With warm and dry conditions across the state, should we be irrigating alfalfa one more time?
With the continued lack of moisture that we have across the state of Nebraska and the warm autumn temperatures, alfalfa stands may benefit from added water. Alfalfa is a drought tolerant crop with a deep root system; however, it does have a relatively high water use requirement. This means that alfalfa can survive between long breaks of irrigation or rainfall events due to its deep root system. However, timely application of water and recharge are critical for success of the stand over time.
We need some surface soil moisture to prevent alfalfa roots from drying out and dying over winter, but too much surface moisture — especially in new stands — can stunt the root development of alfalfa. Soil moisture can help to regulate soil temperatures from dropping too low for alfalfa plants to survive and application of water now in heavy textured soils could allow water to move through the profile for spring capture.
During the peak water use period in summer, it is unrealistic attempt to keep up with the water demand of alfalfa with irrigation alone. Relying on water reserves available in the deeper portion of the root and soil profile are valuable to production. Irrigating in October and into November until soils freeze thus can protect plant roots and improve yields by mitigating stress on alfalfa stands. There are two main advantages to late season water application:
- Low evaporation compared to summer, permitting very high irrigation efficiency
- Moving water lower into the profile for spring
Most irrigated fields of alfalfa never get much water below 4 feet deep, but alfalfa’s powerful taproot can extend 8 feet deep. Allowing for extended water capture capabilities and application of water in fall can help to build a reserve lower in the profile. That water reserve will help to mitigate stress next year while alfalfa is growing rapidly during next summer's heat and allow you to irrigate on a timelier basis.
Since many alfalfa soils have low water infiltration rates, irrigating now may provide an advantage to next spring and summer. It is important to note that irrigating in fall will not be silver bullet to recharging dry profiles, but should be used as a way to mitigate stress on alfalfa stands following dry conditions.