High yield and mitigation of N-loss from paddy fields obtained by irrigation using optimized application of sewage tail water

Abstract

Reuse of treated wastewater effluent for crop irrigation can be a promising strategy to substitute/reduce chemical fertilizers and mitigate contamination of water environment. The effect of the effluent irrigation strategies on crop yield and nitrogen (N) loss to the environment have not been yet well explored. In the present study, a soil column monitoring experiment was conducted for over two years (2016–2017) to assess the effect of domestic sewage tail water (DSTW) irrigation on rice growth and N-loss. DSTW irrigation was established substituting N fertilizer at percentages of 15 %, 30 % and 45 % (namely N3S1, N2S2 and N1S3) with a total nitrogen (TN) input of 210 kg·hm−2; controls with conventional fertilizer (N210) and no fertilizer (N0) but tap water irrigation were also set up. A field plot experiment was also conducted using the same treatments in 2017. The results of the soil column experiment showed that the grain yield from treatments with different proportions of DSTW and N fertilizer were no lower than those subjected to conventional fertilizer in both years. The NH3 volatilization from the treatments using reclaimed DSTW accounted for 20.9 %–34.4 % TN in 2016, but this fell to 6.9 %–16.1 % in 2017. Compared with N210, the DSTW irrigation treatment (N1S3) significantly reduced NH3 emissions by 32.8 %–61.3 % over the two years (p < 0.05). The field plot experiment also indicated that DSTW reclamation could not significantly affect the rice growth and yield, and treatments with a higher proportion of N substituting by DSTW tended to have lower NH3 volatilization. With respect to the rice yield and N-loss, the recommended ratio of N fertilizer substitution is 30 %–45 %; however, long-term trials would be required to further evaluate of any adverse environmental impacts.