Can Humic Extracts and Bacillus megaterium boost Sugar Beet Productivity in a Saline-Sodic Soil?

SOIL salinization is one of the major threats that hinder crop production in arid and semi-arid regions. Due to water scarcity therein, the biological approach could be the optimum solution of soil reclamation. Thus, the current study investigated the impacts of applying humic substances, namely potassium humate (KH), humic acid (HA) and fulvic acid (FA), solely or in combination with P-dissolving bacteria (Bacillus megaterium) to augment sugar beet growth and production in a saline-sodic soil. Also, it assessed changes in soil characteristics by the end of the experimental period in order to evaluate how effectiveness was this strategy for soil reclamation. A field experiment was therefore conducted for two successive seasons, comprising 9 treatments (all received the recommended P-rate, but in different sources): CaH2PO4 (T1), H3PO4 (T2), rock phosphate(RP)+KH (T3), RP+HA (T4), RP+FA (T5), RP+B. megaterium (T6), RP+B. megaterium+KH (T7), PRP+B. megaterium+ HA (T8), RP +B. megaterium+FA (T9). Results revealed that there were no significant variations detected in SPAD among treatments after 80 days of planting (DAP); yet, SPAD in all treatments surpassed the control after 170 DAP. Also, shoot and tuber yields of sugar beet increased significantly; yet combined treatments (T7-T9) were not as efficient as single ones in this concern (T3-T6). In particular, the highest increases in straw-yield were recorded for T3, while the highest corresponding increases in tuber yield were for T2, T4 and T6. In case of proline, it level increased significantly in all treatments versus the control. This component was positively correlated with all growth parameters and yield components, even with soil organic matter (SOM). Additionally, proline and SOM were both positively correlated with P-available content in soil and its distribution within plants. Root secretions likely increased under stress to (1) increase the activities of soil biota as denoted by the increasing dehydrogenase activities, and in particular enhanced P-dissolving bacteria, increasing P availability in soil. (2) Their byproducts build up soil organic matter (dehydrogenase activity was positively correlated with SOM). Moreover, (3), these organics formed aggregates that decreased soil bulk density (BD). There existed positive correlations between BD and each of EC and ESP. Thus, using either humic-extracts or P-dissolving bacteria could be a suitable strategy to increase sugar beet production in saline-sodic soils while significantly decreasing soil EC and ESP. However, even after two growing seasons, the soil remained saline. Thus, it is necessary to test the the long-term efficiency of these reclamation methods to ensure its effectiveness and sustainability, while also considering economic benefits