The following points highlight the twelve major deficiencies of mango fruits along with its symptoms. The deficiencies are: 1. Nitrogen 2. Phosphorus 3. Potassium 4. Calcium 5. Magnesium 6. Sulphur 7. Manganese 8. Copper 9. Boron 10. Zinc 11. Iron 12. Chlorine.
1. Deficiency of Nitrogen:
The total nitrogen content in mango orchard soils (0-15 cm depth) in different parts of the Punjab ranges between 0.018 to 0.045 per cent with a mean value of 0.032 per cent. The mango orchard soils around Malihabad (Lucknow) had total nitrogen content of 0.018 to 0.054 per cent.
The most striking symptom of nitrogen deficiency is the severe retardation of growth, yellow and under-sized leaves. Sand culture experiment of ‘Langra’ mango exhibits retardation of growth under all the degrees of deficiency of nitrogen. The fruit set is greatly reduced and leaves mature without attaining normal size. The leaf stalks form narrow angles with the stem. The mature leaves become yellow. The symptom first appears near the base of the current growth and progress toward the tip.
Twigs become stiff and woody, limited in length and diameter. Under acute deficiency, the fruit size greatly reduced, tended to ripe and drop prematurely. The incidence of physiological disease like soft-nose is increased with an increase in nitrogen fertilization. This can be reduced by maintaining leaf-calcium at 2.5 per cent either by supplying nitrogen as calcium or by adding limestone or gypsum.
2. Deficiency of Phosphorus:
The deficiency of phosphorus causes stunting of growth in mango. As the deficiency persists, causes premature defoliation following, dying back from the tips. The younger leaves become excessively green and slightly smaller than normal. The wood of the main trunk become thin and willowy and cause dying back in some branches.
While growing plants of ‘Langra’ mango in sand, it was observed that the phosphorus deficiency caused slow plant growth and delayed fruit maturity. An early symptom was the development of reddish purple colour on the underside of the leaf, first starting as spots, later spreading over the entire leaf with veins finally becoming reddish purple. The leaves were thick and stunted. The roots were also stunted. The plants were late in setting fruit.
The high level of phosphorus in shoots of Dusehari mango is found favourable for flower- bud formation. During August, there is not much difference in the level of different fractions of phosphorus in potential flowering and non-flowering shoots. As the time of flower-bud initiation approached nearer i.e. November-December, the level of phosphorus fractions except nucleic acid become quite high in the flowering stems. The leaves from the flowering shoots also have a high level of phosphorus but the differences are not so marked as in the case of stems.
Mango trees appear to be quite sensitive to heavy phosphorus fertilization accumulating as much as 0.84 per cent phosphorus in leaves on dry weight basis against 0.08 – 0.175 per cent in normal leaves. This excessive phosphorus resulted in a spotting of mature leaves in fall, first appearing on the lower surface, but later on also on the upper surface.
Necrotic areas also developed on the margins of some leaves. Leaves become chlorotic and shed heavily. It also causes some drying of shoots.
3. Deficiency of Potassium:
The mild potassium deficiency is confused with the symptoms of nitrogen deficiency. Pronounced symptoms of potassium deficiency appear as characteristic type of foliage necrosis. The leaves located near the middle or slightly below the middle of the current season’s growth are the first to be affected. From this portion, the injury spreads towards the distal and basal part of the affected twig. The scorch usually located along the leaf margin and proceeded by dark purplish discolouration. The intensity of the scorch varies with severity of the potassium deficiency.
In Florida, the leaf potassium of 0.3 to 0.8 per cent is suggested as a desirable range for mango. In Philippines, foliar spray of potassium nitrate at 12.5 g per litre induced early, uniform and profuse flowering in ‘Carabao’ mango. The fruiting was heavy with potassium nitrate application leading to smaller fruits. Potassium nitrate spray has not produced such a response in mango under Indian conditions.
4. Deficiency of Calcium:
The calcium deficiency does not cause any definite leaf patterns but the trees deprived of calcium remain small and slightly lighter green than normal. Increasing the calcium level in the tree with heavy application of limestone or gypsum reduce the incidence of soft-nose.
5. Deficiency of Magnesium:
Magnesium deficiency in mango growing in sand cause stunting of plants which become pale, smaller in height and girth. In the developing leaves, yellowing white areas between the main veins are on both sides of the mid-rib run parallel toward the margin. Prominent yellowish specks first visible on both sides of the mid-rib and follows chlorosis. It was reported that adding more than 98.5 kg of magnesium per tree per year in ‘Kent’ mangoes is not useful.
6. Deficiency of Sulphur:
The general behaviour of the minus-sulphur trees is somewhat similar to that of phosphorus-deficient trees. In sulphur deficient plant growth is gradually reduced and severe defoliation occurred. The leaves turn very dark green but upon reaching maturity, they develop necrotic areas along the margins and abscises soon-after. The location of the dead leaf areas is the chief distinction between these two deficiencies, being a tip scorch in the case of phosphorus and a side scorches with sulphur.
High concentrations of sulphur-dioxide in the atmosphere near the brick-kilns and other industrial units burning coal have resulted in Black tip in mango.
7. Deficiency of Manganese:
Manganese deficiency of mango plants in sand culture cause paling and dropping of plants. Lightening of green between the principal veins develops which gradually turn yellow with a band of green along the mid-rib and the lateral veins in the young leaves. As the deficiency progress characteristic mottling of the leaf appears. Later, prominent yellow colour develops with dark-brown pinhead like spots scattered all over the leaf. This is followed by leaf fall. The size and shape of the leaves is quite normal but the number of the leaves and the twigs are less than the normal.
In an experiment, 800 ppm manganese in the nutrient solution proved highly toxic to mango seedlings. There was marginal necrosis of leaves with deep brown colour between the veins gradually proceeding toward the mid-ribs. This was followed by curling and drying of leaves from the margins inward. Apical buds died, growth remained stunted, ultimately resulting in the death of plants.
8. Deficiency of Copper:
No characteristic uniform symptoms of copper deficiency on plants in sand- culture has been observed. However, severe tip burn in old leaves with grey-brown patches is noticed. The plants are pale green in appearance. The minus copper plants turn slightly lighter green than normal and have S-shape limb growth.
9. Deficiency of Boron:
The deficiency of boron on mango plants in sand culture causes stunted growth and short internodes in some plants. The new terminal leaves in the deficient plants are reduced in size, looking pale green, distorted and brittle. The older leaves are normal green but are smaller than those borne by the control plants. Some leaves curved on one side. The midrib turns brown from the ventral side.
10. Deficiency of Zinc:
The zinc deficiency cause stunting of growth within the first six months in sand culture which become more prominent in the second year. The leaves turn pale yellow but less pale than those suffering from nitrogen deficiency, small, thin pointed, narrow and brittle with petioles making acute angle with the stem. Grey brown necrotic patches of irregular shape scattered all over the leaf surface. On some leaves, they spread across the whole leaf surface with distal portion dying. Necrotic areas finally fell off giving a shot-hole appearance. Root growth is also stunted.
Zinc deficiency first appears on terminal flushes with upper part of the tree. The symptom consists of stunted growth of young leaves with interveinal chlorosis. The affected leaves curl backward giving a cup-shaped appearance. The tips and margins of the curled leaves become chlorotic.
The leaves eventually broken down and detach from the lamina. It can be controlled by spraying 1 per cent zinc sulphate or 0.2 per cent zinc oxide, preferably at the beginning of the growing season, thoroughly wetting the foliage. At Ludhiana, a 0.2 per cent zinc sulphate spray gave complete recovery of zinc deficiency symptoms in mangoes growing under field conditions.
11. Deficiency of Iron:
A pot-culture study on mango did not produce any symptoms of chemicals and environmental pollutants may have provided enough iron for normal growth of the plants in the minus-iron cultures. However, in Florida occasional chlorosis observed on young mango trees growing on lime stone area.
12. Deficiency of Chlorine:
Chloride injury in mango manifests as a leaf scorch which starts from the leaf tip, generally 8-10 months after emergence. As the leaf gets older, the scorch becomes brick red and progresses along the leaf margins, slowly covering the major portion of the lamina. Nearly all the affected leaves which emerge in March start abscising in April of the next year. After a few years, the young twigs start drying, giving a sickly look to the tree. The chloride affected mango leaves had 0.02 to 0.09 per cent chlorine as compared with 0.01 per cent chloride in the healthy leaves on dry weight basis.