Abstract
Soil carbon and nitrogen are essential factors for agricultural production and climate changes. A total of 106 soil samples from three agricultural lands (including two rice fields and one sugarcane field) and four non-agricultural lands (including two forest lands, one wasteland and one built-up land) in the Mun River Basin were collected to determine soil carbon, nitrogen, soil pH, soil particle sizes and explore the influence of pH and soil texture on soil C and N. The results show that total organic carbon (TOC) and nitrogen (TON) contents in topsoil (TOC: 2.78 ~ 18.83 g kg−1; TON: 0.48 ~ 2.05 g kg−1) are much higher than those in deep soil (TOC: 0.35 ~ 6.08 g kg−1; TON: <0.99 g kg−1). In topsoil, their contents of forest lands and croplands (TOC: average 15.37 g kg−1; TON: average 1.29 g kg−1) are higher than those of other land uses (TOC: average 5.28 g kg−1; TON: average 0.38 g kg−1). The pH values range from 4.2 to 6.1 in topsoil, and with increase in soil depth, they tend to increase and then decrease. Soil carbon, nitrogen and the C/N (TC/TN ratio) are negatively correlated with soil pH, demonstrating that relatively low pH benefits the accumulation of organic matter. Most soil samples are considered as sandy loam and silt loam from the percentages of clay, silt and sand. For soil profiles below 50 cm, the TOC and TON average contents of soil samples which contain more clay and silt are higher than those of other soil samples.
Highlights
Soil holds more than three times as much carbon as the atmosphere and terrestrial vegetation, playing an important role in global climate change and agricultural production (Lal, 2004; Li et al, 2017)
It is widely acknowledged that soil mitigates climate change by assimilating atmospheric carbon dioxide and converting it into soil carbon by means of total organic carbon (TOC) sequestration (Minasny et al, 2017)
PH values are little influenced by land use and they are relatively lower at the sampling points which are close to the central region of the Mun River Basin
Summary
Soil holds more than three times as much carbon as the atmosphere and terrestrial vegetation, playing an important role in global climate change and agricultural production (Lal, 2004; Li et al, 2017). It is widely acknowledged that soil mitigates climate change by assimilating atmospheric carbon dioxide and converting it into soil carbon by means of total organic carbon (TOC) sequestration (Minasny et al, 2017). Total organic carbon is important for agricultural production because organic matter helps to improve soil structure and capacity of exchanging cation and holding water, exerting positive impacts on soil fertility (West & Post, 2002; De Blécourt et al, 2019; Liu et al, 2019). Soil texture, which is used to describe the size distribution of mineral particles, is reported as another important factor influencing the accumulation soil organic matter (Dexter, 2004). It’s important to learn about soil carbon and nitrogen as well as the relationship between them and other soil properties
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