Davison, J., Solomon, J. and Lawry, T. 2016, Alfalfa Variety Trial in Western Nevada, Initial Results, University of Nevada Cooperative Extension

Introduction

Alfalfa is the most extensive crop in Nevada with approximately 250,000 acres devoted to its production. The annual value of alfalfa grown in Nevada normally exceeds $200,000,000. (Nevada Agricultural Statistic Service). Alfalfa yields in Nevada have averaged approximately 4.5 tons per acre annually over the past several years. Farm revenue is a direct function of yield per acre, and one important influence of yield is the variety planted. The work described in this publication is focused on the yield of 17 alfalfa varieties planted in a yield trial.

The majority of alfalfa fields in western Nevada are harvested three to four times annually. This production system is dependent on dormant alfalfa varieties that cease growth during the winter months. These types of alfalfa varieties can be classified according to fall dormancy and winter survival ratings.

Fall dormancy in an alfalfa variety refers to the ability of that variety to grow in the fall. Shorter day lengths and colder temperatures are the primary factors that affect, fall dormancy and varieties can differ greatly in their fall dormancy. Alfalfa varieties are rated from 1 to 11, with 1 being the most dormant and 11 being the least-dormant. Generally, less dormant varieties will produce a higher yield than more dormant varieties due to a faster “green-up” in the spring, quicker recovery after a harvest and greater growth in the fall. However, if a grower plants a variety with too large of an fall dormancy rating, the plants are at risk of damage from the plant breaking dormancy too early and being damaged by subsequent freezing temperatures.

Winter survival ratings describe an alfalfa variety’s ability to survive extreme freezing temperatures in winter. Winter survival ratings range from 1 to 6, with 1 being the most winter hardy and 6 being the least. As with fall dormancy ratings, varieties with greater winter survival ratings will generally produce less than those varieties with a lower winter survival rating. Alfalfa breeders, however, have done an excellent job in separating fall dormancy from winter survival. This means that a producer can now buy an alfalfa variety with a higher fall dormancy rating while maintaining an acceptable winter survival rating to protect against winter-kill or damage to the selected variety.

Most alfalfa varieties are also rated for their pest resistance for common alfalfa pests. The Pest resistance ratings are characterized as the percentage of plants in a population that are resistant to the identified pest. They range from 0 to 5 percent for susceptible varieties to greater than 50 percent resistant for those varieties rated as high resistance. In all cases a grower should also select varieties with the highest resistance ratings for the most common pest(s) in their production region.

The National Alfalfa & Forage Alliance, National Alfalfa & Forage Alliance, publishes an annual Alfalfa Variety Ratings sheet that details winter survival, fall dormancy and pest resistance ratings for “alfalfa varieties eligible for certification by seed certifying agencies.” The ratings are obtained from the Association of Official Seed Certifying Agencies (AOSCA) and the National Alfalfa Variety Review Board (NAVRB). This publication also lists the company to contact for marketing information. The publication is available on the web at Alfalfa Variety Ratings.

In western Nevada the most commonly planted alfalfa varieties have a fall dormancy rating of 4 to 5 with an occasional 6. Yet, these varieties are normally very winter hardy, with ratings of 1 to 2.

The alfalfa varieties evaluated in this study included one fall dormancy rating 3, eight with a fall dormancy rating of 4, six with a fall dormancy rating of 5 and one with a fall dormancy rating of 6. The alfalfa varieties evaluated in this trial are listed in Table 1.

 

Table 1. Alfalfa varieties evaluated in Western Nevada Alfalfa Trial 2016

Variety Marketer Fall Dormancy Winter Survival Remarks
DKA-44-16 DeKalb 4 2 Roundup ready
DKA50-20 Dekalb 5 2 Roundup ready
4S417 Mycogen 4 2 -
4C610 Mycogen 4 2 -
Alforex 360 Alforex seeds 3 - Low lignin
Archer III America’s alfalfa 5 2 -
Six Shooter Croplan 6 - Roundup ready
Stratica Croplan 4 2 Roundup ready
Nemastar Croplan 4 3 Roundup ready
Nimbus Croplan 5 2 -
PGI 427 Alforex seeds 4 2 -
Gunner Croplan 5 1 -
Cinch Ron’s seed - - Multifoliate
Mutiny Nexgrow 4 2 Roundup ready
6401N Nexgrow 4 - -
6585Q Nexgrow 5 2 -
6516R Nexgrow 5 - Roundup ready

Methodology

The variety trial was located on the University of Nevada, Reno Main Station Experimental Farm. It was planted on a Truckee, silt-loam, 0 to 2 percent sloped site, according to the Natural Rescources Conservation Service soil survey for Washoe County. It is rated as prime farmland if irrigated and drained. The available water holding capacity is high, approximately 10.5 inches. The normal frost-free period is 100 to 110 days. A static water table exists during the irrigation season at a depth of 4 feet.

A soil sample was obtained prior to seeding and sent to a private laboratory for analysis. The sample was obtained from the upper 12 inches of soil. It consisted of a composite sample of 20 subsamples taken from the plot area. The analysis indicated that the nutrient levels were generally adequate, with the possibility of a response to manganese applications if tissue samples indicated a deficiency. Yield results did not indicate nutrient deficiencies. Table 2 depicts the soil sample results.

Table 2. Soil analysis results from the Main Station Farm Alfalfa Variety Trial 2016
Analysis Result Level
Organic Matter 4.5 percent High
Organic Matter- Estimated Nitrogen Release 121 pounds per acre -
Phosphorous/NaHCO3-P/Olsen Method 31 parts per million Very High
Potassium/K 357 parts per million Medium
Magnesium/Mg 504 parts per million Medium
Calcium/Ca 3451 parts per million High
Sodium/Na 298 parts per million High
Soil pH 8.0 -
Cation Exchange Capacity/C.E.C. 23.6 milliequivalents per 100g -
Nitrogen/NO3-N 41 parts per million Very High
Sulfur/SO4-S 36 parts per million Very High
Zinc/Zn 1.0 parts per million Low
Manganese/Mn 2 parts per million Low
Iron/Fe 10 parts per million Low
Copper/Cu 1.3 parts per million High
Boron/B 2.0 parts per million Medium
Excess Lime Rating - -
Soluble Salts 0.6 millimoles per cm Low

The 17 alfalfa varieties were planted on May 2, 2015 at a rate of 25 pounds per acre Pure Live Seed (PLS). All varieties were seeded approximately ¼ inch deep with a cone seeder, into a clean, firm seedbed, with each seed row firmed by a packing wheel at the time of seeding.

Alfalfa Test Plots Main Station Field Lab, Reno, NV 2016

Alfalfa Test Plots Main Station Field Lab

The alfalfa plots and surrounding fields were irrigated with reclaimed sewage effluent from the Truckee Meadows Water Reclamation Chalk Bluff Facility, and have been for a number of years. The facility utilizes a biological nutrient removal process combined with separate nitrification and denitrification processes to remove nitrogen. Phosphorous is removed using biological and chemical processes. These processes result in reclaimed water that has an average pH of 8.0. It is also relatively low in nutrients and total dissolved solids. The soil sample results listed in Table 2 indicate that soil nitrogen and phosphorous levels are in the very high range and should not limit alfalfa production.

The variety trial was irrigated weekly with the reclaimed sewage effluent using sprinklers. The irrigation water supply was unlimited. The 2015 irrigation applications began on May 29 and ended on Oct. 15, 2015. During 2015, a total of 2.25 acre feet was applied to the plots. In 2016, irrigation started on May 17 and ended on Oct. 1. During 2016 (the first full year of production), a total of 1.8 acre feet of water was applied or received as precipitation, with total reference evapotranspiration (ET) recorded as 35.97 inches. The alfalfa plants never displayed any visual evidence of a lack of water, and the authors theorize that the water table supplied adequate water to the alfalfa plants to account for the difference in water applied and recorded ET.

On June 18, 2015, the plots were treated with 5 ounces of Imazethapyr, 8 ounces Clethodim, 1 quart methylated seed oil (MSO) and 1.5 quarts of concentrated ammonium sulfate (AMS) water conditioner per acre in 15 gallons of water per acre. The treatment was targeted to control cool season annual grasses and broadleaved weeds, and was judged to be very effective. The same treatment mix, minus the Imazethapyr, was applied on Aug. 15, 2015 to control warm-season annual grasses. The original treatment regime was again applied on March 23, 2016, and was the last chemical weed control applied.

Rodents (voles, marmots and ground squirrels) caused significant damage to some plots. Damaged areas were noted and adjusted during harvest activities to compensate for obvious damage.

Harvesting Plots 2016

Harvesting Plots

Results

All of the tested varieties performed very well during the 2016 growing season. There were no statistical differences between the first, second and fourth cuttings. The third cutting did result in significant difference between some of the varieties at the P=< 0.04 level. This means that approximately 96 percent of the differences between the varieties are due to the difference in varietal production rather than chance. The varietal means in the “third cut” column followed by the same letter are not different at the P> 0.05 level of probability.

Table 3 displays the results of each cutting by variety and the total seasonal yield for each variety during 2016 with the highest total yield for the season listed first.

 

Table 3. Alfalfa Varietal Testing Results Reno, Nevada 2016: Tons per Acre
Variety 1st Cut (06/08/2016)
Yield in Tons per Acre
2nd Cut (07/13/2016)
Yield in in Tons per Acre
3rd Cut (08/11/2016)
Yield in in Tons per Acre
4th Cut (09/26/2016)
Yield in in Tons per Acre
Total Yield
in Tons per Acre
Nimbus 4.1 3.1 2.4 a 2.3 11.8
Mutiny 3.7 3.1 2.1 bc 2.4 11.3
DKA50-20RR 3.8 3.0 1.9 cd 2.4 11.1
Cinch 3.9 2.9 2.1 bcd 2.2 11.1
Stratica 3.7 3.0 1.9 cd 2.4 11.1
PG1427 3.9 2.9 2.1 bc 2.0 10.9
6516R 3.7 2.8 2.1 bc 2.1 10.8
4S417 3.9 2.7 2.0 bcd 2.1 10.8
6585Q 3.8 2.6 2.1 bc 2.2 10.8
Nemastar 3.7 2.8 2.1 bc 2.1 10.7
Alforex 360 3.9 2.5 1.9 d 2.3 10.6
DKA44-16RR 3.5 2.7 2.1 bcd 2.2 10.6
Six Shooter 3.5 2.6 2.0 bcd 2.3 10.5
4C610 3.6 2.9 2.1 bc 1.9 10.5
6401N 4.2 2.5 1.9 bcd 1.8 10.4
Archer III 3.3 2.9 2.0 bcd 2.1 10.3
Gunner 3.7 2.6 2.0 bcd 1.8 10.2
Mean 3.7 2.8 2.1 2.2 10.8
Standard Error 0.19 0.23 0.08 0.22 0.35
P-value 0.22 0.22 0.04 0.73 0.14
Alpha 0.05 0.05 0.05 0.05 0.05

When selecting an alfalfa variety that is to be grown when irrigation water can be periodically limiting, it is important to consider the distribution of total yearly production by cutting. Normally the highest yields are obtained in the first cut, with yields declining in subsequent cuts. The percentage of each cut to total annual yield was calculated for each alfalfa variety tested in 2016. That information is presented in Table 4.

Table 4. Alfalfa Varietal Testing Results Reno, Nevada 2016: Percent of Total Yield
Variety 1st Cut (06/08/2016)
Percent of Total Yield
2nd Cut (07/13/2016)
Percent of Total Yield
3rd Cut (08/11/2016)
Percent of Total Yield
4th Cut (09/26/2016)
Percent of Total Yield
Total Yield
in Tons per Acre
Nimbus 35 26 20 19 11.8
Mutiny 33 27 19 21 11.3
DKA50-20RR 34 28 20 18 11.1
Cinch 35 27 19 19 11.1
Stratica 33 27 18 22 11.1
PG1427 36 27 19 18 10.9
6516R 34 27 19 20 10.8
4S417 36 25 19 20 10.8
6585Q 35 24 20 21 10.8
Nemastar 35 26 20 19 10.7
Alforex 36 37 23 18 22 10.6
DKA44-16RR 34 26 20 20 10.6
Six Shooter 33 25 20 22 10.5
4C610 34 28 20 18 10.5
6401N 40 25 19 16 10.4
Archer III 32 28 20 18 10.2
Gunner 36 26 20 18 10.2
Average 2016 35 26 20 19 10.8

Discussion

All of the tested alfalfa varieties produced heavy yields in this evaluation. The average yield in 2016 for the four-cut system was 10.8 tons per acre, with a range of 11.8 tons to 10.2 tons per acre.

All of the yields are higher than can be expected in a field production system due to minimal harvest losses as compared to those that occur under commercial production. Minimal respiration losses occur in this evaluation compared to when harvested alfalfa plants are drying in a windrow. Estimates of dry matter losses from these factors may be as high as 20 percent, but may be even higher when field drying time and leaf loss is excessive.

As expected, the first two cuts resulted in a majority of total yield for the season. These two cuts averaged 61 percent of the total for the season. The final two cuts were nearly equal in yields. It is assumed this was the result of the long, warm fall experienced in 2016 and the longer time between harvests (46 days) than the previous three cuts (approximately 30 days).

Producers reviewing these results should look at relative yields of each variety in combination with other factors, including fall dormancy, winter hardiness and pest resistance ratings, when making a choice about which variety best fits their farming operations.

Further references

1) Owens, M. 2013. Nevada Agricultural Statistics Bulletin 2013. United States Department of Agriculture, National Agricultural Statistics Service. Washington, DC. 53 pp.

2) Undersander, D. 2016. What Does Fall Dormancy of Alfalfa Really Mean? Hay & Forage Grower. Fort Atkinson, WI. February, 2016 p. 14-15.

3) National Alfalfa & Forage Alliance. 2016. Alfalfa Variety Ratings, Winter Survival, Fall Dormancy & Pest Resistance Ratings for Alfalfa varieties. 2016 edition. St. Paul MN. 8 pp.

4) SAS Institute Inc. 2013. SAS version 9.4. SAS Institute Inc., Cary, NC 2013.

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