Effects of lateral depth on transport of E. coli in soil and maize production for subsurface drip irrigation system applying treated sewage effluent

摘要

Subsurface drip irrigation is a relatively safe way to use treated sewage effluent for crop irrigation, but there exists a risk of contaminant leaching caused by irrigation and precipitation. This study aims at investigating the effects of lateral depth on E. coli transport and crop production while applying treated sewage effluent during the growing season of summer maize in a semi-humid region. The experiments were conducted with three lateral depths ofO(D1), 15 (D2), and 30 cm (D3) irrigated at 70% (11), 100% (12), and 130% (13) of the difference between crop evapotranspiration and effective rainfall. Soil samples were collected at varying positions from the emitter at different depths to investigate the transport and surviving of E. coli in thesoil during the summer maize growing season. The results indicated that the fate of E. coli in the soil was highly related to the lateral depth and the elapsed time after an irrigation ceased. E. coli was mostly detected in the proximity of emitters andthe population of E. coli in the soil demonstrated a decreasing trend with the growing of crops. For all treatments, no E. coli was detected in the deep layer of 30 to 50 cm from the surface, but E. coli was detected at 10 to 30 cm depth in the treatments with lateral depths of 15 and 30 cm. The yield of maize ranged from 11.7 to 12.8 t-har1, increasing with the lateral depth. There was no significant difference in yield and yield components between the treatments irrigated with treated sewage effluentand the treatments irrigated with groundwater.