Irrigation for agriculture is the primary user of water worldwide, and demand is now exceeding supply. According to the United States Department of Agriculture, 80% of water in the U.S. is used in agricultural irrigation. Unfortunately, this irrigation usage also tends to be highly inefficient and a substantial amount of water is lost to runoff and evapotranspiration.
As world populations grow and food and water demand increases, the agriculture community is focusing on optimizing water usage and increasing efficiency, to conserve water and cut costs.
Efficient irrigation water management can conserve water and save money in all agricultural sectors. Growers can reduce the cost of water, pumping, and fertilizers while producing higher soil quality and increasing crop yield by as much as 100%.
The primary items affecting water efficiency are climate, soil, crop type, and irrigation techniques. By focusing on irrigation scheduling, irrigation methods, water filtration, specific crop types, soil enhancement, and alternative water sources, growers can conserve water and save money.
Because crops need different amounts of water during each phase of growth, proper irrigation scheduling is essential to avoid wasting water, eliminate energy waste, and optimize yield. Growers should measure and track the water demand during all growth cycles, the soil moisture content and water capacity, and the weather.
The way that growers water crops substantially impacts water efficiency. The most common irrigation methods used by growers are:
- Surface – Flooding of a whole field (basin) or small strips (furrow) in the field. This is the cheapest and most commonly used method, but also the most inefficient, with less than 10% plant absorption.
- Sprinkler – Pumped water is sprayed on to a field by fixed or rotating heads. While more efficient, it is expensive because of the pressure requirement. Low energy precision application (LEPA), typically delivered using a center pivot system, irrigates with an arm to spray water on a field, and can save 20-50% in energy costs and has a more than 90% efficiency rate.
- Drip – Water is pushed through pressurized pipes to the plants on the ground surface or below the ground. Because the water is delivered directly to the root, it is highly efficient with yields of up to 100% and water savings of 40-80% compared to conventional systems.
Filtration systems are used to ensure that irrigation systems do not get clogged. It is important to choose a filtration system based on specific watering conditions and the irrigation method. Common filter types include screen, disc, and sand media. Screen filters are the most common type used for irrigation protection. The most efficient and effective option is to select a fully automatic, self-cleaning filter with a self-flushing mechanism, which uses a minimal amount of water to keep the filter system clean. This will help a grower conserve water, save time, and reduce costs and labor.
The reality is that crops' water needs and growing period durations vary based on the environment, which is the main reason for differences in growers’ water usage across the world. If possible, consider planting crops that offer high value, but require less water.
Strategically handling the soil to optimize water use is another way to improve watering efficiency. A few methods include field leveling (even distribution to avoid runoff), furrow diking (earthen dams that fill with precipitation water), residue management (manage surface residue to cut down on evaporation), and water distribution systems (lining and placement that reduces seepage).
As increasing water needs and population growth impact water supply, finding alternative sources of water is important for agriculture to support sustainability. For areas with long dry periods and short seasons of heavy rainfall, rainwater harvesting is an efficient option where rainwater is collected, directed to ponds for storage, and then extracted for irrigation use.
Other innovative options include reuse of properly treated wastewater or desalination of brackish water (most likely from a well source). In such cases, an efficient filtration system is essential to ensure that clogging hazards are removed from the water before it enters the irrigation system.