Effects of rhizobial inoculation and nutrient management on pea and common bean yield, nodulation, nitrogen removal, and nutritional composition in Armenia’s Sevan Basin

Background: Pea (Pisum sativum L.) and common bean (Phaseolus vulgaris L.) are important sources of plant protein and other nutrients. This study evaluated the associations between rhizobial inoculation and nutrient-management treatments and nodulation, yield, estimated nitrogen removal in harvested seeds, and selected nutritional characteristics of fresh seeds under irrigated conditions in the Sevan Basin, Armenia. Methods: Field experiments were conducted in Artsvanist, Gegharkunik Province, Armenia, in 2024–2025. Pea cv. ‘Kangun’ was evaluated in both years, whereas common bean cv. ‘Armenian Red’ was evaluated in 2025. Treatments included non-inoculated and inoculated controls, as well as inoculated treatments supplemented with mineral fertilizer, EcoBiofeed+, or Biohumus. Nodulation, seed yield, and selected seed-composition characteristics were assessed. Nitrogen removal in harvested seeds was estimated from seed yield and crude protein concentration. These estimates represent nitrogen exported through harvested seeds rather than direct measurements of biological nitrogen fixation (BNF). Because nutrient amendments were applied in combination with rhizobial inoculation, their independent effects could not be determined. Results: Rhizobial inoculation was associated with increased nodule numbers from 5 ± 1 to 19 ± 2 nodules plant⁻¹ in pea and from 3 ± 1 to 17 ± 3 nodules plant⁻¹ in common bean. Under the Biohumus treatment, nodule numbers reached 39 ± 4 and 33 ± 3 nodules plant⁻¹, respectively. The two-year mean pea yield was 32.10 ± 0.72 c ha⁻¹ under the Biohumus treatment, compared with 20.40 ± 0.31 c ha⁻¹ in the inoculated control. For common bean, the 2025 yield was 22.40 ± 0.61 c ha⁻¹ under the Biohumus treatment, compared with 12.80 ± 0.28 c ha⁻¹ in the inoculated control. Biohumus was also associated with the highest observed values for dry matter, crude protein, total sugars, crude fat, and ascorbic acid in fresh seeds of both crops. Differences among treatments were assessed statistically. Conclusions: The Biohumus treatment was associated with the highest numerical seed yields and seed-composition values among the treatments evaluated. Further multi-year and multi-location trials are needed to validate these findings, distinguish the effects of inoculation and nutrient amendments, directly quantify BNF, and investigate nutrient bioavailability, processing stability, and potential biological effects. Novelty: The study provides region-specific evidence of the relationships between combined rhizobial inoculation and nutrient management, legume productivity, and selected nutritional characteristics of fresh seeds in the Sevan Basin.