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soil science basic and procedure of soil science.pptx

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Nitrogen is essential for plant growth and is absorbed in various forms. It undergoes mineralization through aminization, ammonification, and nitrification, converting organic nitrogen into inorganic forms like NH4+ and NO3- that plants can absorb. Immobilization is the reverse process that fixes nitrogen when carbon-nitrogen ratios in soil are too high. Nitrogen transformations in soil are mediated by soil microorganisms and influence nitrogen availability for plant uptake.

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soil science basic and procedure of soil science.pptx
Nitrogen (N) No . Functions Deficiency symptoms Diseases 1 constituent of organic compounds ( protein, nucleic acid, hormone etc.) Stunted growth Starvation 2 Integral part of chlorophyll Chlorosis (yellowing) Buttoning 3 It imparts green color to the plant Protein & starch content reduced
Sources of nitrogen ?Organic source :- protein , amino sugar, nucleic acid ?Inorganic sources :- fertilizers , mineralization of organic compounds ?Lightening ?Microbes
Forms of Nitrogen in soil Forms Organic Inorganic ?Proteins ?Free amino acids ?Amino sugar ?Other complexes Ionic ?NH4 + ?NO3- ?NO2? Gaseous N2 2 N O NO NO2 NH3
Forms of N absorbed by plants ?NO3- :- predominated in warm & well- aerated soil. Hence , plants grown in well aerated soil absorb nitrate ion. ?NH4 + :- urea CO(NH2)2, urea is absorbed through leaf epidermis, when urea solution is spread over the foliage , & usually not absorbed by root. ?NO2? :- plant absorb nitrite ions , they are toxic. However they accumulate in soil in small quantities. ?Amino acid & nucleic acid :- absorbed by higher plants , accumulated in soil in small quantities.
Mineralization ? Mineralization is the conversion of organic form of the element to inorganic form or mineral form ? In case of nitrogen NH4 + ,NO3- ,NO2? the inorganic forms ? It takes place in three steps as follows :- 1. Aminization 2. Ammonification 3. Nitrification
Aminization ? Proteins breaks down to yield amines , amino acid , carbon dioxide , energy & other reaction products . ? Protein R-NH2 +CO2 + Energy + other reaction products ? This process is brought about by heterotrophic soil micro organisms ( Bacteria , Fungi , Actinomycetes). ? They cause this process for their1 own interest I.e., for obtaining energy.
Ammonification ? This step starts after completion of aminization. In this step amines & amino acid released by aminization process are converted ammonia as follow : ? R - NH2 + H OH NH3 + R- OH + Energy ? Caused by another group of heterotrophic soil micro organisms ? NH3 released is converted to NH4+
? Two reactions may be suggested to demonstrate the conversion of ammonia to ammonium ion 1. NH3 + H2O NH4OH NH4OH NH4 + + OH- 2. ? 2NH3 + H2CO3 NH3 + HNO3 = (NH4)2CO3 ? = NH4NO3 ? 2NH4+ + CO3- NH4 + + NO3- ? In both reaction the common product is ammonium ions . Hence this step is termed as ammonification
Nitrification ? This step follows ammonification process. ? In this step , a part of ammonium ion ( NH4 +)released by ammonification is converted to nitrate ion ( NO3-) + Energy (first step) ? It is a two-step process. ? 2NH4 + + 3O2 2NO2- + 2H2O + 2H + ? 2NO2 - + O2 2NO3- + Energy ( second step ) ?
Role of enzyme ? In the first step ,ammonium ion are dehydrogenated by an enzyme dehydrogenase , while the nitrogen released by dehydrogenation is oxygenated by another enzyme, oxidase. ? In the second step the oxidation of nitrite ions to nitrate ions takes place by dehydrogenation reaction. ? The enzymes causing nitrification process are secreted largely by obligate autotrophic bacteria. ? They obtain energy from oxidation of inorganic salts and carbon from co2. ? The genera of bacteria which oxidize ammonium ion are : nitrosomonas , nitrosococcus, nitrosocystis, nitrosospira, nitrosogloea.
Immobilization ? Immobilization of nitrogen is the reverse of mineralization where available form of an element is fixed as immobile form, ? It occurs when large quantities of low nitrogen crop residues with wide C:N ratio (>30:1) . ? Nitrogen in soil :- 1. As bound amino acid = 20-40 % 2. As combined hexose amines = 5- 10 % 3. Mineralized = 1-3 % ? When C:N ratio exceed 30 , immobilization occurs C:N > 30 = Immobilization Immobilization & Mineralization both C:N = 15-30 20-30 C:N < 20 = Mineralization ( release of NH3 & NO3- )
? coconut coir or cereal straw begin decomposing in soil, the high amounts of carbohydrates in such residues cause the microbial population to build up quickly. ? As new cells are formed, nitrogen and other essential elements from soil are used to build protoplasm. This leads to a decrease in the levels of inorganic nitrogen for crops. ? A shortage of nitrogen can be avoided in such situations by supplying enough fertilizer nitrogen to compensate for immobilization and to meet the crop requirements
CONCLUSION Among all the essential nutrients, nitrogen is the extensively studied one and still receiving much attention. Plants absorb most of the N in the NH4+ and NO3- forms. The process of mineralization and immobilization leads to various transformation of nitrogen in soil. Fate of released ion in soil is directly utilized by the higher plants, utilized by heterotrophic organisms in further decomposing organic carbon residues, fixed in biologically unavailable form, in the lattice of certain expanding type clay minerals or is released back into atmosphere through volatilization.
Thank you A.Swaroopa rani

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soil science basic and procedure of soil science.pptx

  • 2. Nitrogen (N) No . Functions Deficiency symptoms Diseases 1 constituent of organic compounds ( protein, nucleic acid, hormone etc.) Stunted growth Starvation 2 Integral part of chlorophyll Chlorosis (yellowing) Buttoning 3 It imparts green color to the plant Protein & starch content reduced
  • 3. Sources of nitrogen ?Organic source :- protein , amino sugar, nucleic acid ?Inorganic sources :- fertilizers , mineralization of organic compounds ?Lightening ?Microbes
  • 4. Forms of Nitrogen in soil Forms Organic Inorganic ?Proteins ?Free amino acids ?Amino sugar ?Other complexes Ionic ?NH4 + ?NO3- ?NO2? Gaseous N2 2 N O NO NO2 NH3
  • 5. Forms of N absorbed by plants ?NO3- :- predominated in warm & well- aerated soil. Hence , plants grown in well aerated soil absorb nitrate ion. ?NH4 + :- urea CO(NH2)2, urea is absorbed through leaf epidermis, when urea solution is spread over the foliage , & usually not absorbed by root. ?NO2? :- plant absorb nitrite ions , they are toxic. However they accumulate in soil in small quantities. ?Amino acid & nucleic acid :- absorbed by higher plants , accumulated in soil in small quantities.
  • 6. Mineralization ? Mineralization is the conversion of organic form of the element to inorganic form or mineral form ? In case of nitrogen NH4 + ,NO3- ,NO2? the inorganic forms ? It takes place in three steps as follows :- 1. Aminization 2. Ammonification 3. Nitrification
  • 7. Aminization ? Proteins breaks down to yield amines , amino acid , carbon dioxide , energy & other reaction products . ? Protein R-NH2 +CO2 + Energy + other reaction products ? This process is brought about by heterotrophic soil micro organisms ( Bacteria , Fungi , Actinomycetes). ? They cause this process for their1 own interest I.e., for obtaining energy.
  • 8. Ammonification ? This step starts after completion of aminization. In this step amines & amino acid released by aminization process are converted ammonia as follow : ? R - NH2 + H OH NH3 + R- OH + Energy ? Caused by another group of heterotrophic soil micro organisms ? NH3 released is converted to NH4+
  • 9. ? Two reactions may be suggested to demonstrate the conversion of ammonia to ammonium ion 1. NH3 + H2O NH4OH NH4OH NH4 + + OH- 2. ? 2NH3 + H2CO3 NH3 + HNO3 = (NH4)2CO3 ? = NH4NO3 ? 2NH4+ + CO3- NH4 + + NO3- ? In both reaction the common product is ammonium ions . Hence this step is termed as ammonification
  • 10. Nitrification ? This step follows ammonification process. ? In this step , a part of ammonium ion ( NH4 +)released by ammonification is converted to nitrate ion ( NO3-) + Energy (first step) ? It is a two-step process. ? 2NH4 + + 3O2 2NO2- + 2H2O + 2H + ? 2NO2 - + O2 2NO3- + Energy ( second step ) ?
  • 11. Role of enzyme ? In the first step ,ammonium ion are dehydrogenated by an enzyme dehydrogenase , while the nitrogen released by dehydrogenation is oxygenated by another enzyme, oxidase. ? In the second step the oxidation of nitrite ions to nitrate ions takes place by dehydrogenation reaction. ? The enzymes causing nitrification process are secreted largely by obligate autotrophic bacteria. ? They obtain energy from oxidation of inorganic salts and carbon from co2. ? The genera of bacteria which oxidize ammonium ion are : nitrosomonas , nitrosococcus, nitrosocystis, nitrosospira, nitrosogloea.
  • 12. Immobilization ? Immobilization of nitrogen is the reverse of mineralization where available form of an element is fixed as immobile form, ? It occurs when large quantities of low nitrogen crop residues with wide C:N ratio (>30:1) . ? Nitrogen in soil :- 1. As bound amino acid = 20-40 % 2. As combined hexose amines = 5- 10 % 3. Mineralized = 1-3 % ? When C:N ratio exceed 30 , immobilization occurs C:N > 30 = Immobilization Immobilization & Mineralization both C:N = 15-30 20-30 C:N < 20 = Mineralization ( release of NH3 & NO3- )
  • 13. ? coconut coir or cereal straw begin decomposing in soil, the high amounts of carbohydrates in such residues cause the microbial population to build up quickly. ? As new cells are formed, nitrogen and other essential elements from soil are used to build protoplasm. This leads to a decrease in the levels of inorganic nitrogen for crops. ? A shortage of nitrogen can be avoided in such situations by supplying enough fertilizer nitrogen to compensate for immobilization and to meet the crop requirements
  • 14. CONCLUSION Among all the essential nutrients, nitrogen is the extensively studied one and still receiving much attention. Plants absorb most of the N in the NH4+ and NO3- forms. The process of mineralization and immobilization leads to various transformation of nitrogen in soil. Fate of released ion in soil is directly utilized by the higher plants, utilized by heterotrophic organisms in further decomposing organic carbon residues, fixed in biologically unavailable form, in the lattice of certain expanding type clay minerals or is released back into atmosphere through volatilization.