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

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.



Soil K - The surface soil K was higher for 'Bale grazing', 'Manure + subsoil in fall' and 'Mob grazing' than for other methods of rejuvenation in 2016 (Figure 4). Surface soil K was similar in both years for most methods of rejuvenation. In both years (2016 & 2017), the surface soil K was mostly higher than subsurface soil K.


Soil S - Except for 'Manure + subsoil in fall', which had - lbs S/acre in the surface and subsurface soils, other methods had 16 lbs S/acre or slightly less. Generally, soil S did not appear to change much at both soil depths from 2016-2017 (data not shown).


Forage Dry Matter (DM) Yield and Composition (Table 5)

The total DM yield differed significantly with respect to methods or rejuvenation in 2016 and 2017. In both years, the top 4 forage DM yields were from the treatments 'Bale grazing', 'Break & re-seed', 'Manure + subsoil in fall' and 'Mob grazing'. These top 4 had far more forage DM yield than Check in booth years. Most of the other methods did not significantly improve forage DM yield over Check. In both years, 'Bale grazing' had higher forage DM yield values than other methods. Over the 2 years (2016 & 2017), the mean forage DM yield from ' Bale grazing' as a % of check was up to 200%.


In both years, the total forage DM yield consisted of up to 89% grasses. The grass component of the forage yield was generally higher than legumes and other plants (mainly dandelions). 'Fall seeding with Agrowdrill' and 'Spring seeding with Agrodrill' seemed to have slightly higher forage legume content (particularly clovers, native vetches and alfalfa) than other methods.

Forage Quality Indicators (Table 6)

Crude protein (CP) - the forage CP was statistically similar in 2016, varying from about 9-12% for the methods of rejuvenation. In 2017, forage CP varied significantly from about 8% for 'Spring seeding with Agrowdrill' to 14% for 'Manure + subsoil'. of the 11 methods investigated, only 'Fall seeding with CD', 'Manure & subsoil in fall' and 'Mob grazing' appeared to consistently show some increases in forage CP from 2016 to 2017. Other methods had similar or indefinite trend from 2016 to 2017.


Minerals

Only 4 macro minerals measured in this study and their values are shown in Table 6. The forage Ca was similar in 2016 for all methods, but the forage CA did differ among some methods tested in 2017. The forage Ca content was about 0.30% and above for methods of rejuvenation in both years. Bale grazing was consistently higher in forage Ca than other methods in both years.


The forage P was similar for all methods in 2016, but differed in 2017 among some methods. From 2016 to 2017, no particular method consistently had higher forage P than another method including Check.


The forage Mg varied from 0.16-0.30% Mg for the different methods including Check in 2016. In 2017, the forage Mg varied from 0.13-0.24% Mg. For all methods, the forage Mg was either similar for both 2016 and 2017 or 2016 had higher value than 2017.


Similar to forage P and Mg, no particular method including Check consistently had higher forage K in 2016 than 2017.


Energy

The forage total digestible nutrients (TDN) and other forms of energy measured here are shown in Table 6. The forage TDN was similar for all methods in both years, indicating that the methods did not appear to improve forage TDN much during the study period. The forage TDN varied from 50.3-55.3% TDN in 2016 and from 57.0-61.5% TDN in 2017.


Other forms of energy measured here, particularly metabolizable energy (ME), net energy for lactation (NEL), net energy for maintenance (NEM) and net energy for gain (NEG), did not appear to be different among rejuvenation methods including Check in both years.

Site 2: Grovedale


Soil Quality Indicators

Soil pH and Soil Organic Matter (SOM)

As expected, the soil pH was not significantly affected by methods of pasture rejuvenation. The mean soil pH across methods of rejuvenation only varied from 6.69-6.95 for 0-6” soil depth in 2016 and 2017, and from 6.61-7.08 for 6-12” soil depth in 2016 and 2017.


‘Bale grazing’ appeared to have consistently higher SOM values from 0-6” soil depth than other methods of rejuvenation in 2016 and 2017. In 2017, ‘Bale grazing’ had 1.70 - 3.80% more SOM than other methods, including Check. As expected, generally SOM was higher in the surface soil than subsurface soil in both years for all rejuvenation methods investigated.

Soil Water Infiltration, Compaction and Soil Moisture (Table 8)

The soil water infiltration rate was greatly improved by ‘Subsoil in fall’ and ‘Break & re-seed’ in 2016. In 2017, the top 3 methods and their order with respect to water infiltration rate were: Subsoil in fall > (0.94 inches/ hour) > Bale grazing (0.77 inches/hour) >Break & re-seed (0.49 inches/hour). Infiltration rate generally increased from 2016 to 2017 for all methods (except for ‘Break & re-seed’ and ‘Subsoil in fall’). The greatest increase in water infiltration rate in 2017 over that of 2016 was recorded for ‘Bale grazing’. The rate at which water infiltrated into the soil was the same for ‘Subsoil’ in fall for both years.


In terms of mean soil compaction (average of 1-12” soil depths), only ‘Bale grazing’, ‘Subsoil in fall’ and ‘Break & re-seed’ seemed to reduce soil compaction over control in both years. The mean soil compaction was lowest for ‘Subsoil in fall’, followed by ‘Bale grazing’ and ‘Break & re-seed’ in that order for both years. Looking at soil compaction at different depths, ‘Subsoil in fall’, followed by ‘Break & re-seed’ had the least compacted soil from 1 to 12” soil depths (Figure 5). ‘Bale grazing’ also showed less compacted soil, particularly in the surface soil (0-6” soil depth, Figure 5).

The soil moisture content was similar for all methods in 2016, while ‘Bale grazing’, ‘Subsoil in fall’ and ‘Break & re-seed’ significantly improved soil moisture content in 2017. While ‘Bale grazing’ and ‘Subsoil in fall’ greatly improved soil moisture from 2016 to 2017 by 9.8% and 4.4% respectively, other methods had far less improvement in soil moisture.


Carbon : Nitrogen Ratio (C:N) (Table 8)

The C:N ratio of surface soil (0-6” depth) was similar for all methods in both years.

Soil Nutrients

Soil (Figure 6) - In both years, 'Bale grazing' consistently improved soil N in the surface soil more than other methods. In 2016, other than 'Bale grazing' (which showed higher soil N at 0-6" than 6-12"), other methods mostly had similar soil N at both depths. In 2017, 'Bale grazing', as well as 'Fetilizer application', 'Mob grazing' and 'Break & re-seed' seemed to have increased the amount of soil n in the surface soil more than subsurface soil. In 2016, subsurface soil N did not changee much with respect to methods investigated, but in 2017, 'Bale grazing', 'Fertilizer application', 'Mob grazing' and 'Subsoil in fall' had substantially increased subsurface soil N by up to 6-18 lbs/acre.

Soil P (Figure 7) - The soil P did not vary much in 2016 between the different methods. In 2017, 'Bale grazing' showed significant soil P improvement in both surface (0-6") and subsurface (6-12") soil depths, compared to other methods examined in this study. 'Bale grazing' has 24-36 lbs/acre more P than other methods in the surface soil. Generally, 'Bale grazing, 'Fertilizer application' and 'Mob grazing' showed more soil P in the surface soil in 2017 than in 2016. In both years (except for 'Bale grazing' in 2017), subsurface soil mostly had similar soil P values for any particular treatment.

Soil K (Figure 8) - Only 'Bale grazing' showed greater improvement in soil K over Check treatement in the surface soil in both years. The surface soil (0-6") mostly had higher soil K than subsurface soil (6-12") in both years.

Soil S - for some reason, Check appeared to have higher surface soil S in 2016 and 2017 than other methods (data not shown). Generally, the different methods did not show any consistent trend with respect to soil S from 2016 to 2017.


Forage Dry Matter (DM) Yield and Plant Composition (Table 9)

In both years (2016 & 2017), only 'Bale grazing' and 'Fertilizer application' showed far greater forage DM yield than Check. But in 2017, in addition to 'Bale grazing' and 'Fertilizer application', both 'Break & re-seed' and 'Mob grazing' also showed significant forage DM yield over Check. Across both years, the mean forage DM yield was highest for 'Bale grazing', followed by 'Fertilizer application' and 'Mob grazing', with their mean forage DM yields varying in excess of 704 to 2478 lbs/acre over Check.


In 2016, only 'Break & re-seed' and 'Spring seeding with Agrowdrill' appeared to show some higher proportion of grass plants in the total forage DM yield than Check. In 2017, both 'Bale grazing' and 'Break & re-seed' showed higher proportion of grass in the total forage DM than Check.


In all cases, the proportion of legumes in the total forage DM yield was <50%. in 2017, in both 'Bale grazing' and 'Break & re-seed' had the least amount of legumes in the total forage DM yield.

Forage Quality (Table 10)

Crude Protein (CP) - The forage CP in 2016 was very much similar for all methods, but in 2017, 'Bale grazing' by far had the highest forage CP over Check and all other treatments. In 2017, 'Bale grazing' increased forage CP by up to about 10% over Check and other methods. Other methods that showed significant forage CP improvement over Check in 2017 were 'Fertilizer application' and 'Mob grazing'.


Minerals (Table 10)

The amount of forage macro minerals (Ca, P, Mg and K) measured were not significantly different for the rejuvenation methods investigated here through out the study period.


Generally, across the different rejuvenation methods, the forage macro minerals (Ca, P, Mg and K) had higher mean values in 2017 than 2016.


Detergent Fibres & Non-Fibre Carbohydrates (NFC) (Table 10)

The forage detergent fibres (ADF & NDF) and NFC values were similar for the methods of rejuvenation tested including Check in 2016 and 2017.


Energy (Table 10)

The forage total digestible nutrients (TDN) and other forms of energy (NEL , NEG & NEM) measured here all showed similar forage values for the rejuvenation methods as well as Check in both 2016 and 2017 (except for NEM in 2017). Even for the forage NEM that showed some significant differences in 2017, most of the rejuvenation methods were still similar to some extent.

Discussion

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 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. The improvement strategies implemented in this study considered the seeding of new pastures, the regeneration of existing ones, and even the fertilization of existing pastures to demonstrate practical, sustainable forage production and low cost options with maximal success.


Soil Component (infiltration, compaction, SOM, moisture and soil nutrients)

One evaluation alternative for the implementation of these strategies is through the concept of soil quality proposed by Karlen et al. (1997): “the capacity of a specific kind of soil to function, within natural or managed ecosystem boundaries, to sustain plant and animal productivity, maintain or enhance water and air quality, and support human health and habitation”. This concept is determined by inherent and dynamic characteristics of the soil (Karlen et al., 2003), and is found valid when indicator parameters are present (e.g., air capacity, permeability, penetration resistance) that allows for evaluation of the level of soil quality (Reynolds et al., 2009; Horn and Fleige, 2009). In the present study, at both sites, in an effort to improve soil quality in order to make soil function and sustain plant and animal productivity, and enhance water uptake and retention (without breaking and re-seeding the existing pastures), bale grazing has consistently played a great role in all these.


Bale grazing improved SOM by up to 3.80% over other methods (including check), though bale grazing only appeared to show less compaction in the surface soil (0-6”), and not the subsurface soil (6-12”). Mob grazing, and to some extent Manure + subsoil in fall (site 1 only) also showed greatly improved SOM. Subsoil in fall, Manure + subsoil in fall, and Break & re-seed also consistently played significant roles in improving infiltration rate and reducing soil compaction over the study period.


The improvement in SOM by bale grazing in this study was not unexpected, as various studies in the same environment (Omokanye, 2013, 2014) and elsewhere [based on producers experience as indicated by Jerry Lindquist (Henke, 2017)] have reported similar observations. The SOM is critical for plant growth, and storing water. As observed here, previous studies by Omokanye (2013, 2014) also reported higher SOM in the surface soil (0-6”) than the subsurface soil (6-12”). In addition to the roles played by bale grazing in improving soil function, it is important to note that the combination of Manure + subsoil in fall may also be a strategy to enhance soil health, through improved SOM and infiltration rate, and reduced compaction. The observation from the present study with respect to SOM supports the fact that winter feeding through bale grazing on pasture is an excellent way to add organic matter to the soil. Later in the study (2017), Bale grazing, Subsoil in fall, Manure + subsoil in fall, and Break & re-seed all showed up to 34% higher soil moisture content in the surface soil (0-6”) than Check. The higher soil moisture value obtained over Check could be due to improved SOM and infiltration rate, and reduced compaction, which all helped to retain moisture for those methods of rejuvenation. As earlier indicated by Newport (2013), 2% SOM will hold 32,000 gallons of water (or 21% of a 5.5 inch rain), 5% SOM will hold 80,000 gallons of water (or 53% of a 5.5 inch rain) and every 8% SOM will hold 128,000 gallons of water (or 85% of a 5.5 inch rain).


In terms of soil nutrients (particularly N, P, K and S) at both sites, it is evident from this study that Bale grazing, Manure + subsoil in fall, Mob grazing and Fertilizer application have all shown great potential for improving soil N, P, K and S, compared to other methods including Check (see Figures 2-3 & 6-8 for soil N, P & K). This study also shows that at both sites in both years (2016 and 2017), the surface soil (0-6”) N, P and K was mostly higher than subsurface soil (6-12”). The consistently higher soil nutrients (particularly N, P and K) obtained in this study for both sites after Bale grazing, Mob grazing, Manure + subsoil in Fall, and Fertilizer application, compared to Check and other methods, indicate that for the purpose of improving soil nutrients as part of soil quality/health improvement, there were significant benefits. Therefore any of these methods would have potential to directly influence soil health on an old forage stand. As seen for Manure + subsoil in fall at site 2, it is evident that manure would be a valuable source of plant nutrients.


The findings with using Bale grazing, in particular, as a reliable rejuvenation strategy in this study further reaffirms the benefits of bale grazing in adding nutrients to the soil, as earlier reported in various studies across Western Canada including the Peace Country region (Jungnitsch et al., 2011; Omokanye, 2013 & 2014; Picard, 2010). With Bale grazing, through the residual feed/feed litter and manure accumulation, N is captured on the Bale grazing site and gradually becomes available, through litter decomposition and soil nutrient mineralization, for subsequent pasture production. As observed in the present study, Picard (2010) also reported that soil N, P and K levels increased dramatically in the surface soil of the soil profile within one year after Bale grazing. The present study as well as those of Omokanye (2013 & 2014) and Picard (2010) showed that those soil nutrients remain elevated in the surface soil profile but seem to be stabilizing or dropping with increasing years of forage growth and harvest, either as hay or pasture. As reported earlier for Bale grazing in the Peace Country of Alberta, residual soil N appeared to be moving through the surface soil to the subsurface soil profile within a few years after Bale grazing, indicating a potential for soil N leaching within the system. In the present study, generally, soil nutrients leaching from surface (0-6”) to subsurface (6-12”) soil profile tended to be very minimal.


The present study has also shown that Manure + subsoil in fall, Mob grazing and dry Fertilizer application would reliably improve soil nutrients, particularly in the surface soil profile (0-6”). This therefore, in addition to Bale grazing, provides producers with a wide varieties of strategies they can use for improving their soil nutrient conditions. These other methods may not have more lasting effects than Bale grazing.


Forage Production Component

Forage DM Yield

By increasing forage production on grazing land, higher stocking rates can be used and animal performance may improve, and increasing production on hay land reduces the cost of unit of production, which means reduced winter feed costs per cow (BCRC, 2016).


In this study, over the 2 years of data collection at both sites, the top 4-5 forage DM yielders were Bale grazing, Manure + subsoil in fall, Break & re-seed, Mob grazing and fertilizer application, with up to about 220% higher mean forage DM yield. Two years (2017) after the rejuvenation methods were implemented, Bale grazing (at both sites), Manure + subsoil in fall (site 1) and Fertilizer application (site 2) showed greater improvement in forage DM yield producing 1.5-2.0 tons DM/acre.


The higher forage DM yield produced across the years or in any particular year, could be attributed in part to some or most of the following parameters discussed above: improved soil physical conditions such infiltration rate, soil moisture and compaction; and soil nutrients (N, P, and K in particular). Overall, there is no doubt that Bale grazing would greatly produce far more DM yield than other rejuvenation methods tested here, at least within a few years after Bale grazing has been carried out.


Using Break & re-seed rejuvenation as a method to renew pastures does work well when conditions are favorable (e.g. weather and soil) and with the right management decisions (e.g. right forage mixture, seeding equipment and seeding date, history of site). However, Break & re-seed is a complex and costly challenge for producers. In this study, we did not get the anticipated results from Break & re-seed as a means of pasture renewal, in terms of forage DM yield at both sites. The Break & re-seed treatment was tilled and seeded in 2015, which was a dry year. The amount of rainfall and grasshopper infestation were thought to be responsible for the poor establishment of seeded forage mixture for Break & re-seed treatment. The forage DM yield reported here for the Break & re-seed treatments were only from areas in the field where pasture establishment was better.


In this study, when dry Fertilizer application (at site 2 only) was done as a method of forage stand rejuvenation, the result was impressive compared with Check and some other methods investigated. The resulting benefit from Fertilizer application was 727 lbs forage DM/acre in 2016 and 1786 lbs forage DM/ acre in 2017 over Check, indicating that the residual effect of fertilizer can last for a few years after application. As observed in the present study, research has indicated that fertilization can bring the productivity of a stand back to its original level without the expense of re-seeding (BCRC, 2016). Given the high fertilizer prices and poor margins in the cattle industry in recent years, many producers are hesitant to increase input costs. This is because higher yields do not necessarily translate into lower costs or increased profits (BCRC, 2016).


Seeding into existing pastures using no-till drill equipment as done in this study (Spring vs Fall using Agrowdrill and conventional drill) did not improve forage DM yield to a large extent over Check at both sites. The forage yield advantage from the no-till drill and seeding times was only up to 563 lbs DM/acre at site 1 and 853 lbs DM/acre at site 2. The failure could be attributed again to dry weather, and in particular the effect of competition from the existing vegetation.


Taking into consideration unpredictable weather conditions (rainfall in particular), competition of existing stands with newly seeded pasture using no-till drill (without spraying out the old forage stand), the high cost and loss of productive time that could be associated with forage stand termination and reestablishment, and the fact that one may not get the expected results because of various factors as noted in the present study, it is evident that Bale grazing could be identified as one of the best options for sustaining a forage stand.


Forage Quality Indicators

In the present study, taking into consideration that mature beef cattle require 11% CP, the resulting forages were mostly adequate for mature beef cattle (except on a few instances at site 1) in both years. At site 1, Fall seeding with Agrowdrill and Spring seeding with Agrowdrill were only able to meet the CP requirements of a dry gestating cow either in mid or late pregnancy. The lower forage CP obtained for Fall seeding with Agrowdrill and Spring seeding with Agrowdrill at site 2 is difficult to explain.


At site 1, except for Break & re-seed (in 2017), Fall seeding with CD (in 2016 & 2017) and Spring seeding with Agrowdrill (in 2017), all methods of rejuvenation had adequate forage Ca for mature beef cattle according to NRC recommendations (NRC, 1996, 2000). At site 2, in 2016, all methods exceeded the Ca needed by mature beef cattle. But in 2017, five (Check, Fall seeding and Spring seeding) of the 10 methods fell short meeting the Ca requirements of mature beef cattle.


At both sites the P and Mg requirements of mature beef cattle were not met by all methods tested in both years.


However, at both sites in both years (2016 & 2017), all methods had met and far exceeded the K requirements of mature beef cattle as suggested by NRC (1996, 2000).


Because of the inability or inconsistencies of any particular methods examined in this study to meet the complete macro mineral requirements of mature beef cattle, it therefore suggests that some form of mineral supplementation is needed for cows on pasture or when hay is being fed during fall, winter and early spring.


Except in a few instances at site 1, all methods of rejuvenation as well as Check had enough TDN for a dry gestating cow in mid pregnancy in 2016. In 2017, all methods had adequate TDN according to NRC (1996, 2000) recommended values for dry gestating cows in mid pregnancy, and only Manure + subsoil and Mob grazing met the 60% TDN needed by a dry gestating cow in late pregnancy. However, at site 2, most methods had enough TDN for dry gestating cows in mid and late pregnancy in both years. None of the methods at either site in any year was able to meet the TDN requirement of a lactating beef cow as suggested by NRC (1996, 2000).


In terms of the requirement for net energy for maintenance (NEM), all methods were well within the 1.19- 1.28 Mcal/kg for mature beef cattle, as well as the 1.08-2.29 Mcal/kg needed by young beef cattle as recommended by NRC (1996, 2000). But in terms of net energy for gain (NEG) needed by growing and finishing calves, all methods including Check were within the suggested 0.53-1.37 Mcal/kg at site 2, but not at site 1. At site 1, in 2016 only, Fall seeding with Agrowdrill and Spring seeding with CD just fell short of meeting the required NEG by growing and finishing calves.


Conclusion

Producing high quality forage and maintaining productive forage stands is a major challenge that Alberta’s beef producers encounter, as rejuvenation is a complex and costly challenge. With the high cost 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. In the present study, of the different methods investigated and in terms of soil health improvement (soil compaction, infiltration, soil moisture and nutrients particularly N, P and K), compared with Check, it is evident that Bale grazing, Manure + subsoil in fall, Mob grazing and Fertilizer application (positive effects on infiltration and compaction) have all shown great potential for improving soil conditions for pastures.


The top forage DM yielders were Bale grazing, Manure + subsoil in fall, Break & re-seed, Mob grazing and Fertilizer application. Their performance in terms of forage DM yield could be attributed in part to improved soil physical conditions such infiltration rate, soil moisture and compaction; and soil nutrients (N, P, and K in particular). Overall, Bale grazing produced far more DM yield than other rejuvenation methods tested here. Fertilizer application produced a yield advantage of up 1786 lbs forage DM/acre in 2017 over Check, indicating that the residual effect of fertilizer can last for a few years after application. Fertilizer application could be used to bring the productivity of a stand back, without the expense of re-seeding.


Manure is a valuable source of plant nutrients and organic matter and, when used as a fertilizer, will improve forage production and soil quality as seen with Manure + subsoil in fall method of rejuvenation. Forages offer an opportunity for manure application, though not all of the nutrients in manure are immediately available to the crop. The availability of manure nutrients depends upon the nutrient composition of the manure, method of manure application and weather conditions at the time of application. Nutrient availability must be estimated when determining the manure application rate.


Because of the inability or inconsistencies of any particular methods examined in this study to meet the complete macro mineral requirements of mature beef cattle, it therefore suggests that some form of mineral supplementation is needed for cows on pasture or when hay is being fed during fall, winter and early spring.


References

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