Evaluation of nitrate leaching, fatty acids, physiological traits and yield of rapeseed (Brassica napus) in response to tillage, irrigation and fertilizer management

Purpose Conservation tillage systems, including no-till and minimum-till, benefit soil quality and soil water preservation as well as reduce the economic and energetic costs of agricultural production. Nonetheless, specific knowledge regarding the interactions between conservation tillage and other crop management practices targeting improved system sustainability on crop yield and quality as well as nitrogen dynamics and losses remain understudied in drought impacted, arid and semi-arid environments and sandy soils. This study investigated the effects of different tillage systems (no-tillage, minimum and conventional), fertilizers (no fertilizer, vermicompost, urea and combined urea and vermicompost (VU) and irrigation regimes (normal irrigation and irrigation after 50% field capacity) on various quantitative and qualitative traits of rapeseed as well as soil nitrate leaching (NL). Methods Field trials were conducted between two growing seasons (2017–2018 and 2018–2019) in Karaj, Iran. The experimental design was a randomized complete block with the arrangement split-split-plot and three replications. Tillage system was assigned to the main plot meanwhile, irrigation was considered as the sub-plot and fertilizer was considered as sub-sub-plot. Results Under both the deficit and normal irrigation regimes and across all tillage types, the highest seed yield, oil yield and nitrogen use efficiency (NUE) were found where VU treatment was applied. Furthermore, across all tillage types, the highest NL was observed where urea was applied. When compared with urea, vermicompost and UV treatments respectively decreased the NL by 67 and 50% in no-till plots, 50 and 36% in minimum till plots and 49 and 34% in conventional till plots. Consistent with this, the lowest mean NL (10.4 kg ha −1 ) resulted from plots where the water-deficit condition was combined with no fertilizer meanwhile, the highest mean NL (83.1 kg ha −1 ) resulted where normal irrigation was combined with urea. Conclusion The findings indicate that minimum till in combination with VU treatments support reduced NL over conventional till and urea fertilization practices while improving rapeseed quantitative and qualitative traits.