Document Type : Research Paper

Authors

• Gholamreza Shahidi ¹
• Gholam Akbari ²
• Ali Akbar Asadi ³
• Gholamali Akbari ¹
• Mohammad Hadi Ghafarian Mogharab ⁴

¹ Department of Agriculture and Plant Breeding, Faculty of Agricultural Technology (Abureihan Campus), University of Tehran, Tehran, Iran.

² Department of Agronomy and Plant Breeding Sciences, College of Aburaihan, University of Tehran, Pakdasht, Iran

³ Department of Agriculture and Plant Breeding, Zanjan Agricultural and Natural Resources Research and Education Center, AREEO, Zanjan,Iran.

⁴ Department of Agriculture and Plant Breeding, Zanjan Agricultural and Natural Resources Research and Education Center, AREEO, Zanjan, Iran.

Abstract

Objective: This study was conducted to evaluate the effect of combined nutritional regimes, including organic and inorganic fertilizers along with precise foliar spraying applications, on yield components, grain yield, biomass, and harvest index of pinto bean under challenging water deficit stress condition.
Method:  The experiment was carefully carried out over two growing seasons (2022–2023 and 2023–2024) at the Kheirabad Agricultural Research Station in Zanjan, using a split-plot experiment based on a randomized complete block design with four replications. Treatments included two levels of soil fertilization (control and combined application of 50 kg potassium sulfate + 2 kg humic acid per hectare), four levels of foliar spraying (control or water spray, nano-zinc fertilizer, amino acids, and potassium silicate), and two irrigation regimes (full irrigation at 5-day intervals and deficit irrigation at 9-day intervals). 
Findings: Results clearly showed that water deficit significantly reduced reproductive components and yield. Plant density per square meter, pods per plant, grains per pod, and 100- grain weight decreased by 8.9%, 9.1%, 10.5%, and 6.1% percent, respectively, under stress condition. The highest number of grains per pod (7.92) was obtained under full irrigation combined with potassium silicate, while the lowest value (7 grains) was observed under deficit irrigation without foliar spraying, representing an 11.65% reduction. Grain yield decreased by about 29% under stress, dropping from 3038 to 2150 kg per hectare. Potassium silicate recorded the highest yield with an average of 2733 kg per hectare, about 7% higher than other foliar treatments. Regarding harvest index, full irrigation resulted in an average of 57%, whereas deficit irrigation reduced it to 48%. The highest harvest index (56%) was observed with nano-zinc fertilizer, highlighting its crucial role in the remobilization of photosynthates to reproductive organs. The highest biomass (3165.32 kg per hectare) was achieved under full irrigation with potassium silicate, which was 1.6% and 2.8% higher compared to nano-zinc and amino acid treatments, respectively. Even without basal fertilization, potassium silicate maintained a relatively high biomass level (2762.21 kg per hectare).
Conclusions: Overall, potassium silicate foliar spraying, by enhancing photosynthesis, improving cell wall stability, and reducing lipid peroxidation, was able to effectively mitigate the negative effects of drought stress and enhance yield and biomass. Furthermore, the positive role of nano-zinc fertilizer in improving harvest index was clearly confirmed. These comprehensive results can serve as a reliable basis for developing advanced nutritional strategies to increase the resilience of pinto bean under increasingly unstable climatic condition.

Keywords

• Amino acids Base fertilizer Irrigation interval Mineral
• organic compounds