Wheat is the most widely cultivated cereal crop in the world. It is cultivated on 218 m ha with average production of 713 m tones. Higher yield can be obtained from improved varieties, standard agronomic practices, crop protection measures and balanced nutrient management. Symptoms of nutrient deficiency are depends on few important factors, first, plant could able to obtain nutrient from soil when it is moist; second, pH of the soil must be within optimum range for nutrients to be released in in soil and third, soil temperature must be within range for nutrient uptake to occur. Among these, soil pH plays a major role in availability of nutrients to the plants. Disturb soil pH bound the nutrients in such a form that they could not be available to the crop. In alkaline soil, uptake of Fe, Mn, Zn, Cu is hindered where as in low pH soils, roots cannot uptake P and Mg. symptoms from nutrient deficiency and toxicities results from disturbed metabolism within the plant. Many symptoms directly indicate the specific nutrient deficiency whereas in few cases symptoms are indicative of deficiency of two or more nutrients (Roy et al 2006). Essential nutrients have several functions in plants. They play role in physiological processes, activate enzymes and are an integral part of essential metabolites (Snowball and Robinson 1991). The symptoms of nutrient deficiency are depends on the extent and rate of retranslocation of the nutrients from old leaves to younger leaves. Symptoms of important nutrients deficiencies in wheat are as follows
1. Nitrogen (N):
Nitrogen is most important macronutrient required for wheat crop. It leaches very easily and is required in very large amount. Nitrogen is important in development of chlorophyll and play key role in stimulus of photosynthesis. Light and sandy soils with low organic matter are very low in N content. N deficiency is most common and wide spread across wheat growing area. Correct estimation of soil N content, well-balanced and timely application of fertilizers based on soil test and sufficient supply of Sulphur, magnesium and potash in the soil could avoid N deficiency in soil.
• Symptoms appear first on older leaves; they become pale yellow than newer leaves.
• Chlorosis progress from leaf tip to leaf base.
• Chlorotic plants remains stunted reached maturity before plants with well supply of N
2. Phosphorous (P):
At early growth stage of wheat plant, availability of P ensures strong root growth and good establishment. Phosphorous is crucial for managing energy process with in plants. Acidic soils, soils with heavy structure, high pH soils are deficient in P. To avoid P deficiency, soil should be tested every 3-4 years to monitor P level.
• Symptoms appear first on older leaves; chlorosis begins from leaf tip and progress towards leaf base.
• Growth of seedlings remains stunted, leaves start coiling
• Necrosis of chlorotic tissue starts rapidly with leaf tip becoming dark brown
• Delayed maturity
3. Potassium (K):
Potassium regulates water content and provides greater resistance to stress to plants by providing additional plant strength. Light sandy soils, soils having high level of Ca and Mg, and organic soils faces K deficiency.
• Symptoms appear first on older leaves
• Necrosis of chlorotic tissue starts and spread rapidly from tip as well as from margins.
• Due to necrosis of margins, green tissue in center can form a shape of arrow
• Old leaves start doing rapidly and gave a look like water stress condition.
4. Magnesium (Mg):
Magnesium is important nutrient present in chlorophyll. It is responsible for activating large number of plant enzymes than any other nutrients. Sandy soils, soils with high and low pH, soils with high Ca and K and sandy soils in high rainfall areas are generally deficient in Mg.
• Younger leaves become pale yellow
• Interveinal chlorosis of older leaves
• Older leaves show mottling and finally chlorosis
• Old leaves may show reddish purple coloration along leaf margins
• New leaves become chlorotic and show twisting. Their look appears like drought stress prone.
5. Sulphur (S):
Sulphur is mordant component of may amino acids and proteins. It is also involved in chlorophyll production hence deficiency symptoms are similar to N deficiency. Sandy soils in high rainfall areas, soils with low organic matter are deficient in Sulphur.
• Symptoms are similar to N deficiency however whole plant becomes pale yellow with greater degree of chlorosis in younger leaves.
• Symptoms appear first on younger leaves as a yellowing
6. Calcium (Ca):
Calcium deficiency is rarely observed in wheat growing areas. Calcium is immobile nutrient hence deficiency symptoms are first visible on younger leaves. It plays important role in growth of meristematic tissues.
• Symptoms appear first on younger leaves and gradually spread to older leaves.
• Tips of young leaves become pale yellow, roll inwards, may show twisting and die
• Main root become shortened with stunted laterals.
• Base of the affected leaves remains green and healthy.
• Plant shows stunting with short stout stem
7. Iron (Fe):
Iron deficiency is rare but it can be occur in high rainfall areas or with heavy application of lime on calcareous soils.
• Symptoms appear first on younger leaves.
• Younger leaves become pale yellow due to lack of chlorophyll development.
• Leaves show interveinal chlorosis. An alternate strip of green and yellow color appears on the leaf.
• Under severe deficiency younger leaves devoid of chlorophyll and turn white.
• Old leaves remains pale green and appear healthy
8. Manganese (Mn):
Manganese deficiency in wheat is frequently observed but confined to small patches on soils where patches have been acidified. Mn deficiency affects chloroplast development which results in pale yellow plants.
• Symptoms appear on younger leaves generally middle leaves.
• Plants remains stunted and occur in distinct patches
• Reduced tillering with leaf and tiller death in severe deficiency.
• Pale yellow to gray flecking or strips occur at the base of young leaf
• Leaves show interveinal chlorosis and white necrotic flecks
• Plant shows wilting symptoms
• Affected plant produces small earheads.
9. Zinc (Zn):
Indian soils are low in zinc. Soils inherently low with Zn, heavy limed soils tend to be more affected by Zn deficiency.
• Young and middle leaves show yellow patches in the central region of the leaf
• The regions become necrotic and spread gradually to the margin
• Necrotic patches are surrounded by yellow green areas.
• Stunted plant show 'oil-soaked' leaves.
• Affected leaves bend and collapse in middle way
10. Copper (Cu):
Copper is essential for development of pollen grains. It has also role in chlorophyll formation and strengthening of cell wall i.e. lignification. Deficiency causes pollen sterility which in turn resulted in to poor spikelet fertility and poor grain yield.
• Young leaf shows withertip symptoms but base remains green
• In adequate soil moisture also Plant show wilting symptoms at tillering stage
• Tiller count may increase but die prematurely
• Before flowering, leaf tip weather, get twisted to half of its length.
• Plant show "rat tail head" i.e. head may emerge but grains may not form in the spikelets at the tip of the head.
• Grains in affected plant may shrivel
• Reduced stem strength
11. Boron (B):
Boron is fairly immobile element hence deficiency is most likely to be seen on younger leaves
• Leaf spitting close to the midrib
• Saw tooth notches along the leaf blade
• In severe B deficiency, tillering increases but new shoots show water soaking lesions
• Head sterility occurs; in severe deficiency entire spike may become sterile.
12. Molybdenum (Mo):
Molybdenum is important constituent of enzyme nitrate reductase therefore, its deficiency symptoms varies on high and low levels of nitrogen
• At low level of N the crop is pale with limpness
• At high level of N old leaves become pale green and tip scorching occurs
• Longitudinal yellow strips could be seen on middle leaves
• Severely deficient plant show white head and shriveled grains
Roy, R. N., Finck, A., Blair, G. J., & Tandon, H. L. S. (2006). Plant nutrition for food security. A guide for integrated nutrient management. FAO Fertilizer and Plant Nutrition Bulletin, 16.
Snowball, K., & Robson, A. D. (1991). Nutrient deficiencies and toxicities in wheat: a guide for field identification. CIMMYT.
About Author / Additional Info:
Scientist at Division of Genetics, Indian Agricultural Research Institute. Working on Genetic Improvement of Wheat.