NITROGEN CYCLE


Nitrogen Cycle

Nitrogen cycle involves the complex process by which nitrogen is naturally added and removed from the soil. It is a sequence of reaction, indicating the various means by which nitrogen is added to and removed from the atmosphere and the soil.

Importance of Nitrogen Cycle

Nitrogen cycle is nature’s way of regulating the amount of nitrogen to the soil.


WAYS BY WHICH NITROGEN IS ADDED TO THE SOIL IN THE NITROGEN CYCLE

These are the ways by which nitrogen is added to the soil in the Nitrogen cycle:
(1) Direct fixation by lightning during rainfall (Electrical discharge).
(2) Incorporation into the soil by free living bacteria or non-symbiotic bacteria.
(3) Nitrogen fixing bacteria in the root modules.
(4) Decomposition of organic mater
(5) Application of nitrogenous fertilizers
(6) Ammonification
(7) Nitrification


Soil can gain nitrogen through the following ways:

(1)

Symbiotic Nitrogen Fixation:

Some bacteria, such as rhizobium leguminosarum, which live in the root nodules of legunminous plants can fix atmospheric nitrogen directly into the plant. The plant supplies carbohydrate for use by the bacteria while the bacteria supply the plant with combined nitrogen.

(2)

Electrical Discharge

: Nitrogen can also be fixed into the soil during lightning. Nitrogen in the air combines with oxygen to form nitric oxide which further undergoes oxidation to form nitrogen dioxide. The nitrogen dioxide will dissolve in rain water to form nitrous and nitric acid which later dissociates to form nitrate in the soil.

(3)

Non-Symbiotic Nitrogen Fixation

: Some bacteria such as azotobacter and clostridium also Live freely in the soil and can fix atmospheric nitrogen into the soil either aerobically or anaerobically.

(4)

Ammonification and Nitrification:

The process involving the formation of ammonium and decaying plants and animals and their waste products like urine and feaces is called ammonification. A further reaction known as nitrification involves the conversion of ammonium compounds first to nitrite by nitrifying bacteria called nitrosomonas. These nitrites are converted by oxidation to nitrates by another bacterium called nitrobacter. Plants can only absorb nitrates from the soil.
(5) Application of Organic Manure and Nitrogen Fertilizers: These also add or supply nitrogen to the soil.


WAYS BY WHICH SOIL NITROGEN IS LOST FROM THE SOIL

(1) By denitrification: This process involves the conversion of nitrate to nitrogen gas by certain bacteria. The nitrogen gas escapes into the air.
(2) Soil erosion
(3) Leaching
(4) Soil ph
(5) Bush Burning
(6) Crop removal
(7) Volatilisation
(8) Oxidation reaction
(9) Reduction reaction.




PROCESSES THAT LEAD TO THE FORMATION OF NITRATE FROM ORGANIC MATTER IN THE NITROGEN CYCLE

(i) Putrefaction
(ii) Amminization
(iii) Ammonification/mineralization
(iv) Nitrification

(i) Putrefaction: Decay of plant and animal remains into simpler nitrogenous compounds by micro-organisms
(ii) Amminization: Products from putrefactions reaction converted to simple amino compounds and amines
(iii) Ammonification: Conversion of amino compounds and amines into ammonium (NH2 +) compounds
(iv) Nitrification: Oxidation of ammonium compounds into nitrites and nitrates.
Carbon cycle
Carbon cycle (Fig. 18.4 ) involves the series of processes which contribute to the circulation of carbon in nature.
i. Carbon dioxide is removed from the air mainly by photosynthesis during which plants use it to manufacture their own food.
ii. Carbon is lost in form of carbonates of calcium and magnesium through leaching and drainage
The atmosphere gains carbon dioxide through
i. Burning of fuel like coal and wood,
ii. The action of volcanoes which releases carbon dioxide
iii. The respiration by plants and animals
iv. The death, decay and putrefaction of plants and animals,
v. Diffusion of carbon dioxide form sea and other bodies of water, acting as reservoir of carbon dioxide
Importance of carbon cycle
i. Plants use carbon dioxide obtained from the air to manufacture their food during photosynthesis
ii. It provides carbon which is the major building block of all organic matters
iii. It helps to purify the atmosphere and also to maintain matmospheric level of carbon dioxide
iv. Organic matter which is made form carbon helps replenish the soil nutrients






HERE YOU WILL FIND EVERY AVAILABLE TOPICS ABOUT AGRICULTURAL SCIENCE AND BIOLOGY. AND THE LINKS TO THEIR VARIOUS SOURCES.
1. DEVELOPMENT OF AGRICULTURE
2. IMPORTANCE OF AGRICULTURE
3. SUBSISTENCE AGRICULTURE
4. COMMERCIAL AGRICULTURE
5. PROBLEM OF AGRICULTURAL DEVELOPMENT
6. SOLUTIONS TO POOR AGRICULTURAL DEVELOPMENT
7. AGRICULTURAL LAWS AND REFORMS
8. ROLES OF GOVERNMENT IN AGRICULTURAL DEVELOPMENT
9. AGRICULTURAL POLICIES
10. PROGRAM PLANNING IN AGRICULTURE
34.
FORESTRY
35. WILDLIFE CONSERVATION
37. TOPOGRAPHY
38. SOIL
39. BIOLOGICAL FACTORS
42. CLIMATIC FACTORS AFFECTING AGRICULTURAL PRODUCTION
43. TEMPERATURE
44. RAINFALL
45. WIND
46. SUNLIGHT
47. SOLAR RADIATION
48. BIOTIC FACTOR AND AGRICULTURAL PRODUCTION
49. PESTS
50. BIRDS
51. DISEASES
52. SOIL MICRO-ORGANISMS
53. SOIL PH
54. ROCK FORMATION
55. IGNEOUS ROCK
56. SEDIMENTARY ROCKS
57. METAMORPHIC
58. SOIL AND ITS FORMATION
59. FACTORS OF SOIL FORMATION
60. LIVING ORGANISM
61. PARENT MATERIALS

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