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Response of sunflowers (Helianthus annuus L.) to varying seeding rates and nitrogen fertilizer rates in a no-till cropping system in Saskatchewan

May, W.E., Dawson, M.P., Lyons, C.L.
Canadian journal of plant science 2018 v.98 no.6 pp. 1331-1341
Helianthus annuus, air, crop yield, cropping systems, crops, cultivars, fertilizer rates, growing season, hybrids, nitrogen, nitrogen fertilizers, no-tillage, open pollination, plant density, planters, planting, seeds, sowing, Saskatchewan
In the past, most sunflower research was conducted in tilled cropping systems and was based on wide row configurations established using precision planters. Little agronomic information is available for the no-till systems predominant in Saskatchewan, where crops are typically seeded in narrow rows using an air drill. Two studies were conducted in Saskatchewan to determine the optimum seeding and nitrogen (N) rates for short-season sunflowers in a no-till cropping system. The N rate study used 5 N rates (10, 30, 50, 70, and 90 kg N ha⁻¹) with the hybrid 63A21. The seeding rate study used 7 seeding rates (37 000, 49 000, 61 000, 74 000, 86 000, 98 000, and 111 000 seeds ha⁻¹) with two cultivars, AC Sierra (open pollinated) and 63A21 (hybrid). There was a linear yield increase as the N rate increased from 10 to 90 kg N ha⁻¹. Based on the N rates tested in this study and current N fertilizer costs below $1 kg⁻¹, sunflower yields and gross returns were most favorable at 90 kg N ha⁻¹. Future N response research with a wider range of N rates is warranted to best determine the optimum N rate. The optimum seeding rate was between 98 000 and 111 000 seeds ha⁻¹ for AC Sierra and between 74 000 and 86 000 seeds ha⁻¹ for 63A21. The optimum plant density, approximately 70 000 to 75 000 plants ha⁻¹, was similar for both cultivars. These results are higher than the current recommended seeding rates for wide-row precision planting systems in areas with a longer growing season.