All About Calcium Supplementation in Crops (Part 1)

Release Date:

2021-06-06

Calcium is an essential nutrient for crop growth and development; in 80% of fruit trees and vegetable crops, calcium requirements exceed those for phosphorus. Both root development and the growth of stems and leaves demand substantial amounts of calcium, while calcium uptake by fruits often surpasses that of nitrogen. Calcium deficiency has become a major factor limiting both yield and quality in Chinese agriculture. According to statistics, at least 40 types of physiological disorders in fruits and vegetables are attributable to low or insufficient calcium levels.

I. The Role of Calcium

The physiological functions of calcium are closely associated with cell wall components. Calcium is a structural constituent of plants, primarily forming calcium pectate, calmodulin‑bound proteins, and calcium‑magnesium inositol hexaphosphate, among others. In the vacuole, it exists as abundant organic calcium salts, such as calcium oxalate, calcium citrate, and calcium malate. Calcium helps stabilize cell membranes and cell walls, participates in second‑messenger signaling, regulates osmotic processes, and exhibits enzymatic activity.

1. Calcium can stabilize biomembrane structure and maintain cell integrity.

A stable biofilm environment can enhance a crop’s stress tolerance. Moreover, since calcium increases the selectivity of cell membranes for the uptake of potassium, sodium, and magnesium ions, and potassium and sodium ions, in turn, promote cellular stability, this further improves the crop’s stress resistance.

2. Can help prevent premature aging.

Crop senescence is closely linked to the production of ethylene within the plant, and calcium ions can mitigate ethylene biosynthesis by modulating cell membrane permeability, thereby helping to prevent premature aging. If you want to avoid early crop death, applying calcium fertilizer is essential.

3. Stabilize the cell wall

Calcium deficiency can lead to the disintegration of fruit cell walls, causing the cell walls and middle lamella to soften, followed by cell rupture and the development of watercore and core rot. Moreover, calcium deficiency reduces cell wall rigidity, thereby diminishing the cells’ resistance to fungal infection and resulting in fruit cracking.

4. Calcium has a swelling effect.

Calcium promotes cell elongation, thereby contributing to fruit enlargement. At the same time, it also stimulates root cell elongation, thus enhancing root growth and development.

II. How to identify calcium deficiency in crops?

Calcium deficiency often leads to reduced crop yields, diminished quality, and increased susceptibility to diseases. Many common ailments encountered in routine production are, in fact, linked to calcium deficiency in crops—for example: bitter pit and sunken spots on apples; blossom‑end rot in tomatoes and peppers; browning and rotting at the apex of potatoes; fruit rot and empty pods in peanuts; yellowing of the inner leaves in chives, and so on. Although fruit cracking in grapes, cherries, watermelons, and other crops is often associated with excessive irrigation during ripening, insufficient calcium—resulting in thin, poorly elastic fruit skins—is also a key contributing factor.

Common symptoms of calcium deficiency in crops
1	Symptoms initially appear on the shoot tip and young leaves, then gradually spread to the lower leaf surfaces.
2	Typically, this manifests as damage to the growing point; in severe cases, the growing point may undergo necrosis, leading to soft, drooping stems that exhibit a “broken‑neck” symptom.
3	Young roots are deformed, the root system is stunted, root tips undergo necrosis, and root hairs are abnormal—some appear scale-like—and the overall root biomass is reduced.
4	Young leaves become chlorotic, deformed, and develop a hooked shape; leaf blades wrinkle, leaf tips twist, and leaf margins curl and turn yellow; necrosis occurs between the veins.
5	In severe cases, new leaves struggle to emerge, may even stick together, or exhibit irregularly serrated margins with cracking and necrotic spots.

Crop	Typical symptoms of calcium deficiency
Apple	When apples suffer from calcium deficiency, nutritional imbalance leads to yellowing and premature leaf drop. On new shoots, young leaves develop discoloration or necrotic spots, with leaf tips and margins curling downward. Older leaves may exhibit partial dieback. Fruits often develop bitter pit, characterized by sunken spots on the surface, softening of the flesh, and a bitter taste. Calcium deficiency can also cause watercore, in which the flesh becomes translucent and water-soaked, spreading radially from the center; eventually, the intercellular spaces fill with juice, resulting in internal rot.
Grapes	Leaves turn yellow, are small, thin, and curled; there is severe variation in leaf size, with fruits easily dropping or cracking. On young leaves, chlorosis appears between the veins and along the margins, accompanied by gray‑brown spots; later, needle‑shaped necrotic lesions develop near the leaf edges, and the shoot tips eventually die back.
Kiwi fruit	Leaves turn yellow, become smaller, curl up, lose their texture, and are prone to ulceration; fruits soften and drop easily, shortening both the storage life and shelf life.
Citrus fruits	Calcium deficiency in citrus primarily manifests on new leaves: the leaf tips turn yellow first, with the discoloration spreading toward the leaf margins. The affected leaves are narrower and more deformed than healthy ones. As the condition progresses, the yellowing area expands, leading to extensive dieback of shoots and premature leaf drop. Citrus trees have few fine roots, with weak root growth; the roots easily turn black and rot, resulting in root rot disease. Early calcium deficiency can cause severe fruit drop, small and misshapen fruits, and shrunken juice vesicles. Fruit softens and loses firmness, and because the peel lacks resilience and is not sufficiently tough, cracking may occur.
Pomegranate	After calcium deficiency, pomegranates frequently develop fruit cracking during the growing period, resulting in a reduced yield of marketable fruit.
Peach	In calcium-deficient peach trees, reddish-brown or dark brown necrotic areas develop on the young leaves at the shoot tips, originating from the leaf apex and margins or along the midrib. In severe cases, the shoot tips and tender leaves appear scorched; in even more serious instances, the apices of small branches wither and die, accompanied by extensive leaf drop.
jujube	When jujubes are deficient in calcium, fruit cracking begins as they approach maturity; in severe cases, the cracking rate can exceed 60%.
Wheat	The growth point and stem apex die, resulting in stunted or tufted plants; young leaves often fail to unfold, and the developed leaves frequently exhibit chlorosis. The root system is short with numerous branches, and the root tips secrete a transparent mucilage that adheres to the root tip in a spherical form.
Corn	The plants are stunted, with leaf margins sometimes exhibiting irregular, white, serrated splits. The stem tips curve into a hook-like shape, and the growth of new leaves is severely inhibited, resulting in near-complete chlorosis. Transparent gum exudates cause the leaf tips to stick together, preventing normal expansion; the leaves become shriveled and yellowed. In older leaves, the margins develop white, translucent, irregularly serrated breaks, while the leaf tips show brown, scorched necrosis. The older roots are predominantly brownish‑brown. When calcium is deficient, the leaves are thin and small, with reduced stress tolerance; the stems are slender and prone to lodging, the ears are small with poorly filled grains, and overall grain quality is poor.
Rice	Symptoms first appear on the roots and the young aerial parts; plants become stunted, with tissues aging prematurely, exhibiting senescence before their time. Young leaves curl, and the heart leaves dry out. The terminal portions of the mature heart leaves turn yellow and wither, while older leaves remain green but become distorted and curled. Fruit set is poor, with many empty pods. Roots are few and short, and the tips of new roots turn brown and necrotic.
Potato	Pale green streaks appear along the margins of young leaves, and the leaves become wrinkled. In severe cases, the apical bud dies, while lateral buds grow outward in a clustered pattern. The roots are prone to necrosis, tubers remain small, and abnormal clusters of small tubers develop; vascular bundle cells on both the surface and within the tubers often undergo necrosis.
Soybean	The leaves curl, and small grayish-white spots appear on older leaves; the leaf veins turn brown, while the petioles become weak and droop, soon withering and dying. The stem tip bends into a hook-like curve, preventing newly emerging young leaves from unfolding and causing them to wither and die easily.
Peanut	The first true leaf exhibits malformation, with irregular white spots on the margins and surface of older leaves and scars on the abaxial side. Subsequently, brown necrotic patches develop on the adaxial leaf surface, petioles become weakened, empty pods are abundant, and seeds remain poorly filled.
Cotton	The plants are stunted, with senescent leaves, few fruiting branches, and reduced boll formation. The apical meristem is severely suppressed, resulting in a hooked growth habit; the leaves curve downward, and older leaves fall off prematurely. In cases of severe calcium deficiency, the petioles of new leaves droop and become necrotic.
Tobacco	The tobacco leaves exhibit a pale green coloration, followed by downward bending of the apical bud and withering of the tips and margins of young leaves. The plants become stunted and display an unusually deep green hue; in cases of severe deficiency, the apical bud may die. The lower leaves thicken, and occasionally develop necrotic reddish-brown spots. During the flowering stage, calcium deficiency can lead to wilting of both flowers and buds. Necrosis at the apex of the corolla causes the pistils to protrude conspicuously, and dead spots may appear on the corolla.
Chinese cabbage (cabbage, cauliflower)	The disease typically manifests in the early stages of head formation. The margins of young leaves become water-soaked and translucent, while the heart leaves and leaf veins first develop yellow‑brown discoloration, thinning, or rot. The symptoms then progress outward toward the inner and outer leaves. Upon cutting open the head, one can observe that portions of the heart‑leaf margins turn white, yellow, and dry, with the leaf tissue becoming paper‑like and bearing band‑shaped or irregular lesions (commonly referred to as “dry heart” in Chinese cabbage). In severe cases, the leaf margins of the outer leaves also exhibit water‑soaking, followed by yellowing and desiccation; this is particularly pronounced in fields under continuous cropping or on sandy soils. Prolonged cloudy and rainy weather—or during storage—can trigger bacterial infections, accelerating decay.
Tomato	The upper leaves turn yellow, while the lower leaves remain green, and growth is stunted; the apical bud often dies. Young leaves are small and readily turn brown and die. Necrotic spots frequently appear near the top of the stem. The roots are thick and short with numerous branches; flowers are few and drop easily, with the terminal flower being particularly prone to shedding. Fruit develops blossom‑end rot: in the early stages of fruit enlargement, the flesh at the blossom end becomes water‑soaked and necrotic, after which the affected tissue collapses, turns black, shrivels, and sinks inward.
cucumber	The leaf margins appear edged with gold, and translucent white spots develop between the veins; in most cases, interveinal chlorosis occurs while the midribs remain green. Plants exhibit stunting, with shortened internodes and markedly shortened apical nodes; new leaves are small, and later they dry out from the margins inward. In severe calcium deficiency, petioles become brittle and easily fall off, and the plant dies starting from the top, with dead tissue turning grayish-brown. Flowers are smaller than normal, fruits are small, and the flavor is poor.
Large ginger	Heart rot, downward curling of the leaf margins on the apical lobes (typically occurring in midsummer), flower‑spotting (flower face, flower eye), and cracking.

All About Calcium Supplementation in Crops (Part 1)

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