Drainage

Drainage

Introduction

The main objective of agricultural land drainage is to remove excess

water in order to improve the profitability of farming the land.

There area periods on most land when excess water occurs. However,

these need not be too harmful provided the quantities are small, the

periods of occurrence are of short duration or the excess occurs

during a non critical season. Most land also has some natural drainage

which assists in the removal of a certain amount of the excess water.

It is only when large quantities occur for prolonged durations at

critical periods, that it's removal bt artificial means may be

feasible.

Drainage Problems

Excess water may occur on the land surface or deeper down in the soil

profile. The adverse effects on farming may be broadly classified as

follows -

Impaired Crop Growth : Most crops respire by gaseous exchange in the

rootzone (the process whereby roots absorb oxygen from the soil

atmosphere and release carbon dioxide back into it).

In waterlogged soils, the air content of the soil is low because most

pores are filled with water. Moreover, the exchange between the

remaining air in the soil and the air in the atmosphere above is very

restricted by these conditions. In consequence, respiration is

restricted by the oxygen deficiency while at the same time the carbon

dioxide accumulates to toxic levels, directly impairing the root

growth and the root's ability to absorb nutrients. 1

Waterlogging of the entire rootzone for a period of two to three days

can be fatal when it occurs during the seeding stage. Crops suffer

more from waterlogging under warm than cold condit...

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... in better yields at lower

costs, these returns should be considered in relation to the costs of

the drain and the possible environmental impacts the drain may have on

the landscape.

End Notes

1. R. Q. Cannell, "Effects of soil drainage on crop production".

(London : Pan Books, 1989) pp 15 - 45.

2. J. Erikson, "Irrigation, Drainage and Salinity". (London: Croom -

Helm, 1988) pp 52 - 75.

3. N. W. Hudson, "Drainage in the economy of the farm". (London:

Hutchinson Books, 1992) pp. 21 - 69.

Bibliography

Cannell, R. Q. "Effects of soil drainage on crop production". (London

: Pan Books, 1989) pp 15 - 45.

Erikson, J. "Irrigation, Drainage and Salinity". (London: Croom -

Helm, 1988) pp 52 - 75.

Hudson, N. W. "Drainage in the economy of the farm". (London:

Hutchinson Books, 1992) pp. 21 - 69.