Did you know that approximately 70% of the world’s freshwater is being used for agriculture? In comparison, only 8% of it is reserved for domestic use. Without all this freshwater, farmers around the world could not take care of their crops properly, and the quality and quantity of the food we eat would suffer. But what is all this water used for, exactly?
A lot of it is used as a base for pesticide and fertilizer application. The chemical products that are necessary to protect and nourish crops need to be mixed with water before being sprayed. A good quantity of water is also used to wash equipment, vehicles, farm buildings, and fresh produce.
Most of the water needed in agriculture, however, is used to water crops. As food demands keep increasing, farmers are now forced to grow their crops in regions that are often too dry for agriculture, which means irrigation has to become an important part of their operations. Without the right amount of water, crops will simply die.
Depending on where their crops are located, and on how much water these crops need to thrive, farmers can use different irrigation systems. Here are four common uses of water in agriculture:
1. Irrigation by sprinklers
Agricultural sprinklers are similar to the ones we use to water our lawns, but they are much bigger, of course. With a system of hoses and pipes, water is pumped and moved around the fields to finally be sprayed over them.
Sprinkler systems can be mounted on wheels and moved through the fields, or they can consist of a long arm that sprays water while moving around a central pivot point.
The efficiency of sprinkler systems can vary. Some of them will end up losing 25% of the water that will run through them, while others will only lose 5% of that water. However, even the systems that lose 25% of the water they use can be the right choice, depending on the crops, on the availability of water and on the condition of the soil.
2. Drip irrigation
Drip irrigation is a good option for fields that don’t need to be plowed each year. For this type of irrigation system, hoses and pipes are installed through a field either right at the surface of the soil, or just below it.
Water runs through those hoses and pipes, and will drip onto or below the soil where the crops are growing. Self cleaning irrigation filters are often applied to facilitate this process. Drip systems are generally more efficient than sprinklers, since only 5% of the water used by them will be lost to evaporation before it can be absorbed by the soil.
Drip irrigation is considered localized irrigation, as it will not distribute water to any part of a field that doesn’t need it. On the other hand, sprinklers can end up spraying some water on parts of a field where no plant is growing.
3. Furrow irrigation
Furrow irrigation is a technique that was used by ancient civilizations. It involves digging channels along the rows of crops of a field, so water from a nearby river can be transported there. Of course, this method works best if the field is located on a slope, which allows gravity to do most of the work.
Even though furrow irrigation has been around for a very long time, it’s definitely not the most effective method there is. A high percentage of the water running through the channels will either evaporate before it has a chance to be absorbed by the soil, or it will run off the field.
There is also the problem that unless some pump system is used to increase the speed at which the water is flowing down the channels, the top of the field will get a lot more water than the bottom of it.
In some regions of the world, however, this technique might be preferable to others, for different reasons.
4. Flood irrigation
Finally, flood irrigation is another irrigation technique that relies on a natural source of water. It consists in periodically allowing the water from a river or a stream to completely flood a field. The water soaks into the soil, and only 15% or 20% of it will either evaporate or run off the field.
Just like furrow irrigation, flood irrigation has been used for a long time, and it’s still being used today. This irrigation technique might not be the most efficient one, but it’s convenient in regions where freshwater supplies are not limited.
Flood irrigation is perfect for growing rice, as well as other crops that need to stay submerged at all times.
Each irrigation system has its pros and cons, and the one chosen by a farmer depends on different factors, such as the type of crops they are growing, and the amount of resources they have.