Influence of some biostimulants combined with zinc and boron oxides on the performance of date palm

Although chemical fertilizers increase plant growth and crop yields, their usage over a long period harms soil health, damages the beneficial microorganisms, and reduces soil fertility. Therefore, there is interest in using natural biostimulants in agriculture instead of chemical fertilizers. This study aimed to examine how spraying with zinc (ZnO) and boron (B2O3) oxides, as well as the biostimulants yeast extract (YE) and seaweed extract (SWE), and their combinations affect the yield and fruit quality of Barhi date palm. The trees were sprayed four times starting from mid of February with one month between each two sprays with 50 mg/L ZnO + 50 mg/L B2O3; 100 mg/L ZnO + 100 mg/L B2O3; 0.2% or 0.4% YE; 0.2% or 0.4% SWE; 50 mg/L ZnO + 50 mg/L B2O3 + 0.2 % YE + 0.2 % SWE, (combination 1); 100 mg/L ZnO + 100 mg/L B2O3 + 0.4% YE + 0.4% SWE (combination 2) compared to not-treated trees. The results indicated that applying ZnO and B2O3, YE and SWE either individually or in combination effectively enhanced the productivity and fruit quality of the date palm cv. Barhi compared to the control. The results also showed that the combined application gave a larger improvement in the measured parameters, particularly combination 2, which was the best treatment, followed by combination 1.