Efficacy of Penicillium bilaiae for enhancing yield and phosphorus uptake of fall-seeded canola

E. M. Sanders 2003.

It is unknown whether Penicillium bilaiae inoculated onto canola seed sown in the fall is able to enhance yield and phosphorus (P) uptake. At the initiation of the project fall-seeding canola was thought to be a justifiable practice for Saskatchewan farmers. The objectives of this study were to: 1) determine if fall-seeded canola inoculated with Jumpstart® caused a comparable increase in P uptake and dry matter yield to fall-seeded canola fertilized with 11.2 kg ha^-1 of triple superphosphate; 2) determine if Jumpstart® affected yield and P uptake in a similar manner for fall-seeded and spring-seeded canola; 3) determine if the P. bilaiae organism in Jumpstart® has the ability to survive freezing associated with Saskatchewan winters; 4) determine if the Extender® polymer coating affected the viability of P. bilaiae; and 5) determine if the Vitavax RS® fungicide affected the viability of P. bilaiae. In order to meet these objectives, compatibility, freeze testing and field studies were completed. A decrease in numbers by one log was considered the limit for P. bilaiae survival. Laboratory investigations revealed that the number of colony forming units (cfu) of P. bilaiae remained high enough on seed treated with a fungicide, Vitavax RS® to be considered viable for 2.5 d. Survival of P. bilaiae was lost when applied in combination with Vitavax RS® and a seed polymer, Extender® after 1.5 d. Penicillium bilaiae on canola seed was frozen at a controlled rate of -2 °C per hour to -40°C and then the temperature was further cooled to -196 °C. The numbers of cfu were still above the one log limit at -196 °C resulting in P. bilaiae survival to that low temperature. There was a large initial decrease of 0.6 log in P. bilaiae survival on canola seed when the inoculated seed was placed directly into a -20 °C freezer. There was no further decrease in survival after this initial decrease and survival was still above the one log drop at 100 d. A controlled decrease in temperature to -8 °C followed by a thaw to +2 °C resulted in no change in P. bilaiae numbers after four consecutive freeze-thaw cycles. For the field studies, P. bilaiae was inoculated onto canola seed and seeded in the fall and early spring with or without triple superphosphate fertilizer. The fall-seeded canola was seeded either with or without the Extender® polymer. There was a 37.4 g m^-2 (374 kg ha-1) increase in yield at one site with Extender® where the fall temperatures were above freezing following seeding of the canola. In all other cases, there was no difference. There was on average a 3.3 g m^-2 and 46.8 g m^-2 increase in aboveground biomass at 4 and 6 wk respectively and a 57.7 g m^-2 increase in seed yield when the canola was seeded in the spring compared to seeding in the fall. There were no responses to P. bilaiae at any of the sites. A P fertilizer response compared to the control occurred only at a few sites and at these sites the P response was not consistent among all parameters tested. Seeding date had no effect on the response of canola to P treatment. Precipitation levels were approximately 38% and 66% below normal in 2001 and 2002 respectively. It is concluded that moisture conditions were not favorable for a P. bilaiae inoculant response. However, there is evidence that P. bilaiae has the ability to survive freezing conditions while overwintering on fall-seeded canola.