U of M Extension Home : U of M Home

Minnesota Crop News > 2001-2008 Archives

Drought was no match for good alfalfa genetics and management in Otter Tail County in west central Minnesota in 2007. In their 3rd full production year (2007) on the John Wold farm near Underwood, MN, 19 alfalfa varieties averaged 7.0 tons of dry matter (DM) per acre totaled over 4 harvests. That brought average 3-year (2005-2007) totals to 22.0 ton DM/ac, more than 7.0 ton DM/ac/year (Table 1).
Alfalfa varieties were harvested four times per year for 3 straight years, including a 4th cutting in late September or early October every autumn. Despite this aggressive harvest management, 1st cutting yields each year appeared to be unharmed. For example, 1 June 2007 yields averaged 2.3 ton/ac.

Cutting dates in 2007 were June 1, July 6, August 10, and September 25; that’s ~35-day intervals among the first three cuttings, and ~45 days between the 3rd and 4th cuttings. Past research has shown this harvest schedule produces dairy-quality forage. Average yields (and percentage of total season yield) per cutting were 2.3 (32%), 1.5 (22%), 1.4 (20%), and 1.8 (26%) ton DM/ac for 1st, 2nd, 3rd, and 4th cuttings, respectively.

Among varieties, 3rd-year yields differed by as much as 1.8 ton DM/ac (a good cutting!). Varieties with greatest yields in 2007 were Lightning III, Rebound 5.0, 6415, LegenDairy 5.0, and 54V46, averaging 7.7 ton DM/ac. Varieties that yielded least were Oneida VR, Vernal, and an experimental entry. The 3-year (2005-2007) total yield range among varieties was 4.2 ton/ac – that could be considered good year’s worth of alfalfa production! So while all varieties did well, it clearly pays to plant the best.

WHY ARE OUR YEILDS SO LARGE?

Genetics. The top-yielding varieties in the test over 3 years were Rebound 5.0, 6415, Lightning III, Extreme, and 54V46. Their 3-year total yields averaged 23.5 ton/ac. In contrast, Vernal and Oneida VR checks averaged 20.2 ton/ac over 3 years. How much is that 3.3 ton/ac difference in alfalfa hay worth? We didn’t measure forage quality, but past research suggests that a 4-cut harvest schedule should produce $100+/ton hay. So the best varieties offered a $330/ac advantage over 3 years compared to “cheap” seed. Assuming $4 for “good” seed vs. $2 for cheap seed, a 15-lb/ac seeding rate has only $30/ac difference in seed cost at planting. So over the life of the stand, better varieties provided a 10-fold payback over their marginally greater seed cost!

Variety selection decisions shouldn’t be based on performance in just one trial at one location. However, the varieties that did well in this Otter Tail Co. 2004 seeding have performed well in other Minnesota trials as well.

Minimal field and storage losses. Even with best management, harvest and storage losses during forage conservation on farms will combine to reduce harvested yields by at least 15%. With poor management, however, DM losses can quickly escalate to as much as 50%! Our harvesting system for yield trials is a one-pass green-chop operation. This contrasts with the field curing, fermentation, and storage phases on farm where DM losses inevitably occur. These DM losses are due to a combination of respiration, fermentation, spoilage, leaf loss, and new shoot breakage.

Methods to reduce harvest and storage DM losses include:

• Cut low (3” stubble height)
  
• Make wide swaths for more rapid field curing
  
• Make haylage instead of hay
  
• Ensile at the correct moisture and pack adequately
  
• Bale hay when adequately dry or with propionic acid, and store in a dry place
  
• Limit passes across the field to within just a few days after cutting
  
• Green chop
  
• Graze with high stocking density and 12-hour pasture allocation
  

Good fertility. The Otter Tail Co. test site was heavily manured prior to seeding, and phosphorus (P) and potassium (K) levels were maintained within high ranges throughout the trial. Potassium is important for winter- and general stress-tolerance. Seven tons of alfalfa dry matter will remove about 350 lb of K, so attention to this nutrient is key. Neither sulfur nor boron was applied, but these nutrients can make a difference, particularly on sandier soils.

Protection. Our test site lacked the high or low spots that are typical of alfalfa fields in the region, so there were no yield losses associated with knobs or wet spots. In addition, a tree windbreak provided protection from wind that might blow insulating snow cover off the site. Our site may have also had a water table higher than many fields; high enough to benefit alfalfa during drought, but not high enough to create water logging when moisture was abundant. For commercial fields, more windbreaks and selecting level fields for alfalfa would enhance yields. Since these options are often not available, it becomes that much more important to use the best genetics and good fertility to maximize alfalfa plant health and yield potential. In addition, mixing winter-hardy grasses with alfalfa will enhance yields in field areas where alfalfa struggles, and provide additional insulation and snow-catching residue.

Table 1. Spring stand ratings and total season DM yields of alfalfa varieties seeded May 2004 in replicated plots on the John Wold farm at Underwood (Otter Tail Co.), MN, and harvested 4 times per year for 3 years (2005-2007). Seeding-year (2004) yields (3 harvests) not included in 3-year (2005-2007) totals.

Originally published in Forage Focus (Midwest Forage Association)

printer-friendly PDF