Stable irrigation supply critical for successful alfalfa, grass

By D. Bruce Bosley

Extension Agent/Cropping Systems

Colorado State University Cooperative Extension

Late summer is an excellent time to plant alfalfa and cool season perennial grasses for irrigated hay production or grazed pastures. Warm daytime and moderate nighttime and warm soil temperatures provide excellent conditions for germination and early growth provided the soils have a good supply of stored moisture. The steps for making successful plantings follow.

An assured supply of available irrigation water is needed for successful plantings. Late summer seedings on dryland fields have been successful when stored soil reserves were good and fortuitous rains came. Spring plantings on dryland are normally more successful because soil moisture is normally better and precipitation is more predictable than in the late summer and fall.

For Northeast Colorado, Colorado State University Cooperative Extension recommends planting dates for Alfalfa and cool season perennial grasses from Aug. 20 to Sept. 10. Many producers have successfully established these forages with seedings earlier in August and later in September and even early October, but they have chanced heat and drought losses from early plantings and early freeze losses from later ones.

Weed management is important for successful forage establishment, but it is less problematic in the fall than during spring and early summer. The perennial forages are generally good competitors once established and mostly have weed problems where the plant stands are poor. Summer annual weeds will disappear following fall frosts. The winter annual weeds downey brome (cheatgrass) and mustard species should be avoided by planning to have at least one and preferably two summer crops on fields preceding the forage plantings. Seeding into hay millet, forage sorghum or corn silage fields is an easy way to time late summer alfalfa or perennial grass seedings and they lend themselves to no-till planting techniques.

Proper field preparation is essential to insure good forage establishment and includes having a weed free seedbed. Traditional pre-emergent or preplant incorporated herbicides can be used for solo alfalfa plantings to kill off annual weed seedlings. Grass seedings shouldn't have herbicides applied until they have become well established (seedlings with 5 leaves). There aren't any herbicides that can be used in mixed alfalfa grass pastures at any time. For this reason fall is the best time for making these seedings.

Perennial weeds pose a special problem for new perennial forage seedings. Field bindweed and Canada thistle have well established root systems and abundant stored energy reserves. These perennial weeds may expand in new perennial forage seedings if not managed properly. For this reason attention to controlling these weeds should be a high priority prior to seeding the forage crop.

Alfalfa producers may want to use one of the new round-up ready alfalfa varieties to get an early suppression on these two and other perennial weeds. Suppression of the growth and reducing the energy of perennial weeds during the establishment year of alfalfa and perennial grasses is very desirable. Once established these forages are very competitive and with proper grazing and haying management they provide good suppression of annual and perennial weeds.

Please contact me, Bruce Bosley with your cropping systems or natural resources questions: 970-522-3200, ext. 285. Thank you!

Date: 8/23/06

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