Increasing phosphorus availability by reducing clogging in drip fertigation systems

Abstract

Phosphorus fertigation by drip irrigation (PFDI) system may offer an effective way to alleviate the soil and water pollution caused by the excessive input of phosphorus fertilizer, and also to cope with global phosphorus shortage. However, emitter clogging is the main obstacle to the application and popularization of PFDI, since also reduces the uniformity of phosphorus fertigation. The main results of experiment for assessing the clogging behavior of eight emitters using three types of phosphorus fertilizer (potassium phosphate monobasic, PPM; urea phosphate, UP; ammonium polyphosphate, APP) and three fertilization levels (0, 0.15 and 0.30 g/L) were that the performance of the emitters depended on the type of fertilizers, concentrations and emitters. Compared with non-fertigation, the application of APP induced the most serious emitter clogging as drastically promoted the deposition of carbonate and phosphate. PPM accelerated the precipitation of silicates and carbonates. UP reduced carbonate deposition while significantly increased silicate content and caused the slightest clogging. Consequently, the average discharge variation in UP, PPM, and APP decreased by 4.1%–19.4%, 16.0%–37.3%, and 43.9%–65.4%, respectively. Under the same amount of fertilizer, low concentration and long-term (LCLT) fertilization effectively relieved the clogging issue. The results suggested PFDI should choose UP as the fertilizer type and adopt LCLT fertilization mode, since UP fertigation with the concentration of 0.15 g/L did not significantly aggravate emitter clogging. Moreover, some anti-clogging measures were further proposed based on the clogging behavior of PFDI.