Field assessment of eggshell waste as a soil amendment in soil biosolarization linking soil VOCs, microbial communities, and crop outcomes

Soil biosolarization (SBS), combining organic amendments with solar heating, is a sustainable alternative to chemical soil fumigation for managing soil-borne pathogens. The large and continuous generation of eggshell waste (ESW) poses an environmental challenge, highlighting the need for sustainable management strategies. This study aimed to evaluate the system-level effects of ESW amendment on SBS under field conditions, assessing soil physicochemical properties, volatile organic compound (VOC) profiles, bacterial and fungal communities, weed seed inactivation, residual phytotoxicity, and plant performance using lettuce ( Lactuca sativa L. var. capitata L.) as a test crop. Microbial community analysis revealed both SBS-driven and ESW-associated shifts. Several beneficial genera linked to plant health, including Sphingomonas , Trichoderma , and Talaromyces , increased in relative abundance following SBS across treatments, whereas ESW amendment was associated with enrichment of specific taxa, including Brevibacillus , Aneurinibacillus and Paenibacillus . VOC profiles showed compositional variation, including compounds associated with pathogen suppression, such as dimethyl sulfide and p-coumaric acid. No consistent or pronounced phytotoxicity was detected across most measured endpoints. Following ESW-amended SBS, leaf fresh weight increased by 42–238% compared with the control, based on two independent pots per treatment and transplantation time point. Weed seed germination was effectively suppressed under SBS conditions (0% germination), regardless of ESW addition. Correlation analysis indicated significant associations among VOC profiles, core microbial genera, and soil properties, suggesting complex interrelationships among system components. Overall, ESW amendment modifies multiple components of the SBS system under field conditions, highlighting its potential as a sustainable strategy for managing ESW in agricultural systems.