Introduction

Alfalfa is a major forage commodity in the Klamath Basin. It is grown on over 40,000 acres in Klamath County alone. Major markets for Klamath Basin alfalfa are dairies, cattle ranches, and horse farms in Oregon and California. Premium quality hay suitable for the dairy hay market requires timely cutting, good weed control, and an adequate stand. Little difference in forage quality has been seen between alfalfa varieties in the past. Breeding programs are striving to improve alfalfa quality. Varieties reportedly superior in quality are beginning to be marketed; however, management still appears to have more effect on forage quality than varietal differences.

Few pests attack alfalfa in the Klamath Basin. The main diseases present are bacterial wilt and phytophthora root rot. Verticillium wilt has not been found in the basin, but it occurs in many surrounding areas. The main insect pest is the alfalfa weevil. Some breeding programs are beginning to select for resistance to this pest. Pest resistances are important variety selection criteria.

Winter hardiness is important in selecting a variety for the Klamath Basin. Winter hardiness has been closely linked with fall dormancy ratings; however, less dormant varieties have experienced reasonable stand longevity in recent years, perhaps due to relatively mild winters. Local variety trials are being used to develop empirical winter hardiness and stand persistance measurements to supplement fall dormancy ratings as a measure of variety hardiness.

Forage yield is a function of a complex set of interactions between the alfalfa plant and its environment. Variety trials conducted at the KES provide alfalfa producers locally developed data on the yield potential and persistence of new alfalfa varieties. An alfalfa variety trial established at KES in 1996 is the subject of this report.

Procedures

A trial including 28 released and experimental alfalfa varieties was established in Aug, 1996. Varieties were arranged in a randomized complete block design with four replications. Soil samples from the field were analyzed and the appropriate fertilizer applied prior to planting. Seed was drilled to a depth of 1/4 inch at a rate of 20 lb/acre using a modified Kincaid drill. Plots were 5 x 30 feet with 5-foot borders and alleyways. The crop was sprinkler irrigated with a solid-set system.

Plants were allowed to grow through the first growing season without cutting. Alfalfa was harvested in subsequent years when plants reached early bud stage. The crop was harvested using a flail harvester with a three-foot wide head. All yields are reported on a dry weight basis. Three cuttings were also taken in 1997.

Results and Discussion

There was no significant difference in yield among varieties in the first and second cuttings in 1997 (Table 1). There were significant differences in the third cutting, but not in total forage yield. Failure to distinguish between varieties was not a result of high variability. Coefficients of variation were 10,11, 8, and 6 for first, second, and third cuttings, and total yield, respectively. In the first cutting, forage production ranged from 2.90 ton/acre for ExcaliburII to 2.33 ton/acre for 5246. This is a difference from lowest to highest of just over one-half ton/acre. A similar range in yields was seen in the second and third harvests as well, 0.42 and 0.54 ton/acre, respectively.

Differences in forage quality were not detected in the first harvest year despite low variation as indicated by coefficients of variation (CV's) (Table 2).

The selection of an appropriate alfalfa variety should be based on other factors in addition to yield and quality. Disease and pest resistance and winter hardiness are two very important factors. Varieties selected for the Klamath Basin should be resistant to bacterial wilt, phytophthora root rot, verticilium wilt, and in some areas, stem nematode. Resistance to root knot nematode may also be a factor when in rotation with potatoes. In the past, fall dormancy ratings of 2 to 3 have been recommended for the Klamath Basin; however, recent varieties in groups 4 and even 5 have persisted over a four-year period. Fall dormancy ratings and pest resistance ratings of varieties included in this trial are provided in Table 3.

The collection of only one year of data is inadequate to provide an estimate of the relative yield potential of the varieties in this trial. An additional two years of data are needed to adequately assess yield potential and to evaluate stand survival in this environment.