Water is one of the most important requirements for crop production. Crops need the right amount of water to germinate, grow, absorb nutrients, and produce good yields. Rainfall may provide enough water in some areas, but in places where rainfall is low, irregular, or poorly distributed, farmers may need to supply additional water to their crops and this is were irrigation and drainage system comes in.
At the same time, too much water can also be harmful. When excess water remains in the soil for a long time, it can reduce the amount of air available to plant roots and may lead to poor growth. This is why irrigation and drainage are both important parts of farm water management. Irrigation supplies water when crops need it, while drainage removes excess water from the soil.
Meaning of Irrigation
Irrigation is the artificial supply of water to agricultural land or crops when natural rainfall is not enough to meet their water needs.
The water used for irrigation may come from rivers, streams, lakes, wells, reservoirs, or other suitable sources. It can then be moved to the farm through channels, pipes, pumps, or other systems.
The main purpose is not simply to add as much water as possible. Water needs to be supplied in the right amount and at the right time so that crops can grow properly without creating unnecessary water problems.
Meaning of Drainage
Drainage is the removal of excess water from agricultural land. It helps prevent water from remaining in the soil for too long, especially around the roots of crops.
Excess water can come from heavy rainfall, flooding, excessive irrigation, or a high water table. When the soil remains waterlogged, plant roots may not get enough oxygen, which can reduce crop growth and yield. Drainage helps create better conditions in the root zone.
Types of Irrigation
There are several methods of supplying water to crops. The method chosen depends on factors such as the type of crop, soil, land slope, available water, cost, and available labour.
1. Surface Irrigation
Surface irrigation involves allowing water to flow over the surface of the soil and spread across the field. The movement of water is mainly controlled by gravity.
It is commonly used where the land has a suitable slope and the soil can allow water to spread properly. Examples include basin, furrow, and border irrigation.
Uses:
- Supplies water to crops over a wide area.
- Can be used for many types of crops.
- Does not always require complicated equipment.
- Can be suitable for farms with enough surface water.
2. Sprinkler Irrigation
Sprinkler irrigation supplies water through pipes and sprays it over the crops in the form of small drops, similar to rainfall.
The system can be useful where the land is not suitable for some forms of surface irrigation. However, the equipment requires proper maintenance, and wind can affect how evenly the water is distributed.
Uses:
- Provides fairly even water application when properly managed.
- Can be used on different types of land.
- Reduces the need to move water through open channels.
- Can be useful for crops that need controlled watering.
3. Drip Irrigation
Drip irrigation supplies water slowly and directly to the area around the roots of plants. Small openings or emitters release water from pipes at controlled rates.
Because water is delivered close to the roots, this method can reduce unnecessary water loss. It is particularly useful where water is limited or where crops are grown in rows.
Uses:
- Delivers water close to plant roots.
- Helps reduce water wastage.
- Can provide regular water to crops.
- Suitable for many vegetables, fruits, and other crops.
Types of Drainage
Drainage systems can be grouped mainly into surface drainage and subsurface drainage. Some farms may use one method, while others may use a combination depending on the water problem.
1. Surface Drainage
Surface drainage removes excess water that collects on the surface of the soil. It may involve shallow channels, ditches, or properly shaped land that allows excess water to move away from the field.
This method is especially useful in areas where heavy rainfall causes water to collect on flat agricultural land.
Uses:
- Removes standing water from fields.
- Reduces waterlogging.
- Helps protect crops from excess surface water.
- Allows farm activities to continue after heavy rainfall.
2. Subsurface Drainage
Subsurface drainage removes excess water from below the soil surface. It may use underground pipes or other drainage structures to lower excess water around the crop root zone.
This method can be useful where the water table is too high or where surface drainage alone cannot remove enough water.
Uses:
- Removes excess water from the root zone.
- Helps control waterlogging.
- Can help reduce the build-up of salts in some soils.
- Improves conditions for crop roots.
Importance of Irrigation and Drainage
Irrigation and drainage work together to help farmers manage the amount of water available to crops. Proper water management can support crop growth while reducing problems caused by too little or too much water.
1. Provides Water During Dry Periods
Irrigation allows farmers to supply water when rainfall is not enough. This is especially useful during dry seasons or periods when rainfall is irregular.
With a reliable water supply, farmers can continue crop production even when natural rainfall cannot provide all the water required by the crops.
2. Helps Prevent Waterlogging
Drainage removes excess water from farmland. This is important because waterlogged soil can reduce the oxygen available to plant roots and affect crop growth.
Good drainage therefore helps maintain a more suitable environment around the roots.
3. Supports Crop Production
A well-managed water supply can help crops receive the moisture they need at important stages of growth. Irrigated agriculture can therefore increase production where water is a major limitation. FAO notes that irrigated land produces a large share of global crop value despite representing a smaller share of total cropland.
4. Helps Improve Soil Conditions
Drainage can improve the condition of poorly drained soils by reducing excess water. In areas affected by waterlogging and salt build-up, suitable drainage can help protect the root zone and improve the productive use of the land.
5. Allows More Reliable Farm Planning
When farmers have better control over water, they can plan planting and other farm activities more effectively. Irrigation can provide water during dry periods, while drainage can help fields recover from excess water.
6. Can Improve Farm Income
Better water management can support higher and more reliable crop production. When production improves and losses are reduced, the farmer may be able to earn more from the farm.
Problems of Irrigation and Drainage
Although irrigation and drainage are useful, poor planning or poor management can create problems.
1. High Cost
Some irrigation and drainage systems require money for construction, pumps, pipes, channels, equipment, fuel, and maintenance. This can make them difficult for farmers with limited resources to install and maintain.
2. Water Wastage
Poorly managed irrigation may supply more water than crops need. Some water may be lost through runoff, evaporation, or movement below the root zone.
Using too much water can also increase drainage problems. Proper irrigation management is therefore important.
3. Waterlogging
If irrigation water is applied faster than the soil can absorb or if the land has poor natural drainage, excess water may collect in the root zone.
Waterlogging can reduce root growth and crop performance because plant roots need oxygen from the soil.
4. Soil Salinity
In some irrigated areas, salts can build up in the soil when water evaporates and leaves salts behind. This can make it harder for crops to take up water.
Good drainage can help manage salt build-up by allowing excess water and dissolved salts to move away from the root zone.
5. Maintenance Problems
Channels can become blocked by weeds, soil, and other materials. Pipes, pumps, sprinklers, and other equipment can also become damaged.
If the system is not checked and maintained regularly, water may not reach the crops properly or excess water may not leave the field.
6. Environmental Problems
Poorly managed irrigation and drainage can affect nearby water bodies. Drainage water may carry salts, nutrients, or farm chemicals into rivers, lakes, or other water sources. Proper management is therefore needed to reduce these effects.
Factors to Consider When Choosing an Irrigation or Drainage System
The best system for a farm depends on the conditions of that farm. Farmers should consider the following:
- Type of soil: Different soils absorb and hold water at different rates.
- Type of crop: Different crops have different water needs.
- Land slope: The shape and slope of the land affect how water moves.
- Water availability: The amount and quality of available water must be considered.
- Cost: The farmer needs to consider installation, operation, and maintenance costs.
- Labour: Some systems require more labour to operate and maintain than others.
- Climate: Rainfall, temperature, and evaporation affect the amount of water needed.
- Maintenance: The farmer should choose a system that can be properly maintained with available resources.
Difference Between Irrigation and Drainage
| Feature | Irrigation | Drainage |
|---|---|---|
| Main purpose | Supplies water to crops | Removes excess water |
| Direction of water | Brings water to the field | Takes excess water away |
| Main problem addressed | Lack of water | Excess water |
| Main benefit | Provides moisture for crop growth | Prevents waterlogging |
| Common methods | Surface, sprinkler, drip | Surface and subsurface |
Summary on Irrigation and Drainage System
Irrigation is the artificial supply of water to crops, while drainage is the removal of excess water from agricultural land. Both are important for proper farm water management.
Different irrigation methods include surface, sprinkler, and drip irrigation, while drainage can mainly be divided into surface and subsurface drainage. The choice of system depends on factors such as soil type, crop, land slope, water supply, cost, and labour.
When properly planned and managed, irrigation and drainage can support crop production, reduce water-related problems, and improve the use of agricultural land. However, poor management can lead to water wastage, waterlogging, soil salinity, high costs, and environmental problems.
Revision Questions
- What is irrigation, and why is it important in crop production?
- What is drainage, and how does it help agricultural land?
- State three types of irrigation and explain how each supplies water to crops.
- Mention four problems that can result from poor irrigation and drainage management.
Frequently Asked Questions (FAQs)
1. What is irrigation?
Irrigation is the artificial supply of water to crops when natural rainfall is not enough for their growth.
2. What is drainage in agriculture?
Drainage is the removal of excess water from agricultural land. It helps prevent waterlogging and creates better conditions for crop roots.
3. What are the main types of irrigation?
The main types include surface irrigation, sprinkler irrigation, and drip irrigation.
4. What are the main types of drainage?
The two main types are surface drainage and subsurface drainage. Surface drainage removes water from the soil surface, while subsurface drainage removes excess water below the surface.
5. What are the problems of poor irrigation and drainage?
Poor management can cause water wastage, waterlogging, soil salinity, high costs, equipment problems, and environmental pollution.
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