Spatiotemporal variations in the soil quality of agricultural land and its drivers in China from 1980 to 2018.

Soil quality is essential for maintaining the sustainability of agroecosystems, especially under intensified agricultural activities and rapid land use change. The sampling and analysis of soil properties to assess the status of agricultural land is widely practiced at the field scale; however, the spatiotemporal variations in soil quality and its influencing factors at a large scale remain unclear. Here, we quantified spatiotemporal variations in the soil quality of agricultural land in China during 1980-2018 by using the soil quality index (SQI) area approach, and explored the drivers with a geographical detector method. The results showed that the distribution of the SQI in the two periods had a similar spatial trend, except for that in the southwest (SWC), and the SQI decreased from north to south regardless of land use type. The soil quality of woodland was comparatively good with mean SQI values of 1.55 and 1.53 in 1980 and 2018, respectively, followed by that in grassland and cropland. Soil organic carbon, total nitrogen and cation exchange capacity were the dominant soil indicators explaining the spatial heterogeneity of the SQI in all land uses; moreover, climatic factors (i.e., temperature and precipitation) showed a stronger effect on woodland. From 1980 to 2018, the SQI of grassland decreased deeply, especially in the SWC, which showed a severe decline of 12.5 %. The changes in precipitation and temperature were identified as the largest drivers of SQI temporal changes in woodland and grassland, respectively, and their interaction achieved the highest impact across all land uses. In addition, the bidirectional conversion between cropland and grassland in recent decades has aggravated the deterioration of soil quality. Therefore, quantifying spatiotemporal changes in the SQI and elucidating the role of factors influencing soil quality in agroecosystems can provide a guide for designing sustainable agriculture policies and improving environmental quality.