Mechanism and capacities of reducing ecological cost through rice-duck cultivation

Effects of long-term different-scale rice-duck farming on the growth and yield of paddy rice

BACKGROUND

To maintain rice production and increase revenue, rice-duck (RD) farming is a contemporary ecological cycle technology that has been widely used in Asia. However, due to the clustering activity of duck flocks, the consequences of long-term RD farming on rice growth at different scales are still unknown. Here, we studied RD farming using several different treatments (CK: conventional rice farming; RD1: 667 m2 ; RD2: 2000 m2 ; and RD3: 3333 m2 ).

RESULTS

The results demonstrated that the maximum tillers, effective spikes, dry matter accumulation, and lodging index of rice under RD farming were significantly decreased by 17.9%, 9.8%, 14.8%, and 17.8%, respectively, which ultimately caused a significant decrease in yield of 10.6%. However, RD farming significantly increased root oxidation activity and the ear-bearing tiller rate of rice by 25.5% and 11.1%, respectively, and improved yield stability. For different scales of RD farming, the lodging resistance index of RD1 was significantly lower than that of RD2 and RD3 by 10.0% and 15.2%, respectively, whereas the root oxidation activity and dry matter accumulation of RD2 were significantly higher than those of RD1 and RD3 by 11.1%, 4.7%, 8.6%, and 5.1%, respectively. For rice yield, there was no significant difference among the different scales.

CONCLUSION

This long-term experiment helped elucidate the complicated effects of RD farming at different scales on the growth and yield of rice. It is also critical to consider the economic advantages of different scales of RD farming to assess the impact of this system more thoroughly. © 2023 Society of Chemical Industry.

Transforming agrifood systems in a win-win for health and environment: evidence from organic rice-duck coculture

BACKGROUND

Rice-duck coculture is an ecological agricultural mode; however, the nutritional and environmental benefits of transforming from conventional rice monoculture to rice-duck coculture are unknown. Based on survey data and the life-cycle assessment approach, this study conducted a carbon footprint evaluation of conventional rice monoculture (CR), organic rice monoculture (OR), and organic rice-duck coculture (ORD) using different functional units.

RESULTS

The carbon footprint per hectare of ORD (7842 ± 284 kg CO₂ eq ha^-1 ) was slightly lower than that of CR (7905 ± 412 kg CO₂ eq ha^-1 ), while higher than that of OR (7786 ± 235 kg CO₂ eq ha^-1 ). Although the rice yield of ORD was slightly lower than that of CR, its nutrient density unit (NDU) did not decrease significantly due to the additional duck yield. Thus, the carbon footprint per NDU of ORD was significantly lower than that of OR by 24.3% (P < 0.05) and was 5.8% higher than that of CR, but this was not statistically significant. Due to the higher economic profits of ORD, its unit of carbon footprint per economic profit was significantly reduced (by 47.1-75.7%) compared with the other two farming modes, while the net ecosystem economic budget was significantly increased by 98.5-341.9% (P < 0.05).

CONCLUSION

Transforming from a rice monoculture to a coculture system will contribute to a win-win situation for human health and environmental sustainability. This study highlighted the abundant nutritional output function of the rice-duck coculture and analyzed the urgency and necessity of transitioning from traditional agriculture to ecological agriculture from the production and consumption perspectives. © 2022 Society of Chemical Industry.

Detection of QTLs Regulating Six Agronomic Traits of Rice Based on Chromosome Segment Substitution Lines of Common Wild Rice (Oryza rufipogon Griff.) and Mapping of qPH1.1 and qLMC6.1

Wild rice is a primary source of genes that can be utilized to generate rice cultivars with advantageous traits. Chromosome segment substitution lines (CSSLs) are consisting of a set of consecutive and overlapping donor chromosome segments in a recipient's genetic background. CSSLs are an ideal genetic population for mapping quantitative traits loci (QTLs). In this study, 59 CSSLs from the common wild rice (Oryza rufipogon Griff.) accession DP15 under the indica rice cultivar (O. sativa L. ssp. indica) variety 93-11 background were constructed through multiple backcrosses and marker-assisted selection (MAS). Through high-throughput whole genome re-sequencing (WGRS) of parental lines, 12,565 mapped InDels were identified and designed for polymorphic molecular markers. The 59 CSSLs library covered 91.72% of the genome of common wild rice accession DP15. The DP15-CSSLs displayed variation in six economic traits including grain length (GL), grain width (GW), thousand-grain weight (TGW), grain length-width ratio (GLWR), plant height (PH), and leaf margin color (LMC), which were finally attributed to 22 QTLs. A homozygous CSSL line and a purple leave margin CSSL line were selected to construct two secondary genetic populations for the QTLs mapping. Thus, the PH-controlling QTL qPH1.1 was mapped to a region of 4.31-Mb on chromosome 1, and the LMC-controlling QTL qLMC6.1 was mapped to a region of 370-kb on chromosome 6. Taken together, these identified novel QTLs/genes from common wild rice can potentially promote theoretical knowledge and genetic applications to rice breeders worldwide.

Co-production of knowledge and adaptation to water scarcity in developing countries

Dwindling of freshwater resources is a harsh reality of the arid and semi-arid regions of the world and climate change is expected to deteriorate their situation through major reduction of freshwater supplies. Co-production of knowledge, through active negotiation of experts, government and local stakeholders has been used as a strategy to adapt to water scarcity. However, in many developing countries, co-production of knowledge is not common and adaptation efforts rarely reflects the plurality of involved knowledge sources and actors. Given the urgent need of transition towards water-efficient agricultural practices, the Iran's government applied the knowledge co-production approach and implemented an integrated participatory crop management (IPCM) project in the Bakian village, Fars province. The objectives of this study were to analyze the knowledge co-production process, identify the factors contributing to adoption of the co-produced knowledge and investigate the corresponding social, economic and environmental impacts. A mixed-method research was conducted comprising a case study on 19 informants selected using purposive sampling and a survey of 150 rice producers selected through systematic random sampling. The results indicated the relevance and pertinence of knowledge co-production in recognizing the real problems of the rice producers and suggesting some potential adaptive strategies. Though a wide range of natural, financial, technical, institutional and structural constraints restricted adoption of the proposed adaptive strategies, application of the co-produced knowledge significantly increased water productivity, ensured higher yields and farm-based sustainable livelihoods, and enhanced resilience of the farm households under water scarcity. Some recommendations and implications are offered to increase adaptation of farm families to water scarcity.

Integrating cover crops with chicken grazing to improve soil nitrogen in rice fields and increase economic output

Winter fallow is important for renewing and improving soil fertility under double-cropping rice systems, such as those in southern China. Using a regenerative farming technology of integrating grass-chicken farming in a winter fallow field, we investigated soil nitrogen conversion and assessed the agricultural economic benefits of the whole farmland ecosystem. To test the effects of chicken grazing on the fallow system, we established field treatments involving adding chickens to a field planted with the cover crops, including cover milk vetch (Astragalus sinicus) with chicken grazing treatment (MC) and cover ryegrass (Lolium spp.) with chicken grazing (RC); cover crops only, including cover milk vetch (Astragalus sinicus) treatment (M) and cover ryegrass (Lolium spp.) (R); and a bare fallow field treatment (CK). We found that both cover crops (M and R) and cover crops with chicken grazing (MC and RC) increased nitrate, ammonium, dissolved organic nitrogen, and total nitrogen contents, and the increase was higher in MC and RC treatments. We also observed increased straw biomass and grain yield in the all four treatments, with more increases with chicken treatments as compared with CK. On the economic profits, MC increased by 101.72% and RC increased by 104.12% as compared with CK, while R increased by 5.19% and M reduced by 1.86% as compared with CK. The nitrogen transfer rate (the output/input ratio) of MC, RC, M, and R increased by 66.71%, 71.50%, 65.97%, and 59.97%, respectively, while the nitrogen accumulation rate (input-output) of MC, RC, M, and R increased by 480.56%, 612.98%, 356.74%, and 267.65%, respectively. Our study demonstrates that retaining nitrogen and gaining economic profit by integrating cover crops with chicken grazing is potentially more sustainable than adding cover crops alone. We further suggest that using the integrated grass-livestock farming technology can reduce environmental damage caused by commercial fertilizers.

Rice-duck co-culture integrated different fertilizers reduce P losses and Pb accumulation in subtropical China

Double pollution with phosphorus (P) losses and potential lead (Pb) accumulation in rice fields could lead to eutrophication and crop toxicity, respectively, and affect people's health. To promote the sustainable and environmentally friendly development of agriculture, we conducted field experiments using a randomized block design to explore P losses, Pb accumulation and any potential association between P and Pb forms in rice-duck (RD) co-culture system and rice monoculture (RM) system combined with different fertilizers applied: the no fertilizer (RD and RM), chemical fertilizer (RDF and RMF), organic fertilizer (RDO and RMO), and a mixture of 70% chemical and 30% organic fertilizers (RDFO and RMFO) treatments with consistent P inputs. The results showed that RDFO had the best advantages in reducing the losses of TP (total phosphorous) (by 6.67%) and DRP (dissolved reactive phosphate) (32.72%) as well as the contents of available Pb (by 7.57%) and the accumulation of Pb in grains (26.32%) compared with RMF. RDFO also achieved the highest grain yield, reaching 10.97 t ha^-1, and exhibited a lower soil weak-acid-extracted Pb (readily be taken up by plants) concentration than RDF and RMF. RDO resulted in greater TP leaching (increase by 10.62%) and lower DRP leaching (decrease by 36.57%) than RMF. It also exhibited the lowest concentration of weak-acid-extracted Pb and higher the concentration of grain Pb than that in other treatments. RDF reduced TP (by 5.33%) and DRP (by 16.36%) losses to a greater extent and the concentration of available and grain Pb were respectively 6.58% and 25.57% lower than RMF. Therefore, RDFO was the most recommended agricultural system for the studied region. Furthermore, different soil Pb forms were correlated with different P forms of soil and leakage and runoff water, which depended mainly on the fertilizer type and specific soil redox environment in the rice fields. The ratio of organic to inorganic fertilizer, the choice of organic fertilizer type, the assessment and timing of the detection of potential farmland pollution risks and association between different forms of P and Pb are worthy of further discussion.

Effects of the integration of mixed-cropping and rice-duck co-culture on rice yield and soil nutrients in southern China

BACKGROUND

Biodiversity-based agricultural systems can improve production efficiency and sustainability, with fewer negative environmental impacts and lower use of external inputs. Mixed-cropping and rice-duck co-culture have been shown to produce ecological benefits and to have positive effects on paddy soil. However, the effects of a combination of mixed cropping with different rice cultivars and duck co-culture on soil nutrients availability and grain yields have not been evaluated. A paddy field experiment was carried out over two rice growing seasons to test these effects.

RESULTS

Several combinations of rice cultivars, when integrated with duck co-culture, significantly increased the soil organic matter and total nitrogen contents during the rice growing seasons, as compared to mono-cropping systems. In mixed-cropping combined with duck co-culture (MCDC) systems, the soil alkali-hydrolyzable nitrogen content ranged from 4.33% to 17.86% higher than that in mono-cropping systems. Similar increases were found for soil available phosphorus (8.71-15.91%) and soil available potassium (8.65-39.43%) contents. Furthermore, MCDC produced higher grain yields and harvest indexes for both study seasons.

CONCLUSION

The integration of MCDC systems had positive effects on soil nutrient contents of paddy fields, which could, in turn, lead to yield enhancements, as well as additional income for farmers in the form of organic duck meat. © 2019 Society of Chemical Industry.

Can integrated rice-duck farming reduce CH4 emissions?

Integrated rice-duck farming (IRDF) has proven to decrease methane (CH₄) emissions due to increased dissolved oxygen caused by duck bioturbation. The duck bioturbation, however, also causes many bubbles of CH₄ that were overlooked in previous studies. Therefore, it is uncertain whether IRDF could decrease CH₄ emissions. We hypothesize that the effect of IRDF on CH₄ emissions is related with the intensity of duck bioturbation. We simulated duck's disturbance (trampling and foraging) by stirring and aerating the surface soil in flooded rice fields. Three treatments were disturbed with an interval of 12 h (D12), 24 h (D24), and 48 h (D48), respectively, with non-disturbance as the control (CK). CH₄ emissions as bubbles during the disturbance period (CH₄-A) were investigated. Besides, CH₄ emissions were investigated every 2 h (CH₄-B), which lasted for 4 days during the rice elongation stage. Compared with CK, D12, D24, and D48 decreased CH₄-B emissions by 17.1%, 14.0%, and 10.1%, respectively. However, the CH₄-A emissions under D12, D24, and D48 were equivalent to 14.2%, 14.0%, and 11.9% of CH₄ emissions under CK, respectively. On the whole, simulated duck bioturbation had limited effects on the reduction of total CH₄ emissions.

Nitrogen leakage in a rice-duck co-culture system with different fertilizer treatments in China

Nitrogen (N) leakage in paddy fields can cause groundwater pollution. In this study, we conducted a split-plot field experiment over 2 years to compare N leakage in a rice-duck co-culture system and a rice monoculture system with different fertilizer treatments. Four treatments were applied to each field, with consistent N inputs in each fertilizer treatment: no fertilizer (RD and RM, respectively), chemical fertilizer (RDF and RMF, respectively), organic fertilizer (RDO and RMO, respectively), and a mixture of 70% chemical and 30% organic fertilizers (RDFO and RMFO, respectively). In both years, rice-duck co-culture system had lower N leakage than the rice monoculture for the same fertilizer treatment, with average reductions of 14.3 ± 0.1%, 13.5 ± 4.5% and 10.5 ± 3.3% for RDFO, RDF and RDO, respectively. Within the rice-duck co-culture system, the average N leakage across both years was 36.3 ± 6.3% lower in RDO and 16.9 ± 11.5% lower in RDFO than in RMF. RDFO gave the highest grain yield compared with RDF and RDO, average reached 10.35 t ha^-1 across both years. In conclusion, our results suggested that rice-duck co-culture reduces environmental risks by controlling N leakage and increasing agricultural productivity. Compared with other treatments in this research, RDFO was the most recommended agricultural production mode in this region because it can reduce the inputs of chemical fertilizer, control nitrogen leakage and increase rice yield.

Rice-duck co-culture for reducing negative impacts of biogas slurry application in rice production systems

Nitrogen (N) and phosphorus (P) losses are a potential limitation for the direct application of biogas slurry as a substitute for chemical fertilizer in irrigated rice production systems. The hypothesis was tested that a rice-duck co-culture promotes the rice N and P use efficiencies, reducing the losses of these nutrient elements through run-offs and enabling the use of biogas slurry as a substitute for chemical fertilizers. A field split-plot experiment was carried out to test the hypothesis. Our results showed that the direct application of biogas slurry was harmful for rice production. Compared with rice monoculture under chemical fertilization, biogas slurry application reduced N and P accumulation in grains, P use efficiency, and grain yield by 3.6%, 7.8%, 12.7%, and 14.8%, respectively, but increased the total N and P concentrations in the surface water 1.4- and 2.7-fold, respectively, on average on the eleventh day after fertilization. However, rice-duck co-culture compensated for the negative effects of biogas slurry on rice production. Under the biogas slurry application and in line with our hypothesis, the rice-duck co-culture significantly increased N and P accumulation and use efficiencies, as well as grain yield to levels similar to those acquired with chemical fertilization treatments. Meanwhile, total N and P concentrations were significantly lower for rice-duck co-culture than those of rice monoculture under biogas slurry application. Our results suggest that rice-duck co-culture can maintain rice yield and reduce the risks of N and P loss to local environments when utilizing biogas slurry as a substitute for chemical fertilizers.