Aquaponics combined with field culture using saline groundwater makes effective use of water and reduces environmental pollution

Abstract

Insufficient water and salinization of soils and groundwater are predominantly limiting dryland farming. To address these problems, we developed a system of aquaponics combined with field culture using saline groundwater in a dryland area. By using the same saline water for aquaculture, hydroponics of halophyte, and field culture, this system achieved high efficiencies of water and nutrient use, and halophyte’s ability to absorb salts helped mitigate soil salinization. To evaluate yields and to analyze water and mineral balances in detail, this study recreated the system and operated it with pseudo groundwater applied with 2,922 ppm NaCl [PGW50] or 5,844 ppm NaCl [PGW100]. Swiss chard grown in both treatments grew almost equally well, irrespective of low levels of several elements and the high levels of Na. Total N input into PGW50 and PGW100 aquaculture systems was 70.8% and 60.6% respectively which was distributed to field culture, which enabled basal N dressing to be reduced to about one-fifth of the recommended application rate. Compared to three systems conducted independently, water-use efficiency was 2.8 times greater in both PGWs, and N-use efficiency was 1.90 and 1.68 times greater in PGW50 and PWG100, respectively. Compared to direct irrigation with saline groundwater, Na input to the soil was reduced by 8.93% and 16.5% in the PGW50 and PGW100 systems, respectively. It was quantitatively shown that this aquaponics system is an advanced food production system with highly efficient water and mineral use that can mitigate the salinization problem in field soils.