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Evaluation of pasture rejuvenation methods to determine the most effective & profitable method

Updated: Jan 29, 2021

Collaborators: Soames Smith (Rycroft) and Bill Smith (Grovedale)

Funding Received from: Alberta Crop Industry Development Fund (ACIDF)

Supported by: Agriculture Opportunity Fund (AOF), Alberta Agriculture & Forestry, MD of Greenview, and MD of Spirit River

Research Coordinator: Dr. Akim Omokanye

From: Peace Country Beef & Forage Association 2017 Annual Report


According to a recent report by Statistics Canada (2014), Alberta, with its vast rangelands and plentiful feed supply, dominates Canada's beef production. The 2011 Census of Agriculture by Statistics Canada (2012) showed that Alberta accounted for about 40% of the national cattle herd, with pasture land accounting for 43% of total farm area in Alberta. Cow-calf producers know that grazing on productive pastures can be very profitable. However, over time, the productivity and livestock carrying capacity of seeded hay fields and pastures on beef cattle operations may decline, largely a result of reduced stand vigor, consequence of drought, pests, weeds, the invasion of unpalatable or less productive species, overgrazing and poor soil fertility. Producing high quality forage and maintaining productive forage stands is a major challenge that Alberta’s beef producers encounter. Rejuvenation is a complex and costly challenge for producers. With the high costs and loss of productive time associated with forage stand termination and re-establishment, producers are anxious to identify all options for sustaining a forage stand.


Producers’ questions in the Peace and elsewhere on forage-stand rejuvenation methods always include: How much more forage does a re-seed produce? How will I gain from forage stand rejuvenation? Where will I see the benefits of forage stand rejuvenation? Which re-seeding methods and what seeding equipment should I use? How can I reduce soil compaction and improve soil health conditions, as well as improve water infiltration? Can I seed in fall instead of spring? Are there studies comparing emerging new ideas of methods of rejuvenation to already established methods?


Recent on-farm studies in parts of the Peace region of Alberta identified high soil compaction, reduced soil water infiltration, and low legume content as factors affecting the condition of forage stands (Omokanye, 2015). With these factors, consequently, the profitability of the beef cattle industry is negatively affected. Though different methods of rejuvenation have been examined in Western Canada (e.g. Jungnitsch et al., 2005; Nazarko, 2008; AARD, 2013) and the USA (e.g. Undersander et al., 2001), most of these studies have only examined a few methods at a time. Local on-farm research is needed to compare all, or at least most, of the practical methods of rejuvenation to determine the most effective and profitable methods for producers in comparison to a complete break and reseed scenario. To answer producers’ questions, the present project looked at a dozen methods of rejuvenation of depleted forage stands at two locations in the Peace.


Specific Objective

The objective of this project is to examine various methods of forage stand rejuvenation and types of equipment in an effort to demonstrate practical, sustainable forage production and low cost options with maximal success.


Methods

The project was carried out on-farm from 2015-2017 at the following cow-calf producers’ farms in the Peace River region:

Site 1 is at Uddersmith Dairy- Soames Smith (organic beef farm), near Rycroft.

Site 2 is at Bill Smith’s (conventional beef farm) in Grovedale.


Old pastures were used at both sites. Before the trial commenced in 2015, the sites had been sown to forage mixtures (which included alfalfa & meadow brome), more than 15 years before. The sites had declined in productivity over the years.


The methods of pasture rejuvenation that were examined were established using a Randomized Complete Block Design (RCBD) with three (3) replications at each site. Each treatment plot was about 0.25 acres in size making it approximately 10 acres (including gaps between treatment plots and replicates) at each site.


All the treatments were implemented in 2015. The methods of pasture rejuvenation that we evaluated at the sites are provided in Table 1. Descriptions of each treatment have also been provided (see Table 1).


The forage mixture seeded consisted of 60% smooth brome grass, 10% cicer milkvetch and 30% alfalfa, making it a 60:40 grass-legume ratio.

In spring 2015, prior to treatment implementation, baseline data was collected. Soil nutrients and quality were determined at both sites from May 30 - June 4, 2015. Forage yield and quality, plant composition/ proportion, soil moisture content, soil compaction readings, and water infiltration rate were measured.

Part of the initial soil analysis, which was carried out at EXOVA (Edmonton), consisted of soil particle size analysis, soil texture and base saturation %. This was carried out at both sites in June 2015, from 0-6” at random spots across the entire field prior to any treatment implementation, shown in Table 2. The base saturation (BS,%) is the % of the cation-exchange capacity (CEC) occupied by the basic cations Ca2+, Mg2+ and K+ . CEC is a measure of how many cations can be retained on soil particle surfaces. CEC affects many aspects of soil chemistry, and is used as a measure of soil fertility, as it indicates the capacity of the soil to retain several nutrients in plantavailable form.

Measurements from 2016 to 2017:

  1. Forage yield and quality, and forage botanical composition For the proportion of plant type and forage yield - the stand composition of different forage species, varieties and other plants will be determined from 1 m x 1m quadrat areas (randomly placed at several locations), and clipped at a height of 3-4 inches above the soil surface. Forage biomass yield from several large areas (long and wide strips) will be determined by using conventional hay making methods and equipment. The goal of sampling a large area is to collect a sample that provides good representation for the entire area as well as to reduce sampling error. Forage quality (including trace minerals) from dry composite forage samples will be determined by A & L Canada Laboratory Ltd, a commercial laboratory in Ontario using standard AOAC approved laboratory methods for wet chemistry and NIR

  2. Soil health indicators

  • Soil compaction readings from 1 to 12 inches using a digital penetrometer

  • Surface soil water infiltration rates determined using the ring method (Nicholas, 2004)

  • Soil nutrients, pH & organic matter from 0-6” & 6-12”

  • Carbon & N and C:N ratio from 0-6” soil depth.

Field notes on the initial pasture assessments and seeding establishment success were taken. Establishment success was determined by observing unseeded treatment compared to seeded area for plant counts, DM yield and forage quality.

Results

Site 1: Rycroft


Soil Quality Indicators

Soil pH and Soil Organic Matter (SOM) (Table 3)

The soil pH values did not change drastically for any of the rejuvenation methods over the 2 years. The mean soil pH across rejuvenation methods was similar for both years (6.90 vs 6.95).


In 2016, the surface SOM appeared to be generally slightly higher for the ‘Manure + subsoil in fall’ and ‘Break & re-seed’ methods. In 2017, ‘Bale grazing’ and ‘Manure + subsoil in fall’ had slightly higher surface SOM than other rejuvenation methods. Some rejuvenation methods did not show any significant increases in SOM from 2016 to 2017. Only ‘Bale grazing’ and ‘Mob grazing’, and to some extent ‘Manure + subsoil in fall’, appeared to show some potential for slight consistent increases in surface SOM from 2016 to 2017. SOM increased up to 1.1% for ‘Bale grazing’, 0.5% for ‘Manure + subsoil in fall’ and 0.85% for ‘Mob grazing’. Generally, the surface soil had higher SOM values than subsurface soil for all treatments in both years.

Soil Water Infiltration, Compaction and Soil Moisture (Table 4)

In 2016, the soil water infiltration rate was higher for ‘Subsoil in fall’, ‘Manure + subsoil in fall’, ‘Bale grazing’, ‘Fall seeding with Agrowdrill’, ‘Break & re-seed’ and ‘Mob grazing’ than other rejuvenation methods examined. In 2017, the 2 deep tillage treatments (‘Subsoil in fall’, ‘Manure + subsoil in fall’) and ‘Break & re-seed’ appeared to have far higher infiltration rates than other rejuvenation methods tested here. Overall, ‘Subsoil in fall’, ‘Manure + subsoil in fall’, ‘Break & re-seed’, and ‘Bale grazing’ seemed to consistently infiltrate more water through the surface soil, even after 2 years of implementing those rejuvenation methods.


As observed for soil infiltration rate, across the different rejuvenation methods, mean soil compaction in 2016 and 2017 appeared to be consistently improved with the ‘Subsoil in fall’, ‘Manure + subsoil in fall’, ‘Break & re-seed’, and ‘Bale grazing’ methods more than other methods. In 2016, ‘Break & re-seed’ had the least compacted soil, while in 2017, both ‘Break & re-seed’ and ‘Bale grazing’ had the least mean compaction values (Table 4). Over the 2 years, the mean soil compaction at 0 to 12” soil depth for each rejuvenation method showed that ‘Subsoil in fall’, ‘Manure + subsoil in fall’, ‘Break & re-seed’, and ‘Bale grazing’ were consistently less compacted than other rejuvenation methods (Figure 1). ‘Break & re-seed’ had the least compacted soil up to 12” depth.


Soil moisture seemed to be statistically similar for all rejuvenation methods in 2016. But in 2017, ‘Bale grazing’ had significantly higher soil moisture than the other methods (Table 4). Overall, in 2017, ‘Bale grazing’, ‘Subsoil in fall’, ‘Manure + subsoil in fall’, and ‘Break & re-seed’ had 10-34% higher soil moisture content than check. Other treatments had lower soil moisture content than check.


The C:N ratio of surface soil (0-6” depth) was statistically similar for all rejuvenation methods and only ranged from 11.1 to 12.4 in 2016. In 2017, the C:N ratio showed significant differences with respect to rejuvenation methods, and this varied from 10.7 for ‘Break & re-seed’ to 13.3 for ‘Fall seeding with Agrowdrill’ (Table 4).

Soil Nutrients

Soil N - In 2016, in the surface soil (0-6"), N was greatly improved by 'Mob Grazing', followed closely by 'Bale Grazing'. 'Mob Grazing' exceeded other methods, including 'bale grazing', by 38-124 lb N/acre 9Figure 2). On the other hand, 'Bale Grazing' improved soil N by up to 86 lbs/acre over other methods (excluding 'Mob Grazing'). In 2017, 'Bale Grazing' had the most soil N in the surface soil, followed by 'mob grazing', and then 'Manure + subsoil in fall'. Except for 'Break & re-seed' in 2-16 and 'Manure + subsoil in fall' in 2017, the subsurface soil generally had lower soil N than surface soil.


Overall, 'Bale grazing', 'Manure + subsoil in fall', 'Mob grazing', and to some extent 'Rest', have all shown some potential for improving soil N, compared to other methods. The greatest improvement in subsurface soil appeared to be from 'Bale grazing' and 'Mob grazing' in 2017.


Soil P - The surface soil P was consistently higher for 'Bale grazing', 'Manure + subsoil in fall' and 'Mob grazing' compared to other methods of rejuvenation (Figure 3). In 2016, 'Manure + subsoil in fall' had the most surface soil p, while in 2017, 'Bale grazing' showed higher surface soil P value. In 2016, surface soil had more soil P than subsurface soil. In 2017, in most cases, surface soil P was similar or slightly higher than subsurface soil P.


In general, across the 2 years, 'Bale grazing', 'Manure + subsoil in fall' and 'Mob grazing' all increased soil P more than other methods.