Winter Wheat Cropping System Response to Seed Treatments, Seed Size, and Sowing Density
Authors: Beres Brian L. , Turkington T. Kelly , Kutcher H. Randy , Irvine Byron , Johnson Eric N. , O'Donovan John T. , Harker K. Neil , Holzapfel Christopher B. , Mohr Ramona , Peng Gary , Spaner Dean M. 
Published: April 2016

Poor stand establishment resulting in lower yield is a major constraint to expanding winter wheat (Triticum aestivum L.) across western Canada. To address this issue, we conducted a study totaling 26 site‐years over three growing seasons (2011–2013) to observe crop responses to system manipulations involving seeding rate (200 and 400 seeds m−2), seed size as a proxy for plant vigor (light/thin, moderate, heavy/plump), and a dual fungicide/insecticide seed treatment, on crop establishment, yield, and seed quality. Fall and spring plant density was about 10 plants m−2 greater for heavy seed vs. light seed. Seed treatment improved fall and spring plant density slightly more than 10 plants m−2. The dual seed treatment improved yield and test weight for thin seed size. Hypothesized weakest agronomic systems (low seeding rate and untreated, light seed) that often included the 200 seeds m−2 seeding rate were the poorest performing (suboptimal responses and highly variable) systems; however, a favorable response to seed treatments allowed for partial compensation and grain yield comparable to systems with high seeding rates. Greater instability was generally observed in weak systems irrespective of seed treatment. The economic advantage of the seed treatment was more apparent with thinner winter wheat stands as it resulted in greater gross (CAN+$31 ha−1) and net (+$22 ha−1) returns. This study reaffirms the importance of a strong and integrated agronomic system and indicates seed treatments can help offset weak systems comprised of poor stand establishment and lower yield performance.Core Ideas

Poor stand establishment resulting in lower yield is a major constraint to expanding winter wheat acreage across western Canada.
Hypothesized weakest agronomic systems (low seeding rate and untreated, light seed) that often included the 200 seeds m−2 seeding rate were the poorest performing (sub‐optimal responses and highly variable) systems; however, a favorable response to seed treatments allowed for partial compensation and grain yield comparable to systems with high seeding rates.
Winter wheat crop establishment and grain yield results indicated that producers that intentionally use low seeding rate should use a dual fungicide/insecticidal seed treatment; however, the inherent variability is not entirely overcome with seed treatment.
Inclusion of a dual fungicide/insecticide seed treatment provided the highest gross returns for both levels of sowing density; however, the added input cost of the seed treatment relative to the magnitude of change for grain yield reduced overall net returns at the 400 seeds m−2 seeding rate compared to the check (–$11 ha−1).
This study reaffirms the importance of a strong and integrated agronomic system and indicates seed treatments can help offset weak systems that tend to have poor stand establishment and lower yield performance.