NITROGEN CYCLES

Nitrogen cycles refer to the circulation of certain nutrients like nitrogen, carbon, and water in nature. The nitrogen cycle is nature’s way of regulating the amount of Nitrogen in the soil and air

Ways by which Nitrogen is added to the soil in the Nitrogen Cycle

1. Direct fixation by lightning during rainfall.

2. Incorporation into the soil by free-living bacteria or non-symbiotic bacteria.

3. Nitrogen-fixing bacteria in the root nodules.

4. Decomposition of organic matter.

5. Application of Nitrogen fertilizer.

6. Ammonification

7. Nitrification

Soil can gain Nitrogen through the following ways

1. Symbiotic Nitrogen Fixation

2. Electrical discharge

3. Non-symbiotic Nitrogen Fixation

4. Ammonification and Nitrification

5. Application of organic manure and nitrogen fertilizers

Ways by which nitrogen is lost from the soil are:

1. By Denitrification

2. Soil erosion

3. Leaching

4. Soil PH

5. Bush burning

6. Crop removal

7. Volatilization

8. Oxidation reaction

9. Reduction reaction

Processes that lead to the formation of Nitrate from organic matter in the Nitrogen Cycle

1. Putrefaction: Decay of plant and animal remains into similar nitrogenous compounds by microorganisms.

2. Amminization: Products from putrefaction reactions are converted to simple amino compounds and animal

3. Ammonization: Conversion of amino compounds and amines into ammonium compounds

4. Nitrification: Oxidation of ammonium compounds into nitrites and Nitrates

CARBON CYCLE

This involves a series of processes that contribute to the circulation of carbon in nature.

Explanation

1. Carbon dioxide is removed from the air mainly by photosynthesis

2. Carbon is lost in the form of carbonates of calcium and magnesium through leaching and drainage.

The atmosphere gains carbon dioxide through

1. Burning of fuel like coal and wood

2. The action of volcanoes, which releases carbon dioxide

3. The respiration of plants and animals

4. Death and decay, and the putrefaction of plants and animals

5. Diffusion of carbon dioxide from seas and other bodies of water

IMPORTANCE OF THE CARBON CYCLE

1. Plant use carbon dioxide obtained from the air to manufacture their food during
photosynthesis

2. Provision of carbon, which is the essential building block of all organic matter

3. Organic matter, which is made from carbon, helps to replenish soil nutrients.

WATER CYCLE

This is the continuous movement of water from the atmosphere to the earth and from the earth to the atmosphere.

The atmosphere receives water through

1. Evaporation from oceans and land

2. Transpiration from plants

3. Breathing and respiration by plants and animals

Land receives water through:

1. Rainfall and precipitation

2. Infiltration and percolation

FORMS IN WHICH WATER EXISTS IN THE SOIL

1. Hygroscopic water

2. Capillary water

3. Gravitational water

Ways of conserving water in the soil

1. Stoppage or reduction of water run-off

2. Addition of humus or organic matter

3. Removal of weeds to reduce transpiration and water loss

4. Mulching

5. Cover cropping

6. Contour ridging

7. Appropriate tillage

8. Strip cropping

EVALUATION

1. Explain Nitrification.

2. List five ways the soil can gain nitrogen.

IMPORTANCE OF WATER TO CROPS

1. Water provides the medium for the absorption of mineral salts

2. It facilitates the transfer of nutrients to other parts of plants

3. It is an essential raw material during photosynthesis

4. Facilities for enzymatic activities occurring in crop plant protoplasm

5. It is a constituent of protoplasm

6. It has a cooling effect on crops

7. It helps to sustain life
8.. It helps in seed germination

9. It helps to maintain plant turgor or turbidity

GENERAL EVALUATION

1. List five importance of water to crops.

2. List three forms in which water exists in the soil.

3. List three ways by which Nitrogen is lost from the soil.

4. What is a macronutrient? List five examples.

5. What are micronutrients? List five examples.

READING ASSIGNMENT

SECTION B

1. (a) Differentiate between macro and micronutrients

(b) List three factors influencing nutrient availability in the soil

1. (a) State three functions of Nitrogen to plants

(b) State three importance of the organic matter in Agriculture

We have come to the end of this class. We do hope you enjoyed the class.

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In our next class, we will be learning about Farming Practices.