Enough water supplies are vital for plant growth.
There are two main ways that farmers get water to cultivate crops:
* Rain-fed farming
Rain-fed farming is simply natural supply of water to the soil rainfall-wise. Rain-fed farming is continuously challenging and becoming unreliable due to climate change.
Farmers were particularly worse hit this year due to paucity of rainfalls and almost two months’ droughts. A smart farmer thus needs to realize that farming is no longer business as usual.
Once rainfall is not sufficient, the plants need to survive on additional water via irrigation.
Selecting an appropriate irrigation system is a herculean labour. Irrigation styles are as varied as the people who use them. Different systems can be deployed to supply artificial water to the plants. Each system comes with its own merits and demerits.
However, the right selection depends on soil, water and climatic conditions as well as crop types, farmer’s knowledge and preference, capital and operating costs, and existing farm infrastructure.
This post is mainly for the farmer who chooses to reap huge benefits from dry season farming and he/she has decided to irrigate and is in the process of making a decision on which type of irrigation system will best fit into his or her farm operation and setting.
Over 2,000 years, farmers have been employing irrigation to grow food for teeming hungry populations and enhance standard of living.
According to the Food and Agriculture Organization of the United Nations, irrigation contributes to about 40% of the world’s food production on 20% of the world’s crop production land.
Simply put, irrigation is the means of applying water to soil, essentially to quench the water needs of growing plants. Through pipes, canals, ditches or even streams, water from rivers, reservoirs, lakes, or aquifers is pumped or flows by gravity.
The vast majority of irrigation water use is pumped directly from a water source — river, creek, channel, drag-line, hole, dam or borehole.
Provision of waters to farmland helps to improve the magnitude, quality and reliability of crop production.
Irrigation affords farmers an opportunity to grow more pastures/crops and produce higher quality crops/pastures as water stress can dramatically impact on the quality of farm produce.
Irrigation stretches the crop growing season, enables farmers to start the season at an earlier time and ‘insure’ them against seasonal variability and drought.
Irrigation facilitates maximum benefits of fertilizer applications, and enables farmers to use areas that would otherwise be less productive. Thus, it paves a way to exploit market incentives for unseasonal production.
Many irrigation methods have been developed over time to meet the irrigation needs of certain crops in specific areas.
The three main broad categories of irrigation are surface, sprinkler, and drip/micro.
In surface irrigation, water flows over the soil by gravity without the use of advanced technology.
Sprinkler irrigation provides water to soil by sprinkling or spraying water droplets from fixed or moving systems.
Micro irrigation supplies frequent, small applications by dripping, bubbling or spraying, and usually only wets a portion of the soil surface in the field.
These major broad systems of irrigation are explained in turn below;
1. Surface Irrigation
Surface irrigation applies water by gravity flow to the surface of the field. It is the most popular used irrigation systems and is fit to both mild slopes and regular slopes.
Surface irrigation may involve flooding the entire field (basin irrigation) or the water is supplied into small channels (furrows) or strips of land (borders).
Hence, the three major methods of irrigation under surface irrigation include; basin irrigation, furrow irrigation and border irrigation.
Paddy rice is always grown in basins. Other crops which can also be grown in basins include maize, sorghum, trees, etc. Basins should be avoided in growing crops that cannot stand a very wet soil for more than 12-24 hours.
Furrow irrigation is typically used for irrigating row crops such as maize, vegetables and trees. Crops whose stems or crowns would be damaged if covered with water should be irrigated by furrows.
Border irrigation is a perfect fit for close growing crops such as alfalfa, it may also be employed for row crops and trees.
When compared with sprinkler irrigation or micro-irrigation, surface irrigation is usually considered less efficient because soil, not a pipe, conveys the water within the surface irrigated fields without the aid of mechanical devices.
2. Sprinkler Irrigation
Sprinkler irrigation applies water to soil by sprinkling or spraying water through the air on the soil surface. Sprinkler irrigation is a style of distributing irrigation water which is similar to natural rainfall.
Sprinklers are typically suitable for sandy soils with high infiltration rates although they are adaptable to most soils. Sprinkler irrigation is adaptable to any farmable slope, whether uniform or undulating.
Water is pressurized and delivered to the irrigation system by a mainline pipe, which is often buried so it doesn’t interfere with farming operations.
Water is distributed by overhead high-pressure sprinklers or guns from a central location in the field or from sprinklers on moving platforms.
Three main categories of sprinkler irrigation systems are solid-set, set-move and moving.
Sprinkler irrigation systems include center pivot, linear move, traveling gun, permanent set, and solid set.
Sprinkler and drip irrigation, because of their high capital investment per hectare, are mostly used for high value cash crops, such as vegetables and fruit trees. They are seldom used for the lower value staple crops.
Sprinkler irrigation is used for a wide variety of plants including field crops, vegetables, orchards, turf and pastures.
However, large sprinklers are not suited for irrigation of delicate crops such as lettuce because the large water drops produced by the sprinklers may damage the crop.
The system has high water efficiency, is easy to install, and the equipment is readily available on the market.
However, high investment costs, as well as high fuel costs for the operation of the pressure pumps, have been a major constraint which makes it one of the more expensive options and it has often proved to be uneconomical for most of the food crops cultivated by small-scale farmers.
3. Micro Irrigation
Micro-irrigation applies water at low rates and pressures to discrete areas so irrigation water reaches the root zone with minimal losses.
These systems are typically automated so that water is applied frequently (e.g. daily or multiple times per day) to maintain optimum soil water content near the plants.
Micro-irrigation systems include drip (or trickle) irrigation and micro-sprinklers.
Drip irrigation systems
In drip irrigation, water is applied directly along the crop rows through small drippers fitted on flexible polyethylene tubes. Drip irrigation is adaptable to any farmable slope and suitable for most soils.
On clay soils, water must be applied slowly to avoid surface water ponding and runoff. On sandy soils, higher emitter discharge rates will be needed to ensure adequate lateral wetting of the soil.
The system can be very efficient in terms of water usage, reaching up to 90 percent, and it applies the water very accurately to the crop, which results in optimal crop yields.
Drip irrigation is applied successfully in most high-level commercial fruit and vegetable farms and greenhouses. Generally, only high value crops are considered because of the high capital costs of installing a drip system.
Drip irrigation can integrate well with fertilization and has high productivity for fruit trees and vegetables in extensive areas or greenhouses.
Although an effective technology, drip irrigation systems for small-scale farmers have failed in several cases, as farmers have not been adequately familiarized with the operational aspects of the technology.
Conclusively, no one system is best fit for every application or situation or circumstances.
Consider the following important factors before deciding which irrigation system is best for you. Key factors to be considered in the field to ensure successful implementation of irrigation techniques include:
- Crop type
- Landscape, field lay-out and slopes of the field.
- Climate condition and rainfall pattern during the year.
- Water source (quantity, quality, fluctuations).
- Proximity and accessibility of water resources to the field.
- Costs and complexity of installation.
- Operating costs (labour, fuel costs).
- Labor requirements.
- Technical equipment and support services locally available.
Some circumstances may warrant additional considerations such as whether you own the land or are leasing.
You may also own some equipment, such as a well or pumping unit, and wish to adapt the system to this existing equipment.
To choose an irrigation method, the farmer must know the advantages and disadvantages of the various methods. He or she must know which method suits the local conditions best.
Unfortunately, in many cases, there is no single best solution: all methods have their merits and demerits.
Testing of the various methods – under the prevailing local conditions – provides the best basis for a sound choice of irrigation method.
It is our hope this post offers you some useful insights into selecting the right irrigation method for your farming pursuits.
For further Reading/Reference;
* IRRIGATION Methods, DLBjorneberg, USDA Agricultural Research Service, Kimberly, ID, USA
* FAO Irrigation Techniques for Small-scale Farmers
* FAO Irrigation Water Management: Irrigation Methods
* Factors to Consider in Selecting a Farm Irrigation System. UGA Extension Bulletin 882
* Principles of irrigation scheduling for vegetable crops in Georgia. UGA Extension Bulletin 1511