Drop by drip!

A couple of you had requested to post a blog on drip installation, so here are my initial thoughts and learnings. At the outset, designing and installing drip may seem to be a daunting task but once you have gone through the process, the science and technique can be mastered. Firstly, let me break down the essential components of a drip system -

1) Head Unit: This connects the water source (borewell) to water carrier system (PVC pipes). Depending on the quality of water, it may contain a hydro-cylonic filter and a disc filter to remove sand particles and impurities.

This is our head unit. Blue tank contains heavier impurities which need to be cleaned periodically. Finer impurities are filtered by disc filter (black)

Three control valves that control the water in each direction. This is IMPERATIVE (for big farms) and will save you a lot of walking.













2) Water carrier system: There is mainline that connects the head unit to the end of the plot. Typically, perpendicular to mainline are sub-main lines. The pipe size of sub-mains are smaller than main line. At the junction of main and sub-main lines is a valve to control the flow of water for a particular section of the plot.

Two valves for mango and vegetables. It is a good idea to have separate valves for each to control irrigation and fertigation.

It is always a good idea to have a bypass pipe (the one leading into the tank) to avoid high pressure and potentially bursting of pipes.
We used this while irrigating Brinjal. Area under irrigation was much smaller compared to the outflow of pump, hence water had to be pumped back into the tank (yes, not the most efficient method! )




3) Laterals: This is the pipe that actually delivers the water to the plant. There are two types of laterals - Inline and Online.

• The former is used typically for vegetables, bananas where continuous wetting is required or roots grow laterally or the spacing between plants is close (in cm). There are built-in drippers inside the lateral pipe. 
• The latter is used for orchard crops where the distance between two trees may be large (in meters). In online laterals, external drippers need to be attached to the lateral. The holes in laterals come in multiple spacings (30 cm, 45cm, 60 cm etc). Like wise, the drippers come in different water discharge rates - 4 Liters per hour (lph), 8lph etc. Depending on the crop, water requirement, operating time, your drip installer should be able to tell you which one is suitable.

Online dripper

Inline dripper















  


Some DOs and DON'Ts

1. When you are dealing in big acreages (10 acre +), it is advisable to use a JCB to dig out the trenches. Digging manually is not only inefficient but very time consuming. 
2. When reviewing a drip design, ensure you have the ability to control water to all sections of the farm in a centralized manner. In other words, it is a good idea to have 4 'control valves' for the four directions. Closing one of them should completely shut off the water for that part of the farm irrespective of 'local valves' position. This will save you a lot of walking.
3. You should perform 'flushing' of drip lines (both PVC pipes and laterals) periodically (once in 15 days) to avoid clogging of pipes.
4. If you plan on inter-cropping between orchard crops, make sure there are separate pvc pipes/valves for both for fertigation purpose else you will end up fertigating both the crops at the same time. In other words, you will end up fertigating Urea on Mango and Brinjal when it is only needed for Mango. It seems common sense but a leading drip irrigation provider did not figure this before we pointed this out.
5. Use pressure compensated drippers if your land has a gradient.
6. At the time of irrigation, make sure the pressure valve reading does not exceed 2 kg/cm^2. Higher pressure can lead to bursting of PVC pipes.
7. If your drip irrigation schedule involves multiple sessions (typical in bigger farms), always open the second section's valves first and then close the first section's valves. Again pressure build up can damage the pipes.
8. It is a good idea to have a bypass valve at the water source to create multiple water sources for shadenet or labour quarter etc.
9. If you plan on having avenue trees or trees not irrigated by drip, it is again a good idea to have water outlet points that can tapped from PVC pipes that lead to a central tank. So every time you run the borewell to fill up the tank, you can irrigate trees that are not irrigated by drip.
10. Ensure that the laterals are not very long. More the distance from submain, lesser will be the pressure at the last dripper. Installation folks should be able to tell you what is the maximum length one can go without realizing drastic pressure loss. In our case, it was 40m. This will vary depending on the outlet pressure, topography of land, water requirement of crop etc. 

Hopefully some of these suggestions will save you time and effort. Feel free to respond with additional suggestions for other readers.