Arizona’s Essential Alfalfa and Its Impact on Air Quality
Alfalfa not only offers great nutritional value for livestock but also plays a large role in air quality. When soil is manipulated or disturbed by weather, animals, vehicles and agricultural practices it can be broken into smaller particles called PM (particulate matter) or dust. These smaller particles can now be suspended in the air due to soil erosion.
Perennial crops, like alfalfa, are considered multi-year crops or cover crops which help to reduce soil erosion. In Arizona, it is commonly grown for five years with multiple cuttings per year before it is rotated for another crop. Alfalfa helps by anchoring the soil, reducing equipment passes in the field, and manage its carbon footprint.
Alfalfa is considered a multi-year crop because it is grown on a continuous basis for more than one year. PM emissions come from soil that is disturbed, and multi-year crops provide protection by anchoring the soil from the wind. Alfalfa’s year-round canopy helps protect soil from becoming airborne, thus, preventing dusty conditions and soil being washed away as sediment. The longer alfalfa protects the soil surface, the less time the surface is susceptible to soil and wind erosion.
Most annual crops require multiple passes with tillage equipment which is a major contributor to soil erosion and PM emissions. Alfalfa doesn’t require these tillage operations on an annual basis, thus reducing the number of passes in the field during a growing season. The California Air Resource Board (CARB) estimates the agricultural fugitive dust emissions on average for all tillage operations is 4.8 pounds per acre pass. Fields of alfalfa eliminate the need for unnecessary passes in the field thus reducing dust emissions. These numbers are even better when it comes to harvesting. CARB estimates fugitive dust emissions for alfalfa at 0 pounds per acre per year compared to other crops that range from 1 to 6 pounds per acre per year.
The last benefit of alfalfa for air quality is its ability to minimize its carbon footprint. Unlike most annuals, alfalfa is a legume and requires no nitrogen fertilizer. With tillage being a major contributor to soil erosion, nitrogen contamination of water and air becomes an environmental concern. Not only does alfalfa use less nitrogen but also requires less pesticide use. As a perennial crop, alfalfa also fixes significant quantities of CO2 through photosynthesis which helps to temporarily retain carbon. Alfalfa fields exchange CO2 with oxygen which potentially lessens the effects of global warming and refreshes the surrounding atmosphere. Alfalfa is a highly valued crop for its soil health-building characteristics.
Air quality, specifically PM, is an issue here in the desert southwest. While small compared to other industries and contributors, agriculture is a contributing factor and must play a role in reducing its contribution to PM. Growing alfalfa as a multi-year crop is a best management practice in the Air Quality Agricultural Best Management Practices Program in Arizona. What makes alfalfa a great crop for air quality is it creates a canopy to protect the soil, eliminates unnecessary mechanical passes on the field and helps with minimizing its carbon footprint.
Arizona's essential alfalfa serves a critical role in our economy and our climate.