Coupling effects of phosphorus fertilization source and rate on growth and ion accumulation of common bean under salinity stress.

Many agricultural regions in arid and semiarid climate zone need to deal with increased soil salinity. Legumes are classified as salt-sensitive crops. A field experiment was performed to examine the application of phosphorus (P) fertilizer source and rate on growth, chlorophylls and carotenoid content, DNA and RNA content and ion accumulation in common bean (Phaseolus vulgaris L.) cultivated under salinity stress. An experimental design was split-plot with three replicates. The main plots included two P sources, namely single superphosphate (SP) and urea phosphate (UP). The sub-plots covered four P rates, i.e., 0.0, 17.5, 35.0, and 52.5 kg P ha-1. All applied P fertilization rates, in both forms, increased plant height, leaf area, dry weight of shoots and roots per plant, and total dry weight (TDW) in t ha-1. The highest accumulation of N, P, K+, Mg2+, Mn2+, Zn2+, and Cu2+ was determined in the shoot and root of common bean, while 35 kg of P per ha-1 was used compared to the other levels of P fertilizer. The highest P rate (52.5 kg ha-1) resulted in a significant reduction in Na+ in shoot and root of common bean. The response curve of TDW (t ha-1) to different rates of P (kg ha-1) proved that the quadratic model fit better than the linear model for both P sources. Under SP, the expected TDW was 1.675 t ha-1 if P was applied at 51.5 kg ha-1, while under UP, the maximum expected TDW was 1.875 t ha-1 if P was supplied at 42.5 kg ha-1. In conclusion, the 35.0 kg P ha-1 could be considered the best effective P level imposed. The application of P fertilizer as urea phosphate is generally more effective than single superphosphate in enhancing plant growth and alleviating common bean plants against salinity stress.