LINCOLN, Neb. — Fall frosts have ended the life cycle of many annual plants. In some cases, below-freezing temperatures have reduced insect numbers and finally ended the harvest challenges of extended green soybean stems and corn plants. Despite the cold nighttime temperatures, many crops are still growing. So, the question arises: “How much irrigation should be applied in late fall for perennial and winter annual crops like alfalfa, wheat, rye and triticale?”
Generally, the fall goal is to have adequate stored moist in the upper two feet of soil profile while leaving enough storage room to take full advantage of off-season precipitation. For sandy soils, it may require two inches of water to fill the top two feet of soil, while clay soils may need four inches of water to fill the two-feet profile.
When extreme dry conditions occur in the fall, irrigators will usually water after the winter annual seeds have been sown. Ideally, fall-drilled wheat and rye should have available soil water below the planted seeds. When extreme dry conditions occur in the fall, irrigators will usually apply 1.0 to 2.0 inches of water following drilling season.
For alfalfa, daily water use drops significantly in the fall to less than one-fourth-inch per day due to cooler days. Overall, alfalfa requires six to seven inches per cutting for optimum production.
More Nebraska Extension fall crop irrigation publications are available on our website: NebGuide G1778 “Irrigation Management and Crop Characteristics of Alfalfa” and EC731 “Producing Irrigated Winter Wheat”.
— Todd Whitney, Extension Educator, University of Nebraska-Lincoln