Summary
- Yield at very low seed rates of 0.3 and 0.5kg/ha were comparable to yields at higher seed rates of 1.0 and 2.5kg/ha when using a precision seeding machine.
- Yields in excess of 2.0t/ha were achieved when sowing at 50cm row spacing.
- These results suggest we should continue investigating more precise seed delivery systems.
Background and aim
There are two main reasons to test precision seeding technology. Firstly previous studies in both Western Australia and in Canada show that yields of lupin and canola can be improved when plants are sown in a more uniform distribution. Canadian researchers reported up to 32% increase in yield from uniform plant arrangements compared to non-uniform arrangements when working with 20 plants/m2 and yields of approximately 1.0t/ha. Secondly, seed costs for canola production have increased for growers who have switched from open pollinated to hybrid varieties. Using better seed placement methods and avoiding too much competition between the canola plants may enable seed rates to be lowered without compromising yield.
The aims were to test if growers would benefit from using precision seeding technology and to test very low seed rates of canola.
Trial details
Two trials were conducted in the northern agricultural region; one at Binnu (Northern Agri Group trial site, Ralphs Road) and the other at Ogilvie (Wepowie Farm). The seeder used was an Agricola Italiana K series pneumatic precision drill. This type of seeder is commonly used to plant coarse grains such as corn or soybeans and in horticultural production. The machine is designed to place seed at equal distances along the crop row such that the spatial distribution of the plants is even. The machine used had seven planter boxes spaced 50cm apart (50cm row spacing) hence plots were 3.5m wide and 25m long. The trial was arranged in four replicates. The Ogilvie site was sown on 15 April and the NAG site on 16 April.
Treatments
There were four treatments of different seeding rates; 0.3, 0.5, 1.0 and 2.5kg/ha.
Results
The mean average rainfall for Binnu (Bureau of Meteorology station) is 340mm and for Ogilvie, 386mm; rainfall at both sites exceeded this (Table 1). Significant rain occurred prior to the traditional mid-April sowing date, Binnu 160.2mm and Ogilvie 174.9mm. Both trials were sown on soil moisture from over 40mm received from 7-11 April. On the days of sowing the temperature was close to 30°C causing the soil to dry rapidly. Long periods without rain occurred throughout winter: 12 April-17 May (1.2mm), 19 May-16 June (3.6mm) and 22 June-20 July (1.6mm).
| Site | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Jan-Oct |
| Binnu | 6.0 | 15.4 | 103.0 | 41.8 | 32.0 | 53.2 | 89.4 | 21.8 | 5.4 | 0.0 | 373.4 |
| Ogilvie | 4.0 | 8.2 | 100.2 | 67.0 | 17.4 | 48.0 | 100.4 | 43.8 | 3.0 | 6.0 | 398.0 |
Establishment was lower than targeted at both sites. This occurred because conditions at seeding were not ideal with temperatures close to 30°C causing the seed bed to dry rapidly. Plant densities followed the expected trend given the seeding rates (Table 2 and 3).
Plants cuts were taken at peak biomass on 8 August. Despite the differences in plant density the total biomass production did not differ between the treatments at either site at this time (Table 2 and 3). This occurred because there were large differences in the single plant weight between treatments. Plants in the lowest seed density treatments were approximately six times heavier than those in the highest density treatment at NAG and seven times at Ogilvie. This response was also observed from stem diameter measurements taken at crop maturity, the average stem diameter of plants in the lowest density treatment was approximately three times greater than plants in the highest density plots (Table 2 and 3).
| Seed rate (kg/ha) | Target distance between seeds (cm) | Target p/m2 | Actual p/m2 | Biomass 10/8 (g) | Plant weight 10/8 (g) | Stem diameter 14/9 (mm) |
|---|---|---|---|---|---|---|
| 0.31 | 37 | 6 | 3 | 690 | 177 | 33 |
| 0.54 | 22 | 10 | 6 | 823 | 146 | 25 |
| 1.01 | 11 | 20 | 15 | 843 | 104 | 17 |
| 2.50 | 4 | 45 | 36 | 706 | 20 | 11 |
| Lsd | - | - | 9 | - | 47 | 4 |
| F Prob | - | - | P < 0.001 | NS | P < 0.001 | P < 0.001 |
| Seed rate (kg/ha) | Target distance between seeds (cm) | Target p/m2 | Actual p/m2 | Biomass 10/8 (g) | Plant weight 10/8 (g) | Stem diameter (mm) |
|---|---|---|---|---|---|---|
| 0.31 | 37 | 6 | 5 | 730 | 157 | 37 |
| 0.54 | 22 | 10 | 8 | 833 | 118 | 26 |
| 1.01 | 11 | 20 | 15 | 751 | 59 | 20 |
| 2.50 | 4 | 45 | 40 | 733 | 22 | 12 |
| Lsd | - | - | 5.21 | - | 36 | 4.5 |
| F Prob | - | - | P < 0.001 | NS | P < 0.001 | P < 0.001 |
Mean seed yield was 1814kg/ha at the Northern Agri Group site and 2322kg/ha at Ogilvie. At both sites there was a trend of decreasing yield from high to low seeding rate, although the reduction in yield was less than expected given the very low plant density in the low seed rate treatments. At the Northern Agri Group site this was a significant response with the 0.31 and 0.54kg/ha seed rate treatments yielding less than the 1.01 or 2.50kg/ha seed rates (Table 4). It should be remembered that the 0.31 and 0.54kg/ha treatments had very low plant density of 2.5 and 6.0plants/m2 respectively at this site. At Ogilvie, while there was a trend of lower yield at lower seeding rates this was not statistically significant (Table 5). Another interesting point to note is that the trials were on 50cm row spacings and yields of over 2.4t/ha were achieved. This yield is well above the long term average for canola in the district and indicates that in this environment canola can yield well in favourable seasons when sown at wide row spacings.
As previously discussed there was a high level of plant plasticity to the density treatments (Figure 1). Measurements of pods per plant indicated that there were many more pods on plants in lower density plots, over ten times as many on plants in the 0.31kg treatment compared to the 2.5t/ha treatment (Table 4 and 5).
Seed quality was unaffected by the seed rate (Table 4 and 5). At both sites seed oil percentage was high, as would be expected from Hyola 404, with no significant difference between treatments. Seed weight was also unaffected by seed rate.
| Seed rate (kg/ha) | Yield (kg/ha) | Pods per plant | Oil % | 1000 seed weight (g) |
|---|---|---|---|---|
| 0.31 | 1490 | 1369 | 48.2 | 4.1 |
| 0.54 | 1697 | 993 | 47.8 | 4.1 |
| 1.01 | 2014 | 396 | 47.9 | 4.1 |
| 2.50 | 2057 | 133 | 47.5 | 4.1 |
| Lsd | 299 | 327 | - | - |
| F Prob | P < 0.05 | P < 0.001 | NS | NS |
| Seed rate (kg/ha) | Yield (kg/ha) | Pods per plant | Oil % | 1000 seed weight (g) |
|---|---|---|---|---|
| 0.31 | 2198 | 1622 | 47.6 | 3.8 |
| 0.54 | 2315 | 790 | 47.6 | 3.8 |
| 1.01 | 2312 | 357 | 47.8 | 3.8 |
| 2.50 | 2463 | 136 | 47.5 | 3.9 |
| Lsd | 280 | 258 | - | - |
| F Prob | NS | P < 0.001 | NS | NS |
At the NAG site the gross margin of the 2.5kg/ha and 1.0kg/ha treatments were similar, indicating that $47/ha could be saved in up-front costs without impacting final profit (Table 6). At seed rates lower than 1.0kg/ha gross margins declined. At the Ogilvie site gross margin was similar for the 2.5kg/ha, 1.0kg/ha and 0.5kg/ha treatments - again suggesting that up-front costs could be reduced without impacting profit (Table 7).
| Seed rate (kg/ha) | Seed cost (kg/ha) | Total costs ($/ha) | Income ($/ha) | Gross margin ($/ha) |
|---|---|---|---|---|
| 0.3 | $10 | $380 | $831 | $451 |
| 0.5 | $16 | $391 | $941 | $550 |
| 1.0 | $32 | $416 | $1119 | $703 |
| 2.5 | $79 | $467 | $1136 | $669 |
| Seed rate (kg/ha) | Seed costs ($/ha) | Total costs ($/ha) | Income ($/ha) | Gross margin ($/ha) |
|---|---|---|---|---|
| 0.3 | $10 | $397 | $1217 | $820 |
| 0.5 | $16 | $406 | $1281 | $875 |
| 1.0 | $32 | $423 | $1283 | $860 |
| 2.5 | $79 | $476 | $1359 | $883 |
Conclusions
Yields were impressive given the low seed rates and difficult establishment which resulted in very sparse populations. In both of these trials canola plants demonstrated remarkable plasticity to seeding density, this highlights that re-sowing of canola should only be done if establishment is very poor. The early sowing date and good seasonal conditions are likely to have contributed to this response.
The results of this preliminary work suggest that precision sowing may enable sowing at lower seed rates and that this is concept worth pursuing with further research in canola and other species. However, we realise that establishment rates of canola and other small grains can be low (~50% of sown seed) particularly in difficult conditions and on non-wetting soils. Hence there will always be limitations to how uniform the plant population is regardless of how accurate the seed delivery system is.
Acknowledgements
Thanks to Stephanie Boyce, Jo Walker and the Geraldton RSU for trial management and measurements and to Ben Cripps, Nolan Harris and the NAG group for providing the trial sites.
These trials, 15GE41 and 15GE42, fall under the Tactical Break Crop Agronomy project (DAW00227) co-funded by the Department of Primary Industries and Regional Development and Grains Research and Development Corporation.