Most crop recommendation systems either act as uninterpretable black boxes or struggle to process raw sensor data. In this paper, we built AgriSemNet to bridge this gap by combining a tabular MLP with a Graph Attention Network (GAT) and an external 42-node Agronomic Knowledge Graph. Instead of only predicting a single static crop label, our system generates a practical 4-tier recommendation: the primary crop, a low-risk backup crop, a sustainable crop rotation sequence, and clear biological justifications for the farmer. We also built in two-stage soil safety guardrails to flag extreme or toxic soil conditions before planting. On a benchmark 22-crop dataset, our model achieves 98.79% accuracy and stays remarkably stable against IoT sensor noise, dropping only 1.52% under 20% Gaussian noise, where standard models like Random Forest and XGBoost degrade significantly.
