Alfalfa Development: 1st Crop 2016
May 6th, 2016
Robb D. Wock – DPC, Purina Animal Nutrition LLC
During my travels this week (beginning Monday May 2nd through Thursday May 5th) I have spent quite a bit of time walking Alfalfa fields in southeast Minnesota. For the 2nd year in a row, and the 3rd year out of the past five, 1st-crop Alfalfa growth & development is at least 2 weeks ahead of what we historically see in this part of the upper Midwest. My measurements & evaluations took place on Alfalfa fields as far South as Preston, East to Winona, North to Zumbrota and West near Waseca. In all these areas Alfalfa stands are in good to excellent condition. Most of the stands tend to be a bit younger due to the extreme winterkill most of us experienced just a couple years ago, and all the subsequent NEW seeding that took place since then. These newer stands in particular have a very “evenly-distributed” plant mass with high density. This creates a very thick canopy that in most cases is almost totally covering the soil surface. As things heat-up this will reduce evaporative moisture loss, conserving as much water as possible in order to achieve maximum growth.
Plant height measurements are very consistent across the territory, with the tallest plants throughout the area running 18-20 inches and field average heights between 15 & 17 inches. At this stage everything is still vegetative, and the Relative Feed Value (RFV) estimates for 19-20” plants falls between 215 & 225. From this point on I expect and predict that a significant amount of “buds” will begin to show up sometime in the next 7-10 days, and with rising temperatures our growth rate should meet or exceed ¾ inch / day! If you do the math these stands will grow anywhere from 8-12 inches in the next 10-14 days, which will put the tallest population of plants @ 28-29 inches in height and an average overall stand height of about 26 inches. The predicted range of RFV with budding @ 26 inches in height is around 170-175. Even under the best conditions we are likely to lose 15 points in RFV from the harvesting process, so I would suggest that 10-14 days from now will be a good time to start. That means these stands should be cut somewhere between Sunday May 15th and Friday May 20th – with some flexibility depending on what the weather pattern looks like at the time.
Some of the other means for predicting plant maturation such as the use of “growing-degree-days” (GDD) is yielding about the same answer. GDD for the Rochester MN area at this point in time is somewhere between 500 & 550. It is estimated that a GDD of 750 places NDF plant maturity @ 40%. But keep in mind that GDD have been increasing lately with the rising temperatures so again in the next 10-14 days we will likely see our GDD number rise by 170+ points to around 700 ! With our experience with NDF and understanding the role that it plays in “fiber digestability” (or RFQ = Relative Feed Quality) it is imperative that we complete the harvest before the plant gets to 40% NDF.
I am always here to help if you need assistance in evaluating Alfalfa or any other forage utilized in your crop rotation. Our goal at All-American Co-op Progressive Ag Center & Purina Animal Nutrition is to help you become more successful at what you do so that you can become more profitable.