Managing Genuity® Roundup Ready® Alfalfa

  • Genuity® Roundup Ready® Alfalfa can provide growers higher yield potential, improved forage quality, and digestibility over conventional alfalfa.      
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  • Genuity Roundup Ready Alfalfa contains Roundup Ready® technology, which incorporates genetic tolerance to Roundup® brand glyphosate-only agricultural herbicides.      
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  • This technology provides growers with broad-spectrum weed control and flexible application timing (Figure 1).    
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Stand Establishment

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Profitable alfalfa stands are the result of careful field and product selection, proper soil and nutrient management, and good planting practices.

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Figure 1. Regrowth of Genuity® Roundup Ready® Alfalfa (left) compared to conventional alfalfa (right).
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Site Selection

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Successful alfalfa production requires well drained soils. Sandy loam, silt loam, and clay loam soil types are the most ideal. These soil types provide the best combination of water infiltration, water holding capacity, and aeration. Steeply sloped fields (more than 12% slope) should be avoided, as newly seeded alfalfa stands can be prone to soil erosion.1  

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Soil Fertility

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Alfalfa stands remove high quantities of nutrients from the soil because the above-ground portion of the crop is normally harvested 3 to 5 times per growing season. Soil tests should be used to estimate nutrient requirements, especially phosphorous (P), potassium (K), and soil pH levels. Soil pH should be between 6.3 and 7.5 for optimal nutrient availability and nodulation.1 If soil pH is below this range, lime should be applied at least one year prior to seeding. Alfalfa responds well to fertilization with P and K. Split applications of P and K, based on yield goals, are recommended after the first cutting and again in late summer. Maintaining optimum K levels in the fall is particularly important for winter survival.

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Autotoxicity

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Alfalfa plants produce toxins that reduce the germination and establishment of new alfalfa seedlings. Autotoxicity is generally a problem with stands that are two years or older. After complete removal of an established alfalfa stand, consider growing a different crop for one season before returning to an alfalfa crop to allow time for the toxic compounds to degrade or leach out of the root zone.   

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Seeding Considerations

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Alfalfa can be planted either in the spring after the last day of frost or in late summer, when moisture and temperature conditions are favorable for adequate seedling establishment. Late-summer seeding occurs because of the opportunity to plant alfalfa after another crop. A late-summer seeding should have at least 6 weeks of growth before the first frost.2 The optimal seeding rate for alfalfa is between 15 to 20 pounds of seed per acre, depending on soil and moisture conditions.  Recommendations may run much higher in the irrigated regions of the west or based on the conditions, length of stand, and management of the field.  The best practice is to utilize recommended rates from your agronomist, seed representative, or a local Extension office. In general, alfalfa seeds should be planted at a depth of about 0.25 to 0.5 inch into a very firm soil bed.2,3  Planting deeper than this can result in spotty germination and weak seedlings, except in sandy soils where a slightly deeper planting depth is acceptable.   

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Companion Crops

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Alfalfa can be planted as a monoculture or with a companion crop such as annual ryegrass, oats, barley, or triticale. Check local Extension recommendations for grass species that work best in your location. Companion crops can protect alfalfa seedlings from damage due to low temperatures, provide better erosion control, and minimize weed competition during establishment. Forage quality will be reduced with a companion crop, but total forage yield may increase. Companion crops are not recommended for late summer seeding because moisture limitations at this time can create competition and hinder alfalfa seedling development.   

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Weed Management

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Fields should be free of weeds before seeding. For detailed information on weed management see: Weed Resistance Management in Genuity Roundup Ready Alfalfa online at: http://www.roundupreadyplus.com/Content/assets/docs/forum/Weed-Resistance-Management-in-Genuity-Roundup-Ready-Alfalfa-RRPLUS.pdf.  Geography-specific documents are also available.      

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Forage Quality and Yield Factors

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Alfalfa forage quality is greatest in early vegetative stages when leaf weight is greater than stem weight. For producers who seek higher quality alfalfa, such as dairy operations, the optimum time for harvest may be at the pre-bud stage. When alfalfa is harvested at later stages of maturity (after flowering) higher yields can be expected; however, the quality decreases due to a greater quantity of low-quality stems. An early first harvest, at pre-bud stage, followed by a short cutting interval can give a high yield of quality forage. To increase root reserves and stand persistence, wait to make one cutting after early flowering. Use a longer cutting interval for maximum stand persistence.   

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Fall Management

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Assess the level of risk for winter injury when considering a late-fall cutting. After the final harvest, alfalfa requires a 6 to 8 week rest period prior to the first killing frost in preparation for winter dormancy. Depending on the severity of a typical winter, stand age, and the season’s cutting schedule, it may be better to avoid fall cutting. Managing soil fertility (most importantly K levels) and cutting height can reduce the risk of winter damage after a fall cutting. Leave a 6-inch stubble and uncut strips after a late-fall harvest to catch snow and insulate the roots. Late-fall cuttings in northern states can increase winterkill losses and decrease the initial spring cutting yields, but can be useful for decreasing the number of overwintering insects.   

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Stand Life and Rotation Timing

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Yields often begin to decline in the third year of production in the Midwest, the Northeast, and many irrigated fields in other regions. Weed, insect, and disease pressure may become greater in older stands, requiring increased pesticide applications. Growers who consider shorter rotations may see greater profits with higher yields, higher forage quality, reduced pesticide use, greater nitrogen credits, and an increased corn yield potential of 10 to 15% when rotated after alfalfa.2,5

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