PSXII-14 - Impact of Nitrogen Application and Intercrop Forage Species on Chemical Composition and Yield of Standing Corn and Intercropped Forages

Abstract: This study evaluated the impact of nitrogen (N) application rate and forage species of intercropped corn for potential grazing of beef cattle in late fall/early winter. A split plot design (4 replicates/treatment) was used at 2 experimental sites in Manitoba, Canada with 2 treatment factors: 1) N application rate as the main plot and 2) forage intercrop species as the sub plot. Nitrogen application rates were 45 kg N/ha and 112 kg N/ha. Forage species were: italian ryegrass (Lolium multiflorum), hairy vetch (Vicia villosa), graza forage radish (Raphanus sativus), red clover (Trifolium incarnatum) and a mix of all 4 forages. Intercropped treatments were compared with corn only control treatments with no intercrop at both N rates. Plots were seeded in 2019 with corn from May 8-10 and intercrops seeded from June 17-25. Chemical composition of intercropped forages and corn were determined in early October. Averaged over sites and intercrop treatment, increasing N application increased (P< 0.004) CP of the intercrops from 20.5% (low N) to 22.3% (high N), with CP similar at both sites. On average, radish had the greatest CP (29%), clover least (13.2%), with the remaining crops intermediate (mean 21.7%). Corn CP increased (P< 0.01) with N application (6.6 to 7.5% averaged over treatments), with no effect of intercrop species. Intercrop TDN was not affected by N rate, with greatest concentrations observed in radish (68.2%), least in hairy vetch and red clover (53.6%) and intermediate in the mix and italian ryegrass (mean 60.2%). Dry matter yield for all intercrop and corn treatments were less than expected at both locations due to exceptional drought conditions. Intercrop treatment and its interaction with N rate did not impact corn yield. In conclusion, intercrop CP ranged from 12-29%, thus offering the potential to increase the feeding value of corn for overwintering cattle.