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Testing Brassicas and Forbs for Forage and Inclusion in Cover Crop Cocktails

Research Coordinator: Dr. Akim Omokanye

Location: Fairview Research Farm

From: Peace Country Beef & Forage Association 2019 Annual Report


Forage brassicas are cool season annuals that can be utilized as pasture, fall grazing and swath grazing in winter. Brassicas include tillage radish, turnip, kale and forage rape, and hybrids. They are quick maturing and can be grazed as early as 60 after planting (with the right weather), depending on species. Brassicas are useful in remediating soils high in phosphorus, by taking up P and incorporating it into their plant tissues. There is evidence that a plant metabolite in brassicas (glucosinolate) can reduce enteric methane emissions from ruminants consuming brassicas or brassica by-products (e.g., canola meal). This results in a decrease in the environmental impact of animals, and increase animal production efficiency. Nitrate poisoning and bloating have been reported in beef cattle consuming pure brassicas pastures. This can be avoided by planting brassicas in a mixture with other forage species or only allowing limited access to brassica pastures. Forbs include plants like chicory and plantain.

Objective

The objective of the trial was to test several brassicas and forbs for their forage production potential and for inclusion in cover crop cocktail mixtures for livestock production. Nitrates test have been included in the forage quality test to enable us to assess their nitrate levels, and to see if the levels are safe for beef cattle production.

Methods

Experimental Site: Fairview Research Farm (NW-5-82-3 W6M) on RR #35, MD of Fairview.


Previous Crop: The previous crop at the site was an alfalfa hay crop for several years until the Fall of 2018.

Land Preparation: In the Fall of 2018, the site was sprayed with Roundup at 1.0 L/acre (to kill the existing alfalfa-dominated vegetation) and plowed. The site was disced & harrowed in the spring of 2019.

Soil analysis completed in the Fall of 2018 from 0-6” soil interval showed an organic matter content of 8.2%, pH of 6.2 and an electrical conductivity of 0.21 ds/m. The soil test reports showed 10 lbs N/acre, 14 lbs P/acre and 485 lbs K/acre as well as 9 lb S/acre.

Spring soil moisture at seeding was 12.4% (0-5 cm soil depth) and 14.1% (0-20 cm soil depth).

Spring soil temperature a Seeding was 9.19°C (0-5 cm soil depth) and 7.79°C (0-20 cm soil depth).

Experimental Design: Randomized Complete Block Design with 4 replications.


The treatments consisted of 10 brassicas and 4 forbs listed below:


Brassicas

1. Tillage radish - seeded at 4 lbs/acre

2. Vivant forage brassica - seeded at 4 lbs/acre

3. Purple top turnips - seeded at 4 lbs/acre

4. Winfred forage brassica- seeded at 4 lbs/acre

5. Daikon radish - seeded at 4 lbs/acre

6. Malwira turnip rape - seeded at 4 lbs/acre

7. Akela Brand Forage Rape - seeded at 4 lbs/acre

8. Inka Brand Marrow stem Kale - seeded at 4 lbs/acre

9. Bayou Kale Cross - seeded at 4 lbs/acre

10. Forage Collards - seeded at 4 lbs/acre

Forbs

1. Phacelia - seeded at 4 lbs/acre

2. Plantain - seeded at 4 lbs/acre

3. Chicory - seeded at 5 lbs/acre

4. Buckwheat - seeded at 60 lbs/acre

Seeding date was on May 23. The seeds were sown using a Fabro plot drill equipped with disc-type openers on 9” row spacing. Six rows that were 8 m long were sown per plot. Seeding depth was 0.75”.


Fertility (actual lbs/acre) was applied at: 0 N + 26 P + 0 K + 13 S

Spraying: Pre-emergent herbicide with StartUp (Glyphosate, 540 grams acid equivalent per litre, present as potassium salt) was applied at 0.67 L/acre. StartUp is a water soluble herbicide for non-selective weed control. Assure II + sure mix was used as in-crop herbicide application for the brassicas only. No in-crop herbicide application was carried out for phacelia, plantain, chicory and buckwheat, but instead, the plots were hand weeded twice.

Harvesting for forage dry matter (DM) yield determination was completed on August 29. Forage samples were shipped to A & L laboratory, Ontario for forage quality determination and nitrate-N.

Rainfall received from seeding to forage harvest was 184.7 mm (or 7.27”) and this was comparable to 189.9 mm (7.48”) for the long-term average for the same period.

Results and Implications

Forage Dry Matter Yield

The forage DM yield was far higher for buckwheat (with 5.8 tons DM yield/acre) than other forbs and brassicas tested here (Table 1)

For the brassicas, the highest forage DM yield was produced by Inka brand marrowstem kale, followed by tillage radish, daikon radish and Winfred forage brassica. Purple top turnips produced the lowest forage DM yield.

Overall, the lowest forage DM yield came from chicory with 2,369 lbs/acre. Buckwheat produced 4,226-9,257 lbs/acre more forage DM yield than other forbs as well as all brassicas.

In terms of establishment, buckwheat was quick to establish. We observed that plantain and chicory did not establish well. They both have less stands per acre than other crops tested here. We also observed that most brassicas had severe insect infestations later in the growing season.


Forage Quality


The forage crude protein (CP) varied from 11.4% for buckwheat to 26.0% for purple top turnips (Table 1). The forage CP was generally high for the crops tested here. All crops tested in this study have been able to meet the protein requirements of mature beef cattle including dry gestating and lactating beef cows. Except for buckwheat, other forbs and all brassicas far exceeded the protein requirements of both young (12-14% CP) and mature beef cattle. (11% CP).

The forage total digestible nutrients (TDN), which is a form of energy that is commonly used to evaluate feed quality varied from about 63% TDN for phacelia to about 77% TDN for Bayou kale cross. The forage TDN was mostly high for the crops tested with most having >70% TDN. Except for phacelia, which only had adequate TDN for dry gestating beef cows that need 55-60% TDN, other crops exceeded the 65% TDN needed by lactating beef cows.

All crops had high forage Ca and K, and their requirements by mature beef cows were met by all crops. All crops had sufficient P and Mg for dry gestating beef cows. For a lactating beef cow, only forage collards, phacelia, plantain and buckwheat fell short of the 0.26% needed by this category of beef cattle. Both malwira turnip rape and Inka brand marrowstem kale fell short of the 0.2 Mg requirements by lactating beef cows.

On a general note, all brassicas and most forbs had high forage CP, TDN, Ca and K. Including any of the these crops with good forage production in cover crop cocktail mixtures should help improve the forage quality of such cocktails.

Forage Nitrate-N

The forage nitrate-N content of the crops tested varied significantly. The forage nitrate-N was highest for phacelia (0.56%), followed closely by Winfred forage brassica (0.53%), then bayou kale cross (0.36%) and plantain (0.35%). Purple top turnips, chicory and tillage radish had 0.15-0.29% forage nitrate-N.

Looking at Table 2 below, only 7 of the 14 crops tested here for nitrate-N content would be considered to have generally safe levels of nitrate-N (0.12% N03-N) for beef cattle. The crops with safe nitrate-N levels in this study are: Vivant forage brassica, Daikon radish, Malwira turnip rape, Akela Brand Forage Rape, Inka Brand Marrow stem Kale, Forage Collards, Forbs and Buckwheat.

Generally, going by the nitrate-N test results in this study, caution would need to be taken by producers when feeding tillage radish-dominated feed because of its 0.15% nitrate N. All feeds with up to 0.23% nitrate-N wo d be considered to have high nitrate problems as well (see Table below).


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