Subirrigation

(subsoil irrigation), a method of irrigation whereby water travels along capillaries directly to the root horizon of the soil from a system of underground ceramic pipes with open joints or porous mole drains. Subirrigation is linked to the development of drainage systems and, in particular, two-way land reclamation systems.

For subirrigation, either special systems with irrigation networks composed of piping are built or drainage systems equipped with gates are used. The gates in the canals are closed in the spring when flood waters are dropping (preventive damming) or periodically during the summer (moisture damming). In the latter case water must be fed into the system from a source because summer runoff does not provide adequate moisture. When the gates are closed, runoff stops and the soil is moistened by infiltration of the water from the canals and drains.

Compared to surface irrigation, subirrigation provides better moistening and makes possible the automation of irrigation technology. Subirrigation systems can work efficiently only if the soil is highly permeable to water and the surface of the irrigated fields is level.

Subirrigation is used on relatively small areas in the USA, the Netherlands, the German Democratic Republic, Poland, Great Britain, and elsewhere. In the USSR it is used on the floodplains of the Irpen’, Trubezh (Ukraine), Oressa (Byelorussia), and Moskva rivers.