Physiological disorders in root vegetable crops and their management
In root vegetable crops disorders occur where there is no involvement of pathogen and they are more or less due to the unfavourable environmental conditions like nutrition, water, light, soil etc. The major disorders in root vegetable crops and their management are discussed below.
1. Cavity spot
Cavity spot is characterized by elliptical lesions present on the surface of the roots. It generally occurs due to deficiency of calcium and excess of K as K reduces the uptake of Ca.
Correction measures: Proper and balanced dose of fertilizer should be given, proper water management and irrigation done at correct stage and grow resistant varieties. Physical condition of soil should be maintained good. Increase in Ca level in growing medium results in increased Ca accumulation in plant and leads to reduction of cavity spot. Seeds should be treated with Thiram, Captan and Bavistin before sowing. Grow resistant varieties.
Appearance of longitudinal cracks on the carrot root is known as carrot splitting. Carrot splitting occurs due to genetic factors and other factors (higher dose of ammonical form of N2, irregular irrigation and fertigation at the time of root development, wider spacing).
It is a common disorder in radish and carrots. It generally occurs due to excessive moisture during root development. Forking generally occurs in heavy soil due to compactness of soil. Use of undecomposed organic matter also causes forking.
Correction measures: Reduce the excess moisture from the field by giving balanced irrigation and proper drainage system. Use well decomposed organic manure and grow the crop in sandy loam soil.
Pithiness is characterized by the death of xylem and collapse of paranchymatous tissues in roots. It may lead to production of hollow roots. Pithiness is the sign of senescence and its degree varies from varieties to varieties. Pithiness may occur due to excess N, P and K; high temperature prevailing before harvesting and delay in harvesting.
Correction measures: Select resistant variety, plant at proper spacing, maintain optimum soil moisture, harvest at appropriate maturity stage and avoid excess fertilization and injury to the roots during intercultural operations and harvesting.
The growth of the root is checked. This disorder generally occurs due to deficiency of Boron. It is induced by fluctuation in day and night temperature.
1. Internal black spot (Brown heart or Breakdown of beet)
It is caused due to deficiency of Boron in neutral or alkaline soils. Boron deficient plants remain dwarf and stunted. The leaves remain smaller than normal and may assume a variegated appearance. The roots do not grow to full size and under severe deficiency conditions the roots become distorted and very small and have rough, unhealthy grayish appearance instead of clean and smooth. The surface is often wrinkled and cracked. Its deficiency first affects youngest cells and tissue.
Correction measures: Soil application of boron (5 to 50 kg/ha depending upon type of soil, soil moisture and soil reaction) may overcome or surmount the deficiency of boron or this disorder.
In zoning, alternate dark and light coloured rings are formed on the beet root. Zoning occurs due to high temperature above 30°C, wide-range fluctuation in day and night temperature and irregular supply of moisture during root growth and development.
About Author / Additional Info:
Working as a Senior Scientist at ICAR-Indian Agricultural Research Institute, Pusa, New Delhi