Tuesday, February 24, 2015

Improving your Irrigation

Like to improve your food-garden irrigation?  I talked to Food Garden Group members Wendy, Tara, Gordon and Marg about irrigation methods they use and received a lot of helpful info, comments, tips and hints.  Combined with my own experiences this blog post discusses the pros and cons of six food-garden irrigation methods.  They may inspire you to make changes to how you irrigate.

I wrote this blog post in February 2015.  It is now March 2018, and after three more years of experience with the irrigation methods described below, I decided to document what I learnt (in green, following each section).

1. Irrigation by hand
Nothing wrong with using the good old watering can, but it can be hard on your arms and back because of the weight of water and the need to bend over, especially if you have a large food garden.
Far better to use an watering wand (first photo below) attached to a garden hose.  It saves a lot of time because it allows you to hand-water without having to fill your watering can.  Also, it allows you to water without having to bend over much.  It makes it easy to water under the foliage of plants and you can put exactly the right amount of water precisely where it is needed.


The best watering wands allow you to select type of spray, how far you open the throttle and how much water you get when the throttle is fully open.

Advantages of hand irrigation are:
Low equipment costs, low water costs, can be very satisfying and effective because you give every plant your personal attention
Disadvantages of hand irrigation are: 
Very time consuming

March 2018: after installing irrigation lines in most parts of my garden I still frequently use two watering wands (the expensive ones are worth the money) and two watering cans for pots and spots that  will only get watered if done by hand. That is fine, because the rest of our front and back garden is now watered with irrigation lines and water timers, so it does not take long to water a few things by hand.

2. Overhead irrigation
At her farm at Richmond Tara uses overhead irrigation for root crops that can cope with watering from above.  For over a decade I have used two rotary sprinklers on stands (see photo below).  I switch them on for an hour.  In that time an area with a diameter of around 8 metres is watered thoroughly.  I then put the sprinklers in different spots and repeat the process.  At the end of this, my vegie-garden is well-watered.  If the weather is warm and there has been no rain I repeat the process every second day.  It's not a lot of work, so that is good, but in a garden where you grow all kinds of vegetables, this irrigation method has disadvantages.

Advantages of overhead irrigation are:
Low equipment costs, plants get well watered if you irrigate long enough, with a movable stand and long enough hose you can water anywhere you like, not labour intensive
Disadvantages of overhead irrigation are:
Very inefficient water use through evaporation in the air, wind drift and watering of paths and fences. May cause mildew by putting water on leaves and leaf-burn if you water on warm sunny days.

March 2018: some plants are very hardy, but other plants can get leaf-burn when watered from above, on warm sunny days.  The photo shows leaf-burn on a lettuce leaf.

A leaf of a lettuce seedling burnt by the sun after overhead irrigation
March 2018: Over the last three years I have continued with overhead irrigation in parts of my garden.   I installed a water timer, and now irrigate overhead at 6am in the morning, every second day, for half an hour.  I also now use fixed irrigation stands that are precisely in the right spot, and that can't fall over.  Nothing worse than finding that a sprinkler is lying flat on the ground with a muddy pool around it and nothing around it has been watered.  Below is a photo of one of my current irrigation stands. The hose goes up the star picket to the spray head at the top.  


March 2018: This year I had spuds in the beds you see in the photo above. A bed to the right (not visible in the photo), contained leaf vegetables this season. When it does not rain the bed with leaf vegetables needs half an hour of irrigation every second day. However, the potatoes could have done with no irrigation at all after their foliage died off in December. Instead, they received the same amount of irrigation as the bed next door. Quite a few spuds rotted away in soil that was too wet.

Overhead irrigation is indiscriminate. It covers a large area, and whatever grows there, gets more or less the same amount of water. It is better to irrigate each bed individually, so you can adjust the amount of water to what is actually needed by the crops that grow there. 
By next season I hope to have replaced my overhead irrigation by drip lines (see point 6 below).

3. Drippers on poly-pipe
Drippers or micro sprayers (sometimes on risers) on black poly pipe are really not workable in vegie gardens as they get bumped off too easily.  They are too fragile and get clogged up too easily.  However, I found that tricklers on poly pipe (see photo below) work very well for the large pots in my hothouse, because you position the tricklers precisely where you want, and in this case there is no chance the pipe or the trickler is trodden on.  The pots contain tomato plants that stay in their pots for half a year or more without much manipulation of soil or plant, so drippers on poly pipe are fine.


Marg reported that she uses similar drippers or tricklers for her fruit trees.  Where the pipe is a bit far from where the dripper needs to be, you attach a drip-line (the white narrow flexible pipe in the photo) and attach the dripper to that.  She did say that she installed this system before more robust solutions (see below) became available, but it has lasted and served her well.  She irrigates her fruit trees for an hour each day.

Advantages of drippers on poly-pipe are:
Your drippers are precisely and only where you want water, not expensive if you choose more commonly used drippers and tricklers, it is an efficient use of water, good for use with pots.
Disadvantages of drippers on poly-pipe are:
Fragile, not practical in garden beds where you have frequent new crops and associated gardening activities, can be quite a bit of work to install, can be expensive if you choose less commonly used drippers and tricklers.

March 2018: I continue to use the drippers shown above to water pots. As long as you have them where you won't step on them, they are quite reliable. These drippers are adjustable, so you can irrigate in a smaller or larger circle. Put a filter on your tap if your water may contain contaminations (more about water filters under 'Other relevant points').


4. Soaker hose
Soaker hose (usually green) has been around for a long time and can be an effective way to irrigate.  It is hose with evenly spaced tiny holes.  When laid on the surface and with the tap full on, water will come out in arcs and the system will effectively provide overhead irrigation.  However, if you cover the soaker  hose with mulch and don't open the tap completely it provides effective drip irrigation.


Soaker hose is only available in certain standard lengths, but with some brands the hose's entry connector and end plug can be put in different spots, so you can adjust the length of soaker hose if you want to.  Some brands also allow you to connect up two soaker hoses. Choose a type of soaker hose that can be cleaned out when it is clogged up by removing the end plug and flushing through.

Advantages of soaker hose are:
Easy to install, easy to move out of the way if you need to dig, effective drip irrigation if covered by mulch or soil, best laid in straight lines or gentle curves, durable if you buy quality ones.
Disadvantages of soaker hose are:
Not available in really big lengths.  Entry bits and end bits not for sale separately.  Are really meant to be used 'as is' without any adjustment.  Don't buy cheap ones as they may not even last one season.

March 2018: I no longer use soaker hoses anywhere.  After five or so years (that is not too bad a life span) they developed leaks.  I decided to use other irrigation options that can more easily be adapted to  the layout, size and shape of beds.

5. Weeper Hose
Weeper hose is porous right along its entire length (see photo below).  It is used together with standard poly pipe connectors. It provides efficient drip irrigation on level areas (don't  use it on slopes or on uneven areas with dips).  Use a water filter (see under 'Other relevant points' further down)
Some brands advise that their hose should only be used on top of soil.  Other more expensive brands allow their weeper hose to be covered by up to 50 millimetres of soil or mulch.


Wendy's veggie garden consists of a number of long narrow beds.  She uses weeper hoses as follows:

Here is some of the pipe at the start of a bed, held in place with a stake, and connected to poly pipe by means of a standard poly pipe T-bit and sturdy metal clamps:


Water pressure is measured in Kilo Pascals (Kpa).  Weeper hose works best at low pressure that does not exceed 300Kpa.  To avoid leaks I found I had to lower the pressure further.  I put a pressure reducer on the tap that reduces pressure to 100kPa.   Some brands advise that you turn the tap on slowly when starting and don't fully open it.  Generally a maximum length of 30 metres is recommended.
Price per metre is around $1.25 per metre (2015 prices).

Advantages of weeper hose:
Easy to install, bends easily so no need to use a lot of T-connectors, provides good drip irrigation on level areas, good use of recycled tyres,  easily moved out of the way when you need to dig, also great for circular layouts, some brands can be covered by up to 50 milimeters of soil.
Disadvantages of weeper hose
Some brands develop leaks after a year or so if at soil level, clogs up if water contains sediments, uneven watering on slopes and in dips.

March 2018: In the past I used weeper hose because I liked the fact that water is dispersed everywhere along the line.  With this in mind I installed weeper hose that had been used elsewhere in the garden in parallel lines in a strawberry bed.  Well, I gave up after a month or so, as new leaks developed almost weekly.  Weeper hose really only lasts a few years, and that is, if you don't tread on it, don't have it in full sun all the time, or move it.  That is not durable enough for me.  I no longer recommend you use weeper hose.

6. Drip line
Drip line (see photo below) is plastic tubing with inbuilt drippers at 30 centimeter intervals.  The 'hoses with holes' discussed in method 4 and 5 are fine if your garden bed or area is level and without dips, but if not, you have no control where in the line water will come out.  The inline drippers in brown or purple drip line allow the user to achieve even watering, even if the line is on a slope or goes through dips.
Drip line is used by most professionals.  It provides for durable reliable even irrigation.  It can be purchased in long lengths.  Drip line is best covered with mulch or soil.  Some brands claim to be 'UV resistant' and you see it often installed at soil level.

The tightest circle that can be made with this type of pipe is one with a diameter of around 30 centimeters, so for a garden bed you could consider the following layout:

(The diagram above suggests that the drippers are on top of the line, but they are actually in the line - all you see is small holes 30 centimetres apart).

In this design drippers in every second line are offset by 15 centimeters so they cover different territory.
You terminate the drip line by folding the pipe on itself or by installing a valve that is normally closed.  To clean out the pipes you open the valves or undo the folded ends.
Drip line can also be bought with drippers at 40 or 50 centimeter intervals.
Thinner more flexible drip line of 6 millimetres thickness is also available.

Staff at Irrigation Tasmania (a company mentioned by 3 out of 4 Food Garden Group members I talked to) explained 'you get your soil evenly moist, and then use the drip line system to keep up the moisture levels'.

At Tara's farm at Richmond they lay the drip line in straight long lines right where the potatoes have just been put in. As a result of subsequent 'hilling' the pipe gets buried right above where the water is needed, in other words, on top of the hill.  Tara's watering setup means that she can focus on other things.  She can rely on the fact that her soil is always moist enough for crops to grow.

Gordon on Bruny Island is on tank water.  He uses drip lines and waters for 8 minutes per day, but would like to water longer.

Recommended water pressure is 50 - 250 Kilo Pascals (Kpa).  Price per metre of good quality drip line is around $1.75 per metre (2015 prices).

Advantages of drip line:
Even distribution of water over the entire length of the line regardless of slopes and dips, very durable
Disadvantages of drip line:
Watering only at dripper points, so you need to space drip lines to cater for your needs and adhere to regular watering to keep soil moist.

March 2018: I recently dug out oxalis around and under a dwarf stone fruit tree. I realised how dry the soil under the foliage of the tree was, in spite of regular overhead irrigation. The dense foliage had stopped the water coming from above from reaching the ground. Drip line, arranged in circles under the tree, would wet the soil much more effectively, and use far less water.

For a few years wherever I replaced irrigation lines I installed drip lines.  I began to think that it would be the only type of irrigation line I would install from there on.  It was easy to install, reasonably priced, effective, and durable.  What more do you want?  But then I realised that drip line, like everything, has limitations.
  
I found that drip line only disperses water evenly if it touches the ground. It needs to be on the ground, or below ground level.  If it hangs above ground in the air and is not perfectly level (like the pipe in the photos under the heading 3. Drippers on poly-pipe)the drip will travel along the line, down the line, to the lowest point of the line, and it will then fall onto the ground.  Water will not be evenly dispersed.  
Drippers on poly pipe (solution 3) are the solution if your irrigation line needs to be above ground level.


Other relevant points
  • Best time to water: is at or just after dawn, because there will be low evaporation, water landing on leaves will not stay there long to give mildew a chance, and the sun is not strong enough to burn leaves.  
  • Avoid connecting/disconnecting: the fewer hoses and pipes you need to connect the less work and the less wear and tear on connectors (see photos below).
  • Water filters: if you use tank or river water inline filters are essential.  To people on town water I would say that a water filter is not expensive and it may avoid trouble 'later down the line'.
  • Buy quality gear: whatever irrigation method I recommend that you do not go for cheap materials.  Water is very good at finding the weak spot in your system and exploiting it. Setting up a system with low-grade materials may turn out to be a waste of time, a waste of water and ultimately a waste of money.
  • To cover or not to cover: irrigation lines that are not exposed to UV because they are covered by mulch or soil will last a lot longer, but you will have to get into the habit of digging very carefully, if you decide to hide them that way.  It may also take you longer to spot a leak.
  • Maintenance: it is a good idea to check your lines once a year.  Dig them out if they are covered by mulch or soil, remove them from the bed, check your lines for leaks, open their ends and flush them out, and then put it all back in place ready for another year.
Pressure reducer (black) and timer for automatic watering 

Marg's way to avoid having to connect and disconnect hoses
Wendy's very artistic way of solving the problem

Many thanks to Wendy, Tara, Gordon, Marg and staff of Irrigation Tas for information provided!




2 comments:

  1. Love the Article I thoroughly read all of your Tips and Techniques how maintain our garden using the irrigation pipelines tubes and other marital its all are great! I keep my grass 3" in height. It looks good all summer and I trim it every other week.

    ReplyDelete
  2. Have you found anything remotely similar as far as the colored pieces on DHGate?

    ReplyDelete