Any living organism cannot live without water. Water is an important constituent of any cell either it is a plant cell or animal cell. Plant cell constitutes of 80-90% water but the percentage of water varies in different parts of plant. Water has physiological and ecological importance. It is not only essential to meet the needs of agriculture but it also for industrial use, livestock and domestic consumption.
Water is today’s Liquid Gold due to increasing cost of irrigation projects and limited supply of good quality water. So, it gains a highly valuable commodity. Quantity of fresh water now remains very less. Many countries are going through water scarcity. It is need of hour to save the water for the agriculture irrigation purpose, industrial purpose, livestock and domestic use.
Water_ as an instrument of agriculture is very important. No seed can be reached its maturity; no seedling can be come out from seed without the mercy of water. In the absence of rain, irrigation is practiced in field. Irrigation is the artificial application of water to the plants to fulfill the water requirement of plant and conserve the soil moisture. Irrigation is important as it provides water so that our yield of agricultural crops and horticulture crops increases. Efficient irrigation and irrigation management is required to achieve the goal of best irrigation in field. Efficient irrigation is the controlled application of the water to the plant land in a required quantity at a required time to get an optimum yield. Irrigation management is an art and science which depends on many factors, these managements helps in controlling the irrigation in a field.
To irrigate field water sources matter very much. There are three sources of water as
- Rainfall or effective rainfall
- Surface water
- Sub surface water
Effective rainfall is that rainfall which is directly absorbs by the plant parts and that plays a role in plant metabolic activities especially in photosynthesis.
Surface water consists of ocean, sea, river, lakes etc while the sub surface is the underground water which draws with the help of tube well or electric motors.
In Pakistan, irrigation system that is installed is basically named as Indus Basin irrigation system. This system holds the water requirement in whole country. This system utilizes over 41.6MAf of groundwater. For the best working of irrigation system, there must be good water use efficiency and crop water requirement must consider. CWR is the total quantity of water required by plant for its development and growth of its economical parts. Specific methods should be adopted for best use of water.
Methods of Irrigation:
Application of water to the cropland by different types of layouts is called methods of irrigation. Layout is very important in selecting a suitable method for irrigation. In old days flood irrigation was preferable, no doubt it exits in today’s world but now a days we are suffering from the shortage of water. Africa is suffering from severe water scarcity then Asia. In a survey of last five years Pakistan is in the top 15 countries going through the water stress. So, it has become necessary to save the water by arresting a suitable method of irrigation that will use less amount of water and provide better efficiency. To find a most appreciable method to irrigate the fields there are some factors that influence irrigation method e.g., Soil type, Soil depth, Water sources, Topography of land, Economics, Water seepage pattern, Climate (includes temperature, wind , humidity, rainfall etc), Local tradition & skills, Crops to be grown and many other factors. There are many ways to irrigate a field as
- By flooding (overall piece of land is wet with water)
- By furrow (only the furrows become wet or ground which contain crop)
- By sub irrigation
- By sprinkler ( artificial rainfall or sprinkling water)
- By drip irrigation ( water drop by drop to root zone)
Classification Of Irrigation Methods:
Besides the general ways, irrigation methods are classified into three categories
- Surface or gravity irrigation
- Sub surface irrigation
- Pressurized or irrigation
As water is now Gold Liquid so to save the water, efficient method of irrigation is Drip irrigation which has an efficiency of 80-90%. Below is the efficiency of all irrigation methods.
As water is an Instrument of agriculture and it is a beauty of agriculture. To accomplish the effective irrigation i.e., controlled and uniform application of water to the cropland in a required amount of water at a required time so that we can get an optimum yield hence I will discuss the drip irrigation, its components, merits and demerits.
Drip or trickle irrigation:
Application of water to the crop root zone drop by drop with the help of a device called emitters and a network of pipeline through which water is supplied is called drip irrigation.
The main principle of this irrigation is to utilize the water in a best way and also maintain the field capacity level without any water stress. As this is application of water is at crop root zone based on daily ET demand of crop. Drip irrigation is consist of following components
- Valves ( isolation & controlling valve)
- Backflow preventer
- Pressure regulator or overhead tank
- Main lines
- Sub mains
Drip irrigation components and layout
Valves are fitted in the system of drip irrigation so that to turn on or turn off the water supply. There are two types of valves i.e., isolation valve and control valve. Isolation valve is manually and this is mainly used to shut off the water supply. Control valve may be manual or automatic and it may be more than one for an individual portion of cropland. In same time user can turn on the water supply of one portion (e.g., vegetable portion) and turn off the supply of other portion (e.g., ornamental plants).
Backflow preventer is a gate which prevents the backflow of water from the pipe and regulates the supply of water. Filter this device is installed before the pressure regulator and its function is just to clean the water. Pressure regulator is just to maintain the pressure of water. It lowers the pressure of water to get the steadiness in water. It provides the right pressure for delivery of water to the plant. Low pressure helps in good application of water (drop by drop). There are many types of pressure regulator to attain the better results for irrigation. Main lines take water from the source to the sub main lines and this is made of black poly alkathene pipes, having an inner diameter or 50mm app.
Sub mains lines are those which take water from the main pipes which normally have inner diameter of 37mm.
Laterals are those which are capable to take water from sub mains to the root zone of crop and irrigate the plant drop by drop. They have lesser diameter from both the mains and sub mains. It is also made of black poly alkathene. Their length in a field varies from crop to crop as it depends on the water pressure and the crop in which they are installed. It may be 20-25m in length in a field. Emitters are used at the end of the lateral. Single emitter or dripper is used for single plant. Emitter has many types depending on the discharge capacity as button type, spray type, tap type etc. Emitter controls the quantity of water deliver to the plant root zone.
Drip irrigation is very efficient and it has many advantages as
- It takes time and a slow process so that water easily absorb in the root zone area.
- More suitable for the widely spaced crops such as cotton, sugarcane, tomato chilies, orchard.
- This system can be installed in the tunnel farming.
- There is no seepage, percolation and evaporation loss.
- Yield increases because of drip irrigation as there is efficient use of water.
- Soil moisture is maintained.
- Fertilizer application (fertigation), chemical application, herbicide application can also be done through drip irrigation.
- Water in a specific quantity is provided to plant. So, less water is used and beneficial in water stressed areas.
- This system is applicable for any type of topography.
- More area can be covered with little amount of water and hence it saves the water.
- Not applicable for the low spaced crops.
- Not applicable for crops which required water in a large amount e.g., Rice
- Pipe lines may be damaged by severe climatic conditions.
- Clogging in emitters due to salts contents or other things such as dust, small soil particles etc.
- Proper management and cleaning of drippers and pipelines are very important for the efficient working of this irrigation system.
In the world of water shortage, drip irrigation is the most suitable method to conserve the water in a better way.
Author is Jawaria Johar student of Bsc(hons) agri sciences at University of Agriculture Faisalabad.