Drip irrigation means drop by drop application of water directly to the plant root zone. Drip irrigation saves up to 50% of water on comparison to flood and furrow system of irrigation. Fertigation via Drip is 30% more effective than Flooding. The Combination of drip irrigation and Fertigation increases the productivity by up to 200% and in sugarcane by 133%.
Drip irrigation Saves the energy. Reduces the weed growth. Reduces the Incidence and Transmission of Pests and Diseases. The water that is been used for irrigation is not always pure. it contains several physical (sand. silt. clay etc..). chemical (Carbonates. Bicarbonates etc.…) and biological (microorganisms. algae etc.…) impurities. When the drip irrigation system is not maintained properly.
Several problems arise. They may be Reduction in irrigation efficiency. Blocking or clogging of Drippers or emitters and Blocking or clogging of Lateral pipes. if this problem is not rectified. the life span of the drip irrigation system reduces significantly. leading to the collapsing of entire drip system.
So. in order to get rid of such kind of problems Proper and Regular maintenance of Drip irrigation system is necessary. For optimum performance of drip irrigation system. the maintenance schedule can be divided into daily. fortnightly. monthly and half-yearly maintenance activities.
To maximize the irrigation efficiency and to prevent clogging of primary filter. secondary filter. laterals and emitters daily maintenance activity is essential. The below steps should be followed for the regular maintenance activity.
- Switch on the pump. open the drain valves of Hydrocyclone filter and screen filter for the duration of 5 minutes and then close the drain valves of both the filters. (Hydrocyclone filter is used when the source of irrigation is borewell or tube well).
- In case of sand filter (sand filter is used when the source of irrigation is open water source like rivers. canals. wells etc.) Backwashing is necessary. Generally the irrigation water enters the sand filter from the top through the inlet valve and then water flows down through the sand bed where the algae and other organic and inorganic wastes are trapped. then the partially purified water leaves the sand filter via the outlet valve. Where as the backwashing is the process in which the flow of direction of irrigation water is reversed so that water flows upwards through the sand bed. where the inlet valve is closed and bypass valve is opened. Through the bypass valve the water flows upwards. In this process due to the pressure exerted by the water on the sand. the sand gets lifted up and expands. therefore the dirt which is arrested in it is released. This released dirt is driven out of the sand filter through the backwash valve. If the backwashing is not done regularly. the impurities will accumulate in the sand bed which reduces the efficiency of the sand filter and the system does not get water at the desired pressure.
- Steps for backwashing of the sand filter
- Open the backwash valve
- Close the outlet valve
- Open the bypass valve
- Close the inlet valve
- Start the pump
- As soon as the pump is switched on we can see the dirty water coming out from the backwash valve. The end process of backwashing of sand filter is when the clean water comes out. When the clean water comes out from the backwash valve the normal filtration process should be resumed again.
- Steps for resuming the normal filtration process
- Open the inlet valve
- Close the bypass valve
- Open the outlet valve
- Close the backwash valve
- Start the pump
Now the filters are cleaned. after cleaning the filters go round the field and check for the Leakages or damages. if any defects are reported then replace that particular component With the spare parts. Remove the folds or kinks on the laterals and make them straight
- Check the drippers for the uniformity in discharge. the drippers that are not emitting the water properly open and clean them.
- Checkout the dripper positions. if they are misplaced place them properly at correct location.
- Before flushing the laterals a small test should be carried out. remove the endcap of the lateral and then wrap a clean white cloth and allow the water to pass through it for 1 minute. this helps in identifying the problem in drip system and also plays vital role in decision making for the maintenance problem (based on the impurities we can decide whether we should perform Acid treatment or chlorine treatment) (Acid treatment helps in removing the precipitated salts where as chlorine treatment helps in removing the algal and microbial growth)
- Remove the endcaps and flush out the laterals for about 2 minutes. while flushing the laterals controlling the valves is necessary to get high pressure. operate the ball valves in such a way that water flows with high velocity in the laterals where thorough cleaning takes place.
- Flush the sub-mains via the flush valves. because the impurities are also accumulated at the end of the sub-mains. if these impurities are not flushed regularly. it leads to the clogging of the drippers.
The above steps are related to the daily maintenance activities that has to be performed.
Fortnightly maintenance means the maintenance activities that has to be conducted once for every 15 days.
1. Sand filter
The pressure difference between the inlet and outlet valves of the sand filter acts as an indicator suggesting whether sand filter needs cleaning or not. If the pressure difference is greater than 0.5kg/cm2. this suggests that sand filter needs cleaning.
The salts that are present in the water are deposited on the top of the sand bed. where the upper surface of the sand bed becomes hard like a stone. in this case backwashing of the sand filter is not effective. Therefore for every 15 days clean the sand filter as per the below process.
- On the sand filter there is a lid. open that lid of the sand filter.
- Allow the water to come out of the sand filter via that opened lid. using the bypass valve adjust the flow of irrigation water so that the sand does not come from the opening.
- Gently stir the sand by moving the hand from top to bottom in the sand filter. make sure that you does not disturb the position of the black filter candles that are present at the bottom of the sand filter. if those candles are disturbed the sand enters the screen filter.
- Break the sand lumps by squeezing them in the hand.
- Ensure that half of the filter is filled with the sand. the level is marked on the filter. if the amount of sand inside the filter is less than the marked level. then add the new sand upto the marked level.
- Allow the water to flow till the fresh and clean water starts flowing out of the opening.
- Now put that lid in its position and fix it tightly.
NOTE – Don’t add ordinary sand into the sand filter because the ordinary sand has rounded particles which is unfit for trapping the dirt. In sand filter we use a special type of sand called silica sand which has angular particles say sharp edges. As the particles of silica sand are angular. they interlock with each other. hence the dirt is arrested in this sand.
2. Screen filter
The silt and the fine particles of dirt that escapes the sand filter are arrested on the filtering element on the screen filter (mesh in the screen filter). This affects the filtration process. Hence cleaning the filtering element of the screen filter once for every 15 days is necessary.
To perform this operation. open the lid of the screen filter and take out the filtering element. remove the rubber seals from both the ends of the filtering element. invert them and clean it with fresh water and then fix them again. Now clean the filtering element under the running water with the help of old tooth brush or hand. If you are using the tooth brush rub slowly to avoid any sort of damages. Don’t use wired brush as wired brushes damages the screen.
If the salts. algae and other impurities that are present in the irrigation water enter into the drip irrigation system. the laterals and drippers will get clogged and may stop emitting water. Based on the irrigation water quality and the observations made from daily and fortnightly maintenance activities. the acid or chlorine treatments might be necessary once in an month.
- Acid treatment helps in removing the precipitated salts from the pipeline network and drippers.
- Chlorine treatment helps in removing any sort of biological contamination (Bacterial slime. algae etc.)
- Inspect all the components of the drip irrigation system for physical abuse. mechanical abuse (damage by machinery) and damage by rats and squirrels.
- Don’t perform Acid and Chlorine treatments Simultaneously.
- Replace the media of the sand filter with the new one as the sand particles that are angular turn into round due to continuous abrasion during operation.
- Replace the components with the spare parts where ever necessary.
- Provide adequate lubrication to the pump and the motor because if the pump works efficiently. it generates the adequate pressure head and discharge required to operate the system satisfactorily. Follow the maintenance activities for pump as prescribed by the pump manufacturer.
Importance of operating Drip system at correct pressure
The minimum pressure required to operate the drip irrigation system is 1.5Kg/cm^2. Always maintain a pressure of 1.5Kg/cm^2 at the sub-main. Maintaining proper pressure is important as it directly affects the plants performance that is the plants growth and yield.
Do not keep the system pressure very high or very low. The higher pressure results in discharging more water than required by the plants. This causes runoff and the soil in the root zone will be fully saturated. This kind of over irrigation results not only in wastage of water and nutrients. but also disturbs the air-water balance in the plant root zone. As the plant roots are deprived of oxygen. root growth and the plant growth will be poor. thus there is reduction in the yield.
If the system pressure is lower than 1Kg/cm^2. the drippers tend to supply much less water than the required amount. here in this case the plant will be subjected to water stress. if this condition prevails for longer period of time the growth of the plant will stop or even the plant may die. Therefore always run the drip irrigation system at 1.5Kg/cm^2 (optimum operational pressure).
To increase the life time of the drip irrigation system and to get the higher crop yield
- Always maintain optimum pressure of 1.5Kg/cm^2 at the submains .
- One should always follow the regular/daily. fortnightly. monthly and half yearly schedules of maintenance activities.
Raghavendra Reddy Manda
School of Agriculture.
Lovely Professional University. Phagwara. Punjab