Abstract
The application of arbuscular mycorrhizal fungi (AMF), plant growth promoting rhizobacteria (PGPR) and compost (C) is a biological approach to boost growth of plants. The aim of the study was to evaluate the impact of AMF, PGPR and compost on growth, physiology and biochemical traits of date palm in the absence and the presence of microorganisms in soil. Date palm seedlings were transplanted in sterile (SS) and non-sterile soils (NSS) in the presence and absence of the biostimulants/biofertilizers. After 6 months, the application of AMF combined with compost (AMF + C) revealed significant increments in shoot dry weight (SDW), root dry weight (RDW), stomatal conductance and chlorophyll a by 122, 114, 95 and 119%, respectively in SS. Moreover, PGPR treatment significantly improved the SDW by 482%, while AMF + C + PGPR treatment significantly increased the RDW, chlorophyll b and carotenoids concentration by 864, 211 and 145%, respectively in NSS compared to the control. In addition, the sugar and protein concentrations were significantly enhanced in plants treated with AMF + C + PGPR for SS and NSS, respectively compared to their respective controls. It was revealed that the organic matter, available phosphorus and glomalin were enhanced in soils amended with compost alone and/or combined with AMF and/or PGPR under SS and NSS. This study revealed the positive synergy of the tested native biostimulants with in NSS compared to SS in improving the growth, physiology and biochemical traits of date palm as well as soil fertility.