INTRODUCTION

 

 

Alfalfa is the most productive and widely adapted forage species. Idaho alfalfa acreage was 1 million acres in 2011 (NASS 2012) which was down 130,000 acres from 2010, and down from about 1.25 million acres in 2003.  Production was 4.3 million tons with an estimated gross value of $958 million in 2011, second in the US.  Forage yield and quality vary widely across Idaho environments and operations. The Idaho Agricultural Experiment Station (IAES) conducts alfalfa variety performance trials at several sites in southern Idaho including the Kimberly Research and Extension Center. Over 300 alfalfa varieties are available to US producers, and these performance trials are designed to assist producers in choosing their varieties.

 

Alfalfa varieties are tested for forage yield for at least three production years on irrigated sites. All trials are planted as randomized complete block experiments, with four or six replications. Trials receive adequate fertilization, irrigation, and weed control for optimum production.  The 2008 Kimberly Alfalfa variety trial was planted on September 2, 2008 at the University of Idaho’s Kimberly Research and Extension Center.  A 2011 trial was planted in May 2011 at the Kimberly R&E Center, and in August at the Brigham Young University-Idaho farm in Rexburg, ID in cooperation with Greg Blaser, agronomist BYU-Idaho. Seedling-year production results are limited in value for predicting future performance. 

 

The seed industry contributes significantly to the variety trials.  Besides donating the seed, they pay a significant fee to offset our costs of doing the work.  The Plant, Soil, and Entomological Science Department of the University of Idaho also contributes significantly in salary and equipment—the 5-ft forage harvester purchased for our use costs as much as a big machine.

 

OBSERVATIONS

 

1.   Forage variety trials give potential yields.  The yields are measured on fresh forage with a moisture percentage of about 75%.  Yields are corrected to 100% dry matter but there is very little harvest loss in our trials.  Harvest losses for raking, baling, and stacking dry hay can be as much as 20% of the total dry matter production.  We also intensely manage the plots and we don’t have traffic on the plots 5-9 days after cutting.  Thus I would expect realistic hay yields about 80 to 90% of these, however, green chop or haylage yields would be closer.

 

2.      Phosphate and potash fertilizer was applied pre-planting. 

 

3.      Varieties are listed in rank of highest average yearly yield.  This year yields were not statistically different, so LSD values are not given.  There is a page full of good varieties!

 

4.      Don’t put too much emphasis on 1-year's data from one location.  I suggest looking at results from the Intermountain region of Northern California, Utah State University trials, and others similar in climate.

 

5.      The forage quality data is ranked from highest to lowest neutral detergent fiber digestibility (NDFD).  Digestibility is inversely related to yield, so ‘Vernal’ had the highest NDFD at 57.0%.  The “LSD” statistic given at the bottom of the table tells us that varieties with differences less than that value in that column are not significantly different.  The LSD for NDFD was 2.3 so Vernal was not different for all varieties in order through 54.7% NDFD, or ‘WL363HQ’.

 

6.      Kimberly Trial:  This was the third production year.  The spring and summer was unusually cool with average daily air temperatures 3 to 5 degrees below normal for May 2011. First cutting produced an average of 3.0 tons/acre in 2011 compared to 3.24 ton/acre in 2010 and to 3.68 ton/acre average in the years from 2003-2008.  The 2^nd, 3^rd, and 4^th cuttings were near normal yields.  The stands are good. 

 

7.      Check Varieties:  Vernal is a public check variety used in all trials.   Vernal should yield near the bottom of the list, however this year at Kimberly it yielded near the middle, probably a result of the lower fall dormancy and adaptation to cool weather.  Check 1 and check 2 are several year old commercial varieties.

 

Yield is the most important economic factor for alfalfa profitability.  Average yield over a period of years and at several locations is a good measure of disease resistance and plant persistence.  Generally, the top yielding 1/3 of the varieties are not significantly different for yield.  University trials offer neutral testing of varieties but will not test blends--if the source is different every year, there is no point to test it.  Industry data can be valuable because it usually is for a longer period of time, but you should ask for the complete data from the trial, not just a section of it.  Avoid data with only one year or a single harvest.

 

Forage Quality--Plant more than one variety, especially if you have large acreage and are seeking dairy-quality hay.  Varieties with different maturities will reach the cutting time up to about a week apart, allowing you to cut more hay at the pre-bud or bud stage.  Harvesting at the correct maturity and agronomic practices (proper irrigation and weed control) has a larger effect on quality than does variety. 

 

Variety selection is important but not the only factor affecting yield and quality.  Soil fertility management, irrigation management, weed control, and harvest management may affect your profit more than variety.  However, almost all newer varieties will yield more and be more resistant to pests and diseases than the old public varieties!

 

Sources of Variety Information

 

University of Idaho Forage Extension:  http://www.extension.uidaho.edu/forage/

 

Idaho Hay and Forage Association:  http://www.idahohay.com/

 

National Alfalfa Alliance's:  http://www.alfalfa.org

 

North American Alfalfa Improvement Conference:   http://www.naaic.org/

 

Montana State University Extension:   http://www.animalrangeextension.montana.edu/Forage/forage.htm

 

University of California, Davis:  http://alfalfa.ucdavis.edu/