STEP 3 - IRRIGATION
Intro to Country Living
Step 1- Tilling
Step 2 - Planting
Step 3 - Irrigation
Step 4 - Weed Control
Step 5 - Fertilizing
Step 6 - Cutting
Step 7 - Baling
Step 8 - Stacking
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Irrigation - What to Do When the Rain Doesn't Fall
Since we live in a semi-arid region, there is normally not much rain to speak of during the growing season. As a result, irrigation is normally essential in order to grow a crop in this area. There are many different ways that farmers irrigate in this area. One of the simpler ways is with hand lines. Typically, a hand line is a 20ft long section of aluminum pipe that is 3" in diameter. At the end of each section of hand line is a vertical pipe (riser) on top of which is a sprinkler. The hand lines are designed to plug into each other and latch together. In this way, you can hook up as many as you need to water whatever length of area that you want. If you need to water a large area, then hand lines can be very time consuming if you have to continually move them to different places in the field. A more efficient method of irrigation is with wheel lines. A wheel line is similar to the hand line concept except that there are wheels which are placed along the sections of pipe.
Irrigation Wheel Line Watering My Hay Field
I have 3 wheel lines on our small farm with the longest one being close to 1/4 mile in length. Typically, the wheel line is left watering in one place for 12-24 hours. I like to use 12 hour watering sets, because with the amounts of water that I put down, 24 hour sets tends to cause a lot of run off and can lead to erosion at the edges of the field. After a watering set is done, then the water is shut off and the wheel line is drained. Once it is empty, then the engine is started and the mover is used to roll the wheel line to the next location. My particular system is set up so that I make 3 revolutions between watering sets. The wheel line MUST be drained of water before moving it, because the water in the pipes is very HEAVY. You can twist and break a section of pipe if you try to move it before it is drained. Don't ask me how I know! Each section of pipe in the wheel line has a drain valve located on the underside of the pipe. While under pressure, the drain valve is pressed shut. When the water is turned off, the pressure drops and the drains valves automatically open to allow water to drain more quickly from the wheel line. It typically takes around 15 minutes for the water to exit out the drain valves.
You may be wondering how this long wheel line is moved from place to place. There is a small mover section in the middle of the wheel line that has 4 wheels and a small gas engine. This engine provides the power to roll the wheel line to the next location. On my wheel lines, the engine runs a small hydraulic pump that sends power to hydraulic motors which spin pinion gears that turn a large spur gear. There is also a set of chains and sprockets. All this is part of the transmission that provides the torque needed to move the massive contraption to the next location. You won't break any speed records with an irrigation wheel line! They typically move at a leisurely walking pace.
Irrigation Mover Unit in the Middle of the Wheel Line
Other than the amount of time that you leave the wheel line in one place, you can also try to adjust the amount of water going into the ground by changing out the brass nozzles in the sprinklers and also adjusting the irrigation system water pressure. On my system, I can make small adjustments in pressure with a valve near the pump. I can only close the valve and throttle back the pressure by about 10-15psi before I run the risk of creating too much back pressure and causing pump cavitation. This can destroy a pump, so the valve can only limit the pressure a small amount. If you have too much pressure, then you run the risk of damaging your irrigation system (breaking pipe or blowing out wheel line drains). I have found that a maximum of around 70psi is about the right water pressure limit to prevent system damage. It took me a while to find the proper combination of sprinkler nozzle size and system pressure. I bought hundreds of brass nozzles in various sizes to be able to fine tune my irrigation system.
Irrigating Early in the Season When There Was a Night Time Freeze
It seems that most seasons, I end up getting some night time freezes after I start irrigating. Typically, I try to avoid this by waiting to start irrigating until after the freeze risk is over, but there are often at least a couple nights in early Spring (late winter) when we still get a freeze. It can result in me waking up to some beautiful icicle art that formed on the wheel line overnight; however, it can cause other problems. Thankfully, because there is a lot of water flowing through the pipes, there is very little risk of the water freezing in any pipes during these light freezes. But, the water freezes in layers on the outside of the wheel line and this ice build up can add a lot of extra weight. Too much weight could cause a pipe to break when moving the wheel line to the next location. In addition, the slick conditions on the field causes the wheels to slip and can make it tricky to try to move the wheel line and keep it straight. There so much more to say about irrigating. It's not as simple as one might think. There can be a number of complications or problems that come up with irrigation. In some ways, I envy farmers who have sufficient rainfall to eliminate the need of irrigating. Then again, they also suffer from a different set of problems. There's always a trade off, it seems.
One final note on irrigation... in our area, some farmers use rill irrigation which is essentially just small furrows (ditches) that run the length of the field. These are filled with water and gravity transports the water along the field. Naturally, this only works if the field has the right lay and slope. Most big farms around here use what is known as irrigation pivots (or "circles"). These take the wheel line concept a step further and provide fully automatic operation. As the name implies, this type of irrigation system "pivots" around a central point and sweeps the field in a circular pattern as it waters. The speed at which the pivot sweeps around the field can be controlled, which in turn controls the amount of water being applied to the field.