The Influence of Different Irrigation Levels and Growth Stimulants on Yield Components and Grain Protein in Red Kidney Beans (Phaseolus vulgaris L.)

Abstract

The study aimed to investigate the response of bean yield and yield components to the application of growth stimulants under different irrigation levels. A field experiment was conducted in the Khoy, Northwest of Iran. The experiment was conducted as a split-plot design using a randomized complete block design (RCBD) in three replications. Irrigation was the main factor in three levels, including once every 8, 11, and 14 days and growth stimulating compounds as subfactors in 5 levels, including the use of humic acid with irrigation water, amino acid foliar spraying, rooting stimulant, potassium, and no growth stimulants (control). Drought stress (irrigating once every 14 days) led to the reduction of the absorption of essential plant elements such as nitrogen, potassium, and phosphorus, as well as decrease in the lateral branches/plant, grains/pod, hundred-seed weight (HSW), harvest index (HI), leaf area index (LAI), protein yield, and grain yield. Application of growth stimulants both under normal irrigation conditions and under drought stress increased the examined traits, compared to the control treatment. The results indicated that the impact of mild drought stress during the pod development and grain filling stages has a more pronounced effect on the yield and yield components of red kidney beans. Application of growth stimulants, particularly humic acid, during these stages mitigates the adverse effects of stress and leads to a notably higher grain yield compared to other growth stimulants. The highest grain yield (3076 kg/ha) and protein yield (746 kg/ha) were achieved at the presence of irrigating every 8 days and the application of humic acid. It appears that the use of humic acid can be highly effective in enhancing the agronomic, qualitative, and physiological attributes of red kidney beans, contributing up to 95% improvement under both normal irrigation and stress conditions.

Keywords

• drought stress
• harvest index
• humic acid
• nitrogen percentage
• leaf elements