Abstract:Traditional rice cultivation knowledge management faces challenges, including knowledge fragmentation, retrieval difficulties, and outdated information, which cannot meet the demands of modern precision agriculture. A large language model-driven knowledge graph construction method for rice cultivation domain was proposed. The RC-PKBD dataset containing 409800 Chinese characters from 51 journal articles and 2 professional books were constructed. Based on an improved LightRAG framework with domain-specific prompt engineering strategies, totally 15 entity types and 12 relationship types were defined to achieve efficient extraction of professional knowledge. The construction process involved four key steps: text processing and chunking, entity and relationship extraction using large language models, entity deduplication and alignment through vector similarity calculation, and graph structure construction with storage. A dual-level retrieval mechanism based on graph structure was established, successfully constructing a knowledge graph containing 10723 nodes and 10955 edges. The system demonstrated significant advantages over traditional deep learning methods in semantic understanding depth and domain adaptability. Quality evaluation showed that accuracy reached 91.73% for specific questions and coverage achieved 90.20% for abstract questions, with a 36.60 percentage points improvement in accuracy compared with GraphRAG. The research result can provide an effective solution for rice cultivation knowledge digitalization and has important value for advancing smart agriculture development, while offering a replicable technical approach for knowledge services in other agricultural domains.