Can Conservation Tillage Practice Increase Maize Yields? Causal Evidence From Northeast China

ABSTRACT Conservation tillage (CT) has been widely promoted as a sustainable agricultural practice to enhance soil health and ensure food security. However, despite extensive evidence of its soil conservation benefits in Northeast China, whether these improvements translate into measurable yield gains at a regional scale remains unclear. Existing studies have largely relied on plot‐scale experiments or station‐based observations, lacking systematic regional assessments, and rigorous causal identification of CT's yield effects. To address this knowledge gap, this study evaluates the impact of CT on maize net primary productivity (NPP) across Northeast China for the period of 2016–2020 using a Difference‐in‐Differences (DiD) with multiple time periods framework. High‐resolution remote‐sensing datasets were integrated to quantify spatial and temporal variations in CT effects while controlling for environmental and socio‐economic drivers. During the study period, regional maize NPP increased marginally from 27.35 to 28.01 g C·m −2 ·yr. −1 . On average, CT plots outperforming (27.68 g C·m −2 ·yr. −1 ) than conventional tillage (CVT) plots (26.81 g C·m −2 ·yr. −1 ). DiD estimates further reveal that CT significantly increased maize NPP by 0.280 g C·m −2 ·yr. −1 . Spatial heterogeneity shows the largest yield gains occurred in the Central Daxinganling Region (0.822 g C·m −2 ·yr. −1 ) and the Songnen Plain (0.362 g C·m −2 ·yr. −1 ), whereas water‐limited or poorly drained regions exhibit neutral or negative responses. Temporally, yield gains grew during the first 4 years of adoption but declined under prolonged implementation. These findings emphasize the need for the region‐specific yield‐improving effects of CT and optimizing its implementation.