High yield and nutritional quality of rice for animal feed achieved by continuous irrigation with treated municipal wastewater

Sasaki

et al. 2020

Sci Rep

Self Cite

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 cH 4 and n 2 O 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 subirrigation 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 cH 4 emissions, while higher continuous supply rates significantly increased n 2 O 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 cH 4 and n 2 O 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. Cultivation of forage rice (Oryza sativa L.) has been promoted by the Japanese government to reduce the cost of domestic animal husbandry by reducing the use of imported feedstuffs, which can be of unstable supply and highly priced depending on global markets 1. As a result, there has been a recent increase in forage rice cultivation. However, this has been accompanied by high levels of N fertiliser use to ensure high-yield production, which might lead to inefficient N use and considerable N loss to the environment 2. Effluents from wastewater treatment plants (WWTPs) contain high concentrations of organic and inorganic nutrients beneficial for plant growth and development. Thus, 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 thus, 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. The reuse of wastewater or TWW for rice cultivation has been intensively investigated and is widely practiced owing to its undeniable benefits. For instance, prior studies have demonstrated that rice grain yield from fields irrigated with treated wastewater could be 35-55% higher than that from groundwater-irrigated fields 6. Furthermore, reusing wastewater could lower the...

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confidence: 99%

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confidence: 99%

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confidence: 99%

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Continuous Sub-Irrigation with Treated Municipal Wastewater for Protein-Rich Rice Production with Reduced Emissions of CH4 and N2O

Sasaki

et al. 2020

Sci Rep

Self Cite

“…Bioaccumulation of the heavy metal(loid)s (Zn, Cu, Pb, Cd, and As) in the rice grains and their concentrations in paddy soils were determined by the standard wet-digestion method followed by measurement with either an inductively coupled plasma mass spectrometer (ICP-MS) (Elan DRC II, PerkinElmer, Japan) for Zn, Cu and Pb or by atomic absorption spectrometry (AAS Model AA7000 equipped with hydride generator, Shimadzu Corporation, Japan) for As 37 . Changes in N, P, and K contents in the paddy soil were also investigated following standard methods as previous studies [3][4][5] .…”

Section: Data Collectionmentioning

confidence: 99%

High yield of protein-rich forage rice achieved by soil amendment with composted sewage sludge and topdressing with treated wastewater

Ichikawa

et al. 2020

Sci Rep

Self Cite

Aiming to promote low-cost production of protein-rich forage rice and resource recycling from wastewater treatment plants, a pot experiment was conducted to assess the possibility to substitute mineral fertilizers with composted sewage sludge (cSS) with/without top-dressing with treated municipal wastewater (TWW). Results indicated that a basal application of CSS at 2.6 g N pot −1 replaced conventional mineral fertilization of 1.3 g N pot −1 to produce comparable yields with the same rice protein content, although there might be a risk of increased As concentration in rice grains. Interestingly, CSS application at a reasonable dose of 1.3 g N pot −1 , followed by a topdressing with TWW resulted in 27% higher yield and 25% superior rice protein content relative to the mineral fertilization, with no risk of heavy metal(loid) accumulation in grains and in paddy soils. Here we demonstrated an appealing fertilization practice with zero use of mineral fertilizers in paddy rice cultivation, expectedly contributing towards sustainable rice farming and animal husbandry in Japan. Accelerated generation of sewage sludge and treated municipal wastewater (TWW) along with increasing limitations in availability of resources have required highly efficient and sustainable disposal practices for the sludge and TWW, triggering a rapid change of wastewater treatment plants (WWTPs) from stations for wastewater purification and pollutant removal towards facilities for recourse recovery 1. Rice farming demands large quantities of irrigation water and mineral fertilizers, which allows the great opportunity for recycling plant nutrients and water from WWTPs to reduce the dependence of the crop production on mineral fertilizers and other freshwater sources through soil amendment with sewage sludge and reuse of TWW. Aiming to substitute forage rice for imported feed-stuffs of unstable supply and a price highly dependent on global markets and to avoid the risk of rising production costs of domestic animal husbandry, adoption of forage rice cultivation is drawing increasing attention in Japan 2,3. In attempts to promote low-cost forage rice cultivation while recycling plant nutrients and water from WWTPs, we have developed new irrigation systems for effective reuse of TWW as a sole source of both water and plant nutrients to produce high grain yields of protein-rich rice without the need for mineral fertilizers 3-5. These TWW irrigation systems have proved highly beneficial and applicable to paddy fields located near local WWTPs, from which the effluent is supplied to paddy fields 3 ; however, they frequently face difficulties to attain an even distribution of TWW to paddy fields far from the WWTPs due to the rising cost of instalment of water-distributing pipes/channels. Hence, application of sewage sludge might be an alternative in those paddy fields owing to its abundance in organic matter and plant nutrients, especially N and P 6. Nevertheless, soil amendment of sewage sludge generally raises concerns of environmental and health risks du...

“…We have recently introduced an innovative irrigation system for the cultivation of paddy rice 6 , namely continuous sub-irrigation with treated wastewater (hereinafter, referred to as CSI). The objective of this system is to promote the recycling of nutrients from municipal wastewater treatment plants (WWTPs) in a cost-effective manner and the production of high yielding protein-rich rice without the use of mineral fertilisers [6][7][8] . Importantly, although it was previously claimed that irrigation with wastewater would signi cantly increase CH 4 emissions due to the high availability of organic C in irrigation wastewater 9 , our recent study found that CSI could markedly reduce CH 4 emissions by up to 84% compared with conventional rice cultivation 6 .…”

Section: Introductionmentioning

confidence: 99%

Methane Mitigation is Associated with Reduced Abundance of Methanogenic and Methanotrophic Communities in Paddy Soils Continuously Sub-irrigated with Treated Wastewater

Miyazawa

et al. 2021

Preprint

Self Cite

Herein, we examined emissions of CH4 and the community structures of methanogenic archaea and methanotrophic bacteria in paddy soils subjected to a novel irrigation system, namely continuous sub-irrigation with treated wastewater (TWW). This system has recently been developed by our group to effectively reuse TWW for the cultivation of protein-rich rice. The results showed that despite not using mineral fertilisers, the wastewater reuse system produced a high rice yield comparable to that of a conventional cultivation practice and reduced CH4 emissions from paddy fields by 80%. During the reproductive stage of rice plants, when high levels of CH4 emissions from both treatments were observed, continuous sub-irrigation with TWW not only considerably inhibited the growth of methanogens in the lower soil layer, but also vastly reduced the abundance of methanotrophs in the upper soil layer, which was strongly consistent with the effective mitigation of CH4. The compositions of the examined microbial communities were not particularly affected by the studied cultivation practices. Overall, this study demonstrated that continuous sub-irrigation with TWW was an effective method to produce high rice yield and simultaneously reduce CH4 emissions from paddy fields, and it also highlighted the potential underlying microbial mechanisms of the greenhouse gas mitigation.