What types of calcium fertilizer are there? These soils and crops are prone to calcium deficiency

The calcium fertilizers commonly used in production at present include quicklime, containing 94%-96% calcium (CaO); hydrated lime, formed by quicklime absorbing water, containing 64%-7526 calcium; carbonate lime, made by grinding limestone and marl, whose main component is calcium carbonate; and gypsum, whose main component is calcium sulfate. In addition, some nitrogen, phosphorus and potassium fertilizers also contain a certain amount of calcium. 

The application of calcium fertilizer can be divided into base fertilizer and topdressing:

(1) Base fertilizer, mainly for improving soil. In acidic soil or acidified soil under protected cultivation, lime generally needs to be applied, using 50-100 kg per 667 sq m; on alkaline soil, gypsum should be applied, using 100-200 kg per 667 sq m;

(2) Topdressing. For plants that have already shown calcium deficiency symptoms, 0.3%-0.5% calcium nitrate or calcium chloride can be sprayed continuously 2-3 times, with an interval of 7 days each time, and has a relatively good corrective effect. 

Which soils and crops are prone to calcium deficiency?

China's calcium-deficient soils are mainly distributed in acidic red soils in the south and sandy soils with low exchange capacity. In the saline soils of North China, Northwest China, the western part of Northeast China and the southeastern coastal areas, the pH is mostly above 9, sodium predominates in the soil, and exchangeable calcium is low, sometimes only 1 mg/100 g soil, which also easily causes calcium deficiency in crops. It should be pointed out here that sometimes the soil is not calcium-deficient, but high soil salinity will affect the absorption of calcium by crops, and will also cause crops to show calcium deficiency symptoms, which should be distinguished. 

Different crops have different calcium requirements. Crops with high calcium requirements include purple alfalfa, asparagus, kidney bean, pea, soybean, sunflower, sweet clover, peanut, tomato, celery, Chinese cabbage, potato, sugar beet, grape, etc., while rice, barley and wheat and other cereal crops, pineapple, peach trees, etc. require less calcium. Therefore, on the same soil, crops with high calcium requirements are prone to calcium deficiency.