Background: Two field experiments were conducted at the Research and Production Station, National Research Centre, El-Nubaria Province, El-Behira Governorate, Egypt, during the two successive winter seasons of 2014/2015 and 2015/2016. This work aimed to study the enhancement effect of foliar application of nicotinamide at 5, 10, and 20 mg/L and/or humic acid at 5% on quality and quantity of faba bean plants (cultivar Sakha 4) grown under sandy soil conditions. Results: Data show that nicotinamide at 5, 10, and 20 mg/L and/or humic acid at 5% had a positive effect on growth parameters, photosynthetic pigments, seed yield, and yield components as well as some biochemical constituents of the yielded faba bean seeds (total carbohydrate, total phenolic content, proline, and free amino acids). Individually, nicotinamide treatments had a more positive effect than humic acid treatment and their effect was increased by increasing nicotinamide concentrations. The most promising treatment appeared due to the interaction between nicotinamide at 10 mg/L and humic acid. Hence, this treatment increased plant dry weight/plant by 32.67%, total photosynthetic pigments by 113.2%, seed yield/feddan by 110.16%, total carbohydrate by 9.4%, total phenolic content by 0.33%, proline by 24.83%, and free amino acids by 21.33%. Conclusions: We can conclude that nicotinamide and/or humic acid had a positive effect on growth parameters, photosynthetic pigments, seed yield, and yield components as well as some biochemical constituents of the yielded faba bean seeds. The most promising treatment appeared due to the interaction between nicotinamide at 10 mg/L and humic acid.

Background: Two field experiments were carried out at the Research and Production Station of the National Research Centre, Nubaria region, Behira Governorate, Egypt, during two winter seasons of 2014/2015 and 2015/2016. The aim of this study was to investigate the response of vegetative growth, yield, yield components, and some metabolic constituents of four faba bean (Vicia faba L.) cultivars "Nubaria 2, Sakha 1, Sakha 3, and Sakha 4" to foliar application of fulvic acid (FA) at 0.0, 3, 6, and 9 gL − 1. Results: The results show that all applications of FA increased all vegetative characters (i.e., plant height, number of branches and leaves, and total dry weight/plant, fourth leaf area and leaf area index, specific leaf weight, and crop growth rate), as well as, yield and its components (i.e., number of pods/plant, weight of pods/plant, seed and straw yield/plant, seed and straw yield/feddan, and seed index) of all studied faba bean cultivars, comparing to untreated plants. The results also show the total photosynthetic pigments content in leaves were increased by increasing FA concentration up to 9 gL −1. Treatment FA at 9 gL −1 , significantly improved the nutritional value and quality of seeds by increasing total carbohydrates, crude protein, minerals (nitrogen, phosphorus, and potassium) content, arginine, lysine, phenylalanine, and tryptophan. Conclusions: Generally, foliar application of FA at 9 gL −1 , singly or interaction with Sakha 4 effectively increased seed yield and quality. In conclusion, the growth and yield contributing characters and quality of four bean cultivars could be improved with foliar application of FA treatments.