Background Accurate and efficient determination of soil water retention curve is important for the study of soil water movement and soil erosion. Various measurement methods are based on different mechanisms and each method has different applicability. Comparing method differences across multiple soil types can reflect the influence of soil properties on measurement results of equipment and provide a reference for selecting suitable methods for determining soil water retention curve.

Methods Centrifuge and pressure plate were used to determine the soil water retention curve of black soil, loessal soil, red soil, cinnamon soil and purple soil in the water erosion region. The determination range of 2 methods was 0-15 300 cm, and the data were divided into the low suction stage (0-1 000 cm) and the high suction stage (> 1 000-15 300 cm) to analyze the differences between the two methods. A paired samples t test was used to test the significance of the differences in soil volume water content determined by centrifuge and pressure plate.

Results The water content of 5 soils measured by the centrifuge was lower than that of the pressure plate at low suction stage, contents while the result at high suction stage was the opposite pattern. The measurement results of black soil, loessal soil, cinnamon soil and purple soil had extremely significant differences (P < 0.01) at high suction stage. The measurement difference of red soil was significant (P < 0.05) at low suction stage, and the water contents measured by the 2 methods at high suction stage were very close. At high suction stage, soil types with high clay and silt content caused incomplete soil drainage due to insufficient balance time in the pressure plate, which was significantly different from the water content determined by the centrifuge. Soil types with high sand content were mainly affected by the change of bulk density at low suction stage, which obviously caused the centrifuge measurement result to be lower than that of the pressure plate.

Conclusions Soil texture and pore distribution are the main reasons for the difference in measurement between the 2 methods for different soil types. For soils with high sand content, the soil volume is compressed obviously during the centrifuge determination process; for soils with high clay and silt content, the centrifuge method is relatively more suitable.