Watering or Irrigatng its the same thing!

Believe it or not when watering through a hose or a pipe there is some quite complex physics going on inside the hose or pipe. If you know about this you can very simply increase the efficiency of your watering operation. The faster the water moves through a pipe, the greater the friction between the pipe and the water. This produces a layer of drag,  which has the effect of reducing the inside diameter of the pipe and this in turn restricts the amount of water that can flow down the pipe. OK the physics lesson has finished.



So give you water pump a chance to show what it can do! To allow my pump to work at its most efficient the suction side pipe is maximum spec for the particular pump at 50mm (it is taken out of a water race 75 meters away). On the pressure side my underground pipe that takes water to the various taps around the garden is 25mm and my above ground pipe is all 19mm - this includes hoses and the fixed irrigation lines under the trees. I have one 12mm hose only because it was given to me.

You see a pump has to work harder to get water down a 12mm pipe than a 19 mm pipe. This means that the pump will deliver less volume. The above photo of  a 19mm and a 12mm  hose both about the same length shows what I am saying very graphically!

While on this subject - as you increase water pressure you decrease deliverable volume. What I am saying is pressure and volume are inversely correlated - when one goes up the other goes down :).

I am amazed at how many professional irrigation companies will use 12mm pipe to service a lengths of 50-60 meters. One other little related tip while I remember it - if you need to deliver water to a 30-50m line of small trees down a lane etc., don't have the delivery point at one end and the other end closed off.  Have the delivery point entering the irrigation line pipe at half its length. This will ensure that all the irrigation points will have a more equal share of the available water. Doing it the first way will produce good flow at the delivery point but less and less and less and less and less water as you get to the end of the line. In a similar way, with center pivot irrigation the water has to be fed in at the pivot end and so the irrigation jets start small but get progressively larger as you move toward the end of the center pivot boom.

When I irrigate my garden and some selected lines of trees closer to the house I use 2 methods: single nozzle, circular, garden sprinklers where you can control the area watered and the character of the water jet, and microjets (not drippers) for individual plants in the garden areas. Most of the garden is watered with the jets.. Microjet irrigation where each plant has its own jet is the only way to go in a dry, free draining environment. I started with the single nozzle sprinkler to start with because it was cheaper. When I set the whole garden up with micro jets ( I have 5 seperate lines) the difference was amazing. The watering was far more effective, the humidity under and around the plants increased and each plant received a lot more water. The proof of what I am saying is in the number of plant seedlings that started to grow under the canopy of the larger plants when I started using microjets. In fact I have used such seedlings to replant areas in our garden - Kowhais (a smallish New Zealand native) are very prolific seeders.

The original mirojets I used were Plassay, very well engineered and manufactured. More recently there are various designs you can buy. The jets I use mostly are 90 degrees. But I also use 180 degrees and occasionally 360 degrees in a few areas. For supplementing the lower microjets I use spinners (they are still microjets but they spin!) on stiff alkathene risers (up to 40 cms) which means they water larger areas above some of the lower plants. You can use the flexible riser pipes to take the spinners up to a meter plus by supporting them on fibreglass rods. All the jets I use have 1mm throats. I do it myself with a 1mm driil bit and pliers to hold the bit. I just put the bit at the start of the jets inlet and twist the jet round and round until the bit is through. I notice in some hardware stores you can get jets that are colour coded - red is about 1mm.

I water in the evening or on dull days. If I have to I will water when the sun is shining or it is hot but it is less effective. Basically I will turn the irrigation on at about 4 in the afternoon and leave it on until we go to bed or about 6-7 hours a day in dry weather. The way I have it set up I can get around the garden every 5 days. I use the single nozzle sprinklers to water the lawn and some of the larger trees at the back of the garden.

One important point, I think, is that when you are watering it is best to mimic a good rain. Through experience that is why I leave things going for the length of time I do. We have free draining so can't over water. A really good watering over a relatively short time is good because the water will soak past the root zone making the plant extend its roots.

My neighbour used drippers. OK I suppose when the plants are very young drippers are adequate, but as the plants grow they need more water. Also, if only the shallow surface of the ground is kept damp the roots have no need to extend themselves. What happened to my neigbour was that the drippers were on eucalyptus trees for a significant part of their early development stages so the drippers became totally inadequate for water supply when the trees got bigger. Luckily (or not!) they were at the back of his garden which meant they weren't exposed directly to the  Northwest wind. One particular nasty storm, however, these eucalypts all starting moving like drunken sailors (or any other drunken person.....) and similaly fell over. The cause - (apart from the wind) - the root development of the trees was pathetic! So you can see why the word drippers is in bold in the 5th paragraph.