Aims: the aim of the present investigation is to study the effect of foliar application with humic acid, salicylic acid and paclobutrazol at different concentrations on some morphological, anatomical and seed yield characteristics as well as some biochemical constituents of soybean (Glycine max L.) seed for maximizing its growth, yield and nutritional value.
Methodology: Two field experiments were conducted at the experimental farm station of the faculty of agriculture, Moshtohor, Benha university during 2015 and 2016 seasons. Uniform seeds of soybean (Glycine max L.) Cv. Giza 111 were sown, after complete germination seedlings were thinned into two plants per hill. The applied treatments i.e., humic acid at 2.5 and 5 g/l, salicylic acid at 50 and 100 mg/l and paclobutrazol at 10 and 20 mg/l were used as foliar application at different concentrations, plants of each treatment were sprayed 3 times with different assigned treatments. Randomized complete block design in three replicates was adopted herein. Common agricultural practices of growing soybean plants including fertilization, irrigation, manual weed control and so on were done as usual according to the crop requirement throughout the growing period.
Results: results indicated that all applied treatments i.e., humic acid at 2.5 and 5 g/l, salicylic acid at 50 and 100 mg/l and paclobutrazol at 10 and 20 mg/l were significantly affected on all measured morphological parameters of soybean plant i.e., plant height (cm), stem diameter (cm), number of total branches /plant, number of leaves / plant, total leaf area /plant (cm2), leaf area ratio /plant (L.A.R) (cm2/g) , specific leaf weight /plant (mg/cm2), fresh and dry weights of stems and leaves compared to the control during 2015 and 2016 seasons. Maximum increments in the most studied vegetative growth characteristics were obtained by applying paclobutrazol at 10 mg/l followed by humic acid at 5 g/l and salicylic acid at 100 mg/l. The exception was only in plant height parameter with using PP333 at different studied concentrations which significantly decreased. Also, data revealed that chlorophyll a, b, Chl.(a + b) and carotenoids content were enhanced as a result of all aforementioned growth enhancement compared to the control. As for phytohormones, results cleared that different applied treatments changed endogenous phytohormones content i.e., gibberellic acids (GA3) , indole acetic Acid (IAA), indole butyric Acid (IBA) , cytokinins, abscisic acid (ABA) and salicylic acid of soybean (Glycine max L.) shoots. Also, data indicated that different applied treatments have a positively impact on most studied histological characteristics of Glycine max L. stem and leaf.
With respect to flowering and yield characteristics, results cleared that different applied treatments were increased flowering and yield components of soybean (Glycine max L.) plants in term of number of flowers / plant, number of setted pods / plant, setted pods %, pods yield / plant (g), number of seeds / pod, weight of seeds / pod, weight of seeds / plant (g) and 100 seeds weight (g). Furthermore, content of minerals (N, P and K ), crude protein, total carbohydrates and total lipids % were increased in soybean (Glycine max L.) seed yield as response to the applied treatments. Generally, the obtained results indicated that different applied treatments were significantly affected on morphological, anatomical and seed yield characteristics as well as some biochemical constituents of soybean (Glycine max L.) seeds. Herein, paclobutrazol at 10 mg/l followed by humic acid at 5 g/l and salicylic acid at 100 mg/l, respectively were the most effective treatments compared with other and the control treatments.
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