Modern methods of irrigation include center-pivot systems, drip irrigation and sub-irrigation. Center pivot systems use large mechanical arms mounted on central pivots, creating circular plots of irrigated soil. Drip irrigation involves a piping system designed to deliver small amounts of water directly to root systems. Sub-irrigation pumps water into the soil to raise the water table itself.
Mechanical irrigation systems often feature lots of moving parts. Water can be fed from a central point, or it may flow through movable frameworks that roll over fields, irrigating crops from above. These systems are effective at providing lots of water to selected crops, but they can be expensive to maintain and may use considerable amounts of water.
Drip irrigation improves water efficiency by reducing runoff and evaporation, providing only the amount of water each plant needs and allowing it to drip directly into the soil where it does the most good. These systems can require a lot of infrastructure in terms of running pipes along each row of crops to provide the flow of water.
Sub-irrigation systems require the most intensive construction work, because multiple pumping stations may be required to manipulate the local water table of an entire farm. Once in place, these systems are very resistant to drought conditions and provide moisture and nutrients quickly and efficiently to the crops.