To examine the impact of anthropogenic land reconstruction, particularly the consolidation of small terraces into larger fields, on soil organic carbon (SOC), total nitrogen (TN) dynamics, rice yield, and its components, soil and plant samples were collected from seven newly reconstructed fields in Japanese Andosols in Tochigi, Japan. Samples were obtained from both the former low- and high-elevation sides within each field plot. During harvest season, nine rice plants were randomly selected from each plot (0.675 m2, comprising 3 rows and 3 hills per row), collected from a 3-m stretch along both the east (former low side) and west (former high side) ridges. Soil cores were collected from identical plots at two depths (0–15 and 15–30 cm) and combined into one composite sample per layer. Rice plant samples were air-dried for two weeks until reaching constant moisture content, after which stems and ears were separated and weighed to determine biomass, yield, yield components, and nitrogen uptake. This indicated that land reconstruction significantly affected rice yield and its components between the two sides of all field plots. SOC, TN, and their decomposition following land reconstruction showed notable changes, especially in the 15–30 cm subsurface soil layer. Additionally, grain weight demonstrated significant correlation with SOC, TN, and carbon decomposition in both the 0–15 and 15–30 cm layers, indicating that soil fertility to a depth of 30 cm was crucial for rice productivity after land reconstruction.

hydrological carbon loss  /  runoff and sediment  /  organic manure  /  sloping croplands