Update on Alfalfa Cutting Height Research

Mike Rankin
Crops and Soils Agent - Fond du Lac County
University of Wisconsin - Extension

     Recall that last year we reported on some alfalfa cutting height research from North Dakota State University whereby dry matter yields were significantly influenced by cutter height. Similar research was done in 1999 at the Marshfield Research Station with cutting heights of 2, 3, and 6 inches. Here are the first-year results:

Forage Yield 

     For every cutting, forage yield was increased as cutting height was lowered. The largest differences were seen with the first cutting harvest. On average, total alfalfa yield for the season increased by 0.5 tons/acre for each 1-inch reduction in cutting height. This was similar to the findings of researchers in North Dakota.

Forage Quality 

     In general, as cutting height was reduced, forage quality decreased. Overall, for each 1-inch reduction in cutting height, forage quality decreased an average of 4 to 7 Relative Feed Value (RFV) points. The largest differences were seen with the first and second cuttings.

Milk Yield Per Acre 

     The milk yield per acre equation combines yield and quality into a single term. Past use of this equation tells us that yield is the big driving factor. Such was also the case with this study. Totaled over the three-cut season, milk yield per acre increased by 800 to 940 pounds per acre with each 1-inch reduction in cutting height.

Recommendations to Date

1. Cut healthy, non-stressed alfalfa fields at 1-inch heights to achieve maximum dry matter and nutrient yields.
2. Raise cutting height to accommodate the following situations:

• plants are experiencing moisture or flooding stress.
• the crop has been cut early and frequently whereby root carbohydrate reserves may be low.
• forage quality is more important than yield or you want to improve the quality of a late maturity standing crop of alfalfa.
• rocks are causing numerous mechanical problems to the mower-conditioner.
• harvesting forages in the late-fall.

For more information contact Mike Rankin