| Micronutrient status of Indian soils | ||||||||||||||||||
| 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. | ||||||||||||||||||
| 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). | ||||||||||||||||||
| 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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Micronutrient status of Indian soils
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