Should producers consider an early first cutting harvest on alfalfa fields being rotated to corn?
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With record setting early spring weather, parts of southern Michigan are seeing alfalfa fields with above average growth. Some of these fields may have been slated to be planted to corn and along with the early growth, the question is whether producers should consider taking the first cutting off these fields before planting to corn?
For the dairy producer that needs more high quality alfalfa feed, it’s a quick and easy answer. If they need the feed, go get it, then plan on planting the corn afterwards. The early spring provides time to harvest the alfalfa and still have nearly full potential for the corn crop if planted before May 15. However, producers should consider some of the following points when making the decision about cutting:
- Alfalfa that has a height of 24 to 30 inches will usually have neutral detergent fiber (NDF) levels between 34 and 37 percent and have forage quality in the 160 to 190 relative feed quality (RFQ) range and would have a price near $235 per ton (dry hay).
- There is a shortage of high quality dairy hay available for purchase due to the drought and flooding conditions that occurred during 2012.
- Alfalfa regrowth does make a difference in nitrogen (N) credits. University of Wisconsin research indicates that regrowth of alfalfa over 8 inches will provide an extra 40 lbs. of N per acre (see Table 1).
- What’s the value of the additional 40 N credits? When analyzing the amount of N left in the field following alfalfa plowdown, consider the recent price trends in N. As an example, urea is near $775/ton and 28 percent N is nearing $450/ton. This puts the cost of N between $0.80 - $0.85 per pound and roughly $34 per acre.
- There is a substantial difference in N credit between sandy coarse soils and finer textured soils.
Table 1. N Credits / acre. Medium/fine textured soils; Univ. of Wisconsin Extension (Laboski et al, 2006)
|
Alfalfa stand |
Regrowth | |
|
> 8 inches |
< 8 inches | |
|
Lbs. N/acre | ||
|
Good |
190 |
150 |
|
Fair |
160 |
120 |
|
Poor |
130 |
90 |
Table 2. Alfalfa N credit guidelines for good stands (>4 plants/ft sq) on
medium and fine textured soils. (Yost, University of Minnesota)
|
State |
1st year N credit |
2nd year N credit |
|
Lbs. N/acre | ||
|
Iowa |
120-180 |
90-150 |
|
Illinois |
150-180 |
20-50 |
|
Wisconsin |
150 |
50 |
|
Minnesota |
150 |
75 |
Recent university research suggests that when adequate stands of alfalfa are present (4 plants/ft2), first-year corn grain yield is often maximized without fertilizer N, regardless of alfalfa regrowth management or timing of incorporation, but small N applications may be needed to maximize silage yield. However, research done at the Kellogg Biological Station indicated that alfalfa killed in the fall lost significant N since the fall was mild and that spring will result in less N loss than fall killed alfalfa because of the danger of leaching nitrate during the winter and early spring.
If producers decide to rotate their alfalfa fields to corn, they may want to consider adding 40 lbs. of N if they are in a sandy, coarse-textured soil. Additional N above the 40 lb. level would not be recommended.
If producers are on the fence over whether to keep or rotate a good stand of alfalfa, this spring has been non-typical thus far, and we may see an increased shortage of hay in Michigan if adequate moisture doesn’t occur.
