Despite the availability of high-quality (> 90% germination) seeds for Canola, the initial crop establishment in the field has often been found to be variable and low. Under field conditions, only 40-60% of Canola seeds emerge to form seedlings. The seedling emergence and survival may be even lower under poor agronomic conditions such as drought, low temperatures, high seed depth (exceeding 2.5 cm), or low seed vigor. Since the canola seed is a substantial input cost for the producers, reliable improvements in crop establishment can result in significant savings for the producers.
Precision planters (row crop planters) are increasingly being used to seed canola, particularly in the regions where they have already been used for seeding corn, soybeans, dry beans, and sugar beets. Precision planters provide superior depth control and seed placement at precise distances along the row compared to the conventional seeders, and thus have the potential to improve the proportion, uniformity, and rapidity of canola emergence.
Ken Coles Farming Smarter
Alberta Canola Producers Commission (Alberta Canola), Manitoba Canola Growers Association (Manitoba Canola Growers), Farming Smarter
To determine the efficiency of precision planters for canola seeding, Farming Smarter conducted field experiments at three locations across southern Alberta from 2016 to 2019 comparing the performance of precision planters (12" and 20" seeding row width) and conventional air drill seeder at five different seeding rates (20, 40, 60, 80 and 160 seed/m2) for their effect on the emergence, growth and yield of canola. Additionally, optimum rate of in-row liquid phosphorus (P) application to canola during seeding with precision planters and air drill was determined in a separate field experiment at the same locations during 2016-2019.
Determine the effect of precision planter at two seeding-row widths (12" and 20") compared to the conventional seeder on canola emergence, growth, and yield.
Determine the optimum seeding rate for seeding canola using precision planters (12" and 20") and conventional air drill
Determine the optimum seed-safe rate of in-row liquid P application to canola when using precision planter
Two separate field experiments were conducted at each site for each year. For the first experiment, precision planters with 12" and 20" row spacing and a conventional air drill with 12" row spacing were used to seed canola at five different seeding rates (20, 40, 60, 80 and 160 seed/m2). This experiment was designed as a 3x5 factorial randomised complete block design (RCBD) with a total of 15 treatments, each replicated four times in a split-plot design to reduce the impact of spatial variability on treatments of most interest.
For the second experiment, precision planters (12" and 20") and air drill were used to seed canola with the in-row liquid ammonium phosphate (10-34-0) application at six different application rates (0, 5, 10, 20, 40, 60 kg/ha P). For year 2016, only five application rates of P were used, including 0, 5, 10, 20, and 40 kg/ha. For this experiment, a total of 15 treatments were again replicated four times in a completely randomized block design.
To determine crop emergence we conducted plant counts in two 1-m rows at representative locations in each plot (front and back). Then divided these plant counts into the initial seeding rate for each treatment to determine the percent emergence for each plot.
We conducted a visual evaluation of the uniformity of emergence at the 4-leaf stage for each trial. This qualitative measure rated each plot as either uniform or non-uniform based on observed uniformity of crop stage across each plot.
We determined plant density by counting plants in two, 1-m rows at two representative places (front and back) in each plot. Canopy closure was estimated using three measures - visual canopy rating, normalized difference vegetation index (NDVI) and fractional green canopy cover (FGCC). Visual canopy ratings were taken by estimating the row width vs bare ground between rows. (For example, a row where the canola was approx. 10 inches wide, with 10 inches of bar ground was 50% closure. Twenty inches wide where the canola was just touching the other rows was 100%).
NDVI was measured using a NTech Greenseeker. Plots were sampled at or near solar noon, in a diagonal direction across the plot. FGCC measurements were taken using a smartphone mounted to a tripod using the Canapeo Android App. We also isolated plots using UAV photos and batch processed through the Canapeo software. Both methods were comparable. Visual canopy rating was less reliable compared to the NDVI and FGCC metrics and was obtained for only 5 out 12 site years. Hence the visual canopy ratings have not been discussed in the report, however, the data associated with it has been included in Appendix I.
NDVI measurements were obtained for years 2016 and 2018. FGCC measurements using the Canopeo app were obtained for the years 2017-2019. Additionally, the number of days to the start and end of flowering and days to canola maturity were recorded. Canola yield was determined with plot combine harvestMaster system. The data were analyzed using the linear mixed model in SAS and R programs.
Degree of crop emergence (%), uniformity of emergence and plant stand density were measured. Crop emergence (%) declined with increasing seeding rates. This is an expected trend, since the competition for resources among the emerging seedlings increases with an increase in seeding rates, thus leading to higher seedling mortality. Crop emergence also varied notably between different planters. Emergence (%) for the precision planter (12") was 1.2-1.5 times higher compared to the air drill and 20" planter for seeding rates between 40 to 180 seeds/m2 (Figure 1). Both the planters (12" and 20") led to uniform emergence in 83% of plots across all locations. The air drill had uniform emergence in only 58% of the plots. This trend was consistent at both the irrigated and rainfed locations. The air drill was prone to uneven emergence largely due to variable seeding depth. Differences in seeding depth led to variability in crop developmental stages, such that seeds sown at shallow depth reached the 4-leaf stage while deeper-sown seeds were still at the 2-leaf or cotyledon stage.
Plant density, which measures the number of plants/m² upon crop establishment, also varied between different planters. The three planters did not show any statistically significant difference at the lowest seed rate (20 seeds/m²), but the 12" planter led to a greater increase in plant density compared to other planters at higher seed rates (Figure 1). Plant stand density for the 12” planter exceeded the other seeders by about 5 plants/m² at 40 and 60 seeds/m², approx.10 plants/m² at 80 seeds/m², and 15-20 plants/m² at 160 seeds/m² rate. The trends were similar across irrigated and rainfed locations, with the precision planter (12") leading to higher crop emergence and plant density compared to air drill and precision planter (20") (Figure 1). These data indicate that 12” planter provides a distinct advantage for canola emergence and plant density.
While the competition between plants is low at 20 seeds/m2 rate, the inter-plant competition increases at higher seeding rates. Thus, at higher seeding rates, uniform seed placement and superior depth control provided by the 12" planter leads to higher emergence and plant stand establishment. The 20” planter, on the other hand, does not differ significantly from the air drill in terms of plant emergence and density. This is likely because of the larger inter-row width for 20" planter; more seeds have to be placed in each row to obtain the same seed density as other planters. Thus, higher number of seeds are placed in each row, which increases the competition between plants and is detrimental to early season canola performance.
The effect of different planters on the canopy closure obtained by the crop was of particular interest, since the wider 12" and 20" seed rows are expected to impact the canopy closure obtained by the crop. Canopy closure was estimated using the NDVI and FGCC measurements. NDVI measurements provide a reliable proxy measurement for the photosynthetic activity of the plants. However, extraneous factors such as growth stage of the crop, weed abundance and density, and soil fertility etc. were expected to confound this measurement. The 12" planter also led to higher canopy closure at the irrigated plot in Lethbridge, while the canopy closure at the rainfed plot in Lethbridge was higher for the air drill, thus indicating that that the 12" planter leads to a better canopy cover in increased crop growth conditions (Figure 2).
Across all seed rates, the 20” planter had an average yield of 2114 kg/ha. The air drill and 12" planter by comparison led to an average yield of 2812 and 2972 kg/ha, respectively. Canola yield for the 20" planter was 20-28% less compared to the air drill for different seed rates (Figure 3). The wider rows on the 20" planter led to increased interplant competition throughout the growing season. Furthermore, the wider rows delay canopy closure and limit access to resources such as water, sunlight, and nutrients between the rows.
While the differences in yield between the air drill and 12" planter were statistically non-significant, the 12" planter consistently led to a 2-10 % increase in yield compared to the air drill at all seeding rates (Figure 3). The 12" planter led to an average increase of 160 kg/ha of canola yield, which although small in magnitude, may lead to significant increase in profit across the millions of acres of canola production for the industry.
More importantly, there was a significant difference in the performance of air drill and 12" planter when observed across different cropping conditions. At the irrigated Lethbridge location, the average yield for all planters was higher compared to the rainfed Lethbridge and Medicine Hat locations (Figure 4). However, 12" planter led to a significantly higher yield compared to air drill and 20" planter at the irrigated location, with an increase in average canola yield of 463 kg/ha compared to the air drill and 1584 kg/ha compared to the 20" planter (Figure 4).
At the rainfed locations, the difference in yields between the air drill and 12" planter was not statistically significant, while the 20" planter had a significantly less yield. Similar trends were observed when the canola yield for different planters was observed across the years. During 2016 and 2017, the 12" planter showed a trend of higher yield compared to the air drill for all seed rates (Figure 5). These years had a high cumulative precipitation, with an annual precipitation of 420 and 303 mm at Medicine Hat, and 369 and 278 mm at Lethbridge during 2016 and 2017, respectively.
Conversely, the yields were higher for air drill compared to the planters during 2018, when the annual precipitation was low, with an average annual precipitation of 199.6 mm at Medicine Hat, and 261 mm at Lethbridge. These trends indicate that the 12" planter performs better in the conditions that favor increased crop production, which may be attributed to the precise control of 12" planters on seed placement which helps to reduce interplant competition, thus enabling higher crop production. However, the performance of air drill is comparable to the 12" planter in growth-limited conditions since the inter-plant competition is reduced by limited crop production.
Liquid Phosphorous Study
The major purpose of this trial was to estimate the seed-safe rates of in-row liquid P fertilizer when using precision planters. The data were obtained on plant establishment, growth, and yield parameters similar to the previous trial.
Addition of liquid P at any rate did not affect the plant stand density for the air drill. However, with the precision planters (12" and 20"), plant density at fertilizer rate of 60 kg/ha was lower (Figure 6), thus indicating that high P fertilization rate at 60 kg/ha may have led to some degree of seedling mortality in case of precision planters.
Crop yield did not show any differences amongst the P application rates. When observed across the planters, the air drill and precision planter with 12" spacing showed similar trends with no differences in yield across different liquid P application rates. However, the precision planter with 20" spacing showed lower yield with liquid P application rate of 60 kg/ha, although the differences are not statistically significant (Figure 7). These results in aggregate indicate that higher liquid P application rates (60 kg/ha) may have led to increased seedling mortality in case of precision planters (12" and 20") thus reducing plant stand density at the initial crop establishment phase.
However, crops were able to recover from the initial losses thus leading to no substantial differences between different P rates for crop yield. The recovery may, however, be less effective for the precision planter with 20" spacing compared to the 12" planter, since the 20" planter had lesser crop yield for liquid P application rate of 60 kg/ha compared to other fertilizer rates. The application of liquid P to canola crop at any rate did not improve plant emergence, growth or yield significantly compared to no application of liquid P. Thus, the use of liquid P for canola crop production may be re-evaluated under these conditions.
The results from this 4-year study provide critical information to the crop producers regarding the adoption of precision planters in canola production. Producers are already adopting the row crop planters for planting canola to improve crop emergence. The results of this study indicate that the adoption of wide (20”) row planters to seed canola may lead to significant reduction in crop yield. This is an important observation since many of the producers that are adopting planters for seeding canola are opting for wider (20 or 22”) row planters. This project does not recommend the adoption of wide row planters for canola seeding.
On the other hand, this project indicates that narrow row (12”) precision planters leads to higher crop emergence, growth and yield in canola compared to the air drill and 20" precision planters. The benefits of precision planters to crop growth are more pronounced in favorable crop conditions (e.g. irrigated conditions, high rainfall), and at higher seeding rates (more than 60 seeds/m2). Thus, the study recommends the adoption of narrow precision planters (12") for the seeding of canola.