After reading this article you will learn about Soil Aeration:- 1. Definition of Soil Aeration 2. Importance of Soil Aeration 3. Effects.
Definition of Soil Aeration:
The constant movement of air in the soil mass resulting in the renewal of gases is known as soil aeration. Thus, a well-aerated soil is one in which gases are available to growing aerobic organism (including higher plants) in sufficient quantities and in the proper proportion to encourage optimum rates of the essential metabolic processes of these organisms.
Importance of Soil Aeration:
Soil aeration is a vital process because it largely controls the soil levels of two life- sustaining gasesâ€”oxygen and carbon dioxide. These gases take part in the respiration of the roots of plants as well as soil microorganisms.
The respiration involves the oxidation of organic compounds (Sugar C6H12O6) and liberates carbon dioxide and water. This process in reversed by photosynthesis. Carbon dioxide and water are combined by green plants to form sugars and oxygen. Oxygen is released to be consumed by humans and animals. To continue respiration in the soil, oxygen must be supplied and carbon dioxide removed. For most land plants, the supply of oxygen in the soil air must be kept above 10%.
The role of soil air in relation to fertility of soil and plant growth are given below:
1. Plant and Root Growth:
Soil aeration is an important factor in the normal growth of plants. The supply of oxygen to roots in adequate quantities and the removal of CO2 hampers the growth of plant roots. The abnormal effect of insufficient aeration on root development has been observed.
On the root crops such as carrots and sugar-beets and influence is most noticeable. Abnormally shaped roots of these plants are common on compact, poorly aerated soils. The penetration and development of root are poor so such undeveloped root system cannot absorb sufficient moisture and nutrients.
2. Microorganism Population and Activity:
The microorganism living in the soil also require oxygen for respiration and metabolism. Some of the important microbial activities such as the decomposition of organic matter, nitrification, sulphur oxidation etc., depend upon oxygen present in the soil air.
The deficiency of air (oxygen) in soil slows down the rate or microbial activity. For example, the decomposition of organic matter is retarded and nitrification arrested. The microorganism population, is also drastically affected by poor aeration.
3. Formation of Toxic Material:
Poor aeration results in the development of toxin and other injurious substances such as ferrous oxides, H2s, gas, CO2 gas etc., in the soil.
4. Water and Nutrients Absorption:
A deficiency of oxygen has been found to check the nutrient and water absorption by plants. The energy of respiration is utilised in absorption of water and nutrients. Under poor aeration condition (this condition may arise when water-logged), plants exhibit water and nutrient deficiency. Excess water in the soil can reduce the amount of water absorbed by plants.
5. Development of Plant Disease:
Insufficient aeration of the soil also leads to the development of disease. For example, wilt of arhar and gram, dieback of citrus and peach.
Effects of Soil Aeration:
Soil aeration influences soil properties and soil reaction. The most important of the these reactions are associated with the microbial breakdown of organic residues. Poor aeration slows down the rate of decay, for example, presence of high organic matter level in swampy areas. Oxygen gas content of the soil determine the decay of organic matter.
In the presence of gaseous oxygen, aerobic microorganisms become active and oxidation reactions occur as given below:
In the absence of gaseous oxygen, aerobic microorganism takes over and much slower breakdown occurs.
The reaction is as follow:
Poorly aerated soils are significant sources of methane gas, a pollutant of the upper atmosphere that is in part responsible for long term global warming. Less complete decomposition than that the above two equations, may yield certain organic acids and ethylene gas (C2H4), which can be toxic to higher plants.
Presence of oxygen in the soil determines the forms of inorganic element in the soil. In general, the oxidized forms of elements are more desirable for most common crops on acid soils of humid regions. This is because the reduced forms of iron and manganese are -sometimes present at toxic level in moist, acid soils.
In the drier acidic soils, reduced forms of iron and manganese are preferred. In the dry neutral to alkaline soils, oxidised forms of iron and manganese are tied up in highly insoluble compounds, resulting in deficiencies of these elements (Table 3.2).