Field Estimations of Alfalfa Fiber Content

Ohio has seen its 5^th warmest winter on record but spring temperatures across the state have consistently been 2-6° F below long-term averages. Climatic variations every year make it difficult to know the exact date to determine harvest of our first alfalfa crop. Research has shown % Neutral Detergent Fiber (NDF) can vary up to 10 units on the same calendar day from one year to the next, therefore making harvest decisions based on calendar date is unreliable. Many producers also base harvest decisions primarily on alfalfa maturity. Variable weather conditions affect the rate of bud and flower development in alfalfa, thus relying solely on maturity can be misleading.

The best method to determine alfalfa (NDF) is by traditional wet chemistry analysis; however, these traditional methods for determining %NDF are often too time consuming when a rapid estimation of NDF is needed for making harvest decisions. In the spring, average alfalfa NDF increases about 5 percentage units each week.

Years ago, the University of Wisconsin developed a method to estimate %NDF in the field. This method is referred to as PEAQ, Predicative Equations for Alfalfa Quality. This method uses alfalfa height and maturity to estimate NDF of a standing alfalfa crop. Instructions on how to estimate NDF in pure alfalfa stands can be found here: https://forages.osu.edu/sites/forages/files/imce/Estimate%20Alfalfa%20NDF.pdf

Here is a short video describing the method:

PEAQ was developed for clean pure alfalfa stands. Using this method to estimate NDF of weedy alfalfa or grass-alfalfa stands, will be inaccurate. Cornell University has developed a method to estimate forage NDF for grass-alfalfa mixtures. This method is described here http://blogs.cornell.edu/ccefieldcropnews/2016/05/10/new-alfalfa-grass-ndf-estimation-tool-for-smart-phones/.

Ohio’s cold spring affected alfalfa development across the state. Alfalfa NDF is approximately 4.3 to 10 percentage units behind where development was last year. Over the next few weeks we will be monitoring and reporting alfalfa %NDF across the state.

Even though it is typical to see alfalfa jump 5 NDF units in a week’s time during spring development, the last two weeks across Ohio has shown a change of only 0.8 to 3.4 units of NDF. Below are NDF estimates from last two weeks.

Table 1. Alfalfa Average % NDF for Three Counties in Ohio (Second Week of May)

Table 2. Alfalfa Average %NDF for Five Counties in Ohio (Third Week of May)

Warmer weather and moisture will continue to move alfalfa NDF along quickly. Alfalfa producers in southern regions of Ohio should start thinking about harvesting alfalfa stands soon if the goal is to hit a forage NDF of 40% for high quality alf