Objective Urbanization has resulted in the occupation of gentle-slope cultivated land, whereas newly added cultivated land is concentrated on steeper slopes. As a major grain-producing province, it is of great significance to explore the evolution of cultivated land slope to ensure cultivated land quality and food security.

Methods Based on multi-source data from 1990 to 2020, this study employed methods including slope spectrum curve, slope index, and geodetector to analyze the upward trend of cultivated land slope and the occupation-compensation characteristics under different slope gradients, and to quantitatively identify the key driving factors.

Results 1) The proportion of cultivated land with a slope > 15° in the province increased by 0.55%. The slope of newly added cultivated land was consistently higher than that of lost cultivated land. The proportion of areas with "significant upward-sloping" was the highest during 2000–2005 (55.13%), which was mainly concentrated in Zone Ⅲ-4-1xt and Zone Ⅲ-4-2t. 2) The net change rate of cultivated land remained negative, with the highest intensity of construction occupation. Specifically, the proportion of cultivated land with a slope > 2°−6° occupied by construction reached 27.95%, and this phenomenon was most prominent in Zone Ⅲ-5-3fn. Gained cultivated land was mainly from the reclamation of forestland and grassland, with the proportion of supplementation in the > 6°−15° slope range accounting for up to 10.17%. The proportion of cultivated land gained from other reclamation was relatively high in Zone Ⅲ-5-2w. 3) Among single driving factors, precipitation had the strongest explanatory power (q = 0.201), followed by GDP (q = 0.164) and human activity intensity (q = 0.153). Two-factor interactions exhibited an enhancement effect. In Zone Ⅲ-5-3fn, the interaction between distance to roads and human activity intensity was relatively strong, while in other zones, the interaction between precipitation and human activity intensity exerted a dominant influence.

Conclusions This study confirms that the upward-sloping phenomenon of cultivated land in Shandong province is the result of the synergistic effects of natural and anthropogenic factors, thereby providing a scientific basis for optimizing the cultivated land protection pattern from the perspective of slope.