Decadal shifts in soil pH and organic matter differ between land uses in contrasting regions in China

Abstract

Soil organic matter (SOM) and pH are critical soil properties strongly linked to carbon storage, nutrient cycling and crop productivity. Land use is known to have a dominant impact on these key soil properties, but we often lack the ability to examine temporal trajectories across extensive spatial scales.Large-scale monitoring programmes provide the data to evaluate these longer-term changes, and under different climatic conditions. This study used data from Chinese soil surveys to examine changes in soil pH and SOM across different land uses (dry farmland, paddy fields, grassland, woodland, unused land), with surface soil (0-20 cm) collected in the periods 1985-90 (Survey 1; 890 samples) and 2006-10 (Survey 2; 5005 samples) from two contrasting areas. In the southern part of China the mean pH of paddy soils fell sharply over the two decades between surveys -from pH 5.81 to 5.19 (p<0.001), while dry farmlands in the northern sampling area fell slightly (from pH 8.15 to 7.82; p<0.001). The mean SOM content of dry farmland soil rose in both areas and the mean SOM of paddy fields in the southern area also rose (all p<0.001). Woodland soil pH in the south showed an increase from 4.71 to 5.29 (p<0.001) but no significant difference was measured in the woodlands of the northern area, although the trend increased. The SOM content of woodland top soils rose in the northern (p=0.003) and southern (p<0.001) study areas. The implications and potential causes of these changes over the two decade timespan between surveys are discussed and suggestions made as to how large scale soil sampling campaigns can be designed to monitor for changes and potential controlling factors.

Impact of Soil Factors on the Yield and Agronomic Traits of Hemerocallis citrina Baroni in the Agro-Pastoral Ecotone of Northern China

“…Specifically, both SOM and TN were significantly negatively correlated with pH, indicating that lower pH within a certain range leads to higher SOM and TN contents, resulting in higher yield. This is consistent with the findings of Sun Yiming [33], who studied the variations in soil pH and SOM content under different land uses (dry fields, paddy fields, grasslands, forests, and unused land) over a period of 20 years and observed a sharp decrease in soil pH in northern China and a slight decrease in southern China over this period, with both regions experiencing a notable increase in SOM content. Zainal [34] indicated that applying liquid organic fertilizer to sweetcorn leads to a linear increase in the SOM and TN content, which is consistent with the findings of this study.…”

Crop rotation combined with controlled-release fertilizer promoted the utinization of the reclaimed land along Yanze River through improving soil fertility and nutrients use efficiency

“…This might be due to the strong nitrification process in the aerobic environment during the wheat cropping season in which more H + was generated to counteract the increase in pH from paddy rice season. SOC is critical for soil structure and workability, the ability of soils to store nutrients and water, and for the global C cycle (Sun et al, 2020). In this study, almost all treatments significantly enhanced the SOC, which was dominated by the retention of straw residues (Y.…”

“…Soil pH plays an important role in crop production, nutrient chemistry, soil organisms, and shaping plant community composition (Sun et al, 2020). Both CU and BBU fertilizations resulted in a significant shortterm increase in soil pH under RG and RR rotations (Figs.…”

Does freeze-thaw action affect the extractability and bioavailability of Pb and As in contaminated soils?

“…In summary, values range as follows: soil pH, 7.20-7.59; SOM, 1.78-91.4 g/kg; CEC, 1.31-12.6 cmol/kg; mean particle size, 11.18-115 μm; weight specific surface area, 48.7-296 m 2 /g; conductivity, 45.3-251 μs/cm. The key variables soil pH and SOM are broadly typical for soils from northeast China (Sun et al, 2020;Zhang, 2011). The total concentrations of the major elements Al, Fe and Mn, which can influence the chemistry of Pb, were ~18,000-55,000 mg/kg, ~37,000-130,000 mg/kg and ~690-4,000 mg/kg, respectively.…”