Subirrigation

Subirrigation is a method of applying water beneath the ground surface. It is usually done by creating an artificial water table and maintaining it at some predetermined depth, usually 12 to 30 inches * below the ground surface for farm crops. Moisture reaches the plant roots through capillary movements. Application efficiencies (1) vary from 30 – 50 per cent in some areas up to 70 – 80 under favorable conditions.

Subirrigation requires permeable soil provided that the soil permeability in the rooting zone is homogeneous, and salinity is not a potential hazard. For successful subirrigation, an adequate supply of water of good quality must be available throughout the growing season. The topography must be nearly level and smooth.

A barrier against excessive losses through deep percolation must exist in the soil profile. The barrier may be a relatively impervious layer in the substratum. The distribution system must consist of a well - planned system of main ditch, field laterals, and structures, which will permit the water table to be raised to a uniform depth below the ground surface over the entire areas. An adequate outlet for the draige of the irrigated must be provided for, particularly in humid areas.

The principles involved in subirrigation are the same in all areas, although the means of introducing water into the soil profile may differ. An artificial water table is created over a natural barriers that prevents deep percolation of the water.

Water may be introduced into the soil profile through open ditches, through mole drains, or through tile drains. (2) The first way is most widely used because it is relatively inexpensive and is adapted to all the soil types that can be subirrigated. Mole and tile drains can be used in organic soil.

The main crops so irrigated are potatoes, beets, onion and corn. An effective drainage system has to be provided so that the water table can be lowered rapidly when necessary and harmful salts can be leached out of the profile.

The entire system, when adequately planned, installed, and maintained, provides excellent drainage during the rainy season.

Under limited situations, subsoil irrigation may be a very desirable system of irrigation. In general, however, it must be used with great caution. Danger from waterlogging and salt accumulation is great.

Notes

Application efficiency коэффициент полезного действия

оросительной воды

through mole drains, or through tile drains при помощи кротовых дрен или

гончарных дренажных труб

Ответьте на вопросы.

How do we apply water in subirrigation?

What soils does subirrigation require?

State the main conditions necessary for successful subirrigation?

How many water be introduced into the soil profile in subirrigation?

What are the main crops so irrigated?

Переведите на английский язык.

Система подпочвенного орошения должна быть тщательно спроектирована, а поверхность выровнена так, чтобы глубина контролируемого уровня воды под поверхностью почвы была одинакова на всей площади.

При кротовом подпочвенном орошении вода протекает по кротовинам (through the mole - passagers) проделанным кротовым плугом или дренажно-кротовой машиной.

При поверхностных методах полива вода на орошаемой площади используется менее равномерно (less evenly) по сравнению с дождеванием или подпочвенным орошением.

3.В чем заключается внутрипочвенный метод орошения?

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