Objectives
1. Demonstrate flax yield response to a range of nitrogen fertilizer rates for a variety of Saskatchewan locations.
2. Demonstrate the seed-safety and potential yield benefits of polymer coated urea (ESN) relative to urea when side-banded at high rates.
3. Demonstrate the potential merits of utilizing split-applications of nitrogen in flax to reduce the likelihood of seedling injury and lodging while potentially enhancing yield.
Project Description
In the spring of 2021 at multiple Saskatchewan locations, field trials with flax were initiated to demonstrate crop response to a range of side-banded urea rates and non-traditional nitrogen (N) management practices. The trials were repeated in 2022 and, after removing some sites due to severe weather or errors during treatment applications, eight sites remained and are discussed in the current report. The locations were Indian Head, Melfort, Yorkton, Redvers, and Swift Current. The treatments included a range (17-130 kg N/ha) of side-banded urea rates, high rates of a side-banded ESN® blend, and split-applications where the timing and sources of in-crop N were varied. In addition to residual soil nutrient levels, data collection included plant density, lodging, and yield. The 2021 growing season was considered dry at all locations while most locations, Swift Current being the exception, were wet in 2022. High rates of side-banded urea negatively impacted emergence at 50% of the sites, the exceptions being Indian Head (both years), Redvers 2022, and Yorkton 2022. Where they occurred, the magnitude of these reductions ranged from 11-32%. As hypothesized, substituting side-banded urea with the ESN® blend frequently reduced the stand reductions associated with side-banded urea and utilizing split-applications also helped in this regard. Lodging only occurred at 1 site and increased with N rate but was not alleviated by either the ESN® blend or split applications. When averaged across treatments, yields ranged from 1171-3072 kg/ha and responses to N fertilization occurred, to varying degrees, at all locations. Where responses occurred, maximum yields were achieved with 55-130 kg N/ha, but yields were generally levelling off at 55-105 kg N/ha. Despite the occasional improvements in establishment, yield benefits were never realized by substituting side-banded urea with the ESN® blend or with split applications of N. There was occasional, weak evidence that flax responded better to in-crop N applied during the vegetative versus the reproductive growth stages and to NBPT treated urea versus untreated urea. However, in most cases, the form or timing of in-crop N did not matter and, in one case and on average, the split applications did not yield as well as when all the N was side-banded.
Grower Benefits
This work has shown reasonably strong and consistent responses to N fertilizer. While the optimum rate varied across sites, rates ranging from 80-105 kg N/ha are likely to suffice under most circumstances. Although higher rates of side-banded urea can have a negative effect on establishment, the magnitude of any such effects is likely to be small at typical N rates and not nearly as important as other factors (i.e., seeding rate, depth, soil moisture during and after seeding) in determining the absolute plant populations that are achieved. Striving to do a good job of seeding and utilizing adequate seeding rates is likely far more beneficial than utilizing polymer coated urea or split applications when it comes to achieving optimal plant stands. There were no yield benefits to utilizing controlled release N forms or split applications but, on one occasion, a substantial yield penalty was associated with the split applications. It should be appreciated that the relative performance of different N forms will vary with environmental conditions and in-crop N may occasionally be useful to correct deficiencies during the season; however, side-banded, untreated urea performed consistently well overall in the current project and continues to be the recommended practice under most circumstances.
Flax Response to Non-Traditional Nitrogen Fertilizer Management Strategies 2021 – SK Oilseeds
