~ 3470 ~ Journal of Pharmacognosy and Phytochemistry 2018; 7(3): 3470-3475 E-ISSN: 2278-4136 P-ISSN: 2349-8234 JPP 2018; 7(3): 3470-3475 Received: 21-03-2018 Accepted: 25-04-2018 Nidhi Kamboj Department of Soil Science, CCS Haryana Agricultural University, Hisar, Haryana, India RS Malik Department of Soil Science, CCS Haryana Agricultural University, Hisar, Haryana, India Preeti Dhanker Department of Chemistry & Biochemistry, CCS Haryana Agricultural University, Hisar, Haryana, India Anuj Kumar Department of Horticulture, CCS Haryana Agricultural University, Hisar, Haryana, India Correspondence Nidhi Kamboj Department of Soil Science, CCS Haryana Agricultural University, Hisar, Haryana, India Importance of nickel in crops Nidhi Kamboj, RS Malik, Preeti Dhanker and Anuj Kumar Abstract Prolonged and unbalanced use of chemicals, leads to destruction of physical structure of soil, disturbed biological condition of soil and also change the chemical equilibrium of soil, which in turn affects the availability of other essential nutrients in the soil matrix. Out of seven essential micronutrient (Fe, Zn, Cu, Mo, Mn, B, and Ni) Ni is one of the recently added essential plant nutrient. Nickel is an important metal for plants, which fulfils a variety of vital roles in plants functions. Also, Ni is a constituent of several metallo-enzymes which are actively engaged in Nitrogen metabolism and biological Nitrogen fixation. As it plays a major part in plant metabolism and other mechanisms, Ni deficiency can produce variety of negative impacts on growth and metabolism of plants. A very limited data is available on uptake of Ni in crop plants as most of the studies were conducted by keeping its toxicity problem in view rather than its deficiency. Keywords: nickel, micronutrient, crops, deficiency, toxicity Introduction Nickel is a d-block element occupying 1 st row of transition series. It lies in the 10 th group of the periodic table with other group members including palladium (Pd), platinum (Pt) and darmstadtium (Ds). Nickel exists as silvery-white lustrous metal with a slight golden tinge. It typically exists in the 0 and +2 oxidation states, but also establish less frequently in the -1, +1, +3 and +4 oxidation states. It is relatively prolific and naturally occurring metal, widely scattered in the earth crust. It is the 24 th most copious element found in the earth’s crust as well as the 5 th most profuse element by weight following iron (Fe), oxygen (O), magnesium (Mg) and silicon (Si), constituting a total of about 3% of the earth composition (Cempel and Nikel, 2006) [11] . The prominence of Nickel in soils highly depends upon the its content in the parent rocks, but in surface soils, its amount is also a result of soil- forming processes and pollution (Kabata- Pendias and Pendias, 1992; McGrath, 1995) [27, 37] . The contents are lowest in case of sedimentary rocks that are comprised of clays, lime stones, sandstones and shales, while the highest concentrations exist in basic igneous rocks (Kabata- Pendias and Mukherjee, 2007) [26] . The average concentration of Ni in the earth’s crust is 0.008% and Agricultural soils contain Ni at levels of 3–1000 mg kg -1 (Nagajyoti et al., 2010; Iyaka, 2011) [41, 25] . The actual concentration of nickel in any particular soil sample may vary widely; for example, sandstone and granite may contain less than 0.0001% nickel, whereas, the so-called ultramafic or ultra basic rocks can contain substantially more than 0.3% nickel. Those soils carrying less than 5 mg kg -1 Ni are too acidic to support normal plant growth. Nickel content in soils varied widely and has been estimated to range from 3 to 1000 mg kg -1 ; for the world soils, the grand range is between 0.2 to 450 mg kg -1 , while the grand mean is calculated to be 22 mg kg -1 (Kabata and Pendias, 1992; Cempel and Nikel, 2006) [27, 11] Most frequently Ni is present as hydrated complex (Ni (H 2 O) +6 , in the soil solution. Other than this, it also exists in many different forms in soils such as adsorbed or complex on organic cation surfaces or on inorganic cation exchange surfaces, inorganic crystalline minerals or precipitates, water soluble, free-ion or cheated metal complexes in soil solution (Seregin and Kozhevnikova, 2006) [54] . Nickel is found in all soil types and is also emitted from volcanoes. In the environment, it is found in combination with oxygen or sulphur as oxides or sulphides (Baralkiewicz and Siepak, 1999) [4] . The rocks having low silica, are high in nickel (except for carbonate), and those high in silica are relatively low in nickel. Generally, it is uniformly distribution in soil profile. It is typically accumulated at the surface soil due to deposition through many anthropogenic activities (Cempel and Nikel, 2006) [11] . Nickel can also exist in several other forms in soils that include adsorbed or complex on organic cation surfaces or on inorganic cation exchange surfaces, inorganic crystalline minerals or precipitates, water soluble, free-ion or cheated metal complexes in soil solution (Bennett, 1982) [5] . The complexes are much more mobile in the