Alfalfa Establishment Under Irrigated Conditions

Introduction

Reliable methods for alfalfa establishment are important for productive and long-lived stands and to ensure maximum economic returns. A companion crop provides income during the establishment year, helps control soil erosion, and may be less competitive than weeds. Since companion crops compete for water, light, and nutrients, they must be compatible with the seedling forage.

There has been a lack of information for establishing alfalfa under irrigated conditions in Saskatchewan. A project was begun at CSIDC in 1989 to establish alfalfa under centre pivot irrigation with various companion crops while obtaining maximum returns during establishment.

Establishment Trials

Sceptre Durum, Biggar CPS wheat, Winchester barley, Outlook fababean, Parkland canola, Eston lentil, and McGregor flax were evaluated as companion crops in each of 1989, 1990, and 1991. A pure stand of alfalfa was sown as a check. Two harvests of alfalfa were taken in 1990 from plots established in 1989, one harvest was taken in 1991 from plots established in 1990 (wet weather prevented a second cut), and two harvests were taken in 1992 from the 1991 planting.

Companion crops were sown in mid-May in 1989 and 1990 and in early June in 1991. Seeding was done using a hoedrill on 20 cm row spacings (40 cm for fababean). Beaver alfalfa was solid seeded at 9 kg/ha at right angles to the direction the companion crops were planted.

Recommendation

• Use flax, canola or cereals as companion crops
• Sow companion and alfalfa crops early
• Do not use lentil as a companion crop

Results

Cereal cover crops sown in May in 1989 and 1990 produced respectable yields. Sceptre durum averaged 3750 kg/ha (55 bu/ac) and Biggar CPW wheat averaged 3370 kg/ha (50 bu/ac). Canola averaged 1910 kg/ha (34 bu/ac) while flax averaged 1370 kg/ha (25 bu/ac). Lentil seed yields were low due to competition from the alfalfa.

Cereal grains sown in June in 1991 yielded 75% less than 1989 despite good initial rainfall and moderate irrigation. Canola and flax yields were also low despite good stands (Table 1). Fababean yield in 1991 suffered from a blister beetle infestation and poor crop vigor.

A comparison was made in 1990 and 1991 between durum and CPS companion crop wheat sown on 20 cm and 40 cm row spacings. Grain yield was increased 7% for durum wheat and 17% for CPS wheat with the wider row spacing (Table 1).

A cereal companion crop did not reduce first-year alfalfa yields in 1990 or 1992, but did reduce yields by 9-27% in 1991 (Table 2). Oilseed and pulse crops did not affect subsequent alfalfa yields except for 1992 when yields after canola were reduced approximately 10% (Table 3).

Flax, canola, or cereal grains make satisfactory companion crops. Eston lentil grown for seed cannot be recommended as a companion crop since it does not compete well with alfalfa. Infestations of blister beetles prevented a fair evaluation of fababean.

Conclusion

A companion crop seeded early in the season does not greatly reduce alfalfa yields the subsequent season when centre pivot irrigation is used. Adequate moisture appears to be more important than competition for light in the establishment year.

Early seeding of the companion crop results in greatest grain yield. Fall growth of the alfalfa is improved as well. Late sown companion crops produce good stands but low grain yield. Field observation suggests that the alfalfa can compete strongly with a late sown companion crop during the warm summer months.

The use of a companion crop must be based on the value of hay in the establishment year versus the value of the grain crop produced. When choosing a companion crop it is prudent to take into account the availability of herbicides for weed control in the alfalfa/companion crop blend. Consult the latest version of the Crop Protection Guide for the most current recommendations.

For further information, contact the Canada- Saskatchewan Irrigation Diversification Centre.