Comparison of Response of Canola (Brassica napus L. cv. Hyola 401) to Biofertilizer Inoculation in Optimal and Delayed Cropping Dates

In order to compare the effects of phosphate solubilizing bacteria as biofertilizer and mineral phosphorous application in optimal date of sowing with delayed cropping date on canola (Brassica napus L.) growth and productivity, a split-plot experiment, using randomized complete block design with three replications, was conducted at Dashate-Naz Agronomy Research Station, in 2014. Four levels of bacterial inoculation (Pseudomonas putida, Pseudomonas fluorescens, singly or in combination) were applied as main plots and five levels of mineral phosphorus (P) application (0, 25, 50, 75, and 100 kg·ha⁻¹ of mineral phosphorous) were applied as sub plots. Canola plant were sown at two dates of sowing, one at optimal date of sowing (30 Sept., 2014) and the other one month later as delayed cropping (30 Oct., 2014). The results obtained showed that effects of bacterial inoculation on number of seeds per pod, number of pods on plant, and seed yield were significant at one percent probability level at both sowing dates. Moreover, rates of phosphate application had significant effects on all traits at one percent level. Comparing the means showed that application of mineral P resulted in substantial increase in seed yield. At optimal date of sowing, it was shown that while minimum seed yield obtained at control treatment (1600 kg·ha⁻¹), the maximum (2980 kg·ha⁻¹) obtained with interaction effects of application of both bacterial strains along with 75 kg·ha⁻¹ mineral P, having no statistically difference with that of P. fluorescens, along with 75 kg·ha⁻¹ mineral P (2940 kg·ha⁻¹). It was shown that delayed cropping resulted in decreasing canola growth which is reflected in seed yield and yield components. Minimum seed yield at control plot at first date of sowing (1600 kg·ha⁻¹) decreased to 740 kg·ha⁻¹, in the second date of sowing, showing 54 % decrease. The maximum seed yield also decreased in delayed cropping, from 2980 kg·ha⁻¹ at 30 Sept., 2014, as compared to 1074 kg·ha⁻¹ at 30 Oct., 2014, showing a 64% decrease. The results obtained showed that an increase in P level, eventually enhanced the seed yield. This increasing trend continued until a threshold level (75 kg·ha⁻¹ of P), after which seed yield showed a declining fashion.