84 Intercropping corn with annual forages for potential fall/winter grazing of beef cattle across the Canadian prairies

Abstract The objective of this study was to determine the optimal annual forage species to intercrop with corn for potential fall/winter grazing of beef cattle across the Canadian prairies. Corn is a high energy and yielding crop for grazing beef cattle, however, low CP concentration limits it’s potential value for growing cattle with high nutrient demands. This experiment was a randomized complete block design with 5 treatments and 4 replicates per treatment. Treatments included corn on 152 cm row spacing (44,460 plants/ha) with 1 of 4 annual forage species individually planted between corn rows. The forages were: Italian ryegrass (Lolium multiflorum L.), hairy vetch (Vicia villosa R.), crimson clover (Trifolium incarnatum L.), and forage radish (Raphanus sativuts L.). A Control treatment of monoculture corn planted on 76 cm spacing (88,920 plants/ha) was included. Corn was seeded in mid-late May, with the intercropped forages planted when corn reached the V4 stage of growth. The experiment was conducted at 8 sites across Alberta (Lethbridge, Manning, Olds), Saskatchewan (Redvers), and Manitoba (Carman, Glenlea, Melita, Roblin) in 2022 and 2023. Biomass samples of corn and intercrop were obtained in late September and early November for determination of DM yield and chemical composition (CP, nitrates and TDN) and to examine difference in the treatments over the late fall/early winter period. Data were analysed using the Proc Mixed procedure in SAS 9.4 with treatment, location, year and sampling period included as fixed effects, and replicate as a random effect. The biomass yield of the Control and the combined corn plus intercropped forage treatments ranged from 4,431 – 24,873 kg DM/ha, with the Control higher due to doubled seeding rate. Overall, the combined yield for corn plus intercropped forages was 75% of the Control yield. The CP concentration for intercropped forages ranged from 8.42 - 35.88 % DM. On average, crimson clover was the lowest and forage radish the highest. Combined CP yield across all 5 treatments ranged from 410 – 1,500 kg DM/ha, with corn and intercropped forages producing equivalent compared to Control, overall. Intercropped forage nitrate ranged from 0.03 - 10.08 % DM, with hairy vetch having the lowest mean concentration (0.17 % DM). All intercropped forages had lower nitrate concentrations in early November compared to late September. The TDN for the intercropped forages ranged from 37.75 % DM (crimson clover) to 82.86 % DM (forage radish). Overall, radish had the highest CP and TDN. In summary, intercropping corn with forages showed potential to increase the CP concentration on 152 cm corn row spacing when compared to the Control. However, radish also had the highest nitrates which should be considered to avoid potential toxicity issues when grazing.