Quantitative Assessment of Soil Physical Quality in Northern China Based on S-theory

Abstract

Quantitative assessment of soil physical quality is of great importance for eco-environmental pollution and soil quality studies. in this paper, based on the S-theory, data from 16 collection sites in the haihe river Basin in northern China were used, and the effects of soil particle size distribution and bulk density on three important indices of the S-theory were investigated on a regional scale. the relationships between unsaturated hydraulic conductivity K i at the inflection point and S values (S/h i ) were also studied using two different types of fitting equations. The results showed that the polynomial equation was better than the linear equation for describing the relationships between -log K i and -log S, and -log K i and -log (S/h i ) 2 ; and clay content was the most important factor affecting the soil physical quality index (S). the variation in the S index according to soil clay content was able to be fitted using a double-linear-line approach, with decrease in the S index being much faster for clay content less than 20 %. in contrast, the bulk density index was found to be less important than clay content. the average S index was 0.077, indicating that soil physical quality in the haihe river Basin was good.Keywords: friability, hard-setting, S index, soil water retention curve.

Use of S-Index as a Structural Quality Indicator for Compacted Latosols Cultivated With Maize

“…These authors emphasized the sensitivity of this index to soil structural change, even though it is very small, and concluded that the S-index is a good tool for monitoring soil physical quality. Yang et al (2015) also showed a negative linear correlation between S-index and SD (1.35 to 1.55 Mg m -3 ) in soil samples (150 to 350 g kg -1 clay) collected in northern China, but with low R 2 (0.02), which may indicate a lack of correlation between these parameters; and the SD was considered less important than the clay content.…”

“…Even in view of the uncertain efficiency of the S-index, Yang et al (2015) considered it as an indicator of soil physical quality. They found a mean S-index of 0.77 in the northern China basin and classified it as indicative of good soil quality.…”

Response to De Jong Van Lier's comments on “Quantitative assessment of soil physical quality in northern China based on S-theory” [Rev Bras Cienc Solo. 2015;39:1311-21]

“…Obviously, more analysis is required in future studies. We should have made this clear in the discussion in our study (Yang et al, 2015).…”

“…We are grateful to De Jong van Lier for raising queries about our study (Yang et al, 2015) which merits some clarification, and we would like to reply to his comments.…”

“…The principal purpose of our study (Yang et al, 2015) was to determine soil physical quality in the Haihe River Basin in northern China using the S-index proposed by Dexter (2004). The S-theory, developed with a basis on European soils, has been applied worldwide and produced plausible results.…”