Assessing the Advantages of Using a Full-Season Cover Crop Blend for Forage Production and Soil Health in Alberta’s Peace Country Region
- 2 days ago
- 4 min read
Updated: 2 days ago
Funded by Covers & Co.
Introduction
Traditionally, cover crops are grown primarily to protect and improve soil health. Common examples include hairy vetch, peas, oats, barley, and brassicas such as radish and turnips. They can be planted as monocultures or species mixtures, offering benefits like erosion control, weed suppression, and enhanced soil structure. The effectiveness of cover crops often depends on the diversity and functional traits of the species used. In beef production systems, they also serve as valuable forage for cattle. Cover crops are categorized by growing season—either full-season or short 'shoulder season' types, which grow between the main crop's harvest and the next planting. These may include cool- or warm-season species, or a combination of both.
Objective
The objective of this field trial was to evaluate forage yield, nutritive value, and soil health impacts of a full-season cover crop blend (with and without dry fertilizer application) on a subsequent monoculture oat crop.
Methods
The project was carried out at the Fairview Research Farm (FRF). The experimental design was a randomized complete block design using three replications in small plots measuring 8 m x 1.14 m. Seeding was carried out using a 6-row Fabro Plot Drill equipped with disc-type openers on 23 cm row spacing, complete with mid-row banding.
In 2023, land was seeded to either a full-season cover crop blend or monocrop oats, and each of these treatments was further broken into either no fertilizer (0% application) or fertilizer at 100% of soil test recommendations.
In 2024, a monoculture of oats was seeded across all previous treatments, and no fertilizer was applied.
The monocrop oats were seeded at 300 plants/m².
The full-season cover crop blend was seeded at a rate of 60 lbs/acre
The full-season cover crop blend included:
Hairy vetch (4%)
Italian ryegrass (5%)
Spring triticale (3%)
Forage oats (23%)
Daikon radish (1%)
Berseem clover (2%)
Forage peas (25%)
Forage barley (20%)
Purple top turnip (1%)
Sorghum-Sudan (6%)
German millet (3%)
Flax (1%)
Sunflower (1%)
Non-GMO soybeans (3%)
Buckwheat (2%)
During the growing season, Normalized Difference Vegetation Index (NDVI) was measured using the handheld Trimble Greenseeker® Optical Sensor, which was placed at 31 cm above the plant canopy.
On July 30, 2024, four inner rows were harvested at the milk stage of forage oat using a custom-made self-propelled forage harvester.
Fresh forage was weighed and sub-samples (up to 650 g) were taken and dried for Forage Dry Matter content. The dried samples were shipped to A&L Laboratories, ON for feed quality analysis.
At forage harvest, soil infiltration was measured using the single-ring method and soil samples at 0-6″ were taken and shipped to the A&L Lab to evaluate soil health parameters.
Raw data was analyzed using the R statistical software (version 4.2.3) to determine how the different treatments impacted yield and soil health indicators.
In Field Observations
Oat plants took advantage of the precipitation received during the early growing season. The soil remained moist for most of the season resulting in better stand establishment and growth. The plots were void of weeds. We monitored the re-growth ability of oats after harvest, but unfortunately, plants did not produce sufficient biomass for a second cut.
Results (2024)
Forage Dry Matter (DM) of oat monocrop
The Forage Dry Matter yield of monoculture oats showed no significant difference between treatments (P>0.05). This ranged between 3,292 lb/ac for T1 (plots previously seeded to full-season cover blend with 100% fertilizer) and 3,004.6 lbs/ac for T4 (plots previously seeded to monocrop oats with zero fertilizer). Although not statistically significant, T1 tended to produce higher forage DM yields compared to T2, T3, and T4 (Figure 3), possibly due to the residual benefits of the full-season cover crop blend and fertilization in the previous season.
Forage Nutritive Value
The Forage Nutritional Value of the oat forage showed no significant differences in Crude Protein (CP), Total Digestible Nutrients (TDN), Relative Feed Value (RFV), Calcium, Potassium, and Magnesium between treatments (P > 0.05).
Phosphorus content varied across treatments:
T1 (full-season cover blend + 100% fertilizer): 0.25%
T2 (full-season cover blend + no fertilizer): 0.28%
T3 (monocrop oats + 100% fertilizer): 0.28%
Highest nutrient values by treatment:
T1 had the highest CP (14.3%), TDN (59.5%), RFV (100.7), and potassium (1.46%).
T2 had the lowest CP (13.7%).
The CP content is sufficient to meet the nutritional needs of all beef cattle categories.
The TDN content is only adequate for beef cattle in mid-gestation.
Soil health parameters of soil sampled at 0-3” in fall 2024
Soil biological properties varied significantly between treatments (P<0.05), except for nitrogen fixers.
Overall, T4 (previously seeded to monoculture oats with no fertilizer) exhibited higher levels of active carbon, CO₂ respiration, mineralizable nitrogen, Rhizobium bacteria, and total microbial activity compared to T1, T2, and T3.
Conclusion
Monoculture CDC Haymaker oats produced similar Forage Dry Matter Yield and nutritional values across all treatments (T1, T2, T3, T4), regardless of prior cover cropping or fertilizer use. While T1 (full-season cover crop with fertilizer) showed slightly higher forage yield and nutrient content, the differences were not statistically significant.
All treatments provided adequate protein to meet the needs of all cattle classes, though energy levels (TDN) may only be sufficient for animals in mid-gestation.
In this one-time rotation trial, T4 (previous monoculture oats with no fertilizer) demonstrated the highest soil biological activity, suggesting that even low-input systems can support strong soil health. So why higher in T4? T4 may have resulted in optimal conditions for microbial activity and nutrient cycling, particularly in this trial. However, it’s important to note that growing oats after oats is not a recommended best management practice due to the increased risk of disease and yield decline over time.
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