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 should be cut when nearby alfalfa is 14 inches tall to achieve the desired 50% NDF. Begin cutting 50/50 mixed alfalfa and grass stands when nearby alfalfa is 22 inches tall for the desired 44% NDF. Begin cutting 100% alfalfa stands when alfalfa is 28 inches 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. Predictions are adjusted for the coming week's weather and we are assuming cooler temperatures and slower than normal growth.

In the attached tables locations around the region are listed where we have measured alfalfa height. 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!

May of 2020 brings record or close to record low growing degree days for alfalfa (Base 41) across our region. The fifteen-year average for this date across our region is 242 GDDs since March 1 and we have only had 152 GDDs Base 41 through May 5. We need 41°F to have alfalfa growth and in the next week the forecast is for at least three days in the 30-40s °F. Since our dry run last Tuesday we have only increased alfalfa height 3.5 inches (5 to 8.5 inches). We expect NDF accumulation to slow this week and correspondingly we have increased the days to a predicted harvest date.

We would expect twelve of our thirty-two fields (38%) if they had all grass to be ready for harvest this coming week. However, most other fields are far from being ready. Right now the closest 50/50 mixed field date we would have would be over ten days away at current temperatures. This could change if we get some warmer weather after this coming weekend which has some snow in the forecast. Will have a better handle on that next Tuesday, May 12 when we check fields again.

Right now if soil conditions remain dry stay focused on corn planting unless you have considerable all grass acreage in a few of the locals we have identified as might be ready to go.

See the full report in the pdf.

First Cutting Project is being conducted by Cornell Cooperative Extension of Chenango, Fulton, Herkimer, Madison, Montgomery, Otsego, Saratoga and Schoharie Counties and the Central New York Dairy, Livestock and Field Crops Team