| Micronutrient status of Indian soils |
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| The role of micronutrients in plant nutrition
and crop production has gained importance. List of chronological
sequence of establishment plant essential micronutrients includes Iron
(Fe) in 1843, Manganese (Mn) in 1922, boron (B) in 1923, Zinc (Zn) in
1926, Copper (Cu) in 1931, Molybdenum (Mo) in 1939, Chlorine (Cl) in
1954, and Nickel (Ni) in 1987 of which the deficiency of Zn and B are
wide spread. Real impetus in micronutrient research in India came with
the reports of Khaira disease (deficiency of zinc in rice) in mid
sixties. The total stock of micronutrients in the bench mark soils of
India was reported which largely reflects the diversity in the parent
material of the soil and per se does not truly predict soil supply
capacity. Only the available micronutrient pool in the soil represents
the plant usable form. (Table) |
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| Systematic survey and analysis of more than
2.50 lakh soil samples in 20 states by All India Coordinated Research
Project indicated deficiency of zinc to the extent of 49%, 33% of B, 13,
7 and 4% of samples rating low in Fe, Mo, and Mn. These, in general,
point to the micronutrient problems, the extent and severity could,
however, vary across soil types, agro ecological zones and more
importantly management and productivity of crops and cropping systems.
Coarse texture, calcareous, low organic carbon content, high pH and
excessive leaching often accentuate zinc deficiency. It is wide spread
in the calcareous soils of Bihar, Vertisols and Inceptisols of Andhra
Pradesh, Tamil Nadu, Alfisols of Karnataka, swell-shrink soils of
Maharashtra and Madhya Pradesh, and Aridisols of Haryana resulting in
low crop yields. Zinc is a crucial component of the package of practices
recommended for sodic soils reclamation. Deficiencies of Fe, Mn and Cu
are much less extensive than that to zinc. |
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| The deficiency of Fe was found to be largest 26% in Haryana
followed by 18% in Tamil Nadu, 12% in Punjab and 8 to 9% in calcareous
soil of Gujarat and Uttar Pradesh. Adoption of rice-wheat cropping
system in place of maize-wheat or groundnut-wheat in non-traditional
rice growing areas on highly permeable coarse-textured soils of Punjab
and Haryana has been responsible for occurrence of Mn deficiency (33%)
particularly in wheat. The extent of boron (B) deficiency varied from 2%
in Gujarat to 68% in West Bengal. In general B deficiency is most wide
spread in the red and lateritic soils of Karnataka, leached and acid
soils of West Bengal, Jharkhand, Orissa and Maharashtra (56%), and in
highly calcareous old alluvium of Bihar (22-45%) (Table). |
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| The deficiency of Mo is common in acid soils of humid region.
Deficiency of Cl and Ni has not been reported so far in the Indian
soils. Although deficiency of these micronutrients is not an acute
nutrient disorder today, production of nearly 300-350 Mt of food grains
by 2025 definitely constrain the finite reserves in the soils (Rattan et
al 2008). |
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| Distribution of micronutrients deficiencies across AEZ
indicate zinc deficiency to be about 40% in 1, 2, 5,15,16,18,and 19
zones; 40-50% in 9,11and 12 zones; 50-55% in 4, 7, and 13, and 55% in
the remaining zones. Soils of indo-gangetic plains showed 55, 47 and 36%
zinc deficiency in trans-northern, central and eastern parts of IGP,
while boron deficiency is 8, 37 and 68% in these regions of IGP. Boron
deficiency varies from 2 % in AER 2; 24-48 % in highly calcareous soils
of AEZ 2, 9, and 14 and is most wide spread (39-68 %) in red and
lateritic soils of AEZ 6,13,16,17 and 19. Deficiencies of Cu and Mn
were found sporadic. The problem of Fe and Mn deficiency has emerged in
Trans-northern IGP (zone 9) more so under rice-wheat cropping while
most of the soils tested adequate in available iron. Its deficiency in
all AEZs as well as toxicity in some coastal, submontane and
red-lateritic soils is quite common (Table) |
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| Deficiency of sulfur |
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| Deficiency of sulfur (S) is wide spread in
several agro-ecological zones (AEZ). Most of the Indian soils are either
low in available S or these have depleted due to continuous cropping
and on account of oregular use of sulfur free fertilizer. Out Of nearly
50,000 Samples analyzed, 11-78 per cent of Indian soils showed S
deficiency with a mean of 41 percent. Among 240 districts surveyed,
soils of 60 districts have 30-40 % S deficiency and 72% district
indicated more than 40% S deficiency. |
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