Row Spacing and Seeding Rate Studies in No‐Till Winter Wheat for the Northern Great Plains

The risks of winter kill in winter wheat ( Triticum aestivum L .) for the Northern Great Plains of the Canadian prairies can be virtually eliminated when using a no‐till production system. Because of the needs for no‐till, a re‐examination of the effects of row spacing should be conducted. Narrow row spacings can cause equipment design and trash clearance problems under heavy residue. The objectives of this study were to determine whether the grain yield of winter wheat could be maintained at wider row spacings by varying seeding rates and P fertilizer and using a fungicide seed treatment. The study consisted of three separate trials that were all conducted at the Indian Head Research Farm in Saskatchewan on an Indian Head heavy clay soil (rego black chernozem Udic Haploboroll). The first trial examined eight seeding rates and the effect of the seed treatment Vitavax Dual Powder. The second trial examined three row spacings and six seeding rates for three growing seasons. The third trial involved three row spacings, three seeding rates, and three rates of seed‐placed P over 2 yr. Use of the seed treatment increased grain yield by 4 to 6% in 2 of 3 yr. Optimum seeding rate was about 90 to 120 lb/acre, at which the maximum grain yield was achieved in 6 out of 8 yr. On average, the 8 and 12 in. row spacing resulted in an equivalent or higher (8%) grain yield than the 4 in. row spacing. The effect of row spacings was consistent at various seeding rates, with no row spacing × seeding rate interactions. Seed‐placed P increased grain yield by 21 to 30%. In the more humid regions of the Northern Great Plains where heavy crop residue may disrupt the seeding operation, wide row spacing coupled with proper seeding rates, P fertilizer, and a seed treatment, would ensure successful winter wheat production. Research Question Winter wheat has many advantages in a cropping system because of its growth habit. However successful winter wheat production requires seeding into standing stubble in order to trap snow to provide an insulating layer against low temperatures. The presence of standing stubble and surface residues necessitates a re‐examination of row spacing effects under those conditions because of the physical limitation of narrow row spacings. The research reported examines the effects of row spacing, seeding rate, seed treatment, and seed‐placed P on crop establishment and grain yield in no‐till winter wheat. Literature Summary Our current knowledge of cereal production suggests that grain yields are improved when narrow row spacings are used. However, the presence of surface residues and standing stubble makes it difficult to use narrow spacings. Much of the past research on row spacing was done under residue free conditions. Some research with spring cereals suggests that wider row spacings may perform equally well under no‐till conditions. Study Description Three separate studies were conducted under no‐till conditions at Indian Head, SK, on an Indian Head heavy clay soil. The first study examined eight seeding rates (30, 60, 90, 120, 150, 180, 210, and 240 lb/acre) with and without a seed treatment using Vitavax Dual Powder at a rate of 2.3 lb/ton of seed on 8 in. spacing. The second study examined three row spacings (4, 8, and 12 in.) and six seeding rates (30, 60, 90,120, 150, and 180 lb/acre). The third study involved three row spacings (4, 8, and 12 in.), three seeding rates (60, 120, and 180 lb/acre) and three rates of P (0, 8.6, and 17.2 lb P /acre). Applied Questions What is the optimum seeding rate for winter wheat? Based on the results of this study and for a sub‐humid ecological zone, the optimum seeding rate would be in the range of 90 to 120 lb/acre. Given that these studies were done under weed free conditions, it is recommended that seeding rates of 120 lb/acre be used to provide better crop competition against weeds and to ensure optimum plant populations should some winter kill be experienced. Were there any grain yield benefits observed with the use of a seed treatment? The benefits of Vitavax Dual Powder seed treatment was evaluated. A positive effect on grain yield due to the treatment was observed in 2 of the 3 yr of testing. The average grain yield benefit due to seed treatment over the course of the study was 3.4%. Does row spacing have a significant effect on grain yield in winter wheat under no‐till conditions? The average grain yields of winter wheat at 4, 8, and 12 in. were 49.3, 50.6, and 50.4 bu/acre over a 5 yr period. Based on these results, a yield reduction was not observed as row spacing was increased from 4 to 12 in. Although plant populations showed a significant decrease with increasing row spacing, this was not reflected in the final grain yield. This also strengthens the argument for higher rather than lower seeding rates as discussed in the previous question, especially if the row spacing is widened. How important is the concentration of P placed with the seed? In this study, increased concentrations of seed‐placed P with a wider row spacing did not improve the response to P. Overall responses to P were observed in all years, independent of row spacing. Can the potentially negative effects of wider row spacings on grain yields be alleviated by varying seeding rates and P fertilizer? The lack of a significant interaction between row spacing and seeding rate means that adjustments in seeding rates are not required when changing row spacings. It is important to note that optimum plant populations be attained in order to maximize grain yields, regardless of row spacing. Current recommendations for P fertilizer do not require adjustments with changes in row spacing.