A Quantitative Reconstruction of Nutrient Changes of Quaternary Red Soils (Luvisols) Affected by Land-Use Patterns

The Quaternary red soil widely distributed in China is an important arable land resource. A quantitative understanding of nutrient changes of Quaternary red soils under different land-use patterns is the necessary premise for effective regulation, management, and sustainable utilization. In this study, five typical Quaternary red soil profiles under different land-use patterns were taken as the research object in Chaoyang City, Liaoning Province, China. The results showed that: (1) Buried Quaternary red soils were minimally affected by external disturbances. The contents of nitrogen (around 0.02%), phosphorus (ranging from 0.06% to 0.07%), and potassium (ranging from 3.12% to 3.50%) were at relatively low levels and homogeneously distributed with depth. (2) The total nitrogen content of red soils under each land-use pattern showed an increasing trend in the upper part of the profile (A and B horizons), and a sequence of woodland (CL-04) > grassland (CL-03) > arable land (CL-05) = sparse forest–grassland (CL-02). The nitrogen content in the lower part of different land-use patterns was about 0.02%. The phosphorus content of the topsoil layer remained unchanged (ranging from 0.05% to 0.06%), while the subsoil phosphorus decreased to varying extents. The potassium experienced leaching in both topsoil and subsoil layers, with the topsoil losses being lower than that in the subsoil. The range of total potassium content in the grassland (CL-03) ranged from 2.64% to 4.21%, from 3.91% to 4.44% for sparse forest–grassland (CL-02), from 2.41% to 2.63% for woodland (CL-04), and 2.85% to 2.92% for arable land (CL-05), respectively. The variation in nutrient content was related to the vegetation type, coverage rate, artificial fertilization method and species, etc. The accumulative mass change in the sparse forest–grassland increased by 384.16 g/100 cm², and the other land-use patterns showed a decreasing trend of arable land (83.71 g/100 cm²) > woodland (83.71 g/100 cm²) > grassland (83.71 g/100 cm²), with the topsoil leaching losses being smaller than those in the subsoil layer. The characteristics of windbreak, sand fixation, and soil and water conservation of the sparse forest–grassland could well hold the nutrient-rich loess sediments, resulting in increased nutrients in the Quaternary red soil, which is a reasonable land-use pattern for the Chaoyang area.