QUESTION #18 

How can I determine the variety that is best for my operation? What do I need to know about variety selection? 

EXPLANATION: The first thing variety testing programs do for producers is to eliminate varieties that are not adapted for production in that area. This is not a perfect system, but this alone eliminates the majority of more than 75 varieties released each year. 

Alfalfa producers should only plant varieties that have multiple-pest resistance. Most varieties recently released by reputable breeding programs have similar pest-resistance factors. Most (not all) differences in pest resistance among good varieties are unimportant in production conditions. There are seed sources of old varieties that may be good, but there is no assurance that the seed in the sack is really the variety claimed. 

For a list of alfalfa varieties that performed well in side-by-side comparisons during several seasons, review the most recent publication in the OSU County Extension Office on alfalfa varieties for Oklahoma. At this writing, Production Technology PT 96-22, "Alfalfa Varieties for Oklahoma, 1996," is the most recent. It is normally updated annually to reflect new well-tested varieties.

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QUESTION #19 

How resistant are these new alfalfa varieties to alfalfa weevil? 

EXPLANATION: The weevil tolerance in Cimarron and Cimarron VR is enough to delay spraying for weevils a few days to 2 weeks. During some seasons this may be adequate to avoid an insecticide application. Presently, the best weevil tolerance is a mechanism that allows varieties to grow faster than the weevil larvae consume leaves. It is possible that a new trait available in some experimental strains may confer a better form of resistance to the alfalfa weevil. These new potentially weevil-resistant strains are in early testing stages, and several years will be required to determine the value of the new trait. 

Currently, the most reliable control of alfalfa weevil is an insecticide application at the economic threshold. This is based on degree days, larval numbers, and height of alfalfa. Generally, the economic threshold is reached when the cost of control with insecticide is slightly less than the loss from insect damage.

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QUESTION #20 

Is it worth buying expensive alfalfa seed if I am using alfalfa for only three years in my crop rotation system? 

EXPLANATION: Seed of most varieties costs a little more than $2 per pound to produce, process, transport, and store. There are profits built into the marketing system that vary widely among companies. These may greatly affect the final price charged to farmers. More expensive seed is not necessarily more productive, nor will it necessarily result in longer stand life, it depends on the variety. Higher prices may reflect fungicide treatments and/or pre-inoculation with rhizobium bacteria. (Continued) 

Expensive and cheap seed are difficult to define. It is important to buy seed from reputable seed dealers. Producers should also know the objective differences between varieties. 

Alfalfa seed that costs less than $1 per pound is usually an old variety, and seed quality should be examined closely. Some old varieties are good enough for certain production situations. It is also important to know how much of the material in the sack will germinate. Some seed lots contain an excessive amount of dirt, broken or shriveled seed, weed seeds (sometimes noxious weeds), and other crop seed. Some seed has a low germination. 

All seed sold legally must have the purity and germination (not more than a year old) on the tag. If seed does not have a tag with acceptable current information, it is highly likely that the contents are not a "good buy" at any price. 

Some lots of common seed or VNS (variety not stated) may be good buys for low input enterprises. However, the buyer must be aware that there are certain risks involved. Assume that seed of a proven alfalfa variety costs $2.35/lb and yields 5 tons/A/year in the same tests with a seed lot that costs $0.95/lb and averages 4 tons/A/year. 

Even experienced observers cannot see such a difference in the field when the varieties are side by side. The difference of 1 ton/A certainly cannot be seen if the varieties are grown in different fields. In such cases the main difference that can be seen is between fields (not varieties). Table 3 illustrates how cheap seed may save $16.25/A at planting time, but $80/A/year is loss due to poor yield. Over a 3-year period, the proven variety earned $240/A more for the producer. Yield differences such as this (and more) are frequently measured in standard variety tests. 

Changing the estimated yield advantage to only 10% for the proven variety and sowing the same amount of seed (18 lb./A) does not make the cheap seed a good buy, as illustrated in Table 4. Over a 3-year period the proven variety would earn $120/A more and the savings in seed costs would only be $25.20/A. 

From these two examples, it is clear that the yield advantage of a proven variety must be small and the seed cost differences must be large before cheap seed is cost effective. When taking insecticide costs into account, the advantage of a multiple-pest resistant variety becomes greater if a single application is saved each year. 

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