Natural Biostimulants Improve Saline Soil Characteristics and Salt Stressed-Sorghum Performance

Humus substances (HM) and Moringa oleifera leaf extract (MLE) are considered as biostimulants used for plant growing under normal and salt stress conditions. Therefore, effects of soil HM and foliar MLE applications on soil characteristics and on sorghum growth, physio-biochemical properties, and antioxidant defense system activity were investigated under salt stress using pot experiments. The experimental design was a split-split plot with three soil salinities (S1, S2, and S3) as main-plots, two HM levels (0 and 0.1 g kg‒1 soil) as subplots, and two MLE levels (0% and 3%) as sub-subplots, and each one of the 12 treatments was replicated 20 times. Saline soil properties were improved by HM. Under saline conditions, either HM or MLE increased growth characteristics, photochemical activity, contents of RNA, DNA, phytohormones, osmoprotectants and non-enzymatic antioxidants, and activities of antioxidant enzymes in sorghum plants compared to those in the untreated control plants. The interactive HM×MLE application was most effective at overcoming the harmful effects of soil salinity stress and further increased the abovementioned criteria. This study, therefore, recommends using the integrative HM+MLE treatment for growing sorghum plants in saline soils up to more than 6.12 dS m‒1 without loss in growth characteristics.