Management Practices Affecting Alfalfa Yield and Quality

There is a trade-off between quality and quantity that should be balanced with stand longevity. Focus on four key management tactics: fertilization, pest management, harvest schedule, and storage.

The Trade-off

Historically, there has always been a trade-off between quality and quantity with the date of alfalfa harvest. Allowing conventional alfalfa plants to grow beyond the most desirable growth stages generally increases yield potential; however, due to the increase in lignin, overall quality decreases. A reduction in lignin content as the plant ages would:

  • Increase the digestibility of alfalfa
  • Allow for a longer growing period between cuttings
  • Increase the yield potential
  • Allow a wider harvest window and increase harvest flexibility

The advent of HarvXtra® Alfalfa with the Roundup Ready® Technology trait has caused the quality penalty to be reduced as yield increases.1 However, alfalfa without this trait loses quality as the plant continues to grow in an attempt to maximize tonnage potential. Alfalfa is versatile enough to be used in many types of livestock operations; therefore, management should be focused on the end goal for yield and quality for the type of livestock being fed.

 

Figure 1. Delayed harvest of HarvXtra™ Alfalfa can potentially add yield without sacrificing quality. (Data comes from Forage Genetics International trials comparing HarvXtra® Alfalfa with Roundup Ready® Technology 2017 FD4 commercial varieties to commercial checks. Trials were seeded in 2013 and harvested in 2014, 2015 and 2016 in Boone, IA; Mt. Joy, PA; Nampa, ID; Touchet, WA; and West Salem, WI. Yield increase is directly correlated to the ability to delay harvest.)

Fertlilization

Soil testing is recommended to ensure that soil pH and fertility levels are at the ideal levels. A soil pH level of 6.7 to 6.9 should be maintained to maximize quality and quantity. The key nutrients include phosphorus, potassium, sulfur, and nitrogen. Phosphorus encourages good root growth in stand establishment, while potassium maintains yield and stand longevity. Alfalfa has been shown to be responsive to sulfur, in the upper Midwest. A soil test does not accurately predict sulfur requirements, so a tissue test is required. Nitrogen may help increase stand establishment and yields in the seeding year. Yield goals should be considered when building fertility plan. A yield of 5 tons is fairly typical in non-irrigated systems in the mid-west, while yields in irrigated systems can be in excess of 12 tons.

Harvesting

The most important variable in maximizing the quality of the crop while also maximizing the quantity is determining when to make the first cutting. Harvest first cutting using PEAQ (Predictive Equations Alfalfa Quality) stick by:

  1. Choosing a representative 2-square-foot area in the field. 
  2. Determine the stage of the most mature stem in the area using the following criteria:
      • Vegetative: Stem is more than 12-inches tall with no visible buds or flowers..
      • Bud: Nodes have visible buds with no flowers or seed pods present.
      • Early flower: 1 or more nodes have open flowers.
  3. Select the tallest stem in the 2-square-foot area. Measure it on the correct maturity scale (from step 2) by placing the stick at the soil surface and determining RFQ (Relative Feed Quality) at the tip of the stem (not the tip of the highest leaf). The tallest stem may not be the most mature stem. Measure carefully, making sure the stick is next to stem. Repeat in 5 more areas. If the field is larger than 30 acres, more samples should be taken.

Thereafter, cuttings are usually on a schedule which can be every 28 days in a dairy production system. In beef systems, cutting is usually delayed until about 10% bloom to maximize yield yet maintain a quality suitable for beef production.

An additional consideration on harvesting is the cut height. Generally, it is recommend that cutting height be 2 to 3 inches, except for the final cutting height, where a 4-inch height is recommended in Northern areas to help catch and hold snow. Research has shown that for varieties that do not have the HarvXtra™ trait, every 1-inch reduction in cutting height results in a 0.5 ton/acre increase of dry matter over the course of the season; however, quality decreased by about 4 relative feed value units for each cutting. 2

Wider swaths speed up drying time, decrease dry matter loss in the field and result in improved quality. A wider swath can reach 65% moisture content in 5 to 8 hours, allowing for haylage harvest the same day. Minimizing wheel tracks can also help reduce yield losses for successive cuttings. 

Pest Management

 Using integrated pest management tactics for weeds, diseases, and insects can result in both yield and quality increases. Consult local University Extension staff on local recommendations for management strategies for specific pests in your area.

Storage

Storing hay inside a building results in minimal dry matter losses of 1 to 5%. Hay in contact with soil and left uncovered can lose up to 50% dry matter after 1 year. Even if covered, contact with soil can result in 15% dry matter loss. Moisture can be kept from wicking from the ground with the use of plastic wrap, large crushed stone, ties and/or poles, pallets, or tires.2

For more information, see the Alfalfa Management Guide.

Sources:

1Combs, D. 2016. Low-lignin alfalfa varieties offer potential quality gains. Hay & Forage Grower®. hayandforage.com/article-490-low-lignin-alfalfa-varieties-offer-potential-quality- gains.html

2Wiersma, R.W. and Wiederholt, R. Alfalfa cutting height to maximize forage yield and quality. https://fyi.uwex.edu

3Holmes, B. Dry round hay bale storage costs. https://fyi.uwex.edu