Evolution of Cultivated Land Quality and Its Impact on Productivity in Three Ecological Regions of Arid Regions in Northern China

Cultivated land quality is a critical factor influencing soil productivity and serving as the theoretical basis for scientific fertilization. This study systematically analyzed the evolution of cultivated land quality and its impact on soil productivity across three major ecological regions (northern Shanxi, central Shanxi, northern Shanxi) in Shanxi Province, China, over a 23-year period (1998-2021). This study was conducted using data from 8 long-term experimental sites (1998-2021) and 50 monitoring stations (2016-2021), employing random forest analysis to evaluate temporal trends in key soil productivity indicators. The results revealed that 1) Northern Shanxi showed the greatest improvement in soil fertility, with organic matter content increasing by 98.2%, total nitrogen by 57.2%, available phosphorus by 131.7%, and available potassium by 17.1%; 2) Nitrogen fertilizer application exhibited an increasing trend across all three ecological regions, with the highest growth rate of 29.5% in central Shanxi. While phosphorus and potassium fertilizer inputs generally declined; 3) Crop yields improved substantially, with southern Shanxi wheat and maize showing increases by 15.3% and 20.9%, respectively, while central and northern Shanxi maize yields rose by 30.9% and 75.4%, respectively. Regional characteristics (40%), nitrogen fertilization (20%), and available phosphorus (18%) were identified as the primary influencing factors through the random forest models. Although cultivated land quality has been effectively enhanced in all three ecological regions, overall fertility remains at a medium-to-low level. In particular, region-specific management strategies are recommended: Reasonable use of nitrogen fertilizer is required in all three regions, and then nitrogen control with phosphorus supplementation in southern Shanxi; focused improvement of available phosphorus and potassium in central Shanxi; and increased organic fertilizer application in northern Shanxi. These tailored measures will promote scientific nutrient management and sustainable agricultural production.