ABSTRACT
Tilling the soil has been a central part of crop husbandry since the dawn of recorded history. Tilling the soil is mentioned in the Bible and in the writings of the early Su-merians. Tillage loosened the soil so that seeds of crops could be planted. Tillage destroyed weeds in the field prior to planting and, after the crop emerged, was used to destroy weeds growing and competing with the crop. Tilling the soil buries plant residues and disrupts the habitat of insects living in the soil. Entomologists and pathologists consider tillage to be a means of reducing the incidence of damage from certain insect and disease pests. Tillage incorporates plant nutrients applied to the soil surface and increases the rate of decomposition of organic matter contained in the soil. Since most of the soil nitrogen supply is contained in the soil organic matter, this may be an important factor in the nitrogen nutrition of crops. The supply of nitrogen from organic matter is less critical in areas where inorganic sources of nitrogen fertilizer are readily available but may be the major source of nitrogen for crop production in many parts of the world.
