Limited subsoil moisture after last year’s severe drought could hamper yields in many dryland alfalfa fields again this year, says Bruce Anderson, forage specialist with University of Nebraska Extension.

He explains that alfalfa’s extensive root system, 10-15’ deep in some older dryland stands, allows the plant to tap into subsoil moisture that previous crops could not reach. “As a result, growth and yield during the first several years is supported by both rainfall and subsoil moisture.”

But there is a limit to the amount of subsoil moisture available. And many dryland hay fields, especially those that were three years old or older, exhausted their moisture supply during last year’s drought. “(That) means hay yields this summer will be determined mostly by how much rain falls and gets into the soil during the growing season,” says Anderson. “And unless we receive much more than average rainfall, dryland hay yields will be lower.”

The bottom line: It takes about 6” of water to infiltrate the soil to grow each ton of alfalfa hay. “If you get real lucky, 90% of the rain you receive will actually end up in your soil. And most growers lose at least 20% of the potential yield due to losses during harvest. Putting these numbers together, it could take at least 25” of rain just to yield three tons of hay.”

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