Comparison of soil erosion between wide and narrow longitudinal ridge tillage in black soil region

Wide longitudinal ridge tillage has significant effects for increasing crop yield. Field observation shows that in the black soil region of Northeast China, wide longitudinal ridge tillage has been widely promoted in the intensive farms on which large agricultural machines are used. However, hillslope soil erosion of wide longitudinal ridge tillage is seldom studied. Therefore, in typical black soil region, in this study, two large natural runoff plots with gentle slope gradient were established in Liangshigou watershed in Keshan County, Heilongjiang Province. One was wide longitudinal ridge tillage with 320 m slope length and 3-m slope width and another was narrow longitudinal ridge tillage with 320 m slope length and 2 m slope width. Ridges were established on a field of silty clay loam (USDA classification). The slope gradients ranged from 2°-7°. According to literature review and field measurements of the wide and narrow ridges in black soil region of Northeast China, the used wide ridges were 15-cm high, 110-cm wide; the used narrow ridges were 15- cm high, 65 cm wide. A laboratory simulated rainfall experiment was conducted in the simulated rainfall hall of the State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Yangling City, China. The soil used in the laboratory simulated rainfall experiment was collected in the natural runoff plot. According to the standard of erosive rainfall in Northeast black soil region of China, the simulated rainfall intensities were 50, 75 and 100 mm/h. Each rainfall experiment lasted 60 min. The wide and narrow ridges used in the simulated experiments were consistent with the large natural runoff plot in Keshan County. Based on the runoff plot observation and laboratory simulated rainfall experiments, the differences of hillslope soil erosion between wide and narrow longitudinal ridge tillage in black soil region of China were analyzed. The results showed that under both field runoff observation and laboratory simulation, hillslope soil losses from the wide longitudinal ridge tillage hillslope were 64.4% - 90.4% and 33.2% - 57.9% lower than that from the narrow longitudinal ridge tillage. Field observation indicated that there were significant or strong significant positive correlations among the soil loss, runoff and PI30. The increment of soil loss with runoff and PI30 in narrow ridge-tillage system was larger (P< 0.05) than that in wide ridge-tillage system. The relationship between soil loss and PI30 was power function, while the relationship between soil loss and runoff was linear function (R 2 >0.99). Indoor simulated experiments showed that there were linear relationships between soil loss and runoff under two longitudinal ridge tillage systems (R2 ≥0.81). The increment of soil loss from the wide longitudinal ridge tillage system was lower (P< 0.05) than that from the narrow longitudinal ridge tillage system. Compared with the narrow longitudinal ridge tillage, the reduction of soil loss by wide longitudinal ridge tillage decreased with the increase of PI30; when PI30 was 433.9 - 605.1, the reduction of soil loss by the wide longitudinal ridge tillage was 74.8% -90.4% and when PI30 were 1520.6 and 1708.6, the reduction of soil loss by the wide longitudinal ridge tillage was 64.4%-66.5%. Both field observation and simulated experiments displayed that the wide longitudinal ridge tillage had better effects on controlling hillslope soil erosion, compared with the traditional narrow ridge tillage. Therefore, promotion of wide ridge tillage system might have great significance in protecting Mollisol resources in the black soil region of Northeast China. © 2019, Editorial Department of the Transactions of the Chinese Society of Agricultural Engineering. All right reserved.