Reduction of soil and phosphorus losses by using micro‐dams in furrow irrigation

The suspension of eroded soil in surface runoff ultimately leads to the transfer of nutrients to land and water resources. Placing soil or straw (as a barrier) inside irrigated furrows in order to reduce water flow velocity, as a traditional local practice, has not been investigated from the environmental point of view. In this research, the effect of micro-dams (barriers built inside the irrigated furrows, also known as tied ridges or furrow dikes) on the reduction of soil and phosphorus losses was investigated. Field experiments were performed in four consequent irrigation events. Two erosive inflow discharges (0.6 and 0.9 L/s) and two micro-dam distances (10 and 20 m) were implemented as test treatments. A control treatment, without micro-dams, was used for comparison purposes. For the discharge of 0.6 L/s, micro-dams reduced furrow soil loss by 25% and 33% for distances of 20 and 10 m, respectively. For 0.9 L/s, soil loss was reduced by 25% and 59% for distances of 20 and 10 m, respectively. Micro-dams also reduced dissolved phosphorus losses in runoff water by 13% to 37%, depending on discharge and distance, as compared to the control treatment. Micro-dams can effectively reduce water, soil and phosphorus losses.