Tuesday, March 17, 2015

Soil Properties

Soil is an organized mixture of minerals, organic materials, living organisms, air and water. Soil exhibits both Chemical and Physical properties.  These are influenced by the mineral matter of soil and the size of soil particles such as sand silt and clay.  By adding organic content to the soil its structure and texture are improved.

Chemical Properties

Information on salt tolerance is important for proper soil management practices. Based on salt tolerance level, soil can be split into three categories, they are 

Salt Tolerant Crops (6-8 mmohs / cm) e.g. Watermelon

Moderate Salt Tolerant Crops (3-6 mmohs / cm) e.g. Tomato, Lemon

Salt Sensitive Crops (1.5 – 3 mmohs / cm) e.g. Avocado, Cauliflower

Plants require a number of essential nutrients for growth and development. Both soil and atmosphere can provide these nutrients.  Some of these are need in larger amount ( macro nutrients such as N / P / K ) and some are in lesser amount ( micro nutrients such as  Mn / Fe / Bo / Cu / Zn)

Like the temperature of the human body, soil pH implies certain characteristics that might be associated with soil. A soil pH of 7 is considered as neutral.  Greater than 7 indicates alkaline and less than 7 indicates acidic.

Soil pH affects the quantity, activity and types of micro-organisms in soils which in turn influence decomposition of crop residues, manures and other organics. 
Majority of plants prefer pH between 6.5 to 8.5

Soils in wet climate tend to be acidic.  Soils in high rainfall area tend to be acidic because of leaching.  Acid soils can be improved by adding lime to soil.

Soil in dry climate tends to be alkaline.  Lack of rainfall will not flush the nutrients out of soil and they remain within soil.  In extreme cases this leads to salinization, in which soil contain too many salts, which prevent the growth of many crops.

Physical Properties

Water Table
Availability of water at a certain depth in the soil is called Water Table.  High water table leads to decline in vegetable and fruit crops due to logging conditions.  Water table should be less than 2 meters throughout the year.

Soil Depth & Texture
More organic matter in soil will help vegetable and fruits to grow healthy and require medium textured soil. 

Soil Temperature
In cold soils, chemical and biological activities are slow and availability of nutrients is limited.  Temperature should be 26 – 320 degree Celsius for successive growth of Horticulture crops.  Low temperature will affect the transport of water and nutrients.

Soil structure and Aeration
Soil structure is the key and has to be examined properly. It also varies in different layers.  Aeration is required for growing aerobic organism in the soil to promote metabolic activities of these organisms.

Well drained soil is required for proper aeration and drainage.  Extreme wet and dry soil should be avoided.
See Also :
Types of Soil Found in India
Nitrogen Cycle

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