🌊 Methods of Irrigation I: Surface Irrigation Systems

Different irrigation methods apply water to the field in different ways. Choosing the correct method depends on soil, crop, slope, labour, and available water. This lesson begins the topic by focusing on surface irrigation systems, especially border, check-basin, and furrow irrigation.

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Broad classification of irrigation methods

The source groups water-application methods into four broad ideas:

1. flooding
2. applying water beneath the soil surface
3. spraying water under pressure
4. applying water in drops

In practical classification, the lesson groups irrigation methods into:

1. surface irrigation
2. subsurface irrigation
3. pressurized irrigation

This lesson focuses mainly on the first group.

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What surface irrigation means

In surface irrigation, water is allowed to move over the soil surface by gravity and infiltrate into the soil as it advances.

The main surface methods discussed in the source are:

• border irrigation
• check-basin irrigation
• furrow irrigation

These methods are widely used because they are relatively simple, but they require:

• good field layout
• proper levelling or grading
• matching with soil infiltration characteristics

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Border irrigation

What it is

In border irrigation:

• land is divided into long parallel strips called borders
• low ridges separate the strips
• water is introduced at the upper end
• it flows down as a shallow sheet

The strip has a gentle slope in the direction of irrigation.

Suitability

According to the source, border irrigation is suitable for:

• soils with moderately low to moderately high infiltration rates
• close-growing crops such as wheat, barley, fodder crops, and legumes

It is not suitable for:

• coarse sandy soils with very high infiltration
• very heavy soils with very low infiltration
• rice under usual field conditions

Advantages

The source lists advantages such as:

• simple construction of border ridges
• lower labour requirement than check basins
• fairly uniform distribution
• use of larger irrigation streams
• possibility of surface drainage where outlets are available

Border dimensions

The source gives border width as roughly:

• 3 to 15 m

and suggests border length varies with:

• slope
• soil type

For example:

• shorter borders in sandy soils
• longer borders in clay loam or clay soils

This shows that design must match infiltration behaviour.

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Check-basin irrigation

What it is

The source describes check-basin irrigation as one of the most common methods.

In this method:

• the field is divided into small basins
• bunds are built around each basin
• water is retained until it infiltrates

Suitability

The source indicates that it is suited to:

• small, gentle, and uniform slopes
• soils with moderate to slow infiltration
• grain and fodder crops in heavier soils

It is also useful where:

• leaching is needed
• rainfall conservation is desirable

Advantages

The source highlights:

• good control over water depth
• high application and distribution efficiency
• reduction of soil erosion by holding runoff
• usefulness in salt leaching situations

Limitations

The source also lists important drawbacks:

• ridges interfere with machinery movement
• land is lost under ridges and channels
• surface drainage becomes difficult
• careful levelling is required
• labour demand is relatively higher
• not suitable for crops sensitive to wet stem conditions

This makes check-basin irrigation useful but management-intensive.

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Furrow irrigation

What it is

Furrow irrigation is mainly used for:

• row crops

Here:

• furrows are formed between crop rows
• water flows in the furrows
• infiltration occurs from the furrow into the root zone
• water spreads laterally into the ridges

Suitability

The source lists crops such as:

• maize
• sorghum
• sugarcane
• cotton
• tobacco
• groundnut
• potato

and states that furrow irrigation is suitable for most soils except sand.

Advantages

The source notes that:

• only part of the soil surface is wetted
• labour requirement may be reduced
• less land may be wasted in field ditches compared with some basin layouts

These points help explain why furrow irrigation is popular in wide-row crops.

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Types of furrow irrigation

The source classifies furrows in several ways.

Based on alignment

• straight furrows
• contour furrows

Based on size and spacing

• deep furrows
• corrugations

Based on irrigation arrangement

All-furrow irrigation

Water is applied in every furrow.

Alternate-furrow irrigation

Water is applied in alternate furrows in one irrigation and the remaining furrows in the next.

This is a water-saving technique, not a completely different layout.

Skip-furrow irrigation

Some furrows are permanently skipped, often under:

• water-scarcity conditions
• intercropping situations

The source notes that skip-furrow irrigation may save:

• about 30 to 35% of water

This is an important example of adapting irrigation layout to water limitation.

Furrow irrigation is most useful when the crop is planted in rows and only part of the soil surface needs wetting.

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How to choose among surface methods

From this lesson, the basic logic is:

• border irrigation suits close-growing crops on well-shaped strips
• check-basin irrigation suits level land where water must be retained and controlled
• furrow irrigation suits row crops where only part of the soil surface needs wetting

So method selection depends on:

• crop geometry
• infiltration rate
• levelling condition
• labour and management capacity

Summary Cheat Sheet

Method	Key Point
Surface irrigation	Water flows over the soil surface by gravity and infiltrates into the field.
Border irrigation	Water moves as a sheet along long strips; suitable for close-growing crops and moderate infiltration soils.
Check-basin irrigation	Field is divided into basins surrounded by bunds; useful for controlled ponding and leaching.
Furrow irrigation	Water flows in furrows between crop rows; especially suitable for wide-row crops.
Alternate furrow	A water-saving technique where water is applied in alternate furrows.
Skip furrow	Some furrows are permanently skipped to save water or fit intercropping.
Main lesson	Surface-irrigation method must match crop type, soil, slope, and management need.