PGPR and vermicompost with reduced chemical fertilizer enhances biodiesel production, nutrient uptake and improve oil composition of rapeseed grown under water deficit stress

Abstract

In this study, we investigated the impact of different irrigation regimes and fertilizer treatments on the yield, oil composition, and biodiesel production of rapeseed (Brassica napus). The experiment was conducted over two years (2020–2021) using a split-plot design. The main plots were assigned four irrigation regimes (70, 100, 130, and 160 mm evaporation), while the sub-plots were allocated five fertilizer treatments (no fertilizer, chemical fertilizers, plant growth-promoting rhizobacteria (PGPR) inoculation, vermicompost, and a combination of fertilizers). Our findings indicate that water limitation decreased the nutrient content, grain weight, oil content, and yield of rapeseed. However, it also increased the oleic acid, oleic/(linoleic+linolenic) ratio, and biodiesel yield. The use of chemical fertilizers negatively impacted the quality of rapeseed oil. In contrast, PGPR inoculation, particularly in combination with other fertilizers, increased the grain yield, oil content, and quality, as well as biodiesel production by improving nutrient uptake. An integrated fertilizer management approach can enhance the yield and quality of rapeseed oil while minimizing the use of chemical fertilizers. This approach promotes sustainable production in arid and semi-arid regions. Our research led to a 67% reduction in chemical fertilizer usage while increasing biodiesel production. Furthermore, our study highlights the significance of using PGPR and vermicompost in combination to improve the nutritional uptake and oil composition of rapeseed. Overall, our study provides valuable insights into optimizing irrigation and fertilizer management for rapeseed cultivation. These insights have implications for sustainable agriculture practices in similar environments.