The Effect of Biofertilizer Application on the Improvement of Pigments, Physiological Traits, and Yield of Cowpea (Vigna unguiculata(

IntroductionCowpea (Vigna unguiculata) an annual legume, originated in Iran. It is one of the main sources of protein, amino acids, vitamins, minerals, and energy, and therefore is important for a well-balanced diet with good nutritional value. In recent years, the application of organic fertilizers has increased tremendously in agricultural production. Humic compounds such as HA is one of the organic-mineral fertilizers, which is commonly used for the production of crops. In order to increase the quantitative and qualitative traits of plants, the extract of some plants, such as green tea extract and coffee extract, can be used. Materials and MethodsIn order to investigate the effect of biofertilizers, including humic acid, green tea extract, and coffee extract, on the improvement of pigments and physiological traits of cowpea, an experiment was designed and implemented in 2023 at a private farm in Semnan city. The experiment was a factorial format based on a randomized complete block design with three replications. The test treatments include seed priming at five levels (control, distilled water, humic acid (750 mg/liter), green tea extract (10% concentration) and coffee extract (10% concentration)) and foliar spraying at four levels (control, humic acid (750 mg/liter), green tea extract (concentration 10%) and coffee extract (concentration 10%). Pretreatment of seeds with desired concentrations was done for six hours, following the principles of seed aeration. Foliar spraying was done at the beginning of flowering. Seeds were sown on June 25 (as the second planting). Before planting, all the seeds were disinfected with benomyl and then in each plot, four rows of five meters were planted with a distance of 25 cm between the rows and 8 cm within the row at a depth of 5 cm.Results and DiscussionThe results showed that pretreatment of seeds with humic acid, green tea extract and coffee extract led to an increase in the traits of relative leaf water content, membrane stability index, leaf surface index, photosynthetic pigments, protein yield, and grain yield. In plants grown from pre-treated seeds, the amount of malondialdehyde and soluble carbohydrates in leaves decreased to a significant level. Foliar spraying with these substances led to the improvement of leaf surface index, the amount of photosynthetic pigments, protein yield, and seed yield. Application of foliar spraying also reduced the amount of malondialdehyde and soluble carbohydrates in leaves. Finally, within the scope of the research, the use of humic acid at the rate of 750 mg/liter and green tea at a concentration of 10% is recommended as seed pre-treatment and foliar spraying in the field. More research is needed on the recommendation of seed pretreatment and coffee extract foliar spraying. When seed yield was considered as a dependent trait, the traits of leaf surface index (0.6076), carotenoid (0.7265), membrane stability index (0.6501), leaf soluble carbohydrates (-0.6678), and Malondialdehyde (0.6096) entered the model as main variables. The results of this research showed that carotenoid (0.3764) and membrane stability index (0.2950) had the most positive direct effect on grain yield.ConclusionThe results of this research showed that the photosynthetic pigments, protein yield, and grain yield of cowpea increased to a significant level by using humic acid, green tea extract, and coffee extract as seed pretreatment and foliar spraying. Seed protein percentage, yield components, and grain yield of cowpea increased to a significant level with the application of humic acid, green tea extract, and coffee extract as seed pretreatment and foliar spraying. Finally, within the scope of this research, the use of humic acid at the rate of 750 mg/L and green tea at a concentration of 10% is recommended as seed pretreatment and foliar spraying in the field. More research is needed on the recommendation of seed pretreatment and foliar spraying of coffee extract.