Forage Productivity and Ecosystem Services of Silvopasture Systems

Funded by Rangeland Sustainability Program, Government of Alberta

Collaborators: Kelvin Krahn, Beef Cattle Producer, High Prairie

Forestry and Parks, Government of Alberta

Silvopasture is the intentional combination of trees, forage, and livestock managed as a single integrated practice to transform farmland into a resilient, high-yield ecosystem. This system has the potential to provide multiple benefits to livestock and the plant community, such as providing shade for livestock, expanding pasture acreage and diversity, increasing carrying capacity and forage yields while reducing water consumption, and cost-effective vegetation control.  To evaluate these and other benefits, a field trial was started in 2024 on a beef cattle producer’s farm across three silvopasture systems: an Open System (no tree canopy), a Semi-Closed System (approximately 50% canopy), and a Closed System (full canopy).

Objectives

The objectives of the trial were to evaluate the effects of three silvopasture systems on:

• Forage Dry Matter (DM) yield and nutritive value.

• Livestock performance, measured by body condition scores, weight and temperament.

• Soil health indicators such as carbon sequestration, Total Organic Carbon (TOC), Total Nitrogen (TN), Total Carbon (TC), and soil infiltration rates.

  
  

Methods

Before the implementation of the three silvopasture systems, the following baseline measurements were taken in 2024 for each system:

• Soil sampling (0-15 cm and 15-30 cm depths) and analysis for soil nutrients, TN, TOC, TC, and carbon sequestration.

• Soil infiltration (single-ring method), compaction, moisture and temperature.

• The systems were assessed for the botanical composition of individual plant species in collaboration with experts from Forest Range Health Assessment (Government of Alberta).

• Measurements just before introducing cows for grazing include weekly visits to the site for:

  • Determination of forage DM yield and nutritional value. This aided in DM yield estimates and nutritional value analysis lasting for 3 weeks. 

  • Each paddock had a watering system with a gauge which monitored the weekly water consumption. 

  • Soil moisture and temperature using the FieldScout TDR (Time Domain Reflectometry)-350.

  • Five selected cows were monitored for their temperament and scored from 0-2 (i.e., 0 is good condition, 1 is compromised condition, and 2 is poor condition) twice weekly. The body condition scores of cows were noted before and after grazing.

All forage and soil samples for baseline and subsequent measurements were sent to the A&L Laboratory (Ontario) for analysis.

Grazing Schedule (3 weeks duration)

First Grazing Week

• Grazing of paddock 1 in the Closed, Semi-Closed, and Open Systems started on June 21 with 35, 75, and 45 cow-calf pairs, respectively.

  
  

 Second Grazing Week

• Grazing of paddock 2 in the Semi-Closed and Open Systems commenced on June 28 with 35 cows and 110 cow-calf pairs, respectively. However, the Closed System was re-fenced into a smaller paddock to accommodate only 3 cows. This strategy was needed by the producer for the Closed System to avoid missing the oestrus cycle of cows.

  
  

Third Grazing Week

• Grazing of paddock 3 in the Closed, Semi-Closed, and Open Systems began on July 7 and ended on  July 13 with 3 cows, and 35 and 110 cow-calf pairs, respectively.

  
  

Data analysis

The raw data collected during the 2024 season were analyzed with R Statistical Software (version 4.2.3) using the Analysis of Variance (ANOVA) program.

In Field Observations

Figure 1. Producer partaking in sampling

Figure 2.  Grazing cows in Semi-Closed System

Preliminary Baseline Outcomes for the Grazing Season

Dry Matter Yield 

The baseline forage DM yield from the experimental paddocks varied from 874 for the Closed system to 3,112 lbs/acre for Open system, with an average of 2,132 lbs/acre. The Open System produced 2,200 and 701 lbs/ac more DM than both the Closed and Semi-Closed Systems, respectively (Table 1).

Forage Nutritive Value and Mineral Concentration

• No significant differences in CP, NDF, ADF, TDN, and RFV. (Table 1)

• NDFD48 varied among the three systems.

• Calcium (Ca) content was different for the systems:

  • Highest in the Open System (0.88%).

  • Similar levels in the Closed and Semi-Closed Systems. (Table 1)

• No differences in P, K, Mg, and Na across the systems.

Soil Carbon Sequestration

The average baseline of carbon (0-30 cm) accumulated in the grazing systems showed high carbon in the Open System, approximately 3,700 and 1,872 lbs/ac more than Semi-Closed and Closed Systems, respectively (Figure 3). By comparing the Semi-Closed and Closed Systems, it was apparent that the Closed System sequestered more soil carbon than the Semi-Closed system.

Figure 3. Baseline carbon sequestration within 0-30 cm soil depth under three grazing systems.

Behaviour Monitoring and Scoring

First Week:

• No cases of lameness, bloat, nasal or ocular discharge, or persistent cough.

• All cows in good health (score 0) across all systems.

• Open System cows grouped during the day due to high temperatures (avg. 15°C), reducing daytime forage intake but increasing evening grazing. (Figure 4)

• Closed and Semi-Closed System cows grazed freely throughout the day and ruminated under trees.

Figure 4. Average body temperature of cows under the three grazing systems during the 3-week trial.

Second Week:

• No signs of bloat, ocular/nasal discharge, or persistent cough.

• All cows remained healthy (score 0), except one bull in the Closed System, which was lame.

• Open System cows grazed less, but drank more water (avg. 23°C).

• Closed and Semi-Closed System cows sought shade under trees, with some grazing during the hot afternoons.

  
  

Third Week:

• At 30°C, Open System cows drank more water, but appeared restless. (Figure 5)

• Closed and Semi-Closed System cows continued grazing and sought shade under trees.

• Overall, all cows remained healthy (score 0) with good overall welfare.

Figure 5. Water consumption by cows during the third week of the grazing

Conclusion

Please note that these are baseline results of the three grazing systems. A clearer comparison of effects of the systems will be captured in subsequent years (2025 and 2026). However, we conclude based on our results that:

• The Open System had the highest DM yield, followed by the Semi-Closed and Closed Systems.

• No differences were observed in the nutritive values evaluated, except for NDFD48 and calcium contents, where the Open System had the highest calcium and the Semi-Closed System had the highest NDFD48.

• Soil carbon sequestration was higher under the Open System compared to both the Closed and Semi-Closed systems.

• Though beef cattle in all systems were healthy, their body temperature was higher for those in the open systems, and they also consumed more water compared to the rest.