ROUNDUP READY ALFALFA IS HERE Dwain W. Meyer (May 2006)

Alfalfa joins a long list of crops with the Roundup-resistant gene incorporated, but alfalfa is the first perennial crop. The transformation was made shortly after the time that soybean was first transformed, but the crop was not developed and cleared until June 2005. Forage Genetics at New Salem, WI, was the initial breeder of Roundup Ready alfalfa. Today, all major seed companies have Roundup Ready alfalfa available for producers. Table 1 presents many of the Roundup Ready varieties available with a fall dormancy of 3 to 4 and its brand.

Table 1. Roundup Ready varieties with 3 to 4 fall dormancy (FD) potentially available and its brand name.

FD Variety name Brand 3.0 Alfagraze 300 RR America’s Alfalfa 3.0 DKA34-17RR DeKalb 3.5 AmeriStand 405T RR America’s Alfalfa 4.0 425RR Allied/Southern States 4.0 4G418 Mycogen 4.0 6443RR Garst Seed 4.0 Consistency 4.10RR Croplan 4.0 DKA41-18RR DeKalb 4.0 GH709RR Golden Harvest 4.0 Liberator NK/Syngenta 4.0 RRalph 4R100 Trelay/Eureka 4.0 V-45RR Dairyland 4.0 WL355RR W-L Research _________________________________________________________________

Roundup Ready alfalfa varieties is fairly expensive. The technology fee is $2.50/lb. Add the normal cost of elite varieties of alfalfa of about $4.00/lb and you will fine most Roundup Ready varieties selling in the range of $6.50/lb. What are the advantages of the Roundup Ready alfalfa? First, Roundup Ready alfalfa will increase the success rate of establishing alfalfa by bring on clear-seeded establishment of alfalfa. Presently, we estimate that only about 25% of the alfalfa is established without a companion crop in North Dakota. With clear seeding, successful stand establishment will occur much more often than with a companion crop like oats if the rest of the management is up to snuff. The only Roundup Ready alfalfa that will be seeded with a companion crop will be on very sandy soil areas where wind erosion threatens to eliminate emerging alfalfa seedlings. The companion crop and weeds will be taken out by the Roundup after the alfalfa plants are more mature. Second, Roundup Ready alfalfa will simplify weed control in establishment of clear-seeded alfalfa. Weed control for clear-seeded alfalfa is relatively limited at present and weeds resistance is taking out one of the commonly used herbicides (Pursuit and Raptor). Roundup is relatively cheap and has a very wide spectrum weeds that it controls. Third, Roundup Ready alfalfa provides excellent perennial broadleaf control that was unavailable for seeding and established alfalfa stand. Canada thistle, field bindweed, and other perennial broadleaf weeds can be controlled with Roundup. A common question I receive is how to control dandelions in 2- to 3-year-old alfalfa stands. Roundup will do an excellent job on dandelion control, but remember what dandelion invasion is saying about the stand. When dandelion invades alfalfa, it is indicating that the stand is weakening and probably needs to be replaced in the near future. Fourth, Roundup Ready alfalfa will provide cheaper weed control for producers that have annual grass problems in the second and/or third harvest. We occasionally see this in North Dakota, but it is more common in other areas. Fifth, the excellent weed control will allow producers to qualify easier for the certified weed-free alfalfa market that is expanding. Potential disadvantages of Roundup Ready alfalfa besides the seed cost includes: 1) increased potential for weed resistance to Roundup, 2) a possible yield drag, and 3) acceptance of Roundup Ready alfalfa in foreign hay markets is unknown. Roundup Ready alfalfa varieties are not adequately tested to date to know their yield potential. The gene has been incorporated into elite material so the yield drag should be minimal. However, the forage yield of an experimental line of Roundup Ready alfalfa at Fargo in 2004 and 2005 was 88 to 92% of other varieties. This comparison was not direct and could be biased, but it indicates that there may be a yield drag. More information on performance of Roundup Ready varieties will be available following the 2006 season. Each producer will need to weigh the advantages and disadvantages of Roundup Ready alfalfa in their operation. The technology may have a real advantage in on situation and be an expense alternative in another. However, I believe the Roundup Ready technology in alfalfa will cause the optimum seeding rate to decrease in many areas (reducing the seed cost) and may increase the number of years stands are left in production. I will elaborate on these in the next issue.