Drainage

• Drainage is the removal of excess water either from agricultural land or barren land.
• Much of excess water is removed naturally by surface runoff, deep seepage, evaporation and transpiration but these processes are often too slow to prevent damage to crop and thus removal of excess water must be carried out with the help of drainage.

Objectives of drainage

• removal excess water from the soil to improve the productive capacity of soil
• improvement in soil structure
• increase in depth of plant rooting zone
• improve air circulation, to warm soil
• improve organic matter decay and nitrification
• reduced erosion
• diminished effect of drought
• increased leaking of soil
• prevention of freezing in temperate soil
• removal of salts from the soil by drainage of saline soil from irrigated land and
• check the water logging condition in agricultural land.

Principles of drainage

1) The main drainage lines should follow the lines of natural drainage.

2) Laterals should be laid along lines of greatest slope.

3) Where possible, long parallel laterals should be used.

4) Drainage lines should be made straight or with gradual errors, sharp curve check the flow of water and coarse silt deposition.

5) Silt wells or traps should be put in low spots.

6) The outlet should be protected from erosion and screened against burrowing animals.

7) In heavy clay soils of flat tops surface drainage is preferred.

Benefits of drainage

i) Drainage facilitates early ploughing and planting

.ii) It lengthens the crop-growing season.

iii) It helps to increase root zone depth.

iv) It helps to decrease soil erosion.

v) It leaches excess salt from soil and prevents their accumulation in soils.

vi) It improves soil structure and the infiltration capacity of soil.

vii) It hastens the warming of soil and maintains desirable soil temperature.

viii) It helps to aerate the soil.

ix) It helps to favour growth of soil bacteria.

x) It helps in reclamation of arable soil, low lying or swamp areas