Discrimination of soil losses from ridge and furrow in longitudinal ridge-tillage under simulated upslope inflow and rainfall

Authors: WANG, LEI - Northwest A&f University; ZHENG, FENLI - Northwest A&f University; Zhang, Xunchang; Wilson, Glenn; QIN, CHAO - Northwest A&f University; HE, CHAO - Northwest A&f University; LIU, GANG - Northwest A&f University; ZHANG, JIANQIONG - Northwest A&f University

Submitted to: Soil & Tillage Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/12/2019
Publication Date: 12/19/2019
Citation: Wang, L., Zheng, F., Zhang, X.J., Wilson, G.V., Qin, C., He, C., Liu, G., Zhang, J. 2019. Discrimination of soil losses from ridge and furrow in longitudinal ridge-tillage under simulated upslope inflow and rainfall. Soil & Tillage Research. 198:104541. https://doi.org/10.1016/j.still.2019.104541.
DOI: https://doi.org/10.1016/j.still.2019.104541

Interpretive Summary: Longitudinal ridge-tillage is a system of rows formed into ridges and furrows as compared to flat tillage systems with the rows running up and down the slope. This type tillage can greatly enhance hillslope soil erosion due to increased flow along furrows and sediment delivered to furrows from the sides of the ridges into the furrows. Currently, contributions of soil loss from inflow into furrows by runoff from upslope and runoff from rainfall onto ridges and directly into furrows is not clear. The identification of sediment sources from ridges compared to sediment from within furrows is much needed for predicting and preventing soil loss. A set of experiments on 10-m long by 2-m wide field runoff plots at a 5° slope were conducted in northeast China’s black soil region to quantify upslope inflow and rainfall effects on hillslope erosion and to determine sediment contributions from ridges and furrows in a longitudinal ridge-tillage system. The experimental treatments included upslope inflow alone at five rates (10, 20, 30, 40 and 50 L min-1), rainfall alone at two intensities (50 and 100 mm h-1) and the combination of the five inflow rates simultaneous with the two rainfall intensities. A photographic method was used to measure small changes in the topography of ridges and furrows before and after each run. Compared to the inflow only treatments, soil erosion rates increased by 1.2-2.5 times and 3.1-6.1 times the inflow combined with rainfall for the two rainfall intensities 50 and 100 mm h-1, respectively. Rainfall caused more soil loss in the longitudinal ridge-tillage system than upslope inflow alone. When the inflow rate was almost the same as the rainfall intensity, rainfall accounted for 63% to 72% of the total soil loss. However, for the treatments of the five increasing inflow rates combined with rainfall, the rainfall contributions to soil loss decreased from 80.6% to 29.4% and 92.9% to 60.5% for the two rainfall intensities, respectively. Moreover, in the five upslope inflow only treatments, soil erosion mainly occurred in the bottom of furrows and ridge toe slopes; while for the inflow combined with rainfall treatments, erosion of ridge sideslopes dominated as soil loss from ridge areas accounted for 61% to 65% and 68% to 73% for the two rainfall intensities, respectively. Therefore, ridge sideslope erosion may be the main sediment source in the longitudinal ridge-tillage system. Soil conservation measures need to be developed for protecting these ridge sideslopes.

Technical Abstract: Longitudinal ridge-tillage greatly enhances hillslope soil erosion due to increased flow concentration in furrows and sediment delivery from ridge sideslopes. Currently, contributions of upslope inflow and rainfall to soil loss and identification of sediment sources in a longitudinal ridge-tillage system are still unclear. A set of experiments on 10-m long, 2-m wide field runoff plots at a 5° slope gradient were conducted in the Chinese Mollisol region to quantify upslope inflow and rainfall effects on hillslope erosion to discriminate sediment contributions from ridges and furrows in a longitudinal ridge-tillage system. The experimental treatments included five upslope inflow rates alone (10, 20, 30, 40 and 50 L min-1), two rainfall intensities alone (50 and 100 mm h-1) and the five inflow rates combined with these two rainfall intensities. A stereoscopic photogrammetry method was used to measure micro-topographic changes before and after each run. The results showed that, compared with inflow only treatments, soil erosion rates increased by 1.2-2.5 times and 3.1-6.1 times under treatments of five upslope inflow rates combined with both 50 and 100 mm h-1 rainfall intensities, respectively. Rainfall caused more soil loss in the longitudinal ridge-tillage system than upslope inflow alone. When inflow rate was almost the same as the rainfall intensity, rainfall accounted for 63.4% and 71.9% of the total soil loss. However, for the treatments of the five progressively increasing inflow rates combined with rainfall, the rainfall contributions to soil loss decreased from 80.6% to 29.4% and 92.9% to 60.5% for the two rainfall intentities, respectively. Moreover, in the five upslope inflow only treatments, soil erosion mainly occurred in the bottom of furrows and ridge toe slopes; while for the inflow combined with rainfall treatments, ridge sideslope erosion dominated as soil loss from ridge areas accounted for 61.1% to 64.8% and 68.3% to 73.0% for the two rainfall intensities, respectively. Therefore, ridge sideslope erosion may be the main sediment source in the longitudinal ridge-tillage system. Soil conservation measures need to be developed for protecting ridge sideslopes.