Boron Deficiency in Fiber Crops

Boron deficiency in cotton

Boron has been universally recognized as the most important micronutrient for cotton production. It is essential at all stages of plant growth, and critically so during fruit development—especially with today’s fast-fruiting, high-yielding varieties. University research shows that using as little as 1 lb of boron fertilizer for cotton plants can increase seed cotton yield by more than 500 lbs per acre.

Boron is an essential element that cotton needs during all stages of growth and fruiting. Supplying adequate boron fertilizers will help cotton:

• Develop and retain more squares
• Increase cotton plant bloom pollination and boll set
• Move nutrients and sugars from leaves to the fruit
• Produce strong, well-developed fibers
• Speed maturity

Symptoms of boron deficiency in cotton

Severe symptoms of boron deficiency in cotton appear infrequently. However, boron deficiency without the appearance of any visible foliage and flower symptoms can significantly limit the yield of seed cotton. 

Apart from flower and boll shedding in cotton, many symptoms on the leaves, petioles, flowers, and bolls have been described. However, don’t expect to see all of the symptoms simultaneously in any one field.

One characteristic symptom of boron deficiency is the development of bands (often excessively hairy) on the petioles. The tissue there is typically dying. As a result, the terminal bud often dies. Many lateral branches with short internodes and enlarged nodes then develop. The leaves, which usually do not show any malformation, remain green until the first frost. In cases of severe boron deficiency in cotton, excessive and abnormal vein development results in leaves buckling and irregular leaf shapes.

The cotton plant petals are frequently crumpled and misshapen. Excessive boll shedding in cotton can occur, in both squares and young bolls.

Discoloration of the extrafloral nectaries in cotton is also common due to boron deficiency. Cracks may develop on the stems, at the base of the squares or bolls, and drops of fluid may leak out.

Boron deficiency in kenaf

In the early stages of boron deficiency, the kenaf shoots are dark green and the young leaves may be malformed. The midrib and main veins become necrotic which results in the leaf curving backwards. Ultimately, young leaves fail to expand and the shoots die back.

Petiole collapse, caused by an internal necrosis, can cause the death of otherwise normal leaves. Root growth is reduced and roots are short and dark and have thick tips.

Boron deficiency in sisal

The first signs of boron deficiency in sisal are yellow spots, most numerous near the tip, on both surfaces of the leaf. These are followed by the formation in the epidermis of ramifying fingerlike depressions from the leaf margin, which may later become suberized.

In sand culture experiments, further symptoms have been seen:

• The leaf tip may be hooked
• The leaf spine absent or reduced to a white hair

In cases of severe deficiency, the growing point becomes disorganized and the leaves are short, narrow, twisted, and sometimes split. The plants have a flat-topped appearance.

Boron deficient plants may also be more prone to Fusarium wilt.