Monday, June 10, 2013

Buried Container Irrigation

As I mentioned in Tomato Planting 2013 we are using buried container irrigation for watering the tomato plants. This is based, loosely, on buried clay pot irrigation, which has been in use in different parts of the world for centuries. Our use of buried container irrigation, however, was for very different reasons, and used different materials than the traditional method.

The idea behind buried clay pot irrigation is that water will slowly seep through the walls of the clay pot, depending on the moisture level of the surrounding soil. This allows the pot to be filled with a quantity of water, but dispersed slowly to the plants, as they use up the available moisture. This method is supposedly much more efficient than other irrigation methods.

Our need, however, was simply to deliver a predefined amount of water, in this case one gallon, to each plant during each watering session. We could have accomplished this by using a one gallon watering can, this this would require refilling the can after each plant. This would also not have worked if watering from a hose, attached to a barrel, which we plan to be able to start doing soon.

The idea of buying plastic jugs, with holes punched in them, was mentioned during one of our Gardening 101 classes. We decided that this would be a simple way of ensuring that each plant was getting a consistent amount of water. It was only after doing further research, after we had already decided to use this approach, that we learned of the similarity to buried clay pot irrigation.

Installing the system was simple. After transplanting the tomatoes I dug a hole directly in front of each plant for the jug to be buried. The hole was dug deep enough that roughly half of the jug would be underground. Holes were then punched in the jugs, near the bottom, on the side facing the plant. After placing the jug in the hole, the excess dirt was packed around it so it would not easily blow away when empty.

When the time comes to water the tomatoes, we simply fill each jug with water, then move onto the next. We are currently using creek water, which is carried in 5 gallon buckets. We dip the water from the buckets, and use a funnel, made from the top of a plastic water bottle, to fill the buckets. Once we begin using a hose connected to a barrel containing rain water we'll simply stick the hose into the jug and let it run until full, then move onto the next.

This process is working fairly well, but we have learned several things. First, we found that the distance of the jug from the plant seems to have a significant impact on the health of the plant. I tried to dig the holes as close as possible, but it was hard to get very close without disturbing them. In hindsight, I should have dug the holes for the jugs before transplanting the tomatoes.

We also discovered that the holes in the jugs can get stopped up easily, especially since we are using unfiltered creek and/or rain water that contains small pieces of organic material such as leaves, etc. Sometimes this can be solved by simply shaking the jugs, but other times it is necessary to remove them from the hold and poke something through the hole to unstop it. This means that packing dirt around the jugs to keep them from blowing away was unnecessary since we keep having to remove them anyway.

Lastly, I recently read the recommendation to leave the lids on the jugs, which we did not do. If the jugs have screw-on lids, they can be loosened or tightened, as desired, to alter the amount of air flowing into the jug, which in turn alters the rate at which the water flows from the jug. With no lids on our jugs, they empty within a few minutes, providing the holes do not get stopped up.

After learning about buried clay pot irrigation, I think that it is worth trying sometime. For delivering a consistent amount of water, however, I think that the use of plastic jugs works fairly well. By making adjustments based on the things we've learned I think that the results will be even better next year.

We did conduct a simple experiment to see how well the system worked compared to just pouring the same amount of water on the surface around the plants. When we initially installed the system we were short two jugs, so used those two plants without jugs as a control. We found that, while there was no significant difference, the closest plants that were watered via the jugs were slightly taller. I suspect that this is because the irrigation system delivers the water below the surface, where it can be more easily used by the plants before it evaporates. Of course our test was far from scientific, and lacked sufficient quantity of plants to really be statistically reliable.

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