Page 9 - index
P. 9


               Soils contribute to general ecosystem services. Biomass production from agriculture and forestry
               is one of the seven functions of soil. Presently, soil degradation affects global crop production.
               Out of many reasons, soil degradation due to soil nutrients deficiency affects crop productivity in
               various parts of the world including India. Therefore, assessment of changes in soils to achieve
               the knowledge for improving soil quality and avoiding soil degradation is the need of the hour.

               Essential nutrient elements for plants and their categories
               Soil contains elements in varied proportion. Plants absorb certain elements in different quantities
               from  soil  for  their  growth  and  development.  A  nutrient  element  is  one  that  is  required  to
               complete the life cycle of the organism and its relative deficiency produces specific deficiency
               symptoms.  Soil  available  form  of  a  nutrient  is  that  fraction  whose  variation  in  amount  is
               responsible for significant changes in crop yield and response. Available nutrient constitutes only
               a small portion of the total nutrient present in the soil. An element must satisfy the following
               criteria to be called as an essential nutrient:
                   (i)    Plants  cannot  complete  the  vegetative  and  reproductive  stages  of  lifecycle  in
                          deficiency of the nutrient.
                   (ii)   The deficiency produced by the plants is specific to the element and can be prevented
                          or corrected only by supplying that element.

                   (iii)   The element is directly involved in the metabolic activity of the plants.

               Till  now  seventeen  nutrients  have  been  recognized  essential  for  plant  growth  and  they  are
               carbon(C),  hydrogen(H),  oxygen(O),  nitrogen(N),  phosphorus(P),  potassium(K),  calcium(Ca),
               magnesium(Mg),  sulphur(S),  iron(Fe),  manganese(Mn),  zinc(Zn),  copper(Cu),  boron(B),
               molybdenum(Mo),  chlorine(Cl)  and  nickel  (Ni).  Out  of  which  C,  H,  O  are  called  framework
               element as they contribute more than 90% of plant constituent. Whereas, nutrients like Fe, Mn,
               Zn,  Cu,  B,  Mo,  Cl  and  Ni  are  required  in  relatively  smaller  quantities  and  are  called  as
               micronutrients.  As  per  requirement,  N,  P,  and  K  and  Ca,  Mg  and  S  are  called  primary  and
               secondary nutrients respectively.

               Nutrient  uptake  in  different  crops  is  dependent  on  soil  nutrient  availability,  crop  and  variety
               types and crop management practices. It is very much important to critically assess the secondary
               and  micronutrient  deficiency  in  soil  for  the  inclusion  of  these  nutrients  in  balanced  nutrient
               management schedule for improving crop production and crop quality.
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