Water use in agriculture
As of 2017, Minnesota had more than 68,800 operational farms, generating more than 18 billion dollars in agricultural products. A growing portion of these farms rely irrigation; about 95 billion gallons were used in 2017. The recent upward trend of water use increases the strain on water supplies, threatening the sustained operation of Minnesota farms. As much as 90 percent of this water in Minnesota comes from groundwater. The aquifers where groundwater is extracted usually replenish slower than the rate at which water is used. Effective water conservation ensures that Minnesotan agriculture can continue growing crops decades into the future.
Opportunities for conservation
Conservation methods reduce agriculture water use while effectively irrigating crops. A number of factors affect irrigation efficiency, such as the uniform distribution of water to crops or evaporation. Most irrigation techniques struggle to distribute water evenly. Sprinkler design can improve distribution, effectiveness and efficiency, as in micro irrigation. Alternatives work to apply water directly to plant roots to minimize evaporation. More advanced irrigation techniques can prevent salinity buildup in soils by reducing the amount of water applied to fields. The electrical costs of pumping water are high, so conserving water also reduces energy costs.
Electrical costs associated with pumping water used on crops for irrigation out of underground aquifers are significantly higher than the cost of the water being used. Conserving water not only ensures a more sustainable and stable water supply in the future, but can reduce energy costs in the present.
Protecting water quality from the harmful effects of agricultural production can also help to reduce consumption. Using water more efficiently reduces runoff that washes pesticides and fertilizers into water systems. The Minnesota Agricultural Water Quality Certification Program (MAWQCP) provides a certification program in water quality to help protect surrounding watersheds.
- Sprinkler irrigation
Sprinkler systems improve water efficiency, distributing water evenly and giving irrigators more control over the irrigation schedule of a field. However, most sprinklers are susceptible to water loss from evaporation and wind drift, particularly during the warmest summer months.
Central Pivot Irrigation is the most common form of sprinkler irrigation in Minnesota. Efficient drip nozzles reduce high water loss due to wind and evaporation. Larger sprinkler heads that irrigate multiple furrows at once are susceptible to water loss. Pivot sprinklers with more sprinkler heads spaced closer together, and those that apply water closer to roots, reduce the water loss, have higher efficiency and increased water savings.
Low Energy Precision Application (LEPA) is a high efficiency method of water application. Using pivot or linear move structures, LEPA applies water in furrows near plant roots, instead of into the canopy of crops. It uses low pressure water application, reducing the fine mist of high pressure sprinklers that is susceptible to water loss from evaporation. Close spacing (often around 30 inches) ensures adequate water application at a high rate of efficiency. This reduces water loss from evaporation or wind drift, and results in water efficiency of up to 98 percent.
- Micro irrigation
Micro irrigation is the most consistently efficient method of irrigation available. The methods involve frequent, low-pressure application of water near plant roots. This can lead to higher crop yields, enhanced water penetration in all kinds of soils, and reduced weed growth.
The high cost of installation makes micro irrigation more cost effective for high value crops such as fruits or vegetables, especially if the pipes are located beneath the soil surface for minimal evaporation. Despite the large investment, this irrigation method is highly efficient and sustainable. Many Minnesota farmers now use drip irrigation for traditional row crops to great success.