Reducing carbon footprints and increasing net ecosystem economic benefits through dense planting with less nitrogen in double-cropping rice systems.

Excessive application of nitrogen fertilization in farmland systems can cause nitrogen wastage, environmental pollution, and increase greenhouse gas (GHG) emissions. Dense planting is one of the efficient strategies for nitrogen fertilizer reduction within rice production. However, there are paying weak attention to the integrative effect of dense planting with less nitrogen (DPLN) on carbon footprint (CF), net ecosystem economic benefit (NEEB) and its components in double-cropping rice systems. Herein, this work aims to elucidate the effect via field experiments in double-cropping rice cultivation region with the treatments set to conventional cultivation (CK), three treatments of DPLN (DR1, 14 % nitrogen reduction and 40,000 hills per ha density increase from CK; DR2, 28 % nitrogen reduction and 80,000 hills density increase; DR3, 42 % nitrogen reduction and 120,000 hills density increase), and one treatment of no nitrogen (N0). Results showed that DPLN significantly reduced average CH4 emissions by 7.56 %-36 %, while increasing annual rice yield by 2.16 %-12.37 % compared to CK. Furthermore, the paddy ecosystem under DPLN served as a carbon sink. Compared with CK, DR3 increased gross primary productivity (GPP) by 16.04 % while decreasing direct GHG emissions by 13.1 %. The highest NEEB was observed in DR3, which was 25.38 % greater than CK and 1.04-fold higher than N0. Therefore, direct GHG emissions and carbon fixation of GPP were key contributors to CF in double-cropping rice systems. Our results verified that optimizing DPLN strategies can effectively increase economic benefits and reduce net GHG emissions. DR3 achieved an optimal synergy between reducing CF and enhancing NEEB in double-cropping rice systems.

Achieving phosphorus recovery at pilot-scale anaerobic anoxic/nitrifying-induced crystallization (A2N-IC) process: Performance, assessment, and challenges.

A pilot-scale anaerobic-anoxic/nitrifying/induced crystallization (A2N-IC) process was established for phosphorus (P) recovery and nutrient removal from municipal wastewater with a treatment capacity of 80 m3d-1. Results show that the A2N-IC process can operate stably on a pilot scale; the recovery efficiency of influent P reached 62.2%, and the total P removal efficiency of the IC section was 65.4%. The IC section had little effect on the removal of chemical oxygen demand (COD) and nitrogen (N), and the P removal efficiency was improved. Soluble non-reactive P (sNRP) was the key factor affecting P recovery efficiency. Although P recovery increases the construction and maintenance costs, the process can be profitable if a market for P recovery products is established. To improve the P recovery efficiency, attention should be paid to the effects of sNRP and dissolved organic matter (DOM) on P recovery, and P-rich sludge should be considered.

Conversion from double-season rice to ratoon rice paddy fields reduces carbon footprint and enhances net ecosystem economic benefit.

Ratoon rice (RR) system is an alternative to the double-season rice (DR) system in central China due to its high annual yield and relatively lower cost and labor requirement. However, the effect of conversion from DR to RR on the carbon footprint (CF) and net ecosystem economic benefit (NEEB) remains largely unknown. Here, we elucidated the effect by using two early-season rice varieties (ZJZ17, LY287) and two late-season rice varieties (WY103, TY390) for the DR system, and two RR varieties (YLY911, LY6326) for the RR system. The six varieties constituted four cropping systems, including DR1 (ZJZ17 + WY103), DR2 (LY287 + TY390), RR1 (YLY911) and RR2 (LY6326). The two-year experiment demonstrated that RR had 27.37% lower annual CF than DR, which could be attributed to the significantly lower annual CF (by 87.27%) of ratoon crop in RR relative to that of the late-season rice in DR. Direct greenhouse gas (GHG) emissions contributed the most to annual CF in both systems, accounting for 43.28% and 35.39% in DR and RR, respectively. Furthermore, conversion from DR to RR system significantly increased annual NEEB by 30.95%. This increase could be attributed to the 20.25% higher annual grain yield of main crop in RR relative to early-season rice in DR, and 75.32% and 87.27% lower annual costs for agricultural inputs and CF of ratoon crop than late-season rice in DR, respectively. Rice variety also showed certain effects on the yields and GHG emissions in different RR systems. Compared with RR1, RR2 significantly increased annual yield and annual NEEB, while decreased annual CF and annual yield-scaled CF (CFy). These findings suggest that the conversion of the DR system to LY6326 RR system may be a highly promising strategy to simultaneously reduce CF, promote NEEB and maintain high grain yield in central China.

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

BACKGROUND: Rice-duck cultivation is the essence of Chinese traditional agriculture. A scientific assessment of the mechanism and its capacity is of theoretical significance and practical value in improving modern agricultural technology. RESULTS: The duck's secretions, excreta and their treading, pecking and predation decrease the occurrence of plant diseases, pests and weeds, enrich species diversity and improve the field environment. The rice-duck intergrowth system effectively prevents rice planthoppers and rice leafhoppers. The control effects can be up to 98.47% and 100% respectively; it also has effects on the control of Chilo suppressalis, Tryporyza incertulas and the rice leafrollers. Notable control results are found on sheath blight, while the effects on other diseases are about 50%. Harm from weeds is placed under primary control; prevention of weeds is sequenced by broadleaf weeds > sedge weeds > Gramineae weeds. Contents of soil organic matter, N, P and K are improved by the system; nutrient utilization is accelerated, resulting in decreased fertilizer application. Greenhouse gas emissions are reduced by 1-2% and duck fodder is saved in this system. There is also an obvious economic benefit. CONCLUSION: Compared to conventional rice cultivation, rice-duck cultivation shows great benefits to ecologic cost and economic income.

Molecular characterization of thyroid hormone receptor beta from Schistosoma japonicum and assessment of its potential as a vaccine candidate antigen against schistosomiasis in BALB/c mice.

BACKGROUND: Thyroid hormones (TH) modulate growth, development and differentiation and metabolic processes by interacting with thyroid hormone receptors (THRs). The purpose of this study was to identify a novel thyroid hormone receptor beta encoding gene of Schistosoma japonicum (SjTHRß) and to investigate its potential as a vaccine candidate antigen against schistosomiasis in BALB/c mice. METHODS: The full-length cDNA sequence of SjTHRß, its gene organization, and its transcript levels were characterized, and the phylogenetic relationship between THR, RAR and RXR from other organisms were analysis, the ability of this protein binding to a conserved DNA core motif, and its potential as a vaccine candidate antigen against schistosomiasis in BALB/c mice were evaluated. RESULTS: The SjTHRß cDNA was cloned, verified by 5' and 3' Rapid Amplification of cDNA Ends and shown to be polyadenylated at the 3'end, suggesting the transcript is full-length. SjTHRß is homologous to THRs from other species and has a predicted conservative DNA binding domain and ligand binding domain that normally characterizes these receptors. A comparative quantitative PCR analysis showed that SjTHRß was the highest expressed in 21d worms and the lowest in 7 d and 13 d schistosomula. The cDNA corresponding to DNA binding domain (SjTHRß-DBD) and ligand binding domain (SjTHRß-LBD) were cloned and subsequently expressed in E coli. The expressed proteins were used to immunize mice and generate specific serum against recombinant SjTHRß (rSjTHRß). Western blotting revealed that anti-rSjTHRß-LBD serum recognized two protein bands in extracts from 21 d worm with molecular sizes of approximately 95 kDa and 72 kDa. Electrophoretic mobility shift assay (EMSA) analysis showed that rSjTHRß-DBD could bind to a conserved DNA core motif. Immunization of BALB/c mice with rSjTHRß-LBD could induce partial protective efficacy(27.52% worm reduction and 29.50% liver eggs reduction)against schistosome infection. Enzyme-linked immunosorbent assay showed that mice vaccinated with recombinant SjTHRß-LBD (rSjTHRß-LBD) generated increased levels of specific IgG, IgG1 and IgG2a antibody. Bio-plex analysis demonstrated that rSjTHRß-LBD induced considerably higher levels of T helper 1 cytokines (IL-2, IL-12 and TNF-α) than T helper 2 cytokines (IL-10, IL-4), suggesting that rSjTHRß-LBD vaccination could stimulate mixed Th1/Th2 types with Th1 dominant immune responses. CONCLUSIONS: Our study presented here identified SjTHRß as a new schistosome THR that might play an important role in host-parasite interaction and be a vaccine candidate for schistosomiasis.