What we learned from 70 years of alfalfa variety trials

Craig Sheaffer, Extension Agronomist, University of Minnesota

The alfalfa variety testing program at the University of Minnesota began in the early 1950s and continued for nearly 70 years until 2021. Results were published in the Variety Trials by the Minnesota Agricultural Experiment Station and archived issues of the trials are available. 

The program’s goal was to provide an unbiased evaluation of alfalfa varieties as a service to alfalfa producers and to alfalfa breeders and marketers. Trials showed the improvement in winterhardiness, disease resistance, and forage yield of alfalfa varieties over time.

Winterhardiness

In Minnesota, winter injury and winterkill can occur due to extremely low temperatures, but also when varieties break dormancy during late winter thaw and freeze cycles. One of the first winterhardy alfalfa varieties in the Midwest was “Grimm”. Grimm was selected in Carver County MN, and the University of Minnesota contributed to its development. At its peak use, Grimm was grown on almost a million acres in Minnesota, and it’s winterhardiness genes have been incorporated into many modern alfalfa varieties. The complete history of Grimm alfalfa is described in A Grimm Dairy Tale. 

We continually measured winter survival in our trials and coordinated a multistate winter survival testing program from 1996 to 2005, using the NAAIC standardized method.  Fall dormancy -  a general indicator of winterhardiness (more fall growth less winterhardiness) - has been replaced with a winter survival test. Alfalfa varieties should be selected that are rated extremely winterhardy or very winterhardy. Today, the alfalfa industry conducts independent tests and winter survival ratings are provided in the Alfalfa variety leaflet.

Disease resistance

While Grimm was very winterhardy and had very good forage yields, it lacked resistance to bacterial wilt, a vascular disease that prevents nutrient flow within the plant. Bacterial wilt infection became widespread with increased alfalfa acreage, and new varieties were developed with resistance to the disease. Results from the 1961 Variety Trials show the combination of persistence and yield that made “Vernal” a popular variety (Table 1). From the list of entries shown, only Ranger and Vernal were recommended for producers because of their winterhardiness, bacterial wilt resistance, and seed availability.

The 1992 Variety Trials that summarized trial results from over 120 entries for the period 1967-1991 showed the improvement in disease resistance. Many marketed varieties had high levels of resistance to bacterial wilt, phytophthora root rot, fusarium wilt, and anthracnose. Note that Vernal and Ranger were susceptible to phytophthora root rot that greatly reduced their persistence on wet soils. Resistance to multiple diseases is important for variety adaption to stresses in diverse soils, and we recommend that producers select varieties with resistance to these diseases as well as to Aphanomyces.

Table 1. Bacterial wilt resistance, winterkill following a severe winter and forage yields at Rosemount, MN. Source: Minnesota Agricultural Experiment Station (AES) Varietal Trials, Report 24, December 1961, and USDA AES Technical Bulletin 1571.

Variety	Developer	Year*	B. wilt resistance**	Winterkill	Forage yield
				%	tons/acre
Grimm	W. Grimm	1900	S	39	2.5
Ladak	India	1910	MR	55	3.7
Ranger+	USDA; NE AES	1942	R	19	4.2
Narrangansett	RI AES	1946	S	59	4.3
DePuits	Tourneur Freres	1947	S	83	4.1
Vernal+	USDA; WI AES	1953	R	19	4.5
Lahontan	USDA; NE AES	1954	R	17	2.4
Rambler	Agric Canada	1955	R	46	3.6
Buffalo	USDA; KS AES	1943	R	27	4.3
Teton	SD AES	1958	R	20	3.5

*Year seed was available.
**S=susceptible; MR=moderately resistant; R=resistant
+Recommended varieties; others not adequately tested or lacked winterhardiness or bacterial wilt resistance
++Yields averaged from two trials at Rosemount where bacterial wilt disease resistance occurred. Trials were two years duration and alfalfa was cut two times per year with harvests at flowering.

Forage yields

1967-1991 trials

With improved variety disease resistance, more intensive harvesting and increased soil fertility and insect control, forage yields greatly increased compared to those in the first MN trials (Table 2). For the 1967-1991 data shown in Table 2, several entries had four-year yields that were superior to Vernal, a check cultivar.

Table 2.  Fall growth score, winter survival following a severe winter, four-year average forage yield (1967-1991) relative to Vernal, and disease ratings for bacterial wilt, Phytopthora root rot, Fusarium wilt, and Anthracnose. Except when noted, varieties selected for inclusion were based on a minimum of 1054% of Vernal yield and a minimum of six trials over multiple locations. Trials harvested an average of three times per year.** 

Variety	Fall growth+	Winter survival	Forage yield	Bacterial wilt	Phytop. root rot	Fusarium wilt	Anthracnose
		%	% of Vernal
V. fall dormant
Speador 2	7.5	60	95	HR	S	MR	S
Fall dormant
636	6.3	25	106	HR	HR	R	MR
Profit	6.2	50	108	HR	R	HR	MR
Agate*	6.0	29	102	HR	R	HR	MR
Blazer	5.9	--	108	HR	MR	MR	LR
5262	5.7	60	105	HR	R	MR	--
120	5.5	43	110	HR	R	MR	LR
Ranger*	5.4	57	100	MR	S	MR	S
Dart	5.3	25	108	HR	R	R	R
Arrow	5.2	37	106	HR	HR	HR	MR
M. fall dormant
Elevation	4.7	33	107	HR	R	R	R
Magnum	4.7	36	105	HR	S	R	MR
5432	4.6	29	105	HR	MR	HR	--
Saranac*	4.5	20	102	R	S	R	S
Voyager	4.5	31	108	HR	R	R	MR
630	4.5	28	108	HR	R	R	MR
Target	4.4	24	106	HR	R	R	MR
WL 320	4.2	31	107	HR	R	HR	MR
Hi-Phy	4.1	--	108	HR	HR	MR	--
Epic	3.9	31	105	HR	R	R	S
Vernal (check)	6.5	67	5 T/A	R	S	R	S

*USDA, AES and university-developed varieties of historical interest.
**For complete results and descriptions, see Minnesota Agricultural Experiment Station (AES) Variety trials, Report 223-1992. Selected use of data does not imply endorsement of any entry.
+Fall growth in mid-October: 1=tallest; 9=shortest with classification of very fall dormant, fall dormant, and moderately fall dormant. Note: this fall dormancy index does not follow current NAAIC methods.
++Winter survival after severe test winters. Note: this test does not follow current NAAIC methods.
+++Disease resistance ratings: HR=High resistance (51+), R=resistant (31-50), MR=moderate resistance (16-30), and S=susceptible (<16)

2000-2021 trials

Improved yield potential of modern varieties is demonstrated in trials conducted from 2000 to 2021 in southeast (Rosemount and Zumbro Falls), central (Richmond and St. Martin) and southwest (Lamberton) Minnesota. Alfalfa yields for the top 5 yielding varieties averaged 16, 19, and 10%, respectively, more than the check varieties (Table 3). Over 20 years, this translates to 16, 20, and 10 ton/acre, respectively. Averaged for all locations yields of the top 5 varieties were only about .3 ton/acre more than the average of all varieties in the trial (excluding checks). However over 20 years that still accounts to a yield advantage of 6 ton/acre.

Table 3. Average  annual forage yields for the top five, average and check varieties from 2000 to 2021 in three regions of Minnesota. Yields are the average for the three production years following seeding and are expressed in dry matter in tons per acre.*

Category	Southeast	Central	Southwest
	ton/ac	ton/ac	ton/ac
Top 5 varieties	5.6	6.3	5.0
Average variety	5.3	6.0	4.8
Check varieties+	4.8	5.3	4.5
Top 5 - check difference++	0.8	1.0	0.5

*Southeast MN trials conducted at Rosemount and Zumbro Falls; Central conducted at Richmond and St. Martin; and Southwest at Lamberton. All locations harvest four times per year by early September.
+Check varieties: Vernal, Oneida VR, and 5312.
++Average yield differences between the Top 5 yielding varieties and the check varieties.

Fig. 1. Alfalfa variety forage yields as a percent of the check
varieties (Vernal, Oneida VR, 5312) in trials conducted from
2000 to 2021 in southeastern MN.

The yearly variation in yields as a percent of the checks is shown in Figure 1-3. For all locations, the trend in average and top 5 variety yields is upward although slight. Yearly yield variations are due to differences in rainfall. In southwest MN, yield potential of top 5 and average varieties versus the checks is reduced due to less rainfall than in Central and Southeast, MN.

Central Minnesota

Southwest Minnesota

Figs. 2 and 3. Alfalfa forage yield as a percent of the check varieties Vernal, Oneida VR and 5312 in trials conducted from 2000 to 2021 in central (left) and southwest (right) Minnesota. The blue bars show the range, the red dot is the average for the top 5 varieties while that line is the average of all varieties excluding the checks.

Forage quality

We initiated forage quality testing in the 1990’s because of its extensive use in variety marketing. While there was a range in RFV, RFQ, and milk/ton values among entries, forage quality of the best varieties did not often differ consistently from check entries. In separate tests, we determined that varieties marketed as reduced lignin did have greater digestibility than conventional varieties due to greater stem digestibility. Overall in our testing, we concluded that maturity at harvest and harvest losses had a greater effect on forage quality that variety genetics.

Summary comments

Vernal alfalfa, a winterhardy variety developed in the 1950s by the Wisconsin experiment station, has been included as a check or standard cultivar since the 1960s. Although it lacked resistance to many diseases, it persisted well at many test locations in Minnesota and was considered a “neutral," non-private industry control or check. However, Vernal yields were consistently among the lowest in our trials beginning in the 1990’s and its use is not recommended.

Variety trial results have shown improvement in forage yields over time, due to improvements in winterhardiness and disease resistance. Since University of Minnesota testing results are no longer available in Variety Trials, farmers should seek information from seed marketers regarding the yield potential and persistence of an alfalfa variety within their region. Information from multiple tests in diverse locations should be considered. Because varieties do differ in yield and persistence, producers can gain information about alternative varieties by planting multiple varieties and measuring their yield.

Do variety trial yields represent producer yields?   

There are concerns that variety trial yield results are not representative of those normally achieved by producers. Indeed, producer surveys by the USDA showed that in 2022, statewide alfalfa hay and silage yields averaged only 3.1 ton/acre. These yields correspond to those shown for 1961 in Table 1. Modern alfalfa varieties with disease resistance have much greater yield potential, but it is unknown which varieties were used by producers participating in the USDA survey. 

There are two other explanations for these differences: First, modern yield trials consistently used best management practices including soil selection, fertility, and weed and insect control to optimize alfalfa yield potential. They also minimized harvest losses which can be as high as 20%, and wheel traffic damage which can also be significant for some alfalfa varieties. Second, USDA statistics include estimates from fields of unknown stand ages including older fields when forage yields decline. Yields from our most recent trials are for the first three years following establishment.

Credits    

Alfalfa variety trials were conducted for over 70 years by the Minnesota Agriculture Experiment Station to provide producers information to aid in alfalfa selection. The program’s goal was to provide an unbiased evaluation of alfalfa varieties as a service to alfalfa producers and to alfalfa breeders and marketers. The individuals responsible for the program were L.J. Elling (UMN), D. Barnes (USDA ARS), N. Martin (UMN) and C. Sheaffer (UMN). Technical support for establishment, harvesting, and data summary were provided by D. Smith, D. Swanson, D. Schriever, and J. Larson.