Dryland grain corn production in southern Alberta
Four experiments conducted from 2015 through 2022 under dryland conditions in southern Alberta found that narrow row spacing of 20 inches and planting rates of 25,000 seeds/ac with nitrogen rates between 100 and 160 lbs N/ac optimized yield.
Early maturing grain corn hybrids have expanded where the crop can be grown into southern Alberta. Four separate experiments were conducted at seven rain-fed locations in southern Alberta between 2015 and 2022. Each had six to nine site-years of data. These experiments investigated different tillage systems, planting time, planting rate, row spacing, and N fertilizer application rate to help develop best agronomic management practices for southern Alberta.
Environmental conditions during these years were generally lower in precipitation than average, and ranged from 40 per cent below normal to 20 per cent higher at the different site-years.
For all experiments, corn was seeded using a 4-row Monosem vacuum planter which had a trash remover in front of a plain coulter with a double disc V opener, double wheel packer, and manual depth control. Preseed weed control was conducted with glyphosate and Aim (carfentrazone-ethyl). In-crop weed control used glyphosate alone or tank-mixed with Armezon (topramezone). Liquid ammonium phosphate (10-34-0) was applied in the seed row to target 60 lbs./ac. (67 kg/ha) of available soil plus fertilizer phosphorus.
Plant population and row spacing (Experiment 1)
Five seeding rates were compared over three years from 2015 to 2017 at Lethbridge, Medicine Hat, and Bow Island, Alta. Seeding rates compared were 15,000, 20,000, 25,000, 30,000, and 35,000 seeds per acre (37,065, 49,420, 61,775, 74,130, and 86,485 seeds/ha). Row spacing comparisons of 20 and 30 inches (51 and 76 cm) were conducted. Pioneer P7332R (20205 CHU) was seeded in this experiment. Urea nitrogen (46-0-0) was applied in a side-band targeting 150 lbs. N/ac (168 kg N/ha) soil plus fertilizer N.
Narrow row spacing at 20 inches had better crop emergence by 12 per cent and yield was 15 per cent higher than the wide row spacing of 30 inches. Narrow row spacing yielded 69 bu/ac (4.39 t/ha) while the wider row spacing yielded 61 bu/ac (3.82 t/ha)
Overall, the highest dryland grain yields were achieved with 30,000 and 35,000 seeds/ac yielding around 70 to 72 bu/ac (4.34 to 4.53 t/ha). At site-years with low moisture conditions, seeding rate had no significant effect on grain yield. However, at normal to high moisture conditions, increasing plant population density increased grain yield by up to 28 per cent.
Nitrogen fertilizer rate and timing (Experiment 2)
Nitrogen fertilizer rate and split application timing was compared in 2016 and 2017 at Lethbridge, Medicine Hat, Bow Island, and Vauxhall. Nitrogen rates applied at planting were 0, 50, 100, 160, and 190 lbs N/ac (0, 56, 113, 180, and 214 N kg/ha). Additionally three split application rate/timings were compared at 50 lbs N at seeding + 50 lbs N in-crop at V4-V6 growth stage; 50 lbs N at seeding +100 lbs N at V4-V6; and 100 lbs N at seeding + 100 lbs N at V4-V6. Nitrogen applied at seeding was urea side-banded. In-crop liquid fertilizer urea ammonium nitrate (UAN) was applied with a urease inhibitor stabilizer through streamer bars on 30 inch (76 cm spacing).
Pioneer P7332R (20205 CHU) was planted on 30 inch (76 cm) row spacing at 20,243 seeds/ac (50 000 seeds/ha).
Rate and timing (split applications) of N application did not have a statistically significant impact on crop growth or yield. However, overall trends showed that fertilizer application was optimized at 100 lbs N at seeding, and between 100 and 160 lbs N when split-applied. At N rates above 100 lbs N/ac, few effects on corn yield were observed, and had reduced seedling emergence. This was likely due to low moisture conditions during the study period.
No-till and crop residue rotations (Experiment 3)
No-till and conventional tillage seeding systems were compared at Lethbridge, Medicine Hat and Vauxhall from 2015 to 2017. Crop residue rotations were wheat, soybean, field pea, lentil, mustard, canola, and corn. Pioneer P7332R (20205 CHU) was planted on 30 inch (76 cm) row spacing at 20,250 seeds/ac (50 000 seeds/ha).
Overall corn emergence was four to 25 per cent higher under conventional tillage compared to zero till. Lower corn emergence was seen in the zero-till system when the crop residue was corn (76 per cent emergence), and also lower on canola, mustard, soybean and wheat (85 to 88 per cent emergence). Emergence was higher on lentil (94%) stubble. Average crop emergence under conventional tillage for all crop stubbles was above 95 per cent.
Despite the differences in stand establishment, there was no statistically significant differences in corn yield due to crop residue or seeding system, although there was a trend to higher yield with no-till seeding. The researchers indicated that, “increased water storage in zero-tilled soils may have been especially helpful in this study due to limited precipitation resulting in hot and dry conditions for 3 out of 6 site-years included in this experiment.”
Strip tillage, planting date and corn hybrid maturity interaction (Experiment 4)
This experiment was conducted at Lethbridge, Medicine Hat, Enchant, Bow Island, Stirling and Taber from 2019 to 2022. Strip tillage and no-till were compared at three seeding dates of early planting (between 18 and 30 April); normal planting (between 7 and 14 May), and late planting (between 17 and 28 May). P6909R (1950 CHUs) and P7940AM (2255 CHUs) corn hybrids were planted at 20 inch (51 cm) row spacing at 30,000 seeds/ac.
The earlier maturing corn variety was 10 cm shorter and matured 7 days earlier, but had similar yield as the later maturing hybrid.
Strip-till improved plant establishment at early and normal planting dates compared to no-till seeding, but was similar for both systems at the late planting date.
Compared to the early-April planting, corn yield was five per cent lower for the early-May planting and 10 per cent lower for the late-May planting date.
There was no statistical interaction between seeding time, tillage and corn hybrid maturity on plant density, height, days to tassel, days to silk, and grain yield.
This research was funded by the Alberta Crop Industry Development Fund and Alberta Agriculture and Forestry.
Gurbir Singh Dhillon, Mike Gretzinger, Manjula S. Bandara, Brian L. Beres, Ken Coles, and Thierry Fonville. 2026. Optimal management practices of grain corn production under rainfed conditions in southern Alberta. Canadian Journal of Plant Science. 106: 1-12. https://doi.org/10.1139/cjps-2025-0133
