Alternative Solution to Synthetic Fertilizers for the Starter Fertilization of Bread Wheat under Mediterranean Climatic Conditions

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Under the high temporal variability of the Mediterranean climate, the prompt emergence of wheat seedlings and early vigor are pivotal attributes, positively affecting the final grain yield. Phosphorus (P) fertilization at sowing is largely used in wheat cultivation to support the early-season growth and promote a more rapid crop establishment. While conventional farming can rely on a wide variety of synthetic fertilizers, the number of options available for the starter fertilization of organic wheat is restricted and many are often unsuitable. Nanotechnology applied to fertilizers could provide a valuable means to combat this issue. This study aimed to evaluate the starter effect of a granular soil bio-enhancer (SBE) on bread wheat grown in two locations of Northern Tunisia as compared to conventional fertilization with diammonium phosphate (DAP). The SBE was obtained by physically grinding phosphate rocks at a nanoscale level and further mixing it with azotobacters. Aerial dry biomass, plant height, crop density, tiller density, leaf area index (LAI), and leaf P concentration were determined up to 70 days after emergence (DAE) to assess the early vigor of wheat seedlings. The application of SBE before sowing resulted in a greater early vigor of wheat seedlings as compared to commercial DAP over three consecutive growing seasons. Specifically, the aerial dry biomass and the plant height at 7 DAE were found to have increased by 56% and 48%, respectively. LAI at 70 DAE was enhanced by 8.5%, while moderate percentage increases were detected for both crop and tiller density. Finally, wheat plants fertilized with SBE showed a significantly higher leaf P concentration than DAP-fertilized plants in 2020 and 2021 (+21% and +32%, respectively).