Lou Soil in Guanzhong: Characteristics and Formation from Loess Parent Material

Lou soil, found in Guanzhong region, is derived from loess parent material. The soil profile displays a distinctive Calcic horizon and Argic horizon in the middle and lower parts, attributed to the monsoon climate of the warm temperate zone. Long-term anthropogenic bedding activity has resulted in the formation of Cumulic epipedon on the surface. The profile configuration is primarily A-B or A-B-C, with the overburden layer (Aup+Aupb) in the upper section containing intrusive bodies such as carbon slag and tile. The soil texture is mainly silty loam and silty clay loam, exhibiting a noticeable difference in color between dry and moist sections. Dry soil tone ranges from 2.5Y to 10YR, while moist soil tone varies between 2.5Y, 5Y, 7.5YR, 10YR, and 2.5GY. The profile displays pseudo mycelium or cream-like lime aggregates, clay adhesive film, humus adhesive film, and new bodies of the tattoo class. The soil pH is alkaline, ranging from 6.3 to 9.50. The soil bulk density varies from 0.64 to 1.75g cm-3, with an average value of 1.20g cm-3. The soil organic carbon content ranges between 1.67 and 20.5g kg-1, the total nitrogen content ranges between 0.257 and 2.19g kg-1, and the available phosphorus content ranges between 0.182 and 229.66mg kg-1. The accumulation degree of CaCO3 in the test section varies, with content ranging from 5.79 to 263.74g kg-1. The content of the pile cushion is higher than that of the lower layer, indicating a decreasing trend from top to bottom.