Four-dimensional modelling reveals decline in cropland soil pH during last four decades in China’s Mollisols region

The degradation of fertile Mollisols due to unsustainable management practices poses serious threats to climate change mitigation and food security. Yet, the lack of four-dimensional (4D) dynamic information (i.e., space, depth, and time) on cropland soil pH hinders sustainable soil management. To f...

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Main Authors: Jian Chen, Enze Xie, Yuxuan Peng, Guojing Yan, Jun Jiang, Wenyou Hu, Yuguo Zhao, Khalid Saifullah Khan, Yongcun Zhao
Format: Article
Language:English
Published: Elsevier 2025-01-01
Series:Geoderma
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Online Access:http://www.sciencedirect.com/science/article/pii/S0016706124003641
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author Jian Chen
Enze Xie
Yuxuan Peng
Guojing Yan
Jun Jiang
Wenyou Hu
Yuguo Zhao
Khalid Saifullah Khan
Yongcun Zhao
author_facet Jian Chen
Enze Xie
Yuxuan Peng
Guojing Yan
Jun Jiang
Wenyou Hu
Yuguo Zhao
Khalid Saifullah Khan
Yongcun Zhao
author_sort Jian Chen
collection DOAJ
description The degradation of fertile Mollisols due to unsustainable management practices poses serious threats to climate change mitigation and food security. Yet, the lack of four-dimensional (4D) dynamic information (i.e., space, depth, and time) on cropland soil pH hinders sustainable soil management. To fill this knowledge gap, over 17,000 soil pH samples were first collected from the Mollisols region in Northeast China. Then, an automatic machine learning model coupled with space-for-time substitution (AutoMLst) was developed for mapping the 4D dynamics of cropland soil pH during 1980–2023. Results showed that AutoMLst performed well in 4D modelling of cropland soil pH, with a coefficient of determination of 0.88. The topsoil (0–30 cm) pH significantly declined from 6.83 in 1980 to 6.43 in 2023 in Northeast China, with an average decline rate of 0.0038 units yr−1 (0.0014–0.0063 units yr−1). The pH declines in the deeper soil layers (30–60 and 60–100 cm) were slight and statistically insignificant. The excessive use of chemical nitrogen (N) fertilizers and N deposition jointly contributed to the decline of cropland soil pH, but the impact of N deposition has increased over time. Although implementing China’s zero-growth policy for chemical fertilizer application will increase soil pH under the shared socioeconomic pathway (SSP) 1–2.6 and 5–8.5 scenarios, the current decline in cropland soil pH should not be overlooked to ensure the health of Mollisols. These findings suggest that the sustainable management of Mollisols resources requires strict monitoring of soil pH dynamics to mitigate potential soil acidification risks.
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issn 1872-6259
language English
publishDate 2025-01-01
publisher Elsevier
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series Geoderma
spelling doaj-art-3dbd49bdb4024a848325800cb19df1a22025-01-10T04:36:42ZengElsevierGeoderma1872-62592025-01-01453117135Four-dimensional modelling reveals decline in cropland soil pH during last four decades in China’s Mollisols regionJian Chen0Enze Xie1Yuxuan Peng2Guojing Yan3Jun Jiang4Wenyou Hu5Yuguo Zhao6Khalid Saifullah Khan7Yongcun Zhao8Institute of Soil Science, Chinese Academy of Sciences, Nanjing 211135, China; University of Chinese Academy of Sciences, Beijing 100049, ChinaInstitute of Soil Science, Chinese Academy of Sciences, Nanjing 211135, China; University of Chinese Academy of Sciences, Beijing 100049, ChinaInstitute of Soil Science, Chinese Academy of Sciences, Nanjing 211135, China; University of Chinese Academy of Sciences, Beijing 100049, ChinaInstitute of Soil Science, Chinese Academy of Sciences, Nanjing 211135, China; University of Chinese Academy of Sciences, Beijing 100049, ChinaInstitute of Soil Science, Chinese Academy of Sciences, Nanjing 211135, China; University of Chinese Academy of Sciences, Beijing 100049, ChinaInstitute of Soil Science, Chinese Academy of Sciences, Nanjing 211135, China; University of Chinese Academy of Sciences, Beijing 100049, China; University of Chinese Academy of Sciences, Nanjing 211135, ChinaInstitute of Soil Science, Chinese Academy of Sciences, Nanjing 211135, China; University of Chinese Academy of Sciences, Beijing 100049, China; University of Chinese Academy of Sciences, Nanjing 211135, ChinaInstitute of Soil and Environmental Sciences, PMAS Arid Agriculture University, Rawalpindi 46300, PakistanInstitute of Soil Science, Chinese Academy of Sciences, Nanjing 211135, China; University of Chinese Academy of Sciences, Beijing 100049, China; University of Chinese Academy of Sciences, Nanjing 211135, China; Corresponding author at: Institute of Soil Science, Chinese Academy of Sciences, Nanjing 211135, China.The degradation of fertile Mollisols due to unsustainable management practices poses serious threats to climate change mitigation and food security. Yet, the lack of four-dimensional (4D) dynamic information (i.e., space, depth, and time) on cropland soil pH hinders sustainable soil management. To fill this knowledge gap, over 17,000 soil pH samples were first collected from the Mollisols region in Northeast China. Then, an automatic machine learning model coupled with space-for-time substitution (AutoMLst) was developed for mapping the 4D dynamics of cropland soil pH during 1980–2023. Results showed that AutoMLst performed well in 4D modelling of cropland soil pH, with a coefficient of determination of 0.88. The topsoil (0–30 cm) pH significantly declined from 6.83 in 1980 to 6.43 in 2023 in Northeast China, with an average decline rate of 0.0038 units yr−1 (0.0014–0.0063 units yr−1). The pH declines in the deeper soil layers (30–60 and 60–100 cm) were slight and statistically insignificant. The excessive use of chemical nitrogen (N) fertilizers and N deposition jointly contributed to the decline of cropland soil pH, but the impact of N deposition has increased over time. Although implementing China’s zero-growth policy for chemical fertilizer application will increase soil pH under the shared socioeconomic pathway (SSP) 1–2.6 and 5–8.5 scenarios, the current decline in cropland soil pH should not be overlooked to ensure the health of Mollisols. These findings suggest that the sustainable management of Mollisols resources requires strict monitoring of soil pH dynamics to mitigate potential soil acidification risks.http://www.sciencedirect.com/science/article/pii/S0016706124003641Automatic machine learningFour-dimensional modellingMollisolsSoil pHClimate change
spellingShingle Jian Chen
Enze Xie
Yuxuan Peng
Guojing Yan
Jun Jiang
Wenyou Hu
Yuguo Zhao
Khalid Saifullah Khan
Yongcun Zhao
Four-dimensional modelling reveals decline in cropland soil pH during last four decades in China’s Mollisols region
Geoderma
Automatic machine learning
Four-dimensional modelling
Mollisols
Soil pH
Climate change
title Four-dimensional modelling reveals decline in cropland soil pH during last four decades in China’s Mollisols region
title_full Four-dimensional modelling reveals decline in cropland soil pH during last four decades in China’s Mollisols region
title_fullStr Four-dimensional modelling reveals decline in cropland soil pH during last four decades in China’s Mollisols region
title_full_unstemmed Four-dimensional modelling reveals decline in cropland soil pH during last four decades in China’s Mollisols region
title_short Four-dimensional modelling reveals decline in cropland soil pH during last four decades in China’s Mollisols region
title_sort four dimensional modelling reveals decline in cropland soil ph during last four decades in china s mollisols region
topic Automatic machine learning
Four-dimensional modelling
Mollisols
Soil pH
Climate change
url http://www.sciencedirect.com/science/article/pii/S0016706124003641
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