Smart agriculture has experienced a revolution because of the Internet of Things (IoT) rapid growth, which has made data-driven decision-making, automated operations, and real-time monitoring possible. However, there are several security and privacy issues with IoT integration in agriculture, including data manipulation, illegal access, and inconsistent data sharing between stakeholders. To overcome these problems, this study suggests a Blockchain-Based Secure IoT Framework for Smart Agriculture Applications (BSIoTSA), which makes use of the decentralized, immutable, and transparent characteristics of blockchain technology. The proposed framework provides a transparent platform for information sharing between farmers, suppliers, and regulators, secure data transfer and storage, and improved data integrity. In order to ensure a safe and effective agricultural ecosystem, our solution incorporates smart contracts for the automation of tasks like supply chain traceability, irrigation control, and crop monitoring. Using comprehensive simulations, the performance of the BSIoTSA framework is compared with traditional systems, showing improved data security, decreased latency, and increased scalability. The results show that improving the security and dependability of IoT-enabled smart agriculture applications with the suggested blockchain-based strategy will greatly open the door to a more sustainable and safe agricultural future.