Fertilizers

Fertilizers

Compounds or mixture of chemicals which are added to the soils in order to overcome deficiency of minerals are called as fertilizers.

Soils normally contain sufficient quantities of essential minerals, but they are consumed by repeated cultivation of crop plants and thus the soil becomes deficient of these minerals. 

These minerals are to be replenished in order to maintain the soil fertility. N, P and K are three important critical elements which are depleted from the field and need to be replenished periodically.

Deficiency caused by a critical element (N, P or K) is called Primary Deficiency.

Fertilizers are the chemicals or mixtures of chemicals which are added to the soil to overcome the deficiency of these minerals. There are three types of fertilizers:

• Nitrogenous fertilizers: They supply nitrogen to the soil, e.g., sodium nitrate, ammonium sulphate, ammonium nitrate, ammonium chloride and urea.
• Phosphatic fertilizers: They supply phosphorus to the soil, e.g., superphosphate, bone meal, and rock phosphate.
• Potassic fertilizers: They supply potassium to the soil, e.g., murate of potash.

Mixture containing all the three principal nutrients, N, P and K, are called complete  fertilizer or NPK. 

These fertilizers contain nitrophosphate with potash in varying proportions like 17-18-19 or 15-15-15 (representing % of weight of nitrogen, phosphorus and water soluble potassium). 

The use of fertilizers restores the fertility of the soil but their dosages differ according to the crop, soil, season and other climatic conditions.

• Vanadium is essential for alga, Scenedesmus obliques.
• Rubidium has chemical properties similar to potassium.
• Haemoglobin is made up of four peptide chains while leghaemoglobin in root nodules is single peptide chain.
• Azolla has association with Anabaena and Anthoceros with Nostoc.
• The reclamation disease is named so because of its widespread presence in the reclaimed lands of Europe.
• Internal cork (drought spot) is due to disintegration of softer tisues which is preceeded by hypertrophy.
• Orobanche is a leafless parasite growing in the roots of plants like brinjal, potato and mustard.
• The dry weight of nitrogenous organic compounds is 5 to 25% of total dry weight of a plant.
• Deficiency symptoms are also called hunger signs.
• Arceuthobium is a total stem parasite
• Photosynthetic nutrition is also termed as holophytic nutrition.
• Aulosira fertilissima is the most active nitrogen fixer in rice fields.
• Aldrovanda (water flea trap) is small, rootless, aquatic, free floating herb. The plant resembles Dionaea in its mode of catching in insects.
• White bud disease is caused due to acute Zn deficiency and leaves become white and the buds lose green colour.
• Sodium and iodine are essential for animals but not for plants.
• Mineral elements can be absorbed in the form of molecules as ions.
• Leghaemoglobin a pigment closely related to haemoglobin is found in root nodules of leguminous plants.
• Nitrate is reduced to nitrite by an enzyme called nitrate reductase.
• The nitrite ions are reduced to ammonia by enzyme called nitrite reductase.
• Mixtures containing all the three principal nutrients (N, P and K) are called complete fertilizers.
• Active absorption is absorption which requires an input of energy.
• More than 40 enzymes depend upon potassium for their activity.
• Most common free ion in the cell is K+.
• The element taken in the form of gas by prokaryotes only is nitrogen.
• Molybdenum is the micronutrient required by plants in least quantity.