Optimization of Tobacco-Grain Intercropping Models Based on the Entropy Weight-TOPSIS Method

Alleviating continuous cropping obstacles while ensuring grain security requires sustainable farming system designs. This study evaluated the spatial configuration and crop combinations in tobacco-based systems to balance soil health and economic output. A field experiment was conducted comparing tobacco monoculture (CK) with tobacco intercropped with soybean (B1, B2) or sweet potato (S1, S2) under two spatial modes: furrow (T1) and on-ridge (T2) intercropping. An Entropy-Weight TOPSIS model was employed to synthesize soil enzymatic activity, nutrient cycling, agronomic traits, leaf quality, and economic benefits. The results showed that intercropping significantly regulated the rhizosphere environment. Compared to CK, intercropping improved soil pH and organic matter. Specifically, tobacco–soybean intercropping (T1B1) increased available nitrogen by 35.38%, while tobacco–sweet potato (T2S1) boosted available phosphorus by 17.1% and sucrase activity to 38.98 U/g. Spatially, the on-ridge mode (T2) mitigated interspecific competition more effectively than the furrow mode (T1), enhancing plant height by 10.63% and optimizing chemical coordination (e.g., improved K/Cl ratios and increased protein content). Economically, the T2S1 system maximized synergism, with high-class tobacco reaching 61.6%. The Entropy-TOPSIS evaluation confirmed that intercropping systems outperformed monoculture, with T2S1 identified as the optimal design for achieving the best trade-off between productivity, leaf quality, and soil sustainability. These findings offer a strategic framework for the spatial optimization of cash-grain intensive farming systems.