existing soil. Either acidic or strongly acidic soil. Magnesium in sandy soils is susceptible to rain. Lack of magnesium due to wetting of irrigation water;
3. Potassium fertilizer or phosphate fertilizer application too much, will also inhibit the absorption of magnesium, the expansion of the fruit stage everyone to apply puffed fruit fertilizer with more phosphorus and potassium, will inhibit the absorption of magnesium, the occurrence of magnesium deficiency symptoms. The best thing to do is to supplement together.
4. The amount of organic fertilizer used is small. The soil is compacted, there is a problem with absorption, anyway, it is necessary to plant citrus and dig a ditch once a year. Or you have long-term integration of water and fertilizer.
5. The sensitivity of different species and varieties of citrus magnesium varies, and the order of sensitivity strength is generally grapefruit> sweet orange> wide-skinned citrus.
6. Other factors: improper selection of rootstock. Nematodes are infested and stagnant potassium sulphate fertilizer water causes rotten roots. Factors such as rotten roots can also cause various deficiency symptoms in citrus due to difficult nutrient absorption.