Boron Deficiency in Vegetable Crops

Boron deficiency in artichokes

Boron deficiency causes breakdown of the tissues in the pith of the artichoke, which is seen when the flower is split vertically. In addition, a general crown rot has been associated with boron deficiency.

Boron deficiency in asparagus

The first symptom of boron deficiency in asparagus is the wilting of the tips of spears on young branched shoots. This is followed by a dying back of the wilted tissue and the development of side shoots, which frequently die back. Development of the buds on the rhizome is poor.

Typical recommended ranges for boron boradcast soil application for asparagus is 2-3 lbs of B/acre. Normal plant analysis levels for the best quality and marketability have leaf boron levels in the 40-65 ppm range.*

*Always consult local crop advisors to check the proper dose rates. Rates of boron fertilization should be based on yield goals along with soil tests and/or plant tissue analyses.

Boron deficiency in beans

There have been very few cases of boron deficiency in beans, which are particularly sensitive to excess application of boron. As little as 2.5 lbs/acre of boron has been known to reduce yield. However, boron deficiency also reduces growth, with leaves near the growing point being small and chlorotic. The growing point becomes blackened and dies, and lateral shoots develop near the base of the plant. The flower buds may shrivel and be shed without opening.

Typical recommended ranges for boron boradcast soil application for beans is 0.5-1 lb of B/acre.*


*Always consult local crop advisors to check the proper dose rates. Rates of boron fertilization should be based on yield goals along with soil tests and/or plant tissue analyses.

Boron deficiency in broad beans

The following are symptoms of boron deficiency in broad beans:

• Terminal bud blackens and dies back
• Leaves, which are dark green and leathery, fall prematurely
• Lower leaf surfaces may be yellow or red in color
• Root development is restricted

Boron deficiency in broccoli

The most common symptom of boron deficiency in broccoli in the field is poor and discolored bud formation, which frequently renders the crop unsuitable for marketing. The pith is liable to develop water-soaked areas, and to become necrotic and ultimately hollow.

An early symptom in young seedlings is the rolling and down-curling of the newest leaves, which are abnormally small, brittle, and deformed. Sometimes leaves have a much enlarged midrib and little lamina. If broccoli is not in bud when the deficiency becomes established, the stem stops growing, giving a flat-topped plant with many side shoots.

Typical recommended ranges for boron boradcast soil application for broccoli is 2-3 lbs of B/acre. Normal plant analysis levels for the best quality and marketability have leaf boron levels in the 25-50 ppm range.*

*Always consult local crop advisors to check the proper dose rates. Rates of boron fertilization should be based on yield goals along with soil tests and/or plant tissue analyses.

Boron deficiency in brussels sprouts

The first signs of boron deficiency in Brussels sprouts are swellings on the stem and petioles, which later become suberized. The leaves are curled and rolled, and premature leaf fall of the older leaves may take place. The veins are frequently wrinkled. The growing point may die, followed by the development of two axillary buds leading to twinning of stems. If the deficiency becomes established before the sprouts are formed, very few develop. If the sprouts have started forming, they remain small, fail to heart, and have a loose appearance. The stem pith may be hollow and discolored.

Typical recommended ranges for boron boradcast soil application for Brussels sprouts is 2-3 lbs of B/acre. Normal plant analysis levels for the best quality and marketability have leaf boron levels in the 25-50 ppm range.*

*Always consult local crop advisors to check the proper dose rates. Rates of boron fertilization should be based on yield goals along with soil tests and/or plant tissue analyses.

Boron deficiency in cabbage

The characteristic symptom of cabbage boron deficiency found in the field is the breakdown of the pith of the stem—easily seen when the head is split vertically. Water-soaked spots first develop in the pith, the tissue gradually becomes necrotic, and sometimes a cavity may form.

If the deficiency occurs at the young seedling stage, the new leaves will be small and distorted and often thicker than normal. The death of the growing point can follow, but this is not expected under field conditions. Boron deficiency occurs more often on cauliflower and broccoli than on cabbage.

Typical recommended ranges for boron boradcast soil application for cabbage is 2-3 lbs of B/acre. Normal plant analysis levels for the best quality and marketability have leaf boron levels in the 25-50 ppm range.*

*Always consult local crop advisors to check the proper dose rates. Rates of boron fertilization should be based on yield goals along with soil tests and/or plant tissue analyses.

Boron deficiency in cauliflower

The most common symptom of boron deficiency in cauliflower in the field are poor and discolored curd formation, which frequently renders the crop unsuitable for marketing. The pith is especially liable to develop water-soaked areas, and to become necrotic and ultimately hollow. An early symptom in young seedlings is the rolling and down-curling of the newest leaves, which are abnormally small, brittle, and deformed. Sometimes leaves have a much enlarged midrib and little lamina.

Under severe boron deficient conditions, cauliflower plants showing such symptoms are unlikely to form a head.

Typical recommended ranges for boron boradcast soil application for cauliflower is 2-3 lbs of B/acre. Normal plant analysis levels for the best quality and marketability have leaf boron levels in the 30-60 ppm range.*

*Always consult local crop advisors to check the proper dose rates. Rates of boron fertilization should be based on yield goals along with soil tests and/or plant tissue analyses.

Boron deficiency in celery

Brittle stems and the development of brown stripes in the epidermis above the vascular bundles of the petioles are usually the first signs of boron deficiency in celery. Sometimes, the brown stripes are so close together that they form a continuous line over the vascular bundles. Transverse cracks develop on the outer surface. The broken tissue curls outwards, giving the petiole a hairy appearance.

Blackened and diseased hearts are the most severe symptoms, but they are only found in stunted plants, accompanied by cracked petioles.

Typical recommended ranges for boron boradcast soil application for asparagus is 2-3 lbs of B/acre. Normal plant analysis levels for the best quality and marketability have leaf boron levels in the 25-50 ppm range.*

*Always consult local crop advisors to check the proper dose rates. Rates of boron fertilization should be based on yield goals along with soil tests and/or plant tissue analyses.

Boron deficiency in chicory

Boron deficient chicory plants are stunted. When deficiency is severe, the leaves are twisted and reddened with weak, brittle petioles and midribs.

Boron deficiency in Chinese cabbage

The midribs crack and turn brown when Chinese cabbage is boron deficient.

Boron deficiency in cow peas

When cow peas are boron deficient:

• Upper leaves are pale green and curve down at edges
• Growing points die
• Seed set is very reduced

Boron deficiency in cucumbers

When cucumber plants have boron deficiency, the internodes are short and the young leaves are crinkled and deformed. Yellow streaks on the rind become corky, seriously affecting the value of the crop.

Typical recommended ranges for boron boradcast soil application for cucumber is 0-0.5 lb of B/acre. Normal plant analysis levels for the best quality and marketability have leaf boron levels in the 30-60 ppm range.*

*Always consult local crop advisors to check the proper dose rates. Rates of boron fertilization should be based on yield goals along with soil tests and/or plant tissue analyses.

Boron deficiency in garlic

Boron deficiency has been reported to cause the leaves to bend backwards and to impair the storage properties of the bulbs.

Boron deficiency in kohlrabi

Leaf symptoms in kohlrabi are only observed in cases of severe boron deficiency. The leaves become slightly curled and crinkled, and are held in an unusually erect position. If the boron supply is very limited in the early stages of growth, the edible part of the stem does not develop, but if the supply is not so limited, the kohlrabi will develop further and the surface becomes rough and watery.

Boron deficiency in leeks

Leeks seem to tolerate very low boron supplies without showing any symptoms. Transverse cracks known as “cat scratch” appear to be a characteristic boron deficiency symptom.

Typical recommended ranges for boron boradcast soil application for leeks is 1-2 lbs of B/acre. Normal plant analysis levels for the best quality and marketability have leaf boron levels in the 40-50 ppm range.*

*Always consult local crop advisors to check the proper dose rates. Rates of boron fertilization should be based on yield goals along with soil tests and/or plant tissue analyses.

Boron deficiency in lettuce

Boron deficiency in lettuce causes:

• Reduction in growth
• Malformation of the young leaves
• Development of dark spots, usually near the leaf tip, which later develop into a marginal necrosis

The leaves are thick, brittle, and frequently cupped. Head development is poor and chlorosis also occurs. The yellow heads become rotten in the center following the death of the growing point. Roots on boron deficient plants are brown, short, and knotted in appearance.

Tip burn on younger leaves has been associated with boron deficiency but this symptom is likely due to other factors. The early stages of boron deficiency can be confused with tip burn which, unlike boron deficiency, does not lead to lack of “hearting” and death of growing point.

Typical recommended ranges for boron boradcast soil application for lettuce is 1-2 lbs of B/acre. Normal plant analysis levels for the best quality and marketability have leaf boron levels in the 25-50 ppm range.*


*Always consult local crop advisors to check the proper dose rates. Rates of boron fertilization should be based on yield goals along with soil tests and/or plant tissue analyses.

Boron deficiency in marrow

When marrow is boron deficient, new leaves are small, brittle, and misshapen with long lobes. Cracks appear at regular intervals across the upper surface of the petiole. The petioles become “S” shaped when seen from the side. Longitudinal cracks develop on the fruit.

Boron deficiency in melons and cantaloupes

The terminal bud fails to elongate when melon and cataloupe plants are boron deficient.

Boron deficiency in okra

Boron deficient okra leaves become distorted and brittle. They are reduced in size and have irregular lobe development. The pods remain as short stumps. They do not elongate but remain attached for a long time.

Typical recommended ranges for boron boradcast soil application for okra is 0.5-1 lb of B/acre. Normal plant analysis levels for the best quality and marketability have leaf boron levels in the 20-40 ppm range.*


*Always consult local crop advisors to check the proper dose rates. Rates of boron fertilization should be based on yield goals along with soil tests and/or plant tissue analyses.

Boron deficiency in onions

Boron deficiency in onions causes leaves to turn blue/green, and the younger leaves become mottled with distorted shrunken areas. Cracks may appear on the upper surface of the lower leaves, which become stiff and brittle. Root development is poor. Over-wintering may be impaired by boron deficiency.

Typical recommended ranges for boron boradcast soil application for onion is 1-2 lbs of B/acre. Normal plant analysis levels for the best quality and marketability have leaf boron levels in the 25-50 ppm range.*


*Always consult local crop advisors to check the proper dose rates. Rates of boron fertilization should be based on yield goals along with soil tests and/or plant tissue analyses.

Boron deficiency in peas

It is likely that seed reserves of boron will be sufficient for normal growth. Boron deficiency in peas is only expected when seed produced in a boron-deficient area is used. Boron-deficient seedlings are stunted and have short internodes. The stems are thick and the plant will have a bushy appearance. The young leaflets show a marginal chlorosis and have a tendency to curl inwards. Pod abortion occurs and pods that develop will have thick walls, be small, and often contain few or even no seed.

Typical recommended ranges for boron boradcast soil application for peas is 0-0.5 lb of B/acre. Normal plant analysis levels for the best quality and marketability have leaf boron levels in the 25-50 ppm range.*


*Always consult local crop advisors to check the proper dose rates. Rates of boron fertilization should be based on yield goals along with soil tests and/or plant tissue analyses.

Boron deficiency in peppers

When compared to other vegetables, peppers require a higher level of boron. Symptoms of boron deficiency in pepper plants usually first appears in the leaves, including:

• Loss of color
• Yellowing
• Cupping
• Thickening of leaves near the growth point

When boron deficiency becomes more severe, pepper plants may exhibit the following symptoms:

• Early-stage flower bud termination
• Flower, leaf and/or fruit bud drop
• Stunted, underdeveloped root nodules
• Shoot apical meristem death resulting in dwarfed plants
• Uneven fruit maturity, brown or black marks, deformation, cracking, and cork

How much boron is enough?

Only a small quantity of boron is needed to correct boron deficiency. A soil test can help determine how much boron may be needed. In addition, excess calcium and soil pH can affect boron uptake.

References

• Growing Points: More on Boron with Peppers
• Green Peppers

Boron deficiency in pulses

Boron is an essential micronutrient required for the growth and development of pulses, including broad beans, lentils, Bambara groundnut, chickpeas, pigeon peas, and cow peas.

Symptoms of boron deficiency in pulse crops can be found in the following:

• Stems: Brittle, hollow, and weak stems with a reduced diameter which can lead to plants falling over. Stems may also turn brown.
• Growth: Stunted growth and reduction in plant height
• Roots: Reduced root development and black root
• Flowers: Reduction in the number of flowers
• Fruit set: Decreased fruit and deformed pods with fewer seeds

Boron deficiency in radishes

The leaves of boron deficient radishes are deformed, brittle, and chlorotic. In cases of severe boron deficiency, the leaf tip dies. The roots crack and are pale in color. The water-soaked flesh may show brown flecks. Boron deficiency can increase the production of thiocyanates, which are known giotrogens.

Typical recommended ranges for boron boradcast soil application for radishes is 2-3 lbs of B/acre. Normal plant analysis levels for the best quality and marketability have leaf boron levels in the 20-50 ppm range.*


*Always consult local crop advisors to check the proper dose rates. Rates of boron fertilization should be based on yield goals along with soil tests and/or plant tissue analyses.

Boron deficiency in rhubarb

When boron deficient, rhubarb leaves show reddish markings around the margins and, in the case of severe boron deficiency, eventually die. The plants are dwarfed and die back.

Typical recommended ranges for boron boradcast soil application for rhubarb is 1-2 lbs of B/acre. Normal plant analysis levels for the best quality and marketability have leaf boron levels in the 25-50 ppm range.*


*Always consult local crop advisors to check the proper dose rates. Rates of boron fertilization should be based on yield goals along with soil tests and/or plant tissue analyses.

Boron deficiency in Solanum gilo

The main symptoms of boron deficiency in gilo include:

• Growing point dies
• Upper leaves are small, deformed, and twisted
• Few flowers form

Boron deficiency in spinach

The first sign of boron deficiency in spinach is the development of small pale green leaves. The plants are stunted and tend to lose their upright growth habit, the leaves spreading outwards. The young leaves are liable to be very small and deformed. The roots are dry and dark in color.

Typical recommended ranges for boron boradcast soil application for spinach is 2-3 lbs of B/acre. Normal plant analysis levels for the best quality and marketability have leaf boron levels in the 40-60 ppm range.*


*Always consult local crop advisors to check the proper dose rates. Rates of boron fertilization should be based on yield goals along with soil tests and/or plant tissue analyses.

Boron deficiency in squash

The leaves of boron deficient squash are dark green, cupped, brittle and somewhat rough. The veins, which are thick and contorted, are very prominent, especially when they become chlorotic. The petioles are thick and curled. The growing points die back. Roots are stunted and discolored.

Typical recommended ranges for boron boradcast soil application for squash is 1-2 lbs of B/acre. Normal plant analysis levels for the best quality and marketability have leaf boron levels in the 30-40 ppm range.*


*Always consult local crop advisors to check the proper dose rates. Rates of boron fertilization should be based on yield goals along with soil tests and/or plant tissue analyses.

Boron deficiency in tomatoes

The first sign of boron deficiency in tomatoes is a terminal chlorosis on the younger leaves. In severe cases, the young leaves are grossly misshapen and the growing points die. The stems are short and thick. Failure to set fruit is common and the fruit may be ridged, show corky patches, and ripen unevenly.

Typical recommended ranges for boron boradcast soil application for tomatoes is 1-2 lbs of B/acre. Normal plant analysis levels for the best quality and marketability have leaf boron levels in the 30-80 ppm range.*

*Always consult local crop advisors to check the proper dose rates. Rates of boron fertilization should be based on yield goals along with soil tests and/or plant tissue analyses.