Effect of reducing runoff, sediment, soil nitrogen and phosphorus losses in sloping farmland based on short ridge of clover hedgerow with ridge tillage

Abstract: Based on the demand of non-point source pollution control in Songhua River basin, the technique of short ridge of clover (Trifolium) hedgerow with ridge tillage (SRCHRT) was applied to research the control effect of the runoff, sediment, nitrogen (N) and phosphorus (P) losses in sloping farmland. SRCHRT is a novel technique that could decrease soil and water losses in sloping farmland, in which, the furrow between ridges the short ridge that is as high as ridge is piled up by a certain distance, and grass is planted in these short ridge, the grass and short ridge form hedgerow ridge, and hedgerow ridge and long ridge form the technique that is named SRCHRT. SRCHRT gained the national invention patent in 2018 and can retard runoff and control soil and soil N and P losses. A three-year field experiment was conducted to investigate the effects of application of SRCHRT on reducing sediment, runoff, and soil N and P losses in sloping farmland in the Songhua River basin. There are eight treatments, including two control, three space SRCHRT and three space short ridge of non-clover hedgerow with ridge tillage (SRNCHRT), the two controls were traditional longitudinal ridge tillage (CK1) and cross ridge tillage (CK2), three space SRCHRT were longitudinal ridge tillage + 1 m space short ridge with clover hedgerow (T1), longitudinal ridge tillage + 3 m space short ridge with clover hedgerow (T2), longitudinal ridge tillage + 5 m space short ridge with clover hedgerow (T3), longitudinal ridge tillage + 1 m space short ridge without clover hedgerow (T4), longitudinal ridge tillage + 3 m space short ridge without clover hedgerow (T5), and longitudinal ridge tillage + 5 m space short ridge without clover hedgerow (T6). Clover was chosen as the hedgerow. The results indicated as follow: 1) Compared with the traditional longitudinal ridge tillage (CK1), the sediment and runoff of CK2 decreased 46.9% and 52.9%; T1, T2 and T3 decreased sediment by 44.6%, 44.1% and 42.1%, respectively, and runoff by 50.6%, 49.8% and 49.2%, respectively. T4, T5 and T6 can also decrease water and soil losses in sloping farmland, compared with T1, T2 and T3, T4, T5 and T6 increased sediment by 16.3%, 12.6% and 29.5%, respectively, and runoff by 29.6%, 46.8% and 76.9%, respectively. The SRCHRT method in controlling sediment and runoff losses were close to cross ridge tillage (CK2), but there were significant differences (P<0.05). 2) Compared with the traditional longitudinal ridge tillage (CK1), total N (TN) concentration of sediment and TN concentration of runoff of all treatments were increased but total P (TP) concentration of sediment and TN concentration of runoff of all treatments were unchanged. TN and TP concentration of all treatments were increased and there were significant differences among treatments about TN concentration and no significant differences among treatments about TP concentration. The soil N from sloping farmland was not increased at all because of the higher TN concentration of SRCHRT runoff, and the losses of soil N was reduced by an average of 19.7% because the contribution of runoff reduction was more than TN concentration of runoff increment. 3) SRCHRT had significant effect of water and soil control and can decrease sediment, runoff, soil N and P losses in sloping farmland. From the cost-effective considerations, the 3-5 space short ridge of SRCHRT was recommended, and small spaces were suitable for bigger slope, the top and middle slope, longer spaces were suitable for smaller slope and the down of slope. SRCHRT can increase the corn yield by 5%-5.6%.