Intercropping refers to the cultivation of two or more crops simultaneously on the same field to maximize resources utilization and yield. The aim of this study was to evaluate the yield, phytochemical attributes, and competition indices of the intercropping system of guar(G)-roselle(R) compared to the monoculture system. This research was performed as a split-plot experiment based on randomized complete block design (RCBD), keeping the ratio of guar and roselle in 1:1 (GR), 2:1 (GGR), 1:2 (GRR), 3:2 (GGGRR), 1:3 (GRRR) respectively, along with a sole plot of both crops as the main plot and four levels of nitrogen fertilizer (0, 40, 70,100 kg urea ha1) considered as the sub-main plot. The results demonstrated that interaction of GRR followed by 40 kg urea ha1 obtained maximum biomass (3605 kg ha1) in roselle, while GR with application of 70 kg urea ha1 and GRRR in 40 kg urea ha1 devoted the highest biomass in guar (16,104 and 14,781 kg ha1). Furthermore, regarding sepal yield, GRRR followed by 40 kg urea ha1 caused the greatest (1196 kg ha1). Mean comparison interaction impact results illustrated that sole crop of guar without nitrogen application had the highest guar seed yield (4890 kg ha1). The greatest gum percentage was obtained in 100 kg urea ha1 followed by GGGRR (43.49%). Mean comparison interaction results for total chlorophyll in roselle demonstrated that GR in 70 kg urea ha1 was the most (36.4 mg/g FW). In addition, the highest phenol levels were related to sole crop roselle followed by 70 kg urea ha1. The highest value of LER in roselle and guar was demonstrated in GRR followed by 100 kg urea ha1 and GGGRR without nitrogen application (1.52 and 0.86, respectively). Overall, this study strengthens the idea that relay intercropping guar with roselle can improve the yield and quality attribute of both crops, so this system could be considered as a sustainable practice for field management.
