Spatial Heterogeneity of Soil C:N Ratio in a Mollisol Watershed of Northeast China

Abstract

The spatial variability of the soil C:N ratio (C:N) influences C and N leaching and basic fertility in the field. This paper aims to identify the spatial heterogeneity of C:N in a Mollisol watershed of Northeast China and determine the main mechanisms that drive these differences. A random sampling method was used, with both geostatistical and traditional analysis being used to describe the spatial distribution of the C:N at various depths. C:N was also compared between slope position, previous vegetation and tillage methods in the watershed. The horizontal distribution of the C:N was mainly influenced by structural factors (88·4-99·9%) and often gradually deceased along the hydrographic flow direction, becoming lowest at the watershed outlet. The C:N increased as soil depth increased at all slope positions, and was higher on the back slope than on summit slope, followed by bottom slope in all soil depths. C:N was negatively (significant at p < 0·01) correlated to TN, and positively (significant at p < 0·05) correlated to elevation at all soil depths. Compared to the reforested area, C:N was typically greater in the agricultural area in the 20-60 cm depth. The planting of soybean (Glycine max L) can significantly increase the C:N at the 40-50 cm depth. C:N was higher in cross-slope tillage than in down-slope tillage, especially at soil depths of 40-50 cm. Generally, topographical factors, land use, crop planting and tillage methods can effectively influence the spatial heterogeneity of C:N in this watershed.

A simple method for the extraction and identification of light density microplastics from soil

“…Microplastic in the environment, especially in water bodies (salt or fresh water) and sediment, can be detected, counted and weighed which can be attributed to either the large volume of samples and less impurities or the lager particles (1mm-5mm) being examined (Hidalgo-Ruz et al, 2012;Nuelle et al, 2014b;Wang et al, 2016b). However, soil heterogeneity is complex, especially when considering all of the components such as mineral soil, organic matter, chemical elements and plant/animal residues (Brady and Weil, 2000;Zhang et al, 2014a;Zhang et al, 2016). In our study, not only microplastic were extracted and floated, but organic matter and other residues were also floated in water which was similar to other studies (Brady and Weil, 2000;Dekker and Ritsema, 1994;Hidalgo-Ruz et al, 2012).…”

Spatiotemporal Heterogeneity of Soil Available Nitrogen During Crop Growth Stages on Mollisol Slopes of Northeast China

“…Therefore, soil scientists from all of the world's Mollisols regions are concerned about the sustainability of some of current trends in land use and agricultural practices. In the Mollisol region of north‐eastern China, extreme erosion under intense rainfall events in the summer is considered to be one of the important factors affecting the decline of SOM, TN, and other soil nutrients (Tang, ; Zhang et al, and b; Zhang et al, ). These change the spatiotemporal variability of soil nutrients, which constrains crop yield, as well as economic return for farmers, and also negatively affects the environment (Yan et al, ).…”

Influence of Straw Amendment on Soil Physicochemical Properties and Crop Yield on a Consecutive Mollisol Slope in Northeastern China

“…Formation of soils in the study area began during the Quaternary period on loess deposits under natural grasses and now have a rich, dark organic layer (mean depth of 30 cm) and are classified as Black soil by the Chinese Soil Taxonomy (CST), Phaeozems by the World Reference Base for Soil Resources (WRB), and Mollisols by the US Soil Taxonomy (USST) [26]. Generally, the most slopes are inclined at less than 5 • , but are more 100 meters in length.…”