Commentary: Why alfalfa is ideal for California and the Southwest

By Ayman Mostafa 

The Southwest continues to endure a megadrought, signifying drought conditions lasting at least two decades. Historic water-supply challenges, particularly from the depleted Colorado River, have focused attention on a key agricultural commodity: alfalfa.

The crop is second to almonds in terms of acreage and water use in California. The share of water going toward alfalfa hay production supports dairy and livestock industries in southwestern states including California, Arizona and New Mexico. Alfalfa is the leading crop in terms of gross value in California’s Imperial County and comprises the largest acreage among all crops in Arizona.

Increased demand for high-protein-source dairy products and meat has been reflected in soaring prices of alfalfa hay in recent years. Still, some believe the amount of water used to irrigate alfalfa is a major contributor to the region’s water shortage. They fail to recognize alfalfa’s economic efficiencies, environmental impacts and agronomic benefits to our ecosystem.

Alfalfa is an ideal crop to have in California and the Southwest when it comes to irrigation water usage and efficiency. The crop has one of the highest water-use efficiencies when calculated as yield per water unit. Alfalfa has a unique deep-root system that can help absorb groundwater that is not viable to other crops and can allow the plant to stay alive during long periods of lacking irrigation.

While suspected of higher total applied irrigation water than many other crops, alfalfa actually has greater water-use efficiency. Additionally, the entire above-ground portion of the plant is harvested as many as 12 times per year in the southwestern region. When compared to other crops harvested less frequently, alfalfa’s ratio of harvestable biomass to water applied shows it is far more water efficient. Furthermore, the majority of irrigation water used in alfalfa is recycled back into the environment.

Many studies have proved alfalfa’s ability to sustain different levels of deficit irrigation, meaning that it can be grown with less than optimal water use. Research at the University of California, Davis, demonstrated the viability of different levels of regulated deficit irrigation in alfalfa and approaches to improve water management by adopting more efficient irrigation methods and scheduling. These options can help California growers make optimal decisions for producing alfalfa with limited water supplies, as we experience in the Colorado River Basin.

Growing alfalfa provides numerous environmental benefits. While the crop remains economically important, alfalfa also may help reduce impacts of climate change.

Because it covers the soil for a longer time than any other crop, alfalfa is envisioned as a leading option for soil-carbon sequestration, also known as regenerative agriculture. Incorporating a perennial legume such as alfalfa can help to stabilize soils nutritionally depleted by row-crop or specialty-crop production, as has occurred in many agricultural areas in the western U.S. Alfalfa was introduced into crop rotation in Europe and encouraged globally to reduce the impacts of agriculture intensification on the environment.

Switching from annual forage crop production for dairy animals and livestock feed to perennial alfalfa can help restore depleted soils, minimize inputs and decrease the footprint of agricultural production. Because of its nature as a perennial plant that stays in the field for three to five years, alfalfa helps in trapping sediments and takes up nitrate pollutants. It mitigates water and air pollution. Alfalfa improves soil characteristics with its deep roots; as a legume, it fixes atmospheric nitrogen through bacteria in the root nodules.

Alfalfa is a rich habitat for wildlife and preserves many endangered species from different animal families. Alfalfa fields are important contributors to the biodiversity of agricultural systems by functioning as insectaries for beneficial insects, many of which are pollinators or natural enemies that play important roles in the low-desert agroecosystem.

Western alfalfa production is quite different from production in other areas where nondormant, irrigated varieties provide a year-round habitat for insects. This allows alfalfa to play an important role in insecticide-resistance management by acting as a refuge, especially for aphids and whiteflies.

If alfalfa fields are eliminated or significantly reduced, it is highly likely that most of the original acreage will be converted to residential and commercial uses. This situation will likely decrease farmland and increase population in those areas. As a result, the Southwest may experience shortages of certain food products, thereby relying on food from nonlocal sources, including those imported from abroad.

This will likely increase food prices and extend the supply chain. With the increase in population comes environmental impacts, alteration of ecosystems and pollution of air, water and soil, all of which impacts our carbon footprint. Alfalfa production can make that footprint smaller.

(Ayman Mostafa, Ph.D., is a field crops and entomology specialist and director of the Urban Agriculture Production, Small-Scale and Beginning Farmer Program at the University of Arizona. He may be contacted at ayman@cals.arizona.edu.)