Abstract
Herein, we introduce continuous sub-irrigation with treated municipal wastewater (TWW) as a novel cultivation system to promote resource recycling and cost-effective forage rice production in Japan. However, both TWW irrigation and forage rice cultivation were previously considered to intensify CH4 and N2O emissions. In the present study, therefore, we evaluate the emissions of greenhouse gases (GHGs) and yielding capacity of forage rice between conventional cultivation and continuous sub-irrigation systems employing different water supply rates. Results indicated that continuous sub-irrigation with TWW resulted in high rice yields (10.4–11 t ha−1) with superior protein content (11.3–12.8%) compared with conventional cultivation (8.6 t ha−1 and 9.2%, respectively). All TWW irrigation systems considerably reduced CH4 emissions, while higher continuous supply rates significantly increased N2O emissions compared with the conventional cultivation. Only the continuous irrigation regime employing suitable supply rates at appropriate timings to meet the N demand of rice plants decreased both CH4 and N2O emissions by 84% and 28%, respectively. Overall, continuous sub-irrigation with TWW provides high yields of protein-rich forage rice without the need for synthetic fertilisers and effectively mitigated GHG emissions from paddy fields.
Highlights
Effluents from wastewater treatment plants (WWTPs) contain high concentrations of organic and inorganic nutrients beneficial for plant growth and development
We reported the development of an innovative approach for continuous irrigation with treated municipal wastewater (TWW) in forage paddy fields, which used TWW as the only source for irrigation and fertilisation[1,4]
The treatments employing the continuous sub-irrigation systems (R1, rate of either 25 (R2), and R3) were not supplemented with synthetic fertilisers, their grain yields were not significantly different (p > 0.05) from those attained in the control
Summary
Effluents from wastewater treatment plants (WWTPs) contain high concentrations of organic and inorganic nutrients beneficial for plant growth and development Reusing these effluents for agricultural irrigation has major advantages for crop production and environmental management[3]. Paddy rice cultivation generally demands large amounts of irrigation water and synthetic fertilisers, and would greatly benefit from recycling water and valuable nutrients from WWTPs. To promote forage rice production and establish an effective resource circulation model for the management of agricultural water, we developed new cultivation systems, and treated municipal wastewater (TWW) was effectively reused in paddy fields to produce high yields of forage rice without applying synthetic fertilisers[1,4,5]. Given the differences in reported GHG emissions from paddy fields under different water and fertilisation practices, our continuous TWW irrigation system requires a thorough investigation to understand its effects on the GHG emissions from forage paddy fields
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