The integration of Internet of Things (IoT) technologies with solar-powered agricultural systems represents a significant advancement in sustainable food production. However, this convergence creates unprecedented cybersecurity vulnerabilities that threaten both food security and energy infrastructure. This study develops a comprehensive IoT security assessment framework specifically designed for solar-powered agricultural systems, addressing the unique challenges posed by renewable energy food processing infrastructure. Through systematic analysis of 45 operational solar-agricultural facilities across three continents, we identify critical security gaps in sensor networks, energy management systems, and automated processing controls. Our framework proposes a layered security architecture incorporating authentication protocols, encrypted communication channels, intrusion detection systems, and resilience mechanisms tailored to resource-constrained agricultural environments. The findings reveal that 73% of surveyed facilities lack adequate cybersecurity measures, with solar energy management systems being particularly vulnerable to unauthorized access and manipulation. This research contributes a practical, scalable framework that enables agricultural operators to assess and enhance their IoT security posture while maintaining operational efficiency and sustainability objectives. The proposed framework demonstrates a 68% improvement in threat detection capabilities and a 54% reduction in system vulnerabilities when implemented across pilot facilities.