Results & Discussion

Results

Experiment I

Grain Yield

A multi-factor ANOVA (Table 8) shows significant N rate, Location and N rate*Location interaction effects on grain protein content. It also shows insignificant N form effects on grain protein content. Due to the significant interaction effect, further contrast comparisons were performed in regard to N rate. Contrasts between N rates (Table 9 and Figure 18) show a significant difference between all treatments.

N form did not affect grain yield or protein. Different N rates regardless of N form affected yield and protein content. Averaged across all site years, the N rate of 180kg/ha produced the highest yield and the lowest yield was seen in the 60kg/ha N rate. N rates of 120, 180 and 240kg/ha were insignificantly different from each other in their effects on yield, but all produced significantly higher yields than the 60kg/ha rate. Grain protein content increased almost linearly with N rate and significant differences between each rate were observed.

Effect size statistics

Site specific example - Edmonton 2019 Yield

Since N rate has been determined to significantly affect grain yield, effect size statistics will be calculated on it. In order to perform effect size statistics regarding the effects of N rate on yield, the data from the Edmonton 2019 site year was chosen due to its resemblance towards the entirety of experiment I. The significant effects shown in table 10 are similar to the mean results of experiment I.

Since the N rate of 180kg/ha had the largest yield, it will serve as reference for effect size statistics. As presented in Table 11, 180kg/ha has a very high probability for gains greater than 10% compared to 60kg/ha. This diminished substantially when compared to 120kg/ha as the probability for gains greater than 7.5% are less than 0.1. Finally, gains greater than 2.5% are extremely improbable (0.03) relative to the N rate of 240kg/ha.

Experiment II

Grain Yield

A multi-factor ANOVA (Table 12) shows significant Cultivar, N timing, Location and N timing*Location interaction effects on grain yield. N form is shown to insignificantly affect grain yield. Due to the significant interaction effect, further contrast comparisons were performed. Contrasts between N timings (Table 13) show significant differences in yield between all N timings.

Grain Protein Content

A multi-factor ANOVA (Table 14) shows significant Cultivar, N timing, Location and N timing*Location interaction effects on grain protein content. N form is shown to insignificantly affect grain protein content. Due to the significant interaction effect, further contrast comparisons were performed. Contrasts between N timings (Table 15) show a significant difference in grain protein content between 1 N application and 2 or 3 applications, but no significant difference between 2 and 3 applications.

N form did not affect grain yield or protein content. Cultivar significantly affected grain yield and protein. There were significant differences between each N timing of application in terms of grain yield (Figure 20) and protein (Figure 21) with the exception of an insignificant difference in protein between 2 and 3 split applications. Yield and protein content decreased in both cultivars from 1 N application to 3 split applications. AC Stettler had higher protein content whereas AAC Viewfield had higher yields at each N timing respectively.

Effect size statistics

Site specific example - Lethbridge Irrigated 2019 Yield

Since N timing has been determined to significantly affect grain yield, effect size statistics will be calculated on it. In order to perform effect size statistics regarding the effects of N timing on yield, the data from the Lethbridge Irr 2019 site year was chosen due to its resemblance towards the entirety of experiment II. The significant effects shown in Table 16 are similar to the mean results of experiment II.

The all side-banded N treatment (1 application) had the highest yield, so it will serve as reference for effect size statistics. In AC Stettler (Table 18), 1 N application will deliver 5% greater gains over 2 split applications with a high probability (0.87) but soon lowers (0.48) once greater than 10% gains are asked. 1 N application will also deliver yield gains upwards of 30% over 3 split applications with high probability (0.85). Similar results are seen in AAC Viewfield (Table 19) with slightly lower probabilities at each level (except 1 over 3 at 5 and 10% gains).

Discussion and conclusions

Experiment I

Across all site years, grain yields generally began to level off with N rates above 120kg/ha illustrated by the insignificant difference between yield at 120, 180 and 240kg/ha. At the highest N rate level of 240kg/ha, yields began to reduce showing a negative response to additional N. Conversely, protein response continually increased with an increase in N rate. This response is well documented where the plants can only convert so much N into yield and at a certain point the plant shifts to a protein synthesis response (Simmonds, 1995). These results are promising, as they enforce the notion that grower can apply heavier N rates to induce a protein synthesis response. This would be ideal for a grower who is concerned they may not make grade qualities for CWRS milling. A cautionary note however, is that applying more N does not always equate to higher yields as seen here, and by following this logic, a grower would be wasting resources chasing higher yields by solely applying more N.

With the results of effect size statistics performed in Table 11, we can say that N rates of 180kg/ha will have at least a 10% yield gain compared to 60kg/ha with 99% confidence. We are also only 65% confident in saying that 5% yield gains are probable using N rates of 180 over 120kg/ha. From this we can infer that by using N rates of 180kg/ha we would probably expect yield increases of only about 5% while incurring 1.5 times the cost. This would likely result in 120kg/ha being the most profitable N rate based on the results depicted here.

Experiment II

In general, the N application timing which yielded the highest and resulted in the highest grain protein content was banding at planting. This is supportive of the common style of side banding all nutrients during seeding which is prominent in Western Canada. The split applications seen here varied in benefit with the two way split application seeing more promise than the three way split. Split applications that broadcast fertilizer by their nature leave fertilizer on the soil surface. This can be lost on its way to the crop and could account for a lower yield or protein content.

By using the results of Tables 18 and 19, we can say with 99% confidence that yield gains of at least 20% are probable by applying all N at seeding rather than 3 split applications in AC Stettler. We can also can also make this same statement in AAC Viewfield, with 90% confidence. In regard to 1 N application in AC Stettler, we are 87% confident in saying that yield gains of 5% are achievable over 2 split applications, while only being 42% confident in AAC Viewfield. Overall, 1 N application at seeding is greatly beneficial for yield over 3 split applications and slightly beneficial over 2 applications.

Enhanced Efficiency Fertilizers

In both experiments, N form did not significantly affect grain yield or protein content. The different enhanced efficiency fertilizers studied here do not show improvements over conventional urea. This suggests the use of enhanced efficiency fertilizers may not be best for improving existing yield and protein returns seen with urea. Proper N rates to apply sufficient nutrients to the crop were reinforced here with rates of 120kg/ha or greater being needed to attain higher yields. Applying all N at seeding was also observed to show greatest yield and protein returns.

From this research, applying an EEF or urea at planting with a target rate of at least 120kg/ha of N, is best to optimize yield and protein for CWRS production in Western Canada.