The effect of salinity stress and the application of Zinc on the chlorophyll content, soluble proteins, growth, yield, and the mineral nutrients of soybean (Glycine max L.)

Soil salinity is one of the major abiotic stresses that adversely decreases the crop yield and quality. In an attempt to study the effects of salinity on crop yield and quality, a factorial experiment was conducted including two factors, i.e. salinity at four levels (0, 33, 66, and 99 mM sodium chloride) and the zinc fertilizer at two levels (0 and 10 mg kg-1 soil). The study followed a randomized, complete block design and was carried out with three replications in the greenhouse of the faculty of Agriculture in Kurdistan University. The results indicated that the treatments had significant effects on shoot dry and fresh weight, chlorophyll content, the soluble proteins of the leaves and the root, and potassium (K), sodium (Na), and phosphor (P) concentrations of the leaves. The application of zinc did not have any significant effect on phosphor (P) and sodium (Na) concentrations of soybean leaves. Salinity decreased shoot dry and fresh weight, yield, the soluble proteins of the leaves and the root, and chlorophyll content at three growth stages (before flowering, after flowering, and seed filling). Nonetheless, the application of zinc significantly increased these parameters. Potassium (K) and phosphor (P) concentrations of leaves significantly decreased under salinity stress, whereas sodium (Na) concentration of the leaves increased in NaCl-treated plants.