Objectives
The objectives of this project were: to demonstrate the potential benefits of seed treatments for flax when combined with low, medium and high seeding rates and either early or late seeding dates.
Project Description
Overall, this project has demonstrated that successful flax establishment depends on numerous factors and that, while seed-applied fungicides can be beneficial in this regard, they will not necessarily provide tangible benefits under all conditions. A common basic recommendation for good establishment is to seed into warm soils at adequate rates; however, seeding date effects on emergence and plant densities varied depending on the specific environmental conditions encountered. At 2/3 sites better establishment was achieved with later seeding (i.e. warmer soils) while at one, the driest of the three, there was a slight (not significant) reduction in plant populations with delayed seeding. As expected, increasing seeding rates was an effective means of increasing plant populations; however, in addition to the added cost, excessive seeding rates can result in more plants than are desired under some conditions which could potentially lead to undesirable side effects such as increased lodging or disease pressure. Seed treatments are seen as relatively low cost, easy to use tool for improve establishment by warding off seedling diseases and potentially resulting in more vigorous growth under stressful emergence conditions. While using a seed-applied fungicide did result in higher plant densities at 1/3 site-years (IH-16), the difference in response was difficult to explain as the benefits were observed under the most optimal conditions with warm soils and frequent precipitation after seeding. With respect to seed treatment effects on emergence, there was no evidence to suggest stronger responses when combined with either early seeding or low seeding rates.
Seed-applied fungicides resulted in a statistically significant but agronomically inconsequential reduction in maturity of 0.4-0.6 days. While maturity can be concern with flax, particularly in more northern growing areas such as Melfort, the observed seed treatment effects were too small to have much impact on harvest date or noticeably reduce the risk of yield/quality loss associated with fall frost. The effect of seeding rate on maturity was also small with less than a 2 day spread (on average) between the highest and lowest rates; however, it did show the potential for lower plant populations to delay maturity. Higher seeding rates may be seen as one way to improve crop stage uniformity across variable landscapes but, on average, cannot be expected to have a major impact on maturity and there can be drawbacks if populations are too excessive. Seeding date had, by far, the greatest and most consistent effect on days to maturity with the later seeded crop maturing up to 10 days ahead of the early seeded crop. That said, the early seeded crop was still always ready to combine first so if earlier harvest or reduced risk of fall frost damage is an objective then seeding earlier is still the most desirable option.
Flax yield was not affected by seed-applied fungicide treatment at any site-years, regardless of when or at what rate the crop was seeded. In the year where the positive effect on emergence was observed, overall populations were always well-above the recommended minimum; therefore, a yield response to the increase in populations was not necessarily expected. The highest yields were consistently achieved with early seeding although the response was not always statistically significant and, at Indian Head in particular, much of the observed difference was attributed to wildlife damage in the late-seeded crop. Seeding rate effects on flax yield were rare and, when observed, inconsistent with the expected results. The only case in which seeding rate had an effect on flax yield was IH-16 where it declined linearly with increases in seeding rate. While it not entirely clear why the negative response occurred, overall plant populations that season were more than twice the recommended minimum in certain treatments (i.e. 845 plants/m2 with late seeding and a 75 kg/ha rate of treated seed). Lodging was not observed in any treatments and the plots were sprayed with foliar fungicide at an optimal time; however, it is conceivable that disease was more limiting at the highest plant populations under the wet conditions encountered that season.
Overall, results from this demonstration suggest that flax should be seeded early (within the first 2 weeks of May) at rates of approximately 55 kg/ha to achieve the earliest maturity possible and optimum yield. Seed treatments have potential to improve establishment but this will not necessarily occur under all circumstances and yield responses are likely to be even less frequent. It is possible and worth noting that small plot trials, typically conducted on relatively uniform and well drained land, may not be ideal for capturing the potential seed-treatment benefits that may occur on a larger scale where the factors affecting emergence and development of root disease are more spatially variable.
