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Improving Forage Total Digestible Nutrients of Cover Crop Cocktails with Forage Type-Cereal Crops

Research Coordinator: Dr. Akim Omokanye

Location: Fairview Research Farm

From: Peace Country Beef & Forage Association 2019 Annual Report


The total digestible nutrients (TDN) is a useful measure for energy content of beef cow rations that are primarily forage. For a mature beef cow, using percent TDN, the Beef Cattle Rule of Thumb suggests 55% in mid pregnancy, 60% in late pregnancy and 65% after calving. Data emanating from PCBFA cocktails studies and producers’ cocktail feed tests in the Peace Country indicate that the TDN requirements of dry, pregnant gestating) beef cows can always be met by cover crop cocktails. However, for a lactating beef cow (which requires 65% TDN) and backgrounding and finishing calves (that require 65 - 70% TDN), most cocktails would normally be short of these requirements.

Objectives

To investigate the effects of adding forage-type cereal crops (corn, wheat and soft white wheat) at different seeding rates to a PCBFA standard cover crop cocktail to increase forage energy for beef cattle.

Methods

Experimental Site: Fairview Research Farm (NW-5-82-3 W6M) on RR #35, MD of Fairview. The previous crop at the site was an alfalfa hay crop for several years until the Fall of 2018. 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 depth 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: 12.3% (0-5 cm soil depth) and 13.6% (0-20 cm soil depth). Spring soil temperature a Seeding: 9.48°C (0-5 cm soil depth) and 8.09°C (0-20 cm soil depth).

Experimental Design: Randomized Complete Block Design with 4 replications.


A cocktail, which is considered a PCBFA standard cover crop cocktail (CCC) was seeded alone (34.4 plants per square feet) and with 39F44 corn hybrid (2,000 corn heat units), AAC Jatharia (soft white wheat) or AC Stettler wheat (hard red spring wheat). The CCC consisted of oats, fall rye, hairy vetch, frosty berseem clover, Winfred forage brassica, phacelia, chicory, forage peas and white proso millet. Each of the corn, soft white wheat (SWW) and hard red spring wheat was seeded at 10, 20 and 30% of the recommended seeding rate as shown below:

1 CCC @34.4 plants/sq ft (control)

2 CCC @34.4 plants/sq ft+ 10% corn (0.07 plants/sq ft)

3 CCC @34.4 plants/sq ft+ 20% corn (0.15 plants/sq ft)

4 CCC @34.4 plants/sq ft+ 30% corn (0.22 plants/sq ft)

5 CCC @34.4 plants/sq ft+ 10% wheat (3.43 plants/sq ft)

6 CCC @34.4 plants/sq ft+ 20% wheat (6.85 plants/sq ft)

7 CCC @34.4 plants/sq ft+ 30% wheat (10.3 plants/sq ft)

8 CCC @34.4 plants/sq ft+ 10% SWW (3.43 plants/sq ft)

9 CCC @34.4 plants/sq ft+ 20% SWW(6.85 plants/sq ft)

10 CCC @34.4 plants/sq ft+ 30% SWW(10.3 plants/sq ft)

Seeding date was on May 24.

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”.

No fertilizer was applied. All legumes were inoculated at seeding.

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.

Harvesting for forage dry matter (DM) yield determination was completed on August 21. Forage samples were shipped to A & L laboratory, Ontario for forage quality determination and nitrate-N.

Rainfall received from seeding to forage harvest for the triticale and soft white wheat was 175.1 mm (or 6.89”), which was comparable to the long-term average for the same period of 176.7 mm (6.96”).

Results and Implications

Forage DM Yield

The forage DM yields for the CCC control and those of CCC with corn, wheat and soft white wheat at different seeding rates were similar in most cases (Table 1). Only CCC + 30% Jatharia produced higher forage DM yield than CCC control. The forage DM yield advantage from CCC + 30% Jatharia over CCC control was an increase of 2,276 lbs DM yield/acre. The CCC with corn and wheat showed decreasing forage DM yield with increasing seeding rate of corn and wheat from 10 to 30%. This shows that the CCC with AAC Jatharia may have potential to increase forage DM yield when the AAC Jatharia soft white wheat is added to a CCC at 30% seeding rates.

During the crop growth and at crop harvest for forage DM yield, the different cover crop species and varieties seeded were assessed visually and also cut for determination of botanical composition. We observed that the corn in the CCC at the different seeding rates did not do well. In most cases, the corn did not germinate and where the corn germinated, the corn stands were not impressive. All emerged corn stands had stunted growth.

Forage Quality

Crude protein - The forage CP for the CCC control was 12.7%, while it varied from 10.7 - 18.1% CP for CCC with added corn, wheat and soft white wheat (Table 1). For some reason, the CCC + 10% corn had higher forage CP (17.1%) than CCC + 20% corn (10.8% CP) and CCC + 30% corn (11.3% CP). For the CCC + wheat, the forage CP improved greatly from 11.7% CP for CCC + 10% wheat to 18.1% CP for CCC +30% wheat. For the CCC + AAC Jatharia (SWW), the forage CP was higher for CCC + 20% AAC Jatharia than either of CCC + 10% AAC Jatharia or CCC + 30% AAC Jatharia. Overall, only CCC + 10% corn, CCC + 30 wheat and CCC + 20% AAC Jatharia statistically showed significantly higher forage CP than CCC control.

The forage CP obtained from the different cocktails as well as CCC control seemed to be adequate for mature beef cattle. In a few cases, the forage CP was either well within the 12 - 14% CP needed by young beef cattle or it far exceeded this range.

Total Digestible nutrients (TDN) - The CCC control had similar forage energy (% TDN) and 6 other CCCs with added cereals had >70% TDN (Table 1). Of the 9 CCC + cereal crop seeding rate combinations tested, only 2 (CCC + 20% corn and CCC +10% SWW) showed significantly higher forage TDN than CCC control.

All CCC treatments including the control seemed to exceed the %TDN needed by mature beef cattle. Similarly, the 65-70 %TDN requirements by young calves have been conveniently met by all CCC tested here including CCC control.

Forage Minerals - The macro minerals measured here (Ca, P, K, Mg, Na) are shown in Table 1. All CCC treatments including the control showed sufficient amounts of Ca, P, K, Mg and Na for a dry gestating beef cow. For a lactating beef cow, the requirements of P (except for CCC + 10% AAC Jatharia), K, and Mg by mature beef cows were generally met by all CCC treatments including control. None of the treatments produced enough Ca ( >0.58% Ca) required by a lactating beef cow, while only CCC + 10% AAC Jatharia had enough Na for a nursing beef cow.

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