Liao Xiaolan

Effect of ducks on CH4 emission from paddy soils and its mechanism research in the rice-duck ecosystem

The effect of ducks on CH4 emission from paddy soils and its mechanism were probed in order to decide the optimum number of ducks in the rice-duck ecosystem. Methane emission fluxes from paddy soils were measured by the static box technique. The correlations between methane emission and soil physical and chemical characteristics were also analyzed. The results showed that significant differences (p < 0.01) existed in the dissolved oxygen content of water body in the treatment fields, and the more the ducks, the higher the dissolved oxygen content. Secondly, the soil redox matter content and methanogenic bacteria population of the rice-duck ecosystem reduced more sharply than those of the no-duck rice farming, resulting in a lower methane production. Thirdly, the amount of methane emission differed between the treatments—the more the ducks, the less the methane emission. Other related analyses showed that the negative correlation was significant (p < 0.001) between the methane emission flux and dissolved oxygen content of water body. However, CH4 emission flux had significantly positive correlation (p < 0.01) with the soil redox matter content and rice field methanogenic population.

Analysis of the components and control effect on Rhizoctonia solani of duck manure extract.

Duck manure from rice-duck eco-farming plays a crucial role in controlling Rhizoctonia solani.In this study,the antibacterial activity and effective components of duck manure extracts were analyzed for R.solani.Duck manure extracts via ethanol respectively has highest inhibition rate of 88.64% and EC 50 of 26.11 mg·mL-1 against R.solani.The extract was further separated into two parts and one part separated by ethyl acetate while the other was separated by petroleum ether.Based on the inhibition experiment against R.solani,ethly acetate extract has a rather strong effect on R.solani with 89.70% inhibition rate and 15.52 mg·mL ?1 EC 50.The effect of petroleum ether extract on R.solani is relatively weak.The former was again divided into five parts in silica gel column,of which the second part significantly inhibits R.solani.During the periods of 24 and 48 hrs,the inhibition rate of the second part on R.solan is respectively 89.58% and 80.36%.GC-MS analysis suggests that the second part contains phenol sour and sulfur alcohol,which best suits further purification and identification.

Effect of large-scale rice-duck eco-farming on the composition and diversity of weed community in paddy fields.

Changing characteristics of weed community,weed-controlling effect of large-scale rice-duck eco-farming (SF),conventional rice-duck eco-farming (CF) compared to mono-cropping rice (CK) were analyzed in order to explore the dynamics of weed communities in large-scale rice-duck eco-farming paddy fields.The study shows that weed density in paddy fields significantly decreases with more than 94% grass-controlling effect under SF compared with CK.Before rice booting stage,weeds compose mainly of Alopecurus pratensis,Echinochhloa crausgalli,Cynodon dactylon,Alternanthera philoxeroides,Mouochoria vaginalis,Murdannia triquetra and Eclipta prostrata in SF.During heading to ripe stage,weeds are mainly A.philoxeroides,E.crausgalli,C.dactylon,M.triquetra.At tillering,species richness,Simpon index and Shannon-Wiener index are higher while Pielou index is lower in SF than in CK.From booting to ripening,weed species richness,Simpon index and Shannon-Wiener index are lower while Pielou index is significantly higher in SF than in CK.In the entire rice growth period,weed density,weed fresh weight and species diversity are not significantly different between SF and CF,but species diversity is higher in SF than in CF.SF changes the structure of weed community and decreases weed species diversity,effectively limiting weed infestation in paddy fields.