<p>The win-win situation of grain yield increases and chemical fertilizer reduction under the backdrop of food security is a significant issue. This study investigates the impact of land consolidation (LC) on fertilizer use intensity and fertilizer input efficiency using a fixed-effects model and panel data from 54 counties or districts in Jiangsu Province (2008–2018). The analysis further explores the heterogeneous effects across different consolidation types, producing areas, and topographic conditions, along with the lagged effects of LC. Results showed that the lagged terms of farmland consolidation and land development decreased fertilizer use intensity, with the effects being more pronounced in regions with higher grain yields and regions with lower slopes. Notably, in regions with higher grain yields, farmland consolidation exhibited lagged effects that reduced fertilizer use intensity while simultaneously enhancing fertilizer input efficiency. In regions with lower slopes, the current year’s land reclamation and land development demonstrate negative impacts on chemical fertilizer reduction. Additionally, only the lagged terms of LC contributed to fertilizer reduction, indicating that the effects of LC need to take some time to manifest. The findings emphasize the ecological transformation, continuous monitoring, and classification management of LC, which have valuable implications for ensuring food security while maintaining the sustainability of the agricultural system.</p>