Drip irrigation is when water is dripped onto or near a plant. The drip is usually on for a period of time (several hours), then off for a period of time. Drip irrigation was first practiced in India using bamboo tubes with small holes drilled in them. Water dripped through the holes onto plants.
The next reference to drip irrigation was when Dr. Lester Kellar introduced his method of dripping water onto avocado trees from a pitcock in a water line. This was at a symposium in Riverside, California, in 1917.
In 1956, Ludwig Bass's patent issued, with drip emitters placed on a pressurized line, which dripped 1 gallon per hour or less from each emitter. The slow but steady drip of water causes the water to penetrate deeper, without spreading across the surface of the ground. The emitters reduced the flow of water from a pressurized spray to a slow drip.