Similar to animals and human beings, plants too require food for growth and development that are available to plants from external environment. This food is composed of certain chemical elements obtained either from biological sources or mineral sources. At present sixteen chemical elements are recognized to be vital for normal plant growth. Inadequate supply of one or more of these essential nutritional elements limits the yield of a crop.
To achieve a momentum in sustainable agriculture, balanced use of essential plant nutritional elements is mandatory. This necessitates the use of proper blend of all essential nutrients through integrated use of chemical fertilizers, manures, soil amendments etc. to maintain soil fertility and to sustain the tempo of growth in agricultural production for achieving agricultural production targets. But soil is seldom able to provide the required plant nutrients. Under intensive cropping, nutritional requirement of crops need to be properly satisfied as the soil nutrients are depleted much more quickly.
According to the modern concept of farming, the chemical elements considered to be equally important and essential in plant nutrition are classified into three categories such as Primary nutrients, Secondary nutrients and Micro nutrients.
Carbon, Oxygen and Hydrogen needs are met from the atmosphere through the plants’ ingenious process called photosynthesis. All other nutrients are to be met by application of auxiliary fertilizers. Nitrogen, Phosphorous and Potassium are called major or primary nutrients because they are utilized by plants in considerable quantities. Calcium, Magnesium and Sulfur are popularly known as secondary nutrients because of their requirement being less than that of primary nutrients.
|Germination & establishment||Vegetative growth||Flowering & reproduction||Fruit sizing & maturity|
|N P||N K||N K||N P K|
|Ca Mg||Ca Mg||Ca Mg||Mg|
|Fe Mn Zn B||B Cu Fe Mn Zn||B Cu Mo||B Cu Mn Mo|
The below depiction shows the essential nutrients that the plant requires for a healthy life and how they can be made available to plants through foliar application. The requirement of Oxygen, Carbon and Hydrogen are available in nature. Other elements like Primary (N.P.K), Secondary (Ca, Mg & S) and Micronutrients (B, Cu, Mn, Fe, Mo, Zn, Cl etc. are to be provided through application of approved ingredients in the soluble form.
As Nitrogen, Phosphorous and Potassium are utilized by plants in considerable quantities the soil generally tends to be deficient in these nutrients most of the time. Hence, the fertilizer industry invariably concentrates mainly in the production of Nitrogenous, Phosphatic and Potassic fertilizers. But ironically N, P & K nutrients cannot be absorbed by the plants in the absence of secondary and micronutrients. Recent research and experiments have revealed that they are also found to play other key roles in plant metabolism. Nevertheless, from nutrition point of view, they are indispensable like any other essential nutrient.
Our systems are in the continuous process of getting revamped to meet future growing demand and nutritional security of this huge population. This calls for an ongoing study of the situation and creation of awareness of the necessity of these elements under healthy cropping system in order to achieve crop production target and hence for global food security.