Physical, chemical and biological emitter clogging behaviors in drip irrigation systems using high-sediment loaded water

High-sediment water in drip irrigation (HSWDI) technology offers the opportunity to alleviate water shortages in agricultural irrigation. Emitter clogging, caused by active suspended particles, salt ions, and microorganisms present in water with high sediment load, poses considerable technical challenges to HSWDI. To date, emitter blockage of HSWDI is attributed to physical clogging, little is known about the physical, chemical, and biological clogging behaviors and their interactions for HSWDI. Here, X-ray diffraction and 16S rRNA gene sequencing were applied to determine the physicochemical minerals and microbial community structure of the foulants for HSWDI, using three types of flat emitters and two fertilization modes (no-fertigation and fertigation with ammonium polyphosphate, APP). Results indicated that HSWDI emitter clogging was not only caused by physical clogging (induced by particulates) but also caused by chemical clogging (i.e., precipitates) and biological clogging (i.e., biofilms). The main particulates in HSWDI were found to be quartz (accounting for 41.8–56.3% of total clogging foulants) and feldspar (13.6–21.1%), while the precipitates that contained calcite, dolomite and aragonite contributed 14.6–26.7%. The dominant flora in foulants were Proteobacteria (relative abundance ranged: 41.7–53.9%) and Bacteroidetes (13.6–17.3%). Moreover, the coupling effect of three types of fouling was the main reason affecting clogging (accounting for 36.3%), while the effect of two or single fouling was less (accounting for 14.4–25.3% and 0.7–2.6%). In addition, APP application caused the increase in microbial diversity and the proliferation of microorganisms, resulting in the interactions between biofilm and other two foulants (i.e., precipitates and particulates) were exacerbated, thus aggravating emitter clogging. This study opens a frontier for the investigation of physical, chemical, and biological clogging behavior, in-depth clogging mechanisms, and anti-clogging measures for HSWDI, which will facilitate the utilization of high-sediment water in agricultural irrigation.