Optimizing basil production and fertilizer use efficiency with consortia of plant growth-promoting bacteria

Abstract

The basil, a widely cultivated aromatic plant, plays a crucial role in various industries but relies heavily on synthetic fertilizers, which contribute to environmental pollution. Plant growth-promoting bacteria (PGPB) offer a sustainable alternative to reduce reliance on synthetic fertilizers. In this study, three PGPB consortia and one single-strain inoculant were evaluated under reduced nitrogen and phosphorus fertilization to assess their effects on biomass production, photosynthetic efficiency, and nutritional quality. The results showed that consortium comprising Herbaspirillum sp., Azospirillum brasilense, and Rhizobium leguminosarum, as well as the consortium with Rhizobium sp. and Azotobacter chroococcum, significantly increased fresh biomass production-by over than 130%-compared to non-inoculated plants. Similarly, inoculation with 50% fertilization increased nitrogen and potassium uptake by over 50% compared to receiving the complete recommended fertilization without inoculation, while phosphorus uptake increased by more than 28% relative to the same control. These findings indicate that PGPB consortia offer not only an environmentally sustainable alternative to conventional fertilizers but also an effective strategy for enhancing biomass production and improving nutrient uptake in basil crops.

Keywords: Ocimum basilicum L.; consortium; fertilization reduction; nutrient uptake. 2; photosynthesis.

Figure 1

Daily climatic parameters: radiation, relative humidity, and temperature at the C.I. Nataima research center of AGROSAVIA, in Tolima, Colombia. Days were counted since the sowing of the basil seeds.

Figure 2

Fresh biomass per basil plant under three different nitrogen and phosphorus fertilization rates (0%, 50% 100%) (n=9). Different letters represent significant differences between treatments with Tukey’s HSD test (P < 0.05) for parametric data, while pairwise Wilcoxon rank-sum tests with a Bonferroni correction for non-parametric data.

Figure 3

Fresh biomass per basil plant at 75 days after sowing under three nitrogen and phosphorus fertilization rates: (A) 0%, (B) 50%, and (C) 100%, across four microbial treatments (B02, AC1+AC10, AP21+T88+D7, and B02+AC1+AC10). Different letters indicate significant differences between treatments, based on Tukey’s HSD test (P < 0.05) for parametric data, and pairwise Wilcoxon rank-sum tests with Bonferroni correction for non-parametric data.

Figure 4

Photosynthetic parameters evaluated in basil, under three nitrogen and phosphorus fertilization rates (0%, 50%, 100%), and four different consortiums with 50% of nitrogen and phosphorus fertilization. (A) net assimilation rate, (B) intercellular CO₂ concentration, (C) transpiration rate, and (D) stomatal conductance. Different letters represent significant differences between treatments with Tukey’s HSD test (P < 0.05) for parametric data, while pairwise Wilcoxon rank-sum tests with a Bonferroni correction for non-parametric data.

Figure 5

SPAD units of basil plants under three nitrogen and phosphorus fertilization rates (0%, 50%, 100%), and four different consortiums with 50% of nitrogen and phosphorus fertilization. Different letters represent significant differences between treatments with Tukey’s HSD test (P < 0.05) for parametric data, while pairwise Wilcoxon rank-sum tests with a Bonferroni correction for non-parametric data.

Figure 6

Loading and score plots from principal component analysis (PCA) of shoot length (SL), stem diameter (SD), fresh weight biomass (FW), assimilation rate (Pn), intercellular CO₂ concentration (Ci), transpiration rate (E), stomatal conductance (g_s), and nitrogen, phosphorous, and potassium foliar uptake (N, P, K) in basil plants subjected to 0%, 50%, and 100% N and P fertilization rates with four different PGPB inoculation.