Investigation of the application of urea fertilizer, mycorrhiza, and foliar application of humic acid on quantitative and qualitative properties of canola

Nutrient management plays an essential role in canola grain production. Nitrogen is essential for crop growth and yield, so nitrogen deficiency is a significant crop production limiting factor. Mycorrhizal fungi have symbiotic relationships with the roots of most crops, enhancing the growth and yield of host plants by enhancing their ability to absorb water and nutrients and resist disease. Humic acid can increase enzymes and proteins by enhancing a plant's ability to absorb nitrogen, thereby enhancing plant growth and yield. This study aimed to examine the substitution and reduction of chemical fertilizer application with mycorrhiza fertilizer and foliar application of humic acid. This study was conducted in split-split plots arranged in a randomized complete block design with three replications in 2019-2020. Experimental treatments included three levels of nitrogen fertilizer (0, 50, and 100 kg ha-1 nitrogen from urea) as the main factors and mycorrhizal inoculation and foliar application of humic acid (use and non-use) as sub-factors. Each experimental plot comprised six planting lines with a distance of 40 cm. Each replication consisted of 12 plots, with a distance of 2m between replicates and 1 m between treatments. Mycorrhiza fertilizer contained 100 active fungal organs per gram and three species: Funneliformis mosseae, Glomus etunicatum, and Rhizophagus irregularis. A manual sprayer was used to apply 2 liters of Humic acid per hectare at the beginning of the stem and at the time of flowering (50% flowering of rapeseed). The co-treatment with 100 kg ha-1 nitrogen fertilizer and mycorrhizal inoculation and non-inoculation treatments yielded the highest grain yield at 3838.4 kg ha-1 and 3551.7 kg ha-1, respectively, an increase of 72% and 59% over the control and non-inoculation treatments. The highest seed oil content was observed in the 100 kg ha-1 and 50 kg ha-1 nitrogen fertilizer treatments, with increases of 12.5% and 11.3% over the control treatment. The application of 100 kg/ha of nitrogen with mycorrhiza and spraying with humic acid resulted in the highest grain protein at 20.44 and 19.4%, with increases of 34.7% and 27.9%, respectively, compared to not applying nitrogen fertilizer, mycorrhiza, and humic acid. The treatment with 100 kg ha-1 of nitrogen fertilizer and mycorrhiza inoculation produced the highest grain phosphorus at 0.58%, while the treatment with no nitrogen fertilizer and no mycorrhiza inoculation produced the lowest grain phosphorus at 48.7%. The results demonstrated that there was a significant difference between the levels of nitrogen fertilizer. However, grain yield is improved with the application of nitrogen and mycorrhizal fertilizers together. Compared to nitrogen fertilizer and mycorrhiza treatments, humic acid did not result in a statistically significant increase in the studied traits. It is recommended, however, that this test be evaluated for a number of years in other regions. Overall, the simultaneous application of 50 kg ha-1 of nitrogen and mycorrhizal inoculation seemed acceptable for canola yield. Although in this study, 100 kg ha-1 of nitrogen fertilizer produced the highest yield, reducing the use of chemical fertilizers and increasing the use of mycorrhiza fertilizers reduces costs and environmental damage.