Categories: Canola; Fertility
ECODA project number: B.5
Principal investigator: Bao-Luo Ma
Field experiments were conducted across Eastern Canada to investigate the growth, yield and quality traits of canola crop to preplant and sidedress application of nitrogen (N) fertilizer as urea at various combinations with soil applied sulphur (S) as ammonium sulphate, and soil and foliar applied boron (B) in the form of Alpine Boron. A greenhouse experiment was also conducted on soils collected from three field sites (Ste‐ Anne‐ de‐ Bellevue, Ottawa, St‐ Augustin) to determine the impact of application of N, S and B on main soil quality indicators. Overall, the following conclusions can be drawn:
- Canola yields are highly dependent on weather, soil N and S fertility. There is also a definite yield advantage when the application of N was split between planting and the rosette stage. The addition of N fertilizer significantly increased canola yields.
- Sidedressed N fertilizer appeared to be better utilized by the crop and therefore producing greater yields than the crop that received equivalent amounts of N all at preplant. For every kg ha‐1 N fertilizer, yields increased on average by 9.7 kg ha‐1 for preplant application, but increased by 13.7 kg ha‐1 when sidedress N was applied later at the rosette stage.
- The severe drought that occurred in Eastern Ontario and Southern Quebec in 2012, increased variability and lower yield potential that inhibited detection of any yield response to N fertilizer rates, either preplant or sidedress application, indicating devastating drought effect on canola production.
- Preplant S at 20 kg ha‐1 in the form of ammonium sulphate significantly increased yields over plots that received no sulphur.
- The lack of difference in yields between plots with boron and plots that received no boron may indicate that the tested fields were sufficient in boron or soil boron was unavailable to the crop when it was needed. However there appeared to be a yield advantage when boron is applied foliarly at the 20% flowering stage, suggesting that the plants are very efficient at boron uptake through their leaves.
- Canopy reflectance measured by commercial instruments, CropScan, Greenseeker, or the UniSpec—DC, appeared to be a good indicator of the crop health. Canopy reflectance, expressed as normalized difference vegetation index (NDVI) values from these instruments were strongly correlated with the amounts of N added to the soil before seeding. NDVI readings at the rosette and 20% flowering stage are also strongly correlated to final yields. These data indicate that measurements of canopy reflectance have the potential to be used as a crop need‐based indicator for guiding sidedress N application rates.
- Aboveground biomass at the 20% flowering stage and leaf area index (LAI) significantly increased with increasing amounts of preplant N, with the lowest LAI values in the 0 N treatment and the highest LAI readings in the 150 (2011) or 200 kg N ha‐1 (2012) plots. At the early flowering stage, the plots that received additional N at sidedressing (50+50, 50+100, 50+150 kg N ha‐1) had similar LAI and biomass values to the plots that received 50 kg ha‐1 preplant N, indicating that it took some time for the N to be hydrolyzed from the applied urea, taken up by the crop, and exhibited a positive effect on the plant growth.
- Plant heights, number of branches per plant, number of pods per plant, number of seeds/pod and number of seeds per plant all significantly increased with increasing the amounts of preplant N application.
- The seed from all sites was categorised as grade No. 1 canola seed as there was less than 2% distinctly green seed and less than 5% damaged seed (which includes the green seed) at the Ottawa site in both years, indicating high seed quality canola can be produced in Eastern Ontario.
- Nitrogen fertilizer significantly affects the protein and oil content of the seed. Increasing amounts of N generally increased seed protein concentration (meal quality), but actually suppressed seed oil concentration (oil yield) at all sites. This suggests that high level of N application could increase canola meal quality for animal feed, but may reduce the oil extraction rates.
- Soil amendment with sulphur had no effect on either oil or protein levels. However oil levels appeared to be lower in plots that received foliar boron compared to plots that receive no B or soil‐applied B (2 kg ha‐1) at preplant.
- The drought conditions in Ottawa and Montreal in 2012 also affected the seed protein and oil concentrations, with higher protein and lower oil content in 2012 than those in 2011.
- Seed oil concentrations estimated by the Unity Scientific SpectraStar 2500x NIR spectrometer were generally lower than those measured by the Foss InfratecTM 1241 Grain Analyzer. Seed oil concentrations of the same samples estimated in 2011 and 2012 using the same instrument (Unity Scientific SpectraStar 2500x NIR spectrometer) differed by up to 4%, indicating that caution must be taken when interpreting the NIR spectroscopy results and timely and frequent calibration with chemistry procedures are necessary.
- Nitrogen concentrations in plant and seed components increased significantly with increasing amounts of N application (P < 0.01) with the highest N concentrations found in plants from plots that received sidedressed N. At early flowering stage, N concentrations of the whole plant were higher for fertilized plots than those receiving no or low N fertilizer, reflecting soil N supply power. At harvest canola seed contained much higher N concentrations than the straw, indicating that N has been translocated from the vegetative components to the grain during the grain filling period.
- Under drought conditions, plant straw at harvest contained much higher N concentrations (10‐15 g kg‐1) than plants that were grown under more or less normal conditions (3‐5 g kg‐1), indicating N remobilization under drought conditions was restricted. This will affect soil N transformation and soil N supplying power to the succeeding crop.
- Biofertilizers identified and screened at the controlled greenhouse conditions showed negligible effect on canola growth and final yield under field conditions. This is likely due to the fact that extreme drought that occurred in 2012 canola growing season had substantially suppressed canola yield potential and that there was a likely confounding effect between biofertilizer and drought stress.