Project Site: Wanham Provincial Grazing Reserve
Research Program Manager: Dr. Akim Omokanye Collaborators: Dianne Westerlund, Lekshmi Sreekumar From: Peace Country Beef & Forage Association 2018 Annual Report
In pastures, weeds and shrubs or brush encroachment can be a serious problem, and can be difficult to control. Controlling weeds and brush in pastures will restore pasture health and productivity, and improve and sustain forage quality. Rejuvenation can be a pasture management strategy for rapid improvement of existing and/or depleted forage stand/pasture that can bring new vigor or usefulness to a pasture and thereby restore it to its original state (Acharya, 2015; Schellenberg, 2016). Breaking and reseeding old forage stands is the traditional method of pasture rejuvenation (Waddington, 2017), but this can be a complex and costly challenge, as well as time consuming for producers (Omokanye et al., 2018; Waddington, 2017). The high costs associated with the traditional method has encouraged producers to search for alternative strategies and technologies for improving and sustaining pastures. The objective of this study was to investigate several methods of pasture rejuvenation to enable a proper assessment of different methods on-farm.
An on-farm study was conducted from spring 2016 to summer 2018 at Wanham Provincial Grazing Reserve. The soil at the site from 0-6” depth had the following: organic matter = 10.7%, pH = 6.3, electrical conductivity = 1.85 dS/M, nitrate-N = 16 lbs/acre, P (Bray 1-P) = 76 lbs/acre, K = 1200 lbs/acre and sulphate-S = 28 lbs/acre. The initial soil N was considered deficient for yearly forage production.
The treatments (pasture rejuvenation methods) were arranged in a randomized complete block design with 3 replications. Plot size was 90 feet x 420 feet (0.87 acres). The following 11 pasture rejuvenation methods were evaluated:
1. Check (control) - no treatment was done.
2. Broadcast forage seed mixture + aerate/spike in spring (BSAS) - Broadcast seeded forage seed mixture at 19.4 lbs/acre on June 8, 2016.
3. Broadcast forage seed mixture + aerate/spike in fall (BSAF) - Broadcast seeded forage seed mixture at 19.4 lbs/acre on October 5, 2016.
4. Aerate/spike in fall (AF) - AerWay® land renovator was used on October 5, 2016.
5. Aerate/spike in spring (AS) - AerWay® land renovator was used on June 8, 2016.
6. Spray GrazonTM herbicide in spring (GRAZON) - GrazonTM XC was sprayed on June 12, 2016 at 2.5 L/acre.
7. Fertilizer application (FERT), lbs/acre - Broadcast fertilizer at 77 lbs N/acre + 37 lbs P/acre + 13 lbs S/acre on June 6, 2016. The initial soil tests showed sufficient amount of K in the soil, so no K fertilizer was applied.
8. Spray herbicide + direct seed forage in spring (RSS) - Sprayed Roundup at 1.5 L/acre on May 30, 2016. Seeded forage seed mixture at 15 lbs/acre on June 7, 2016.
9. Spray with herbicide in fall & broadcast forage seed mixture the following spring (RFBSS) - Sprayed Roundup at 1.25 L/acre on August 30, 2016. Broadcast seeded forage seed mixture at 19.4 lbs/acre on May 19, 2017.
10. Spray herbicide only in spring (ROS) - Sprayed Roundup at 1.25 L/acre on May 30, 2016.
11. Broadcast forage seed mixture only in Spring (BSS) - Broadcast seeded forage seed mixture at 19.4 lbs/acre on June 8, 2016.
The forage seed mixture used consisted of 40% hps® brand meadow bromegrass, 35% hps® brand orchardgrass, 20% hps® brand regular blend alfalfa and 5% grindstad timothy. Seed broadcast was done with an all-terrain vehicle (ATV) mounted broadcast seeder/spreader (Model GT-77; Herd Seeder Company, Inc., Logansport, Indiana, USA) that covered 7.32 m in width. Direct seeding was done with a John Deere 1590 drill, 4.6 m in width and 19.1 cm row spacing. Where seed was broadcast (treatments 2, 3 & 11), seeding rate was 30% higher than drilling rate. For both treatments 4 & 5, the AerWay® poked the surface soil to a depth 6-8 cm at regular intervals. Roundup WeatherMax® was used for the Roundup herbicide.
Forage botanical composition (% grass and % legume), forage dry matter (DM) yield and quality were determined from on June 6, 2016 (base data); June 22, 2017 and June 21, 2018. The forage quality parameters (% DM basis) were determined in a commercial laboratory (A&L Canada Laboratories Inc., London, Ontario).
The collected data (forage composition, yield and quality) were analyzed on a yearly basis using the GenStat statistical package (2009, 12th Edition). Where ANOVA indicated significant treatment effects, the means were separated by the least significant difference (LSD) at the 0.05 probability level.
Generally, before treatments in 2016 and after treatments (2017 and 2018), there were more grasses than legumes from all methods (Table 1). The legumes were mostly clovers and some native vetches. Alfalfa was very negligible across the entire field before treatment. In 2018, four of the methods that involved seeding (RSS, BSS, RFBSS and BSAS) had higher amounts of legumes (15-29%) than the other methods (with 3-10% legumes) in the total forage production. Therefore, RSS, BSS, RFBSS and BSAS methods have successfully been used to introduce alfalfa into the pastures. In 2018, RSS had the most alfalfa in the field. As expected, GRAZON treatment had the most grasses (100%) after treatments because GrazonTM will effectively control brush, forbs and other broadleaf weeds, hence the reason for 100% grasses in the GRAZONTM method.
In the years following treatments (2017 and 2018), RSS consistently had significantly higher forage DM yield than other methods (Table 1). Similarly, FERT showed higher forage DM yield than most methods (except for RSS and RFBSS). Overall, in both 2017 and 2018, only 3 methods (RSS, FERT and BSAS) had consistently higher forage DM yield than control. The forage yield increases from RSS, FERT and BSAS over control were 52-90% in 2017 and 18-75% in 2018. Comparing 2017 to 2016 (before treatments), there was a greater increase in forage DM yield from both FERT (311%) and RSS (235%) than other methods. Generally, regardless of pasture rejuvenation methods, forage DM yield was generally higher in the year following treatments (2017) than before treatments (2016).
Mechanical aeration partially disturbed the soil surface and did not generally reduce forage productivity in the present study. ROS was used with the intention of killing the existing vegetation, and to initiate new seedling establishment from existing seed bank in the soil. However, this method did not seem to work well, as no significant seedlings came from the existing seed bank, but rather encouraged weed invasion, left the soil exposed and prone to nutrient runoff and erosion. So, ROS wouldn’t be recommended as a method to rejuvenate pastures.
Forage Nutritive Value
The forage CP was not different in 2016 before treatments, and 2018 (3 years after treatments), but it was in 2017 (Table 2). In 2017, RSS had significantly higher forage CP (13%) than most methods. Also, in 2017, of the 11 methods, only 4 (RSS, ROS, BSAF and FERT) showed higher forage CP than control. The consistently higher forage CP obtained for RSS in the years following treatment clearly shows the benefit of new forage stands, and the presence of more legumes than other methods. Though ROS also had impressive forage CP in both 2017 and 2018, it is not recommended as a pasture rejuvenation method because it encouraged weed invasion, and left the soil exposed and prone to nutrient runoff and erosion. In 2018, though not significantly different from other methods, both GRAZON and FERT tended to have lower forage CP values than other methods, probably because both GRAZON and FERT had slightly higher grass and lower legume components in the total forage production.
In 2017, except for RSS and ROS, which both exceeded the 11% CP requirement of mature beef cattle, other methods were only able to meet the 7-8% CP recommended for a dry gestating beef cow. However, in 2018, only FERT and GRAZON fell short of meeting the suggested 11% CP for a lactating beef cow.
Forage energy (total digestible nutrients, TDN) was not influenced by rejuvenation methods (Table 2). When using TDN as the energy source for beef cattle, the rule of thumb is 55-60-65 (%TDN, DM). This rule says a mature beef cow requires 55% TDN in mid pregnancy, 60% TDN in late pregnancy and 65% TDN after calving. In the present study, with a few exceptions, most treatments only met the 55-60% TDN recommended for a dry gestating beef cow. Generally, no treatments had adequate TDN for a lactating beef cow, which needs 65% TDN.
Table 3 shows forage minerals in 2018 (3 years after treatments). RSS had the highest forage Ca but only significantly higher than 3 methods (BSS, GRAZON and AF). Only RFBSS had significantly higher forage K than most methods. Forage Cu was similar for most methods, but only RFSS, RSS, AS and ROS showed significantly higher forage Cu values than control. Overall, for forage Ca, P, Ca:P, K and Cu, 3 methods (RFBSS, RSS and ROS) were consistently in the top four and RFBSS ranked first in every respect.
Only RFBSS, RSS and ROS had sufficient Ca, P, K, Mg and S for mature beef cattle. Generally, except for Na, all treatments in most cases exceeded the Ca, P, K, Mg and S requirements of a beef cow in mid pregnancy, but they all fell short of meeting the requirements of a beef cow in late pregnancy for the same set of minerals. When compared to control, RFSS and RSS particularly showed greater improvement in most forage minerals than other treatments.
Three years after treatments were implemented, pasture rejuvenation methods investigated significantly affected forage DM yield, botanical composition, and forage Ca, P, Ca:P, K, Mg and Cu, but did not have any influence on forage CP, S, Na, Fe, Zn, Mn and TDN. Spring herbicide application + direct seeding (RSS), fertilizer application (FERT) and fall herbicide application + broadcast seed in spring (RFBSS) improved forage production and some forage quality parameters more than other methods over control. The amount of legumes in the total forage production was as much as 29% for RSS compared to about 2-17% for other methods including control. The consistently higher forage CP obtained for RSS in the years following treatment clearly shows the benefit of new forage stands and the presence of more legumes in the total forage production. Both GRAZON and FERT tended to have lower forage CP values than other methods, probably because both GRAZON and FERT had slightly higher grass and lower legume components in the total forage production. The higher forage DM yield from RSS and RFBSS in 2018 further confirms the need for adequate suppression of existing vegetation before direct (sod) seeding. Generally, there was no particular method that was consistently able to meet mineral requirements of lactating beef cattle, which would normally be on pasture during that time. A feed strategy to help compensate for such inadequacies is therefore needed. Such strategies may include feeding cattle on pasture a free choice mineral supplement, protein lick or block.
This project was funded by the Alberta Beef Producers (Project #: FRG.13.15). We also received financial support and donations (land, seed, fertilizer and equipment) from the following: Wanham Grazing Association (WGA), Birch Hills County, Special Areas Board, Rocky Mountain Equipment, Nutrien Ag Solutions (formerly Dynamic Seeds and CPS, Fairview), James & Jodi Bozarth (Sexsmith, Alberta), Soames & Melissa Smith (Uddersmith Dairy, Spirit River). We thank Gilbert Wasieczko (Farm Manager, WGA) for his support and, the staff and summer students of Chinook Applied Research Association and Peace Country Beef & Forage Association for their technical assistance. Thank you to the following beef cattle producers in Fairview, Alberta for initiating the project: Garth Shaw and Allan McLachlan.