Synergistic effect of Trichoderma harzianum and chitosan nanoparticles on garlic plants in arid regions

The intensive use of agrochemicals is not conducive to sustainable agricultural production, as it leads to soil degradation, harms soil organisms, and causes environmental pollution. Hence, adopting natural and biological practices in plant production management is a sustainable and environmentally friendly strategy. Therefore, this study investigated the effectiveness of combining Trichoderma harzianum inoculation and chitosan nanoparticle spraying in garlic cultivation, where two levels of T. harzianum inoculation (inoculated and uninoculated) and three levels of nano-chitosan spraying (0, 50, and 100 ppm) were used in an open-field experiment. Overall, Trichoderma fungi and chitosan nanoparticles, either alone or in combination, increased nutrient uptake, improved physiological status, promoted plant growth, and increased garlic yield. However, garlic plants inoculated with T. harzianum and sprayed with 100 ppm chitosan nanoparticles presented superior results over all the other treatments, increasing nutrients (N, P, K, and S), photosynthetic pigments (chlorophyll a, b, and carotenoids), and antioxidants (phenolic compounds, flavonoids, and vitamin C), resulting in significant increases in plant height (16%), bulb fresh weight (22%), bulb diameter (15%), and bulb dry weight (25%). These findings suggest that microbial and natural biostimulants, such as Trichoderma and chitosan, can be considered successful and sustainable agricultural practices to increase physiological performance, bioactive compound accumulation, and yield of vegetable plants.