Policy-driven improvements in cultivated land productivity: Changed determinants in Huang-Huai-Hai Plain, China

Sustainably improving cultivated land productivity (CLP) contributes to food security and environmental sustainability. Over the past 30 years, a portfolio of national cultivated land improvement programs (NCLIP) has been implemented in China's important agricultural production area, the Huang-Huai-Hai Plain, to increase cultivated land productivity. Quantifying the contributions of NCLIPs and the changed determinants of productivity improvement is crucial for informing effective agroecosystem management practices to promote sustainable agriculture. Here, we developed an integrated framework based on multi-source data and ensemble learning models. The contributions and changing determinants of NCLIP on CLP improvement were quantified from the 1990s to the 2020s using Light Gradient-Boosting Machine (LightGBM) models. From the 1990s to the 2010s, the county's average CLP increased by 2.5 t/ha, and 53 % (1.3 t/ha) of this increase could be attributed to the contribution of NCLIP implemented. The decadal effect of NCLIP gradually declined from 0.85 (74 %) to 0.02 (25 %) t/ha. In the 1990s, improved agricultural inputs and infrastructure were the main contributing factors, while after 2000, soil fertility improvement became the primary factor contributing to CLP improvement. Improving soil fertility and agricultural infrastructure can further improve CLP and reduce its variability in the 2020s. Our findings highlight the significant and evolving role of national cultivated land improvement programs in sustainably enhancing productivity, offering valuable insights for future policy-making toward food security and sustainable agroecosystem management.