Feasibility of applying intermittent irrigation on solute leaching

In order to compare leaching efficiencies of continuous and intermittent irrigations, the HYDRUS-1D dual-porosity model was applied to simulate water and salt movement in soils under difference schemes of irrigation. Results showed that there was a critical depth above which intermittent irrigation would result in higher salt leaching efficiency. Simulations of sandy soils showed that when total irrigation amount was 20 cm, critical depth would decline from more than 60 cm to 0 cm as potential evaporation rate increased from 0 mm/d to 6 mm/d; but it would rise from 20 cm to almost 80 cm as total irrigation amount increased from 10 cm to 40 cm when potential evaporation rate was fixed to be 2 mm/d. Generally, soils with higher water conductivity, higher porosity of micro-pores and lower exchange rate of water and solute between micro and macro pores held higher critical depth, and simulations of sandy, loamy sandy, loamy, clayey loamy and clayey soils indicated that sandy soils were more likely to hold higher critical depth. When total irrigation amount was 30 cm and potential evaporation rate was 2 mm/d, critical depth of clay and sandy soil were 56 cm and more than 100 cm, respectively. In conclusion, there is no universal answer on whether intermittent irrigation would promote leaching efficiency, but critical depth could explain former contradict conclusions on this problem.