Surface Salinization of Soil under Mulched Drip Irrigation

The mulched drip-irrigation technique has been widely employed in Xinjiang, China, however, it was found to result in the buildup of salt in the surface soil. To ascertain the effect of mulched drip irrigation on salinization, experiments were carried out during 2009-2010 in two fields of mulched soil drip irrigated for three and 13 years. The solute transportation in soil was simulated with the MATLAB system based on the Richards equations. Results showed that the soil mulched by plastic film did not accumulate salt, but the bare soil surface accumulated salt and the salinity distribution in bare soil was in the 'Gamma' pattern. The soil layer below a depth of 20 cm in the bare area showed desalination because its salt content was 22% less than the surface. The salinity of bare surface soil including cultivated horizon was reduced by 17% after 13 years of drip irrigation. The simulation results indicated that the solutes of mulched soil were transported vertically to deep soil and transversely to the bare soil with drip irrigation. Thus, the salt accumulated on the surface of bare soil came from the soil mulched by plastic film, not from groundwater or saline irrigation water and did not cause secondary salinization.