Robb D. Wock – DPC, Purina Animal Nutrition LLC
During the past few days I’ve spent quite a bit of time walking Alfalfa fields in SE Minnesota as a means for understanding maturity, yield potential & overall health. For the 3rd year in a row, and the 4th year out of the past six, 1st-crop Alfalfa growth & development is 7-10 days ahead of what is considered “normal” in this part of the upper Midwest. While most stands, particularly those in their 1st & 2nd year, are in good to excellent condition, there are some indications of reduced yield potential on some fields. For example, older stands or stands harvested very aggressively (possibly 6 cuttings in both of the past 2 growing seasons) show signs of growing at a slower rate and some loss in yield potential. This is most obvious upon evaluating “density”. Fields harvested VERY aggressively are somewhat lower in plant density, with somewhere around 40-45 stems per square foot. While this is still considered adequate, the goal is 55 stems or greater ! And although it appears to be a very good year for dandelions, these lower-density stands are more severely affected with weed infestations and so this will likely have some effect on yield. Root health, particularly the crown area and taproot below the crown, have been mostly firm & white with the exception of areas where soil drainage was an issue. Certainly Growing-Degree-Days (GDD) are increasing at a more rapid rate now and so the Canopy is filling in nicely leaving little or no soil exposure, which means a reduction in evaporative moisture loss & the opportunity for maximum growth.
Plant height measurements are fairly consistent across our trade territory, with the tallest plants up around 19-20 inches and an average field height of 16-17 inches. However I have run into some fields showing uneven growth, which is usually damage to crown buds over the winter. The new shoots that are regenerated are commonly 3 inches or so shorter giving the canopy an uneven look. Fields affected in this manner show a slightly slower rate of growth with the tallest plants at 17-18 inches and an average field height of 14-15 inches … generally 2-3 inches behind undamaged stands. Damage or not, everything is still vegetative, and estimates for Relative-Feed-Value (RFV) on 19-20” plants is about 220+, while 17-18” plants are closer to 230-235 RFV. Our understanding of undigestable fiber, lignin, and various fiber fractions has taught us that Relative-Feed-Quality (RFQ) is a better indicator of feedability. Thus plants 19-20” are likely to have an RFQ of 235 or greater, and plants 17-18” closer to 250 RFQ.
With temperatures consistently above 70 degrees, and in some cases approaching 80, the growth rate on Alfalfa should approach 3/4th of an inch per day. Since overnight temps this time of year are still moderate it is unlikely we would see the FASTER maturation that often occurs with 2nd, 3rd or 4th crops. If you do the math this means Alfalfa will grow 6-9 inches in the next 8-12 days, which puts our tallest plants 26-28 inches in height on even & undamaged populations, and 24-26 inches on those that are uneven or weed infested. Most likely we will see some “budding” at this point in time, so the RFV will be between 170-175 and RFQ at least 10 points higher than that. With harvest losses of 15 points RFV, this puts the final storage RFV at 155-160, and hopefully an RFQ that is slightly higher. It is imperative that you complete the harvest BEFORE the plant gets to 40% NDF !! So if your goal is to store DAIRY-QUALITY Alfalfa I would suggest you plan on cutting sometime between May 20th & May 24th, with the range put in to allow some flexibility depending on what the weather pattern looks like at that time.
The Feed Team at All American Co-op is always here to help if you need assistance in evaluating Alfalfa or any other forage utilized in your crop rotation. We want to help you become more successful so that you can become more profitable.