Improving the Forage Energy Content of Cover Crop Cocktails for Beef Cattle through Seeding Rates

Project Site: Fairview Research Farm

Research Program Manager: Dr. Akim Omokanye From: Peace Country Beef & Forage Association 2018 Annual Report

Multispecies annual crop mixtures have recently become more popular in northern Alberta. Producers need information on the performance of mixtures to implement successful production/farming operations. The findings from recent PCBFA trials, as well as feed test reports on cocktails from producers’ farms, appeared to show an average of 66% total digestible nutrients (TDN). Such feed tests show that cocktails would always have sufficient TDN for a dry gestating beef cow and may occasionally fall short of the requirements of a lactating beef cow. For backgrounding and finishing calves, cocktails have always had inadequate TDN. The objective of the study was to determine seeding rates that optimize forage production and improve TDN for mature and young beef cattle, while simultaneously maintaining diversity of species for maximum ecosystem benefits.

Methods

The study site was at the Fairview Research Farm (NW5-82-3W6) on RR #35, MD of Fairview. The initial soil tests at 0-6” depth showed an organic matter of 7.1%, a pH of 5.4, and an electrical conductivity of 0.44 dS/m. The soil nutrient analysis showed the following: soil nitrate-N = 96 lbs/acre, P = 53 lbs/acre, K = 243 lbs/acre and sulfate-S = 17 lbs/acre. Nine (9) cover crop cocktails (CCCs #1-#9) and an oat crop (CDC Haymaker oat - check) ) were tested at 2 seeding rates. The seeding rates consisted of what is considered a normal seeding rate (N) for most cocktails in the area and a high seeding rate (H, which was 150% of normal seeding). We had 4 replications. Table 1 on the next page shows the crop mixtures tested at the 2 seeding rates.

Seeding was done on May 28 with a 6-row plot drill at 9” row spacing. No fertilizer was applied during or after seeding. Roundup was used as apre-emergent herbicide. No in-crop spraying was done. Hand weeding was done on July 6.

Harvesting for forage yield determination and quality analysis was done on August 16 at the milk stage for oats. Two composite forage samples were sent to A & L laboratory in Ontario for quality determination.

The data for forage yield and quality were analyzed with ARM statistical software.

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Results

The initial soil tests done before seeding showed that the soil had 96 lbs N/ac. This amount was considered optimum for average oat production.

Table 2 shows the forage dry matter (DM) yield, crude protein (CP), TDN, Ca, and P for the treatment combinations (cocktails x seeding rates). Forage DM yield was statistically similar for CCC by seeding rate interaction. Similarly, both seeding rates did not differ in mean forage DM yield when pooled across the cocktails tested. However, crop mixtures did differ in mean forage DM yield, with CCC #2 producing the highest mean forage DM yield (8340 lbs/ac), followed by CDC Haymaker oats (8025 lbs/ac) and CCC #6 (8025 lbs/ac). Of the 9 cocktails tested, only 2 compared well with CDC Haymaker oats in terms of forage DM production (yield). Other cocktails produced 319 - 2140 lbs/ac less forage DM yield than CDC Haymaker oats.

The forage CP was highest for CCC #7 at the normal seeding rate (15.9% CP) and lowest for oats at the high seeding rate (8.77% CP). Across both seeding rates, both CDC Haymaker oats and CCC #5 (cereal dominated cocktail) had lower mean forage CP (9.85-9.04%) than thr other CCCs, which had 11% CP or more. Pooled across the cocktails, the higher-than-normal seeding rate seemed to reduce mean forage CP (13 versus 11% CP). CDC Haymaker oats and the cereal-dominated CCC (#5) had lower CP than the other cocktails, however, CDC Haymaker oats and CCC#7, as well as CCC #5, all had higher mean TDN values than the others across both seeding rates. Both CCC #5 and CCC #7 had more cereals, hence the reason for their higher forage TDN. Statistically, the mean forage TDN was similar for both seeding rates.

The forage Ca was consistently higher for all cocktails at any particular seeding rate than for CDC Haymaker oats. Pooled across the cropping treatments, the mean forage Ca content was highest for CCC #9, followed by CCC #8 and then CCC #2.

The forage P was statistically similar with respect to cropping treatment by seeding rate interaction, the effect of seeding rates (pooled across cropping treatments) and cropping treatments (pooled across seeding rates). Overall, only CCC #1, CCC #2 and CCC #3 at both seeding rates were able to sufficiently meet the P requirements of mature beef cattle (0.26% P). Other cocktails were only mostly able to satisfy the P requirements of a dry gestating beef cow but not lactating beef cow.

Conclusion

In terms of forage TDN, only CCC #1, CCC #5 and CCC#7 when seeded at the normal seeding rate were able to compare well with CDC Haymaker oats. CCC #1, CCC #5 and CCC#7 were also the only ones that produced a forage with >71% TDN.

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