Organic farming has been practiced since ancient times. Before the advent of modern agricultural techniques at about the beginning of the 20th century, all soils across the world would have been healthy and living. In 1950s and early 1960s agricultural research and agricultural technologists have concentrated on the NPK (Nitrogen, Phosphorus and Potassium) theory of plant nutrition. To feed a hungry world and meet the demand for increase in food supply artificial forms of nitrogen, phosphorus and potassium and all micronutrients must be added as some form of chemical salt to grow food. Such an agricultural practice leads "Green Revolution". Here a new high-yielding varieties and large quantities of mineral fertilizers, pesticides and water were introduced. Thus, production of food grains increased nearly four times. So farmers were encouraged to start using artificial chemical fertilizers on to soils which in most cases were organic soils of very good fertility. This fertility being the result of thousands of years of careful husbandry where all the plant residues and all the domestic animal manures were returned to the soil.
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