The effects of Co-Application of Humic Acid and Phosphorous Fertilizer on Vegetative Growth Indices and Phosphorous Availability in Canola

Humic acid has a pseudo hormonal activity that increases plant growth and nutrient uptake. In the present study, the effects of different levels of humic acid and phosphorus fertilizer on vegetative growth indices (Plant height, Fresh and dry weight of stem and leaf, number of flowers, number of leaves and branches) and phosphorus availability in canola (Brassica napus L.) cv. Hyola 50 were investigated. For this purpose, the pot experiment as factorial based on completely randomized design in three replications has been conducted. Treatments include phosphorous fertilizer as super phosphate in three levels 0, 50 and 100 mg/kg, humic acid in three levels 0, 0.5 and 1 g/kg and application methods of phosphorous and humic acid. Based on the results, the effect of different concentrations of phosphorus, humic acid and its method of application, and their interaction in all studied traits, except for the number of branches, were significant (p≤0.01). Results of the interaction effect of humic acid concentration and its application methods in the presence of phosphorous treatments showed that the highest amounts of fresh and dry weight of leaves and stem obtained in 100 mg/kg phosphorous and 1 g/kg humic acid applied with irrigation water. The highest phosphorous content in leaves and stem by 0.3 percent observed in 1 g/kg humic acid and 100 mg/kg phosphorous applied with irrigation water. Additionally, different concentrations of phosphorous and humic acid and their application methods and their interactions decreased canola flowering period from 144 days to 93 days. Combined application of 100 mg/kg phosphorous and 1 g/kg humic acid within irrigation water resulted in maximum increase in vegetative growth indices and phosphorous content in canola shoot.