Soil Fertility And Productivity
Soil fertility: is the capacity/ability of the soil to supply the plant nutrients required by the crop plants in available and balanced forms. Or
It is the capacity of soil to produce crops of economic value to man and maintain the health of the soil for future use. Or
The soil is said to be fertile when it contains all the required nutrients in the right proportion for luxuriant plant growth.
Plants like animals and human beings require food for growth and development. This food is composed of certain chemical elements often referred to as plant nutrients or plant food elements. These nutrients are obtained from soil through roots.
Plants need 16 elements for their growth and completion of life cycle. In addition to these, 4 more elements viz. sodium, vanadium, cobalt and silicon are absorbed by some plants for special purposes.
Classification and source of nutrients:
Class Nutrient Source
Basic C, H, O Air and water
Macro N, P, K, Ca, Mg, S Soil
Micro Fe, Mn, Zn, Cu, B, Mo & CI Soil
Four more recognized nutrients are NA, Co, VA & SI.
Basic nutrients (C, H, and O) constitute 96% of total dry matter of plants. Macro (Major) nutrients (primary-N, P, K, and secondary-Ca, Mg, S) are required in large quantities while Micro nutrients (Trace elements-Fe, Zn, Cu, B, Mo, Cl, and Mn) are required in small quantities. These trace elements are very efficient and minute quantities produce optimum effect. On the other hand, even a slight deficiency or excess is harmful to plants.
Function of the plant:
Elements that provide basic structure to the plant – C, H, O.
Elements useful in energy storage, transfer and bonding – N, S & P. these are accessory structural elements which are more active and vital for living tissues.
Elements necessary for change balance – K, Ca & Mg, act as regulators and carrier.
Elements involved in enzyme activation and electron transports. Fe, Mg, Cu, Zn, B, Mo & Cl are catalysers and activators.
Criteria of Essentlailty: Armon and Stout (1939) proposed criteria of essentiality which was refined by Arnon (1954) as:
The plant must be unable to grow normally or complete its life cycle in the absence of the element.
The element is specific and cannot be replaced by another.
The element plays a direct role in metabolism and
The deficiency symptoms of the element can be corrected or prevented by application of that element only.
In general, an element is considered as essential, when plants can’t complete vegetative or reproductive stage of life cycle due to its deficiency when this deficiency can be corrected or prevented only by supplying this element and when the element is directly involved in the metabolism of the plant.
Nicholas (1961) proposed the term functional nutrient for any mineral nutrient that functions in plant metabolism whether or not its action is specific. E.g.: Na, Co, Va and Si.
Soil fertility denotes the capacity of the soil to produce crops of economic value and maintain the health of the soil for future use. Or
It is the capacity of soil to supply essential nutrients to normal plants in adequate amounts and in a balanced proportion.Or
It is better to cultivate small piece of fertile land than large nutrient needs of the crop. Or The soil is said to be fertile when it contains all sixteen of the required nutrients in the right proportion for luxuriant plant growth.