By Harry Brook
After an improved hay season from 2019 (the harvest from hell), some may be thinking there is a good second cut of hay out there. Most of our hay crops are a mix of grass and alfalfa. Once grasses have headed out there is limited regrowth. However, for the “queen of forages”, alfalfa, the second cut can be of very high quality, being primarily alfalfa. Time of cutting is critical to keep that hay healthy.
There is often confusion about quality versus condition when hay is being sold. Quality, the nutrient concentration of hay, is highest when hay crops are harvested early, when the crop is not fully mature. The dairy industry uses a measurement called the Relative Feed Value to evaluate quality. It is based on the digestibility of dry matter, relating to fibre content, which affects how much can be consumed. The lower the fibre content, the more can be consumed and the higher the protein and quality. Hay condition, on the other hand, is related to how little weathering occurred on the hay, once it is swathed. When good quality hay, with high protein levels and relatively low fibre levels, gets rained on in the swath, you may lose some of the soluble sugars in the feed, thus lowering energy content, but it doesn’t affect protein levels too much.
Timing, as with most things in life, is everything in cutting that second cut of hay. There is a critical period when it is not advisable to cut hay, especially if you want that hay field to be productive for a long time. Don’t be cutting your hay from early August to the first killing frost, usually sometime in the middle of September. The reason why this is a problem is that cutting the hay then will stimulate regrowth. Plant regrowth comes from the energy that is stored in the roots. A plant that is cut or grazed has to draw on root reserves for energy to get new leaf material started. The root mass contracts and leaves start the regrowth process. The problem with cutting in August or early September is that the plant does not have enough time to produce enough leaf material to recharge the roots and thusly, the plant's energy reserves.
Going into the winter with depleted root reserves means the plants will be more susceptible to winter kill and that leads to more weeds invading the hay, poorer productivity and a shorter lifetime for the hay field.
Once a killing frost has occurred it is safe to cut the second cut of hay. There should be little, if any, alfalfa regrowth after cutting and root energy reserves should be retained for next spring. It gets a bit tricky in the fall, too. Once that killing frost has hit there is limited time to cut the hay before the leaves start falling off the plant and there goes the most nutritious part of the plants.
One common concern about the first frost is related to nitrate accumulation in crops hit with a frost. Although this can be a problem in annual forages, it IS NOT a problem in hay or alfalfa. Hay fields almost never have a pool of unused nitrogen in the soil, especially in the fall. They tend to self-regulate nitrogen with their nitrogen-fixing bacteria.
Second cut hay can be your highest quality feed but you need to know when you should cut and when you should wait. If you wait until after the first killing frost, you should be able to keep that field productive for many years.