Soybean Varieties for Forage Production

Trial Site: Fairview Research Farm

Research Coordinator: Dr. Akim Omokanye

From: Peace Country Beef & Forage Association 2017 Annual Report

Soybeans are a warm season annual legume that is grown mainly for the oil and protein value of their seed. Forage soybeans may be an option to consider. Forage soybeans are high in protein and highly palatable, and can be harvested for hay or silage. Seed varieties of soybeans can be used as forage. Harvesting soybeans for silage is preferred over baling as dry hay, because more dry matter is retained during harvest and storage. Soybeans may also be included in cocktail mixtures (with appropriate varieties). Agronomically, soybeans have the advantage of fixing nitrogen when properly inoculated, and do not require a lot of specialized equipment to grow. Crop species and variety choice for silage or greenfeed is one of the most important decisions any beef cattle producer makes.


Objective

To test and select soybean varieties for forage yield and quality for livestock production.


Methods

  • Project Site: Fairview Research Farm (NW5-82-3W6) on RR #35, MD of Fairview.

  • Previous crop: Oats for greenfeed in 2016 and 2015.  Site soil information (0-6” depth): Soil tests done at Exova laboratory (Edmonton) prior to seeding showed pH = 5.6 and soil organic matter = 8.0 %.

  • Experimental Design: Randomized complete block design in 3 replications in small plots (118.8 ft2 )

  • Nine Roundup Ready soybean varieties (see Table 1 below) were seeded on June 1, 2017 with a 6-row Fabro plot drill at 9” row spacing. Inoculated soybean seeds were used.

  • The field was cultivated (disked and harrowed) before seeding soybeans.

  • Fertility was 50 lbs/acre of 11-52-0.

  • Seeding rate was 222,672 seeds/acre (5.1 seeds/ft2 ).

  • Roundup was used for in-crop weed control twice.

  • Harvest for forage yield estimation and feed quality testing was done on September 11.

Results & Interpretation

Forage DM Yield

The forage DM yield was highest for Reson RR2Y2 with 7138 lbs/acre. Generally, all the soybeans tested had >5000 lbs/acre (2.5 tons DM/acre). The forage DM yields obtained for soybeans tested were generally lower than the forage DM yields obtained for the 4 forage-type peas tested this year (see report on forage type-legumes in this Annual Report). The soybean varieties tested here yielded 623-3602 lbs DM/acre less than the forage-type peas tested this year.


Forage Quality

The forage Crude Protein (CP) content varied from about 12% CP for Akris R2 to 16.8% CP for TH 35002. The forage CP met and in most cases far exceeded the protein requirements of growing and finishing calves (12-14% CP) as well as mature beef cattle (11%).


The forage Ca content was generally high for all soybean varieties tested and in all cases, the Ca requirements of young and mature beef cattle were exceeded.


Forage P varied from 0.17% P for Akris R2 to 0.28% P for both Starcity RR2X and Belmont RR2X. All varieties had enough P for a dry gestating beef cow, but only Starcity RR2X and Belmont RR2X were able to meet the P requirement of a lactating beef cow.


The S (except for Watson RR2Y and Leroy RR2Y), K, Mg, Zn, Mn (except Watson RR2Y) and Fe requirements of mature beef cattle were all met by the soybean varieties tested.


None of the varieties had adequate forage Cu or Na for mature beef cattle.


Forage energy content (total digestible nutrients, TDN) was mostly >65% for soybean varieties tested. All varieties conveniently met the TDN requirements of mature beef cattle, except for Akris R2, which just barely met this requirement.

Conclusion

Soybeans can be harvested as a hay or silage crop. The forage yield potential of soybeans can be as high as 3.6 tons DM per acre with the right variety for the area. Soybeans also appear to have high forage quality.

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