Before you relegate that rain-damaged or mature alfalfa to the feeder stacks, you might want to get it tested. You could be sitting on several tons of low-potassium (K) hay — worth considerably more than common feeder hay.

“Some milk producers are paying as much for their low-potassium hay as they do for quality dairy alfalfa,” says Cornell University dairy nutritionist Mike Van Amburgh. “There is a huge market in low-potassium hay because of transition-cow issues with milk fever.”

From roughly 60 days before calving to 20 days after, too much K in a cow's diet can literally be a killer. So dairy producers are looking for low-K hay to feed during that period.

In a sense, U.S. dairy producers are victims of their own success. In an effort to feed the highest-quality hay and then apply their dairy manure back on their fields, they have been inadvertently increasing their soil potassium levels. That translates into high K levels in both their alfalfa and corn silage.

Regular dairy hay can have up to 4% of the nutrient. Low-K hay tests around 1.5% K.

Cornell dairy nutritionist Larry Chase agrees that low-K hay is the best option for transition cows. He sees the demand increasing as more dairy operators reach the same conclusion.

“With a growing awareness, there is more of an opportunity for finding a niche market in low-K hay than there was five years ago,” says Chase. “A number of hay brokers in this area are already bringing in low-K hay from Ohio and other parts west.”

However, hay growers thinking about targeting the transition-cow hay market should proceed with caution. Steps taken to reduce K levels, such as reduced fertilization, can hurt yield. For growers who consistently harvest premium dairy hay, switching to low-K hay might not make sense.

It's also a good idea to check the local demand. Prices paid for low-K hay vary, depending on demand and other factors. While it may be worth as much as premium dairy hay in the Northeast, it's priced about halfway between premium dairy and feeder hay in the Northwest.

Chase says that one way a dairy hay grower can cash in on the low-K market is to seed his less-productive fields to grass instead of alfalfa.

“Alfalfa needs high-fertility, well-drained soils and is challenged by the heavier clay soils,” says Chase. “The grasses, on the other hand, can do well.”

He adds that it's easier to reduce the K level in grasses than in alfalfa. Recommended grasses for low-K hay production include timothy, smooth bromegrass and reed canarygrass.

Growers who plan to produce low-K hay should soil test before seeding. There is a direct correlation between K levels in soil and in plants grown in it.

But if soil tests high in K, it shouldn't be automatically written off. You can reduce soil potassium levels by planting a grass crop and applying moderate to high rates of nitrogen. That will force plants to use more soil-based potassium, reducing the amount available for future harvests.

Increasing the number of cuttings of either alfalfa or grass will also stimulate K uptake.

To minimize the amount of the nutrient in alfalfa hay, cut the crop close to the ground. The highest K concentrations are in the upper stems.

Also, alfalfa's K level drops as it matures. In one study, it declined from 2.75% to 1.75% from late-vegetative stage to one-fourth bloom.

Once the hay is lying in windrows, K levels can significantly be reduced by rain and leaching. Recent research showed that 0.6" of rain reduced tissue K from 2.5% to 1.9%.