Funded by Results Driven Agriculture Research (RDAR)
Due to changing climatic conditions, warmer season crops such as corn are an attractive option to Prairie beef producers for both in silage production and/or grazing. This is due to the fact that grazing corn has the potential to extend the grazing season into the fall and winter months, ultimately leading to a reduction in winter feeding expenses. This reduction is particularly significant as it is a key factor in the overall production costs for beef cattle operations in the Canadian prairies. Corn as a winter grazing group can stand above snow; able to resist lodging and with minimal leaf loss; and can provide windbreak for cattle grazing it. As a forage crop, it is high yielding, has low fibre levels and consequently high feed intake and digestibility in cattle consuming it.
The corn heat unit (CHU) provides an indexing system to assist farmers in selecting the most suitable corn hybrids for their area. A hybrid with a higher CHU rating than the local conditions provide will not have time to reach maturity before it is harvested or frozen, and will contain more fibre, more moisture, fewer cobs and less starch than ideal. It will also be less palatable and nutritious, whether harvested for silage or left for grazing. On average, 150-200 fewer CHUs are required for grazing or silage corn to reach 65% whole moisture (35% dry matter) as compared to grain corn. In The Peace region, where the long-term average CHUs during the growing season can be quite close to the minimum CHU rating of available hybrids, it is important to continuously assess the suitability of new corn hybrids to this unique agroecology.
Materials and Methods
The trial took place at Mark Pellerin’s Farm in Debolt. Sixteen (16) corn hybrids were seeded in strips. The corn hybrids tested and their corn heat unit (CHU) requirements are provided in Table 38.
The following methods were used:
Seeding rate: 33, 000 kernels per acre
Seeding depth: 1.5"
Seeding date: May 30, 2022
Seeding method: Fabro plot drill. Row spacing used for corn = 18"
Fertility and fertilizer application: 102 lbs/ac N, 20 lbs/ac P, 80 lbs/ac K, and 10 lbs/ac S.
Harvesting was done on October 13, 2022.
Results and Implications
The yield and forage quality attributes of the 16 corn hybrids are given in Table 39. Plant height varied by 7.1 % from 149 to 171 cm but did not significantly differ between corn hybrids. The total DM yield ranged from 1.74 – 3.81 tons/acre with 3 PICKSEED hybrids PS2320RR, PS Ex Seed LFRR and PS2420RR topping the chart in terms of this parameter. These yields compare poorly with those obtained planting nine of these hybrids in Teepee Creek in 2020 where yields of between 5.0 – 6.0 tons/acre were obtained (PCBFA, 2020). Favorable growing conditions in Teepee Creek (higher OM, soil nutrients, absence of drought) certainly accounted for this difference. Crude Protein narrowly ranged between 6.2 – 9.8 % and varied significantly (p = 0.04) between corn hybrids. This will meet the nutritional requirements of mostly cows at mid and late pregnancy. High protein requiring beef cattle stock, such as growing or finishing calves or lactating cows, will need some form of protein supplementation. Fibre (NDF and ADF) contents ranged from 48.4 – 55.1 % and 26.9 – 32.8 % respectively and did not significantly differ between corn hybrids. Contrarily, energy (TDN) significantly differed (p = 0.001) despite narrowly (6.8 %) ranging 51.3 – 63.0 % between corn hybrids. High-requirement beef cattle grazing most of these corn hybrids will need some form of energy supplementation, typically in the form of additional grain. This is necessary because the energy values of these hybrids averaged below 60%. Hybrids with the highest CHU had the lowest energy such as PSExpandLFRR hybrid (CHU 2725; TDN 51 %) and PSExSeed LFRR (CHU 2400; TDN 54 %). For minerals, ranges of 0.18 – 0.27 % for Ca (Table 39); 0.08 – 0.1 % for P; 0.19 – 0.31 % for Mg; 0.48 – 0.68 % for K; 48.4 – 55.1 ppm for Fe; 26.9 – 32.8 for Zn and 54 – 63 ppm for Mn where recorded (Table 40). Mineral supplementation would be needed as most corn hybrids had concentrations that were just at the borderline of meeting requirements for most beef cattle stock.
Conclusion
The corn hybrids tested produced appreciable forage biomass with most surpassing the 3,000 lbs/acre mark and with potential for higher forage DM yields under better growing conditions. Protein supplementation will be needed for high producing beef cattle stock grazing only these corn hybrids. The hybrids with very high CHU (>2400), such as PSExpandLFRR hybrid and PSExSeed LFR, produced low energy forage and may not be recommended for the short growing season of The Peace region. Also, mineral supplementation will be required as most hybrids had just borderline concentrations regarding nutrient requirements.
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