By Dr. John Goeser
Let’s take a look at the last few months. First, we had a warm and dry winter. Next, summer came early in the upper Midwest with March temperatures in the 80s. Then the chilly temperatures came back for most of April. We even saw frost return to some areas. This roller coaster of weather makes us scratch our heads and wonder how the 2012 alfalfa crop will be affected. Effects on plant growth
With the warm March, we saw early growth of alfalfa across the entire upper Midwest. According to Dr. Dan Undersander
, University of Wisconsin-Madison agronomy professor, this early growth will be limited by a couple of factors. First, this winter’s drought led to low soil moisture. Second, April’s frost stunted some of the alfalfa crop as well. But before we go into panic mode, let’s take a step back and assess the situation. Remember that alfalfa is a very frost-hardy plant. It takes temperatures below 24 degrees F for more than four hours to freeze alfalfa top growth. That means the plant will most likely be okay if temperatures stay above that mark or only dip for a small period of time. That said, if cold enough for long enough, frost can kill the terminal bud of the alfalfa plant (the bud at the top of the stem where new growth occurs) because it’s most exposed to the elements. The plant will still try to grow even if the terminal bud is killed, but will not grow taller. It may develop axillary buds at intersections of lower leaves of the stem. Thus, the plant may continue to grow and produce some additional forage, but yield will be depressed and, at some point, we will need to cut the plant to allow full regrowth (second crop). Making first crop harvest decisions
Before you decide to cut, slow down and closely monitor plant performance. We do not recommend harvest at 10 to 12 inches of height unless the plants are completely dead and we really have not seen that kind of total loss in our area. This year, we’re likely going to have lower yields as plants are shorter, but we’ll probably see improved forage quality. That’s because forage quality is the ratio of stem tissue to leaf tissue. This is where the cool weather is actually on our side. With cooler temperatures, the xylem in the stem won’t grow as thick with lignified tissue, leading to higher NDFD. Plus, we’ll likely see a greater leaf-to-stem ratio, meaning higher RFQs. If your fields are damaged, take a closer look; watch plant height and take scissor clippings to assess forage quality. If PEAQ height doesn’t agree with scissor clip results (e.g. 18-inch height, but 140 RFQ scissor results) and you see a lot of leaves on the ground, your feed value will not improve and it makes sense to cut at that time. If the leaves are still there, let your fields recover and continue monitoring plant quality over the following week. Also watch for buds. The alfalfa plant will stop growing in height when it starts to bud and flower. This is where you need to combine PEAQ stick measurements (which generally aren’t accurate until the plant reaches 15 to 17 inches in height) with scissor clippings to make an educated decision about harvesting your first crop. It may make sense to cut the plant at that point and let second crop grow. Keep in mind, the effects of this spring will likely extend to second and third crop as well because of early injury to the plants and poor stand.
Inoculants are important
When you decide to cut, don’t forget that bacterial inoculants are especially important this year. The low temperatures will cause a low natural population of Lactobacillus
bacteria in the field. That makes it all the more important to have a known quantity of proven Lactobacillus
bacteria applied to the forage when it’s stored. This will allow for a more rapid fermentation and improved digestibility and palatability. This year’s weather – and the subsequent effect on alfalfa – is something we haven’t seen before, so we have no precedent for basing our decisions. Instead, we simply need to monitor plant performance and make our decisions on a case-by-case basis after carefully considering all of the factors. Your agronomist and nutritionist can help you in this process. Stay tuned for our next Dairy Performance article when we will discuss other factors affecting the 2012 alfalfa crop. Click here
for a UW Extension technical bulletin from Dr. Dan Undersander regarding frosted alfalfa. Watch Dr. Undersander’s recent webinar on alfalfa quality in the video window below. About the author: Dr. John Goeser, formerly with Vita Plus, works with Rock River Laboratory, Inc. He grew up on his family’s 1,200-cow dairy in eastern Wisconsin. He earned master’s degrees at the University of Wisconsin-Madison in both plant breeding and genetics and dairy nutrition. His researched produced a better understanding of how corn silage genetics influence dairy cattle productivity. He went on to earn his PhD in dairy nutrition and spent five years in research at the university. His doctorate research developed an improved method for measuring fiber digestibility, which UW-Madison patented and is now being used commercially.