Irrigation: Drip, Spray and Misty!

We were lucky to purchase a farmland that has a water source (a bore pump) with the water table at around 80 feet and free, state government sponsored electricity. Our current irrigation system depends on these two. We hope to regenerate a well in our land that is dry at present and produce most of our own electricity through bio-gas and may be an investment in a Wind Mill in the next 2-3 years.  Regardless of the sources of water and power, our irrigation system is designed to be a permanent system and can be compared to arteries in a human body (will come back to why this comparison is significant).

The predominant method of irrigation around the world for centuries has been surface irrigation. This method uses gravity to transport water across a field through channels that run around the planting area. It did not seem like a good idea to us for many reasons:

Water is scarce in this part of India there and surface irrigation uses more water than is required by the plants.
Another issue with surface irrigation is that the irrigation channels must be recreated after each harvest to suit the irrigation needs of the next crop.
For the entire period of watering (say 6 hours), constant attention of a person is required in order to plug and unplug the channels (with mud) to ensure water reaches all the planted area.

Our initial requirement was to irrigate only the trenches in which we had planned to plant tree saplings which translates to 20% of the total area. Since we were going to do a lot of mulching in the trenches around each planted sapling, the water requirement is reduced by more than half (the mulch retains soil wetness by preventing evaporation due to sunlight and wind). So we decided to do drip irrigation in all the trenches.

We laid 2.5 inch PVC pipes one foot deep in the ground as main line running south to north in the middle of the farm. And we laid 2 inch pipes as sub-lines connected to the main line that runs parallel as well as perpendicular to the main line as required by the shape of the land. We inserted 1 inch lateral pipes (locally called as “lattar”) into the sub-lines and laid these east-west into the trenches. We also laid one or two additional lateral pipes in the 25 feet distance between two trenches to be used for irrigating whatever we would plant in that space.

We punched holes every six feet on the lateral pipes in the trenches and inserted 6mm micro-tubes in those holes. We cut a lateral pipe into hundreds of pieces each around 2 inches long, punched a hole in the middle of each piece and inserted the other end of the micro-tube into these pieces. These lateral pipe pieces attached to each micro-tube act as a cap and make the water from the pipe drip into the trench (instead of jetting from the micro-tube out of the trench as it would do without the cap). A better system has now become available for low cost that uses mini taps attached to the micro-tube instead of the costlier dripper that consultants use. We used micro-tubes of a smaller diameter where the water pressure is more in the lateral pipe and a bigger diameter where the pressure gets low. With the mini taps, we can half-open the taps in high pressure areas and open them full in low pressure areas. The same can be done with the official dripper that comes with all commercial drip-irrigation kit but it costs almost double that of the mini tap.

For irrigating plantains planted in the space in between two  trenches , we used Spray Irrigation. This looks similar to a sprinkler system with a raiser (a stick) that has a head attached to it and to the head one can attach a rotating or stationary sprinkler or a micro-sprinkler that sprays water like mist. We used the micro-sprinklers between the trenches. And in the one acre of land where we had created raised beds, we used rotating sprinklers to irrigate vegetable and grain crops.

So we have three types of irrigation in farm: Drip, Sprinkler and Spray irrigation. The basic irrigation structure for all these three types of irrigation is the same: Main line pipes, sub-line pipes and lateral pipes. In a plain land like ours without much gradient, this system would work well.

Our irrigation system is a permanent system like arteries. In a human body, arteries carry the blood to every cell of the body. Arteries are permanent tubes that remain in the same place because down to the last cell, every entity in a human body has a specific, non-changing location. Similarly, in our farm, all entities – the fence, the trenches, the raised beds and whatever is planted in these three areas are unchangeable. The fence has fencing plants and trees, the trenches have trees and the raised beds have vegetables and grains. The kind of plants, trees, vegetables and grains we plant every season may vary but what we plant in each area will be the same. Also, we would not do any tilling or even any weeding in our farm. With no need to run a tractor or any other machines in the farm, with designated planting areas for different type of crops, our irrigation system which has pipes from 2.5 inches to 6mm act like arteries supplying life-giving water to all the crops.

We have valves to open and shut water supply to every acre of land. So, all we need to do is to switch on the bore-well motor and open the particular valve that irrigates a particular acre. No constant presence is needed like surface irrigation. To make opening the valve easier and protect the valve from getting buried in mud due to rain, we placed plastic drums open at both ends on top of the valves. And we made a 2 feet “key” with a square iron rod which looks like the letter “T” at the holding end and the other end is shaped like the valve with which the valves can be opened easily. This is an example of local, self-made technology that is hard to get with consultants.

While all of this sounds straightforward and easy, it sounds so only because of the in-person, ever vigilant guidance of Fr.V. Without his guidance, we would have contracted an irrigation consultant who would have not customized the irrigation system for our farming needs and would have doubled or even tripled our cost. Most irrigation consultants charge Rs.30,000 – Rs.50,000 or even more for one acre of good quality drip irrigation installment and more for sprinklers. Whereas, our cost was roughly Rs.19,000 per acre for not just drip irrigation but for sprinkler and spray irrigation combined.

The fundamental reason (that leads to other reasons) for the increase in cost by the consultants is that most of them do one survey, one planning and one installation and very little design. Even the increased cost would be fine if the system works well for the farm’s needs. But since the consultants have a standard package to offer, it does not fully meet the specific irrigation needs of a farm. Whereas, we did a complete design first and our planning and installation were done in stages evaluating and analyzing our requirements at each stage and allowing time for ourselves to think through each action while the work is being done.

This was possible only because we did the design by ourselves and hired labourers experienced in this job and gave them clear, specific instructions for every small action (otherwise they would go on autopilot and do what they have done working for a consultant). Own design, iterative planning and implementation helped us save material, simplify the method (using micro-tube and caps instead of costlier dripper that consultants use), customize for our need (adding sprinklers and micro-sprinklers to the same system) and extract better work out of the labourers so that there is less maintenance in the long run. Perhaps there are honest, client-caring consultants who do a good design and charge less. Would like to know who they are as we have many friends interested in installing drip/sprinkler irrigation in their farms.