Progress Report on Fall or Spring Management Options for Pastures: Renovate or Rejuvenate?

Funding Received from: Alberta Beef Producers (ABP)

Collaborators: Wanham Provincial Grazing Reserve, Wanham Grazing Association, and Chinook Applied Research Association (CARA)

Trial Site: Wanham Provincial Grazing Reserve

Research Coordinator: Dr. Akim Omokanye

From: Peace Country Beef & Forage Association 2017 Annual Report

Background

Over time, the productivity and livestock carrying capacity of seeded hay fields and pastures on beef cattle operations may decline. This is 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. Rejuvenation is a complex and costly challenge for producers. With the high cost and time associated with forage stand termination and re-establishment, farmers are anxious to identify all options for sustaining a forage stand. Local on-farm research is needed to compare all or at least most of the practicable methods of rejuvenation, in order to determine the most effective and profitable methods for producers in comparison to a complete break and reseed scenario. It was thought that comparing a break and reseed scenario to other minimal soil disturbance methods will show the advantages and disadvantages of these practices as well as identify the most cost effective methods/options that may exist for beef cattle producers.

Objectives

1. To test a variety of methods for rejuvenating the productivity of low producing forage stands and improving soil conditions under a grazing system.

2. To examine the effect of herbicide application on brush control in pasture and forage stand rejuvenation.

3. To demonstrate practical and sustainable forage production with minimal costs under farm conditions.

4. To provide a guide for the producer or manager when alternatives to breaking need to be considered.

Methods

Site: Provincial Grazing Reserve (PGR) in Wanham (Birch Hills County, Alberta).

Treatments: The following treatments are being examined in 3 replications:

1. Check

2. Plow– This was supposed to be break & re-seed, but after plowing in 2016, we couldn’t seed because of the wet soil conditions, which persisted for a long period. We decided to leave it as a Plow only treatment after we noticed the impressive forage growth from the seed bank in the field after plowing. A seed bank is a reserve of dormant seeds in the soil that enables some types of plants to re-establish themselves after a drastic disturbance of the established vegetation.

3. Fertilizer application (broadcast)- Fertility was 77 lb N + 37 lb P + 0 lb K +13 lb S.

4. Grazon® herbicide application to kill brush

5. Aerate in spring

6. Aerate in fall

7. Roundup WeatherMAX® herbicide application

8. Roundup WeatherMAX® herbicide application/re-seeding in spring– Roundup was sprayed and a forage seed mixture (grasses and legumes) was seeded with a no-till drill. Fertility at seeding was 77 lb N + 37 lb P + 0 lb K +13 lb S.

9. Broadcast forage seed mixture (grasses and legumes)/aerate in fall

10. Broadcast forage seed mixture (grasses and legumes) /aerate in spring

11. Broadcast forage seed mixture (grasses and legumes) only in spring

Last year (2016), we collected all of the necessary baseline data in June. The treatments listed above were implemented in 2016.

On June 21-22, 2017, soil water infiltration, soil compaction, forage yield, botanical composition of the forage, forage quality and soil nutrients (0-6” and 6-12”) were measured.

Results

Soil Component

The soil organic matter (SOM), pH and nutrients (N, P, K and S) are shown in Table 1.

The SOM in 2017 (Y17) did not show any significant improvement over the 2016 (Y16) baseline data for most treatments. However, in 2017, five methods of rejuvenation (‘Roundup/seed in spring’, ‘Plow’, ‘Aerate in spring’, ‘Broadcast seed/aerate in fall’ and ‘Roundup’) seemed to have higher SOM (8.1-9.4%) than the others tested here. The SOM was higher for surface soil than subsurface soil for all treatments.

The soil pH for the different methods of rejuvenation was mostly similar for both years (2016 and 2017). The pH was also similar for both soil depths (0-6” and 6-12”).

Soil N was particularly higher in 2017 than 2016 for the treatments ‘Plow’, ‘Roundup/seed in spring’, and ‘Fertilizer application’. The soil N in the surface soil (0-6”) was significantly higher than the sub-surface soil (6-12”) for ‘Roundup/seed in spring’, ‘Fertilizer application’ and ‘Roundup application’.

For some reason, the soil P was generally higher in 2017 than 2016 for all methods of rejuvenation tested. ‘Roundup/seed in spring’ and ‘Plow’ treatments had far more soil P than other methods of rejuvenation at both depths (0-6” & 6-12”).

In 2017, soil K was particularly higher for the treatments ‘Roundup/seed in spring’ and ‘Plow’ than other methods at both depths.

Soil S did not change much for most treatments from 2016 to 2017.

Soil infiltration and permeability describe the manner by which water moves into and through soil. Generally, infiltration rate was low, varying 0.18 to 1.08 inches/hour. Going by the permeability class (Table 3) and as expected, only the ‘Plow’ treatment improved infiltration significantly. Infiltration was moderate for ‘Plow’, while it was slow to moderately slow for other treatments methods.

In 2017, the mean soil compaction from 0-12” soil depth was far lower for the treatment ‘Plow’ (166 PSI) than other methods, which had 393 to 653 PSI. Readings of 400 to 500 PSI would indicate potential soil compaction. In 2017, only ‘Plow’ showed great improvement over 2016. Except for treatment ‘Plow’ in 2017, looking at Figure 1, it is evident that soil compaction was generally high in both the surface soil (0-6”) and subsurface soil (6-12”) in both years (2016 & 2017) for all treatments.

Forage Yield and Botanical Composition

The forage dry matter (DM) yield was generally higher in 2017 than 2016. In 2017, the treatments ‘Plow’, ‘Roundup/seed in spring’ and ‘Fertilizer application’ had significantly higher forage DM yields than other treatments. The treatment ’Plow’ had the highest forage DM yield (3792 lbs/acre), followed closely by ‘Roundup/seed in spring’ (3644 lbs/acre) and then ‘Fertilizer application’ (2528 lbs/acre).

With the exception of the treatment ‘Roundup’, which was dominated by mostly dandelions and brush, the forage stand was mostly dominated by grasses in both years (2016 & 2017) for all treatments. Forage legumes were very minimal in the stands of the treatments.

Forage Nutritive Value

The forage CP seemed to be slightly improved in 2017 over 2016 for the treatments ‘Plow’, ‘Roundup/reseeding in spring’ and ‘Roundup’.

Forage energy appeared to be increased by the treatment ‘Plow’ in 2017 over 2016. Also, ‘Plow’ had the highest TDN (62% TDN) of all other treatments.

Forage Ca and P did not seem to improve from 2016 to 2017 for any of the methods of rejuvenation tested here.