Horticulture :: Plantation Crops :: Coconut-Physiological Disorders

Horticulture :: Plantation Crops :: Coconut - Physiological Disorders - Minor Nutrients

Physiological Disorders

Minor Nutrients

1.Boron (B) Deficiency

Symptoms

Symptoms always occur on newly emerging leaves, and remain visible on these leaves as they mature and are replaced by younger leaves.
One of the earliest symptoms of B deficiency on coconut palm is leaf wrinkling and manifested as sharply bent leaflet tips, commonly called “hook leaf”. Leaves have a serrated zigzag appearance.
Other common symptom is the failure of newly emerging spear leaves to open normally. In a chronic stage, multiple unopened spear leaves may be visible at the apex of the canopy.
Boron deficiency also occurs in inflorescence and nuts. The inflorescence and nuts are become necrotic.

Diagnostic Techniques

Boron deficiency symptoms are quite distinctive and are usually sufficient for diagnosis by themselves. Manganese deficiency produces symptoms similar to those of B deficiency, but no other common deficiency produces symptoms that could be confused with those of B deficiency. Because B deficiency is so transient in nature, the element is immobile within the palm (cannot move from one leaf to another), and deficiencies affect only leaf primordial developing within the bud area, leaf analysis is not particularly useful.

Management

Foliar spray of 0.2 % (2g in 1 lire of water) borax at the rate of 75 – 100 ml per seedling. Spraying is commonly practiced when coconut palms are at the nursery stage. 1 year old – Borax 5-10 g/plant per year 2-3 years old – Borax 15- 20 g/plant per year 4 years old and more – Borax 30 -50 g/plant per 2 years

Leaf Fail to Open Properly

Leaf Wrinkling and Distortion

Necrotic Inflorescence

Severe Leaf Distortion

Boron deficiency symptoms

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2.Manganese (Mn) Deficiency

Symptoms

Manganese deficiency is very common on alkaline soils. The newest leaves of Mn deficient palms emerge chlorotic with longitudinal necrotic streaks. As the deficiency progresses, newly emerging leaflets appear necrotic and withered on all but basal portions of the leaflets. This withering results in a curling of the leaflets about the rachis giving the leaf a frizzled appearance (frizzle top). In severely Mn- deficient palms, growth stops and newly emerging leaves consist solely of necrotic petiole stubs.

Diagnostic Techniques

Visual symptoms may be sufficient to diagnose this disorder, but leaf nutrient analysis is also suggested, since symptoms of boron (B) deficiency can be similar. Late stage potassium (K) deficiency symptoms are virtually indistinguishable from those of Mn deficiency at a distance and close examination is required to look for characteristic longitudinal streaking and basal symptom distribution of Mn deficiency.

Management

Soil application of MnSO4 @ 25kg/ha



Manganese (Mn) deficiency symptoms

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3.Magnesium (Mg) Deficiency

Symptoms

Magnesium deficiency appears on the oldest leaves of palms as broad chlorotic (yellow) bands along the margins with the central portion of the leaves remaining distinctly green. In severe cases leaflet tips may become necrotic. Older leaves become bronzed and dry appearance. Leaflets show necrosis and turn to reddish brown with translucent spots yellowing starts at the tip and spreads to the base.

Diagnostic Techniques

Visual symptoms alone are usually sufficient to diagnose Mg deficiency. Magnesium deficiency symptoms differ from those of K deficiency in that symptom severity of discoloration K- deficient leaves is usually orange to bronze, shading gradually to green at the base of the leaf, whereas Mg- deficient leaves have distinctly green leaf centers and bright lemon yellow to orange margins.

Management

Soil application of MgSO4 1-2 kg/tree/year. Root feeding of 200 ml of 0.2% MgSO4 twice a year.


Magnesium (Mg) deficiency symptoms

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4.Zinc (Zn) Deficiency

Symptoms

Zinc deficiency is characterized by formation of small leaves wherein the leaf size is reduced to 50%. Leaflets become chlorotic, narrow and reduced in length. In acute deficiency, flowering is delayed. Zinc deficiency will also lead to button shedding.

Management

Soil application of ZnSO4 @ 25kg/ha

Reduced Leaf Size

Small Nuts

Button Shedding

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5. Iron (Fe) Deficiency

Symptoms

Iron deficiency usually appears on palms growing in poorly aerated soils or those that have been planted too deeply. Water logged soils and deep planting effectively suffocate the roots and reduce their effectiveness in taking up nutrients such as Fe.
The main symptom of iron deficiency is chlorosis or yellowing between the veins of new leaves (Uniform chlorotic new leaves as the deficiency progresses, the tips become necrotic and leaf size reduced).

Management

Application of Feso4 0.25 to 0.5 kg/tree/year