Trial Site: Fairview Research Farm
Research Coordinator: Dr. Akim Omokanye
From: Peace Country Beef & Forage Association 2016 Annual Report
Soybean plants may be grazed or harvested from the flowering stage to near maturity for use as high-quality hay. Soybeans may also be grown as a silage crop in pure culture or 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 important decisions any beef cattle producer makes. The objective of this trial was to test and select soybean varieties for forage yield and quality for livestock use based on local growing conditions.
Methods
Site used was the Fairview Research Farm (NW5-82-3W6) on RR #35, MD of Fairview. The site had oats planted for greenfeed in 2015. The soil test at 0-6” soil depth done at Exova laboratory (Edmonton) prior to seeding showed an organic matter content of 7.1%, a pH of 5.5 (acidic) and an electrical conductivity of 0.35 dS/m. The field was cultivated before seeding.
Demonstration strip design was used in small plots measuring 11.04 m2 (118.8 ft2).
10 Roundup ready soybean varieties (see Table 1) were seeded on May 18, 2016 with a 6-row Fabro plot drill at 9” row spacing. Inoculated soybean seeds were used.
Fertility was 40 lbs/acre of 11-52-0. Seeding rate was 222,672 seeds/acre (5.1 seeds/sq ft).
Roundup was used for in-crop weed control once. Hand weeding took place twice.
Notes were taken on seedling emergence, flowering, lodging and plant height. Crop harvest for forage yield estimation and feed quality test was done on August 25, 2016.
Results
Forage Moisture (Table 1)
The forage moisture content at harvest of standing soybean forage (on August 25, 2016) varied from 64-70% and at this stage the varieties were within the 65% moisture for ensiling.
Forage DM yield (Table 1)
The forage DM yield was highest for Vito (6167 lbs DM/acre). Only 4 (Vito, TH 330033, Mammoth R2 and Agris R2) out of the 10 soybean varieties tested produced 5600 lbs DM/acre or more.
Forage Quality
The forage protein (CP) content varied from 15-25% for soybean varieties tested here (Table 1). Only 3 (Alotus R2, Mcleod R and Pekko R2) out of the 10 varieties had <20% CP, others had 20% CP or more. The forage CP far exceeded the protein requirements of growing and finishing calves (12-13% CP) as well as mature beef cattle (11%).
The forage Ca and P were generally high for all soybean varieties tested. Comparing the forage mineral values obtained in this study with beef cattle (young and mature) mineral requirements, only Na and Cu requirements were not met by any of the soybean varieties tested. Other mineral requirements by beef cattle were met by all soybean varieties.
Forage energy content (TDN) was >60% for all varieties and this was sufficient for cows in the mid- and late- pregnancy stages, but only 6 varieties had adequate TDN for a lactating cow (65% TDN) (Table 2).
Conclusion
Soybeans can be harvested as a hay or silage crop. By August 25, 2016, when the varieties were harvested, all varieties were within the 65% moisture content for ensiling. The forage yield potential of soybeans can be as high as 3.1 tons DM per acre. We observed that soybean forage varieties are similar to most legumes, making soybeans a good forage if harvested properly and at the right stage of maturity.