Research Coordinator: Dr. Akim Omokanye
Location: Fairview Research Farm
From: Peace Country Beef & Forage Association 2019 Annual Report
In northern Alberta, the latest trend among beef cattle producers is growing a multispecies annual crop mixture for forage production. Growing multi-species annual crop mixtures (4 to 6 or greater number of species) or annual crops sequences/intercrops may often be considered as a practical application of ecological principles based on biodiversity, plant interactions and other natural regulation mechanisms as well as improved soil C stocks. Such mixtures could increase forage production, improve water and soil quality, increase nutrient cycling, moisture conservation, and crop productivity. Cover crop species for cocktails can be selected from a diversity of plant categories, such as cereals/grasses, brassicas, legumes, and forbs/herbs, which correspond to different plant functional groups and traits (e.g., biological N-fixation, deep root system for nitrogen scavengers). Each crop species in a mixture may reach maturity at slightly different times, therefore providing available immature forage continuously through the growing season.
Objective
The objectives of the study are to:
1. Determine seeding rates that optimize forage production, while simultaneously maintaining diversity of species for maximum ecosystem benefits,
2. Explore the merits of ecosystem services provided by cocktails (e.g. nitrogen retention, soil organic carbon storage) and how they benefit agricultural systems, and
3. Determine the economic advantage of cocktails relative to cereal monocrops (controls).
We hypothesize that cocktails could 1) provide greater forage production and quality and 2) increase soil organic carbon stock and provide ecosystem services that are essential in mitigating environmental issues associated with northwestern Alberta soils.
Project Duration: (2019-2021) This is a 2-year project, which started this year with the final crop season in 2020. Only the highlights of the project are presented here. The full report will be available in 2021.
Methods
Experimental Site: Fairview Research Farm (NW-5-82-3 W6M) on RR #35, MD of Fairview. The previous crop at the site was an alfalfa hay crop for several years until the Fall of 2018. In the Fall of 2018, the site was sprayed with Roundup at 1.0 L/acre (to kill the existing alfalfa dominated vegetation) and plowed. The site was disced & harrowed in the spring of 2019.
Soil analysis completed in the Fall of 2018 from 0-6” showed an organic matter content of 8.2%, pH of 6.2 and an electrical conductivity of 0.21 ds/m. The soil test reports showed 10 lbs N/acre, 14 lbs P/acre and 485 lbs K/acre as well as 9 lb S/acre. Spring soil moisture at seeding: 12.3% (0-5 cm soil depth) and 13.6% (0-20 cm soil depth). Spring soil temperature a Seeding: 9.48°C (0-5 cm soil depth) and 8.09°C (0-20 cm soil depth).
Experimental Design: Factorial design (9 x 3 with 4 replications) with the following treatment factors:
1. Cover crop treatments (9 in total – see Tables 1 and 2 below):
2. Seeding rates (3): The cover crop treatments are to be seeded at:
a) Recommended monoculture seeding rate (normal rate, N)
b) 125% monoculture seeding rate (125)
c) 150% monoculture seeding rate (150)
A substitutive approach (i.e., proportional replacement design) was used, such that seeding rates for each species in the mixture was proportional to their recommended monoculture seeding rate. The seeding rates for individual species in the mixture was then determined by dividing each recommended seeding rate by the total number of species in the mixture (e.g., divide by 4 for the 4 species mix).
Seeding date was on May 24. The seeds were sown using a Fabro plot drill equipped with disc-type openers on 9” row spacing. Six rows that were 8 m long were sown per plot. Seeding depth was 0.75”. No fertilizer was applied. All legumes were inoculated at seeding.
Pre-emergent herbicide with StartUp (Glyphosate, 540 grams acid equivalent per litre, present as potassium salt) was applied at 0.67 L/acre. StartUp is a water soluble herbicide for non-selective weed control.
Harvesting for forage dry matter (DM) yield determination was completed on August 29. Forage samples were shipped to A & L laboratory, Ontario for forage quality determination and nitrate-N. Rainfall received from seeding to forage harvest was 184.7 mm (or 7.27”) which was comparable to 189.9 mm (7.48”) for the long-term average for the same period.
Data collection in 2019:
Soil health & nutrients (before seeding and after forage harvest)
· Soil pH, organic matter and nutrients (including soil inorganic N concentration [the sum of ammonium (NH4 +) and NO3–]) from 0-15 & 15-30 cm soil depths
· Retention of N (i.e., the prevention of NO3– leaching)
· Potential aboveground biomass N contributed to the agroecosystem
· Soil organic C stock and sequestration rates
Crop growth and forage production
· Canopy normalized difference vegetation index (NDVI) with GreenseekerTM sensor
· Assessment of nodulation in legumes during flowering
· Forage botanical composition - proportion of each crop in the cocktail
· Forage yield & quality (including selenium and nitrate). Harvesting for forage dry matter (DM) yield determination was done on August 29. Forage samples were shipped to A & L laboratory, Ontario for forage quality determination and nitrate-N.
Some Preliminary Results
Forage DM Yield
The forage DM yield varied from 4,620-10,287 lbs/acre for the cocktail X seeding rates treatments (Table 3). Four of the top cocktail by seeding rates treatments with >90,000 lbs/acre came mostly from cocktails with 125% seeding rates (i.e. barley seeded at 125%, 2 species seeded at 125%, 5 species seeded at 125%). In terms of seeding rates effect on forage DM yield, overall, seeding at 125% of the cocktail seeding rates seemed to have potential to produce higher forage DM yield than N (normal) and 150% seeding rate.
Forage Quality
The forage crude protein (CP) generally varied from 8.10% for barley X N seeding rate to 13.7% for 7 species X N seeding rate (Table 3). Overall, the forage CP appeared to be similar for the 3 different seeding rates within each cover crop treatment. All cover crop treatments including both barley (except barley–N) and oats monocultures had sufficient CP for a dry gestating beef cow. For a lactating beef cow, the 7-way species cocktail mixtures consistently exceeded the 11% CP needed by this category of mature beef cattle.
Five of the cover crop cocktail X seeding rate treatments (oats-N, oats-125%, 3 species-125%, 5 species-150%, 6 species-150%) had 70.0% TDN or more compared to others with 65.9 - 69.5% TDN (Table 3).
The forage Ca content varied from 0.18% for barley X N seeding rate to 0.80% for 5 species X N seeding rate. With the exception of 5 species X N seeding rate, which had >0.58% forage Ca, none of the cover crop treatments were able to meet the 0.58% Ca needed by lactating beef cows. However, for dry gestating beef cows that require 0.18% Ca, other cover crop treatments mostly far exceeded the 0.18% Ca needed by pregnant cows. All cover crop treatments including the cereal monocultures had sufficient P for pregnant cows, but only 2 cover crop treatments (2 species X 150% seeding rate and 7 species X N seeding rate) showed adequate amount of P for nursing beef cows. The forage K was generally adequate for mature beef cattle.
Except in a few cases, both forage Mg and Na were able to meet the requirements of pregnant and lactating beef cows. The only exception was with 5 species X N seeding rate, which fell short of meeting mature beef cattle Na requirements.
Forage Nitrate-N
The nitrate-N (%N03-N) levels varied from 0.00-0.03% for cocktail by seeding rate treatments (Table 3). Looking at Table 4 below, all tested cocktail X seeding rate treatments would be considered generally safe for beef cattle.
