October 26, 2012

Given this fall's dry soil conditions, late season irrigation may be just what your alfalfa needs to survive the winter.

Alfalfa in many areas may need more surface soil moisture to prevent alfalfa roots from drying out and dying over winter. Soil moisture also helps keep soil temperatures from dropping too low for alfalfa plants to survive.

Subsoil moisture also will be needed for top yields next year. During peak water use next summer, it can be impossible to keep up with alfalfa's water needs without a water reserve in the deeper root and soil profile. Irrigating now and until soils freeze can protect plants and improve yields.

One advantage to irrigating now is that evaporation is lower than in summer, permitting very high irrigation efficiency. Another advantage is in the alfalfa plant itself. Most irrigated alfalfa fields never get much water below 4 feet deep, but alfalfa can develop roots down 8 feet or more. You waste some of the water collection ability of alfalfa by not building water reserves below 4 feet. Don't waste this ability. That water reserve will keep your alfalfa growing rapidly during next summer's heat and allow you to irrigate on a more timely basis. 

Since many alfalfa soils have low water infiltration rates, irrigating now may be the only time you can build that water reserve.

Bruce Anderson
Extension Forage Specialist