Timing Last Alfalfa Harvest with GDD

By Ben Beckman

Allowing for alfalfa to winterize before dormancy is a key factor preventing winterkill across a stand. Traditionally, my recommendation has been to time the last cutting for roughly six weeks before the first frost.

While this general guideline has proven its worth over the years, many producers would love to have a bit more accurate method to time last cuttings. One way to narrow the no-harvest window down is by utilizing growing degree days (GDD). Work from Dr. Dan Undersander with the University of Wisconsin calculated winterkill risk looking at GDD at a base 41°F accumulating until a killing frost of 24°F. The two GDD levels of importance for alfalfa stands were 500 and 200.

By providing at least 500 base 41°F GDD after harvest, research trials showed that there was sufficient time for alfalfa to winterize. If harvest occurred with under 200 GDD left, alfalfa plants did not have sufficient time to regrow and deplete carbohydrate reserves to a level that would negatively impact winterization.

While other factors like ground cover and stress of the stand over the course of the year need to factor into the decision for a late cutting, this gives us a more accurate calendar point to shoot for if forage is needed.  We also need to keep in mind that late cuttings may have a difficult time drying down in a timely fashion.

Most of the state is right at the edge of our 500 GDD threshold. To decide where you stand, the High Plains RCC CLIMOD can be used to look at past years GDD. Using accumulated 41 GDD for past years and your expected first freeze dates, we can avoid the 500-200 GDD no harvest zone and plan a late alfalfa cutting if needed.

Nitrate Management for Grazing

By Samantha Daniel

While dry conditions can result in high nitrates in annuals, drought isn’t the only thing that may cause nitrate issues. Shade, frost, hail and herbicide damage can all contribute to high nitrate levels. Grazing forages that have high nitrates can be successful, but how it is done can mean the difference between life or death.

Grazing growing cover crops or annual forages with higher nitrates is possible because the fresh forage releases nitrates into the rumen slower than a dry forage like hay. Some specific bacteria can also use the high energy to utilize the nitrates directly. Allowing these microbes to adapt gradually to higher diet nitrate levels is critical to the ability to safely handle otherwise toxic levels later on. Grazing aids in this as the slower rate of dry matter intake on fresh forages allows microbes to better keep up with incoming nitrate amounts. That being said, grazing is still a calculated risk.

To minimize risk, make sure cattle are turned out full with plenty of water and consider using lower risk cattle such as stockers. Adapt the animals slowly by starting in the lowest nitrate fields first or stocking lightly, and avoid force-grazing of the lowest portions of the plant where nitrates are more highly concentrated. Another consideration is to supplement energy in the diet, like low amounts of grain, while adapting cattle so that the rumen microbes can convert the nitrate into bacterial protein more efficiently.

Testing Hay Quality

By Jerry Volesky

Do you know the quality of the hay that you harvested this past season? It is important to know how much protein and energy your cows will get when you start feeding, or how much supplement to feed. This may be especially important if your hay crop was affected by rain, drought or significant delays in harvest.

Maybe the most important step in sampling hay is deciding which bales and stacks should be included in each sample. Ideally, each sample should include only bales that were produced under similar conditions.

Obviously, the place to start grouping is to separate different types of hay, like alfalfa, CRP, cornstalk or meadow hay. But each cutting of hay is probably different from the other cuttings also, so there is another separation. And no two fields or meadows are ever exactly the same, especially if they were cut more than several days apart — this makes another grouping. And what if part of the field was rained on before it was baled? The hay made without rain damage will likely be different from hay with rain damage.

After you’ve made all these separations — which could result in quite a few groups of similar bales — then and only then are you ready to sample. From each group, gather a dozen or more cores from different bales or stacks and combine them into one sample. Be sure to use a good hay probe that can core into at least 12 to 18 inches into the bale.

Finally, send these samples to a certified lab for tests of crude protein and energy content. If you had drought conditions this past year, testing any annual forages or salvaged dryland crops for nitrates is a good idea.

Then use this information to feed your cattle as profitably as possible.

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