Utilization of aquaculture drainage for enhancing onion crop yield under surface and subsurface drip irrigation systems

The main objective of the present study is to improve onion crop yield using aquaculture drainage under surface and subsurface drip irrigation systems. Field experiments are carried out on onion crop under conditions of two different water resources (groundwater and aquaculture drainage), two types of filters (screen filter for groundwater, while screen, sand and combined screen-sand filters for aquaculture drainage) and four different pressures (1.0, 1.2, 1.4 and 1.6 bar). The performance of the tested drip irrigation systems is evaluated based on filtration efficiency, discharge reduction, application efficiency, emitters clogging, emission uniformity, onion yield and water-use efficiency. The obtained experimental results show that irrigation with aquaculture drainage gives the highest onion yield of 19.17 Mg/fed for surface drip irrigation and 17.03 Mg/fed for subsurface drip irrigation compared to groundwater, which gives 17.55 Mg/fed for surface irrigation and 14.20 Mg/fed for subsurface irrigation. Surface drip irrigation achieves the lowest emitter clogging (5.98 % for groundwater and 5.86 % for aquaculture drainage) and the highest emission uniformity (90.22 % for groundwater and 89.91 % for aquaculture drainage) in comparison with a subsurface drip irrigation system that gives the lowest emitter clogging (7.98 % for groundwater and 7.55 % for aquaculture drainage) and the highest emission uniformity (91.04 % for groundwater and 90.54 % for aquaculture drainage) at 1.6 bar pressure. It is recommended to use aquaculture drainage for operating surface drip irrigation systems under pressure of 1.4 bar, using combined screen-sand filters for aquaculture drainage filtration, while screen filter for groundwater filtration.