（1）生理原因

Physiological reasons

土壤中施入大量氮、钾肥后，因钾离子竞争能力强于钙离子，易使作物缺钙。磷与钙结合而使钙难以吸收;氮过量造成叶片生长过旺而影响钙的吸收。

When a large amount of N and K fertilizer is applied to the soil, the competition ability of K ion is stronger than that of Ca ion, so the crop is prone to lack of Ca.Phosphorus binds to calcium and makes calcium difficult to absorb;The excess nitrogen caused the over-growth of leaves and affected the absorption of calcium.

土壤速效钾低于正常水平时, Ca2+ 过量太多, 使植株更缺钾。所以在土壤中施用过量过磷酸钙等钙肥会造成反作用，影响果树对钾营养元素的吸收。同时也会影响到镁Mg2+、硼B等元素的吸收根部施钙由于钙的特性难以被吸收到果实中去效果大大差于叶面喷施，传送速度慢根部对钙的吸收靠蒸腾作用进行，天气不好或树势差会影响到钙的吸收，在苹果树体内很难移动；

When the soil available potassium was lower than the normal level, there was too much Ca2+ in the soil, which made the plant more potassium deficient. Therefore, excessive application of calcium fertilizer such as superphosphate in soil will cause reaction and affect the absorption of potassium by fruit trees. At the same time, it can also affect the absorption of magnesium, magnesium, boron and other elements. Because of the characteristics of calcium, calcium is difficult to be absorbed into the fruit, and the effect is much worse than that of foliar spraying. The absorption of calcium by roots depends on transpiration. Bad weather or poor tree vigor will affect the absorption of calcium, which is difficult to move in apple trees;

果实因重量远大于叶片，但蒸腾作用相似，易产生局部性缺钙；果实旺长期分配钙少易缺钙；水果因套袋减少呼吸易缺钙；果树只有.嫩根尖才能吸收到钙。

Fruit weight is much larger than leaf, but transpiration is similar, so it is easy to produce local calcium deficiency.Calcium deficiency is easy to be distributed in fruit flourishing period.Fruits are prone to calcium deficiency due to reduced respiration by bagging;Only the tender tips of fruit trees can absorb calcium.

（2）钙的吸收特性

Absorption characteristics of calcium.

目前果园补钙主要是通过土壤施用，而土壤中钙含量高达0.2%-20%，缺钙并不是土壤缺钙。

At present, calcium supplement in orchard is mainly through soil application, and the content of calcium in soil is as high as 0.2% - 20%.calcium deficiency is not soil calcium deficiency.

植物根部吸钙能力有限，一般来说，植物根部(只有嫩根尖可吸收)吸收30%钙，其它70%通过叶面及果实吸收，尤其是果实吸收.重要,因为根部与叶面吸收的钙难以补充到果实中去。

The ability of plant root to absorb calcium is limited. Generally speaking, the root (only the tender root tip can absorb) can absorb 30% calcium, and the other 70% can be absorbed by the leaves and fruits. Especially the fruit absorption is the most important, because the calcium absorbed by the root and leaf surface is difficult to supplement to the fruit.

钙绝大部分存在树干、老叶里面、嫩叶极少，这也是果实易缺钙的原因；

Most of calcium was found in the trunk, in the old leaves and in the young leaves, which was also the reason why the fruit was easy to lack calcium.

石灰质土壤钙素过多，土壤偏碱而根部吸收钙在苹果树内运输时容易形成草酸钙，运输到树冠的有效钙大大减慢、减少，这种趋势与树高度相关，树龄越大越明显。土壤板结，使铁、锰、锌、硼成不溶性，导致缺素症的发生。

Calcium in calcareous soil is too much, and the soil is alkaline, and calcium oxalate is easily formed when calcium is absorbed by roots in apple trees, and the available calcium transported to the crown is greatly slowed down and reduced. This trend is related to tree height, and the older the tree is, the more obvious it is. The soil hardens and makes iron, manganese, zinc and boron insoluble, leading to the occurrence of deficiency.

（3）市场原因

 Market Reasons

目前，由于我国叶面肥市场相对准入制度比较低，整个行业鱼目混杂，很多不法厂商生产的产品钙的含量极低甚至含量为零，再加上农民在用肥认识上的误区更助长了这些不法厂商的生存。

At present, due to the relatively low market access system of foliar fertilizer in China, the whole industry is mixed, and the content of calcium in the products produced by many illegal manufacturers is extremely low or even zero. In addition, the misunderstanding of farmers in fertilizer use has contributed to the survival of these illegal manufacturers.