This is our third week of monitoring 1st cutting for quality in 2021. If you are not familiar with our procedures we use alfalfa height to predict Neutral Detergent Fiber (NDF) for alfalfa, alfalfa/grass mixed and grass stands. Alfalfa height has proven to be a reliable indicator of NDF values in the field. Here are numbers that are helpful when using alfalfa and grass height as an indicator of NDF content. In general: 

Begin cutting 100% grass stands when nearby alfalfa is 14" tall to achieve the desired 50% NDF.

Begin cutting 50/50 alfalfa/grass stands when nearby alfalfa is 22" tall for the desired 44% NDF.

Begin cutting 100% alfalfa stands when alfalfa is 28" tall for the desired 40% NDF.

To achieve the desired NDF it is necessary to begin cutting at NDF values slightly lower than the desired value assuming some harvest and storage losses which the above alfalfa height values reflect. For example 28 inch tall alfalfa is closer to 38% NDF but you will need to start then to end up at 40% NDF.

Predicted days to cut are based on daily NDF increases for grasses of 1% point, 50/50 mixed stands of .8% points and alfalfa of .5% point. Typically, NDF increases about 0.8 to 1.2/day for grasses expecting the lower end of that range in cooler weather and the higher end in warm. Alfalfa NDF increases about 0.4 to 0.7/day again figuring the lower end of that range with cool temperatures and the higher in warm. See 'Predicting Spring Fiber Content of Forages' pdf below for more details.

Here is this week's chart, but you can use the location and elevation as a guide to conditions that may be similar to your own. Always check your fields to verify your heights and conditions!

To summarize, here's a chart showing the relationship between elevation and alfalfa heights across our region. If your location isn't listed, you can roughly estimate your alfalfa's height within a few inches based on your elevation; just follow the line. As the weeks go by, the change in alfalfa height is becoming slightly more predictable by elevation (smaller range of heights at a given elevation), but the line is leveling out (higher elevations have been catching up). This week, the general decrease in alfalfa height is by about an inch for every ~135 ft rise in elevation.

This is going to be a busy week for just about everyone, either planting corn or taking first cutting and planting corn. When it comes to taking first cut, we need to triage our fields: focus on those that can give us the highest quality now and shift focus away from those that are past their prime. "With the unique spring weather patterns this year, there are likely scenarios where fields are not accessible when the forage is at target maturity. As these fields become over mature set them aside (they likely still have value for non-lactating animals) and focus efforts on harvesting fields that are at target quality." - Betsy Hicks (CCE-SCNYDFC) and Joe Lawrence (PRO-DAIRY). 

See 'Dynamic Harvest Schedules' pdf below for more information.  So keep a close eye (literally) on the maturity of your forage grasses - and watch the height of the seed head in relation to the height of your cutter bar.