The effect of soil texture and depth on nutrients in agricultural systems of China

Researchers investigated agricultural lands in the watershed of Lake Yilun (a low-latitude plateau in southwest China), collecting a total of 216 soil samples. The study simultaneously determined total organic carbon, total nitrogen, and total phosphorus (SOC, TN, TP), as well as available forms of carbon, nitrogen, and phosphorus (DOC, AN, AP). Using path analysis, the scientists evaluated the direct and indirect relationships between soil texture type (clay, loam, clay loam, sand) and depth (0–20 cm, 20–40 cm, 40–60 cm) with nutrient stoichiometry measurements.

The obtained data demonstrate differences in nutrient limitations and leaching risks. Loam showed the greatest capacity to retain carbon and nitrogen. Clay loam showed reduced phosphorus availability due to immobilization by iron and aluminum oxides, as well as pronounced nitrogen limitation. Sandy soils, despite being rich in available phosphorus, had the lowest C:N ratio, indicating an increased risk of carbon and nitrogen leaching.

Soil depth also had a noticeable effect on element ratios: the cultivated layer (0–20 cm) showed pronounced nutrient enrichment, whereas the subsoil layer (40–60 cm) recorded an increased TN:TP ratio, which may indicate enhanced nitrification with depth. Path analysis confirmed that texture directly regulates nutrient ratios and indirectly affects the C:N:P balance through SOC, AP, and AN content, while depth exerts its effect through pathways such as TP. The results of the work provide a scientific basis for differentiated and precise management of nutrients in the agroecosystems of Lake Yilun and other ecologically vulnerable areas.