The Types of Irrigation & Why They Matter
According to a US Geological Survey report, agriculture accounted for 42% of the US’s total freshwater withdrawals in 2015. When precipitation is insufficient, irrigation allows for crop production in arid regions (where there is typically little-to-no precipitation) and supplements soil moisture in humid regions. However, water use, overall efficiency, and cost vary widely among the different types of irrigation.
Furrow Irrigation
One of the oldest methods of irrigation, furrow irrigation is when a trench is dug along the crops and is subsequently filled with water. Water then seeps slowly into the soil. Because furrow irrigation is easy and inexpensive, many developing counties prefer this method. Despite a ~66% efficiency rate and a ~20% runoff/evaporation rate, furrow irrigation requires little technology.
Flood Irrigation
As the name suggests, flood irrigation is when an entire field is flooded with water. This method is quite easy and simple but tends to be disruptive to plants. The soil can be consequently waterlogged and plants can drown. This method has a ~80% efficiency rate and a ~20% runoff/evaporation rate.
Waterlogging
Overwatering can saturate soil, filling the soil pore space with water. The result is what is known as waterlogging. As a result, air (oxygen) cannot enter the pores, stunting growth and potentially killing crops.
Drip Irrigation
Despite being the most costly method, drip irrigation is the most efficient method of irrigation with over a 95% efficiency rate. Drops of water are slowly dripped at or near plants through holes in a hose.
The Solution?
Drip irrigation helps to prevent waterlogging and conserves water overall, as runoff and evaporation are minimized.
Spray Irrigation
A relatively costly method, ground or surface water is pumped into spray nozzles that reign above the plants. While more energy (machinery technology) is required, this method is fairly efficient.
Conclusion
To become better proponents of sustainability, we must understand the economic contexts of farmers. For smaller farms, the cheaper and more wasteful methods of irrigation are essentially a requirement; the farm would not survive otherwise. Despite there being more efficient and more sustainable methods of irrigation, cost is a major factor. We must be sympathetic to farmers and workers in agriculture while simultaneously promoting sustainability. Please consider donating to organizations such as Conserva Irrigation or becoming of the Irrigation Association.
