Effect of Applying Different Levels of Humic Acid and Salicylic Acid on Yield and Quality of Chickpea (Cicer arietinum L.) Seed

IntroductionChickpea (Cicer arietinum L.) is one of the most significant crops in the legume family, ranking third globally after beans and peas. This plant plays a crucial role in biological stabilization and serves as an important source of nutrition for humans, as well as animal feed and forage. The majority of chickpea production in Iran occurs through spring sowing under rain-fed conditions, where terminal drought stress particularly during seed filling significantly impacts growth and productivity, leading to yield reductions of up to 70%. To enhance plant growth under dryland conditions, using compounds that improve drought tolerance and metabolic activities in plants represents a practical strategy. Among the identified compounds, humic acid (HA) and salicylic acid (SA) have shown promise. Humic acid has a significant effect on root growth and the emergence of lateral roots and increases the levels of auxins, cytokinins, and gibberellins in plants Salicylic acid stimulates flowering and enhances defensive responses to water deficiency conditions. External application of SA reduces cellular lipid peroxidation and hydrogen peroxide accumulation, thereby mitigating membrane damage in leaves of water-stressed plants. Thus, this study aims to investigate the effects of varying levels of humic acid and salicylic acid on the yield and quality of chickpea seeds.Materials and MethodsThis study was conducted as a factorial experiment based on a randomized complete block design with four replications. The experimental factors included foliar spraying of humic acid at three levels: 0, 3, and 6 L ha-1 as the first factor, and salicylic acid at four levels: 0, 50, 100, and 150 mg L-1 as the second factor. The plants were sprayed with these treatments at two stages: during vegetative growth and just before flowering. The following variables were measured in this experiment: number of pods per plant, seeds per square meter, weight of 100 seeds, grain yield, biological yield, harvest index, and the content of protein, potassium, phosphorus, iron, zinc, and manganese in the seeds. The experimental data were analyzed using SAS 9.1 statistical software, and the comparison of the means was conducted based on the Least Significant Difference (LSD) test at the 1% and 5% probability levels.Results and DiscussionResults revealed significant effects of salicylic acid on pod number per plant, seed number per square meter, 100 seed weight and seed and biological yield, while humic acid did not have a significant effect on chickpea yield and yield components. The highest number of pods per plant (20.95) was achieved with the application of 150 mg L-1 of salicylic acid. Foliar spraying with this concentration led to increases of 35.27% in the number of seeds per square meter and 26.80% in the weight of 100 seeds, compared to the untreated control. Additionally, the application of 150 mg L-1 salicylic acid resulted in the highest seed yield (1488.85 kg ha-1) and biological yield (3451.93 kg ha-1). Results indicated significant effects of both humic and salicylic acid on the protein content and nutrient levels (potassium, phosphorus, iron, zinc, and manganese) of chickpea seeds. As the concentration of salicylic acid and humic acid increased, so did the levels of protein and potassium in the seeds. Conversely, foliar applications of humic acid and salicylic acid on chickpea plants not only enhanced the nutrient content and protein levels in chickpea seeds but also improved the overall quality of the seeds.ConclusionThis study highlights the effectiveness of foliar application of humic acid at 6 L ha⁻¹ and salicylic acid at 150 mg L⁻¹ in improving growth, yield, and nutritional quality of chickpeas under dryland conditions. Salicylic acid particularly enhanced reproductive success and biomass allocation, whereas humic acid improved nutrient availability and metabolic activity. These findings suggest that simultaneous applications of HA and SA could serve as effective strategies for boosting chickpea productivity and quality under challenging dryland farming conditions.