abstract

Introduction

Common bean (Phaseolus vulgaris L.), particularly the pinto bean variety, is a vital legume crop in Iran, prized for its high protein content and significant role in ensuring food security and improving household nutrition. However, its productivity is severely limited by environmental stresses and poor soil fertility, especially phosphorus (P) deficiency. Phosphorus is an essential macronutrient critical for root development, energy transfer, photosynthesis, and flower and seed formation. In the calcareous soils, P becomes fixed and unavailable to plants, leading to low use efficiency from conventional fertilizers. Recent innovations in agricultural nanotechnology have introduced nano-phosphorus fertilizers as a promising solution. These fertilizers, characterized by their ultra-small particle size, high surface area, and controlled-release properties, enhance P availability, uptake, and utilization efficiency by plants. While the benefits of nano-P are recognized, a significant research gap exists regarding the field evaluation of genotypic responses of pinto bean to nano-P fertilization, particularly under the specific ecological conditions of Iran. This study was therefore designed to bridge this gap by comprehensively assessing the impact of nano-P fertilizer on the yield, its components, and the seed quality attributes of nine distinct pinto bean genotypes.

Materials and Methods

A field experiment was conducted during the 2020 growing season on a private farm in the Arallou region, Ardabil, Iran. The experiment was laid out as a factorial arrangement based on a Randomized Complete Block Design (RCBD) with three replications. The factors consisted of nine pinto bean genotypes (Koosha, Ghaffar, Saleh, Local Ardabil, Sadri, Talash, and Lines 80, 90, and 16) and three nano-P fertilizer treatments: foliar application at a concentration of two and one per thousand and an untreated control. The nano-P fertilizer (commercial name: Khazra, 17% P chelate) was applied at three critical growth stages: stem elongation, pre-flowering, and podding. At physiological maturity, yield components, including the number of pods per plant, number of seeds per pod, and hundred seed weight, were measured. Grain yield was calculated and extrapolated to kg per hectare. Collected data were subjected to analysis of variance (ANOVA) using SAS software, and mean comparisons were performed using Duncan's Multiple Range Test at a 5% probability level.

Results and Discussion

The results demonstrated significant main effects of both genotype and nano-P fertilizer on all measured parameters. Foliar application of nano-P fertilizer markedly enhanced overall crop performance. It increased grain yield by 26.4%, from 1706.7 kg ha⁻¹ in the control to 2156.5 kg ha⁻¹in second level of fertilizer. Additionally, the number of pods per plant, number of seeds per pod, and 100-seed weight increased by 8%, 19%, and 8%, respectively, compared to the control. Seed nutritional quality significantly improved, with the nitrogen, protein, phosphorus, and potassium content of seeds in the nano-phosphorus treatment showing a significant increase compared to the control. Significant genotypic variation was observed. The genotype Talash recorded the highest grain yield (2313.8 kg ha⁻¹), primarily driven by a superior number of seeds per pod (4.68). In contrast, Line 16 presented a balanced and desirable profile with high yield (2181.2 kg ha⁻¹) coupled with exceptional seed quality, achieving the highest seed phosphorus (0.588%) and potassium (4.46%) content, along with high protein (25.55%). Nano-P application significantly boosted seed nutritional quality. Seed nitrogen content increased from 3.45% to 3.98%, protein from 21.57% to 24.88%, phosphorus from 0.441% to 0.599%, and potassium from 3.41% to 3.88%. Correlation analysis revealed a strong, positive, and highly significant relationship between seed nitrogen and protein content, which is biologically expected. A notable negative correlation between the number of pods per plant and the number of seeds per pod suggests a compensatory trade-off between these two components. The identification of high-performing and responsive genotypes like 'Talash' and 'Line 16' is crucial for future breeding programs.

Conclusion

In conclusion, this study unequivocally demonstrates that foliar application of nano-phosphorus fertilizer is a highly effective agronomic strategy for significantly enhancing the productivity and nutritional quality of pinto beans. It effectively mitigates the challenges of phosphorus fixation in calcareous soils. The significant genotypic differences highlight the importance of selecting appropriate varieties. Genotypes 'Talash' and 'Line 16' are highly recommended for cultivation under similar conditions due to their outstanding yield and quality characteristics, respectively. The trade-off between yield components underscores the need for a balanced breeding approach.