Effect of wastewater irrigation on soil hydrological properties in reed marsh

To study the effect of papermaking wastewater irrigation on soil hydrological properties in saline reed field, different wastewater irrigation frequencies were employed in the saline reed field of Yellow River Delta. Soil infiltration course and hydrological properties were determined in field and laboratory. After wastewater irrigation, the change of the soil pH value, soil salt content and soil hydrologic-physical properties were observed. The results were showed that: 1) After wastewater irrigation, the mean reduction of soil pH value was 6.0%. In 1 irrigation time and 2 irrigation times treatments, soil salt content decreased by 11.7%, and soil salt content increased by 12.6% in 3-4 irrigation times treatments. 2) After irrigation, the mean reduction of soil bulk density was 6.5%, and the mean increment of soil total porosity was 18.1%. With the irrigation frequency increasing, soil density was decreased and soil total porosity was increased. 3) Soil infiltration course of reed field irrigated by wastewater fitted Horton infiltration model well. After wastewater irrigation, the first infiltration rate decreased, but the stable infiltration rate promoted with the wastewater irrigation frequency increasing. 4) Soil water-holding capacity was increased by wastewater irrigation. The maximum water-holding capacity in capillary was 90.15 mm in the treatment of irrigation 3 irrigations, and the maximum water-holding capacity in non-capillary was 4.15 mm in treatment of 4 irrigations. The papermaking wastewater irrigation had obvious benefits to reduce soil salinity, improve soil hydrologic-physical properties and enhance soil infiltration and water-holding capacity. However, there was the significant different in soil properties between treatments. These results provide the scientific basis for determining suitable irrigation frequency and the irrigation volume of papermaking wastewater in saline reed field of Yellow River Delta, which is of great significance to the exploitation and utilization of papermaking wastewater resources.