Changes in bacterial community and abundance of functional genes in paddy soil with cry1Ab transgenic rice

A field experiment involving cry1Ab transgenic rice(GM) and its parental non-cry1Ab rice(M) has been on-going since 2014. The diversity of the bacterial communities and the abundance of the microbial functional genes which drive the conversion of nitrogen in paddy soil were analyzed during the growth period of rice in the fifth year of the experiment, using 16 S rRNAbased Illumina Mi Seq and real-time PCR on the amoA, nirS and nirK genes. The results showed no differences in the alpha diversity indexes of the bacterial communities, including Chao1, Shannon and Simpson, between the fields cultivated with line GM and cultivar M at any of the growth stages of rice. However, the bacterial communities in the paddy soil with line GM were separated from those of paddy soil with cultivar M at each of the growth stages of rice, based on the unweighted Uni Frac NMDS or PCoA. In addition, the analyses of ADONIS and ANOSIM, based on the unweighted Uni Frac distance, indicated that the above separations between line GM and cultivar M were statistically significant(P<0.05) during the growth season of rice. The increases in the relative abundances of Acidobacteria or Bacteroidetes, in the paddy soils with line GM or cultivar M, respectively, led to the differences in the bacterial communities between them. At the same time, functional gene prediction based on Illumina Mi Seq data suggested that the abundance of many functional genes increased in the paddy soil with line GM at the maturity stage of rice, such as genes related to the metabolism of starch, amino acids and nitrogen. Otherwise, the copies of bacterial amo A gene, archaeal amo A gene and denitrifying bacterial nir K gene significantly increased(P<0.05 or 0.01) in the paddy soil with line GM. In summary, the release of cry1Ab transgenic rice had effects on either the composition of bacterial communities or the abundance of microbial functional genes in the paddy soil.

Raw material of water-washed hydrochar was critical for the mitigation of GHGI in infertile paddy soil:a column experiment

Water washing is a meaningful method to improve the surface’characteristic of hydrochar produced using hydrothermal carbonization and minimize the negative effect on crop growth.However,the greenhouse effect resulting from water-washed hydrochar application was unclear in agricultural ecosystems.Hence,the effect of water-washed hydrochar on methane and nitrous oxide emissions was analyzed in an infertile paddy soil based on a soil-column experiment.Sawdust-derived hydro-char(WSH)and wheat straw-derived hydrochar(WWH)after water washing were selected and applied with low(5‰,w/w;8.5 t ha^(−1))or high addition rate(15‰,w/w;25.5 t ha^(−1)).The study indicated that water-washed hydrochar could increase the grain yield;the difference between WWH with 5‰application rate and CKU treatments was significant.WSH signifi-cantly decreased CH4 and N2O emissions in comparison with WWH addition treatments.For the same material,there were trends in reducing greenhouse gas(GHG)emissions at low application rate,although the differences were not significant.Compared with all treatments,WSH with 5‰application rate achieved the lowest seasonal emissions for both GHGs.The mcrA gene was the critical factor affecting CH4 emission;soil NO_(3)^(−)-N concentration and the copy numbers of nirK,nirS,and nosZ jointly affected N2O emissions.Benefits from the high yield and low global warming potential,GHG emission intensity(GHGI)at low application rate was lower than at high application rate for WSH.Overall,the response of GHG emissions to water-washed hydrochar varies with the derived feedstock;WSH is a good additive for the mitigation of GHGI.

Effect of Trichoderma viride biofertilizer on ammonia volatilization from an alkaline soil in Northern China

Ammonia（NH3） volatilization is one of the primary pathways of nitrogen（N） loss from soils after chemical fertilizer is applied, especially from the alkaline soils in Northern China, which results in lower efficiency for chemical fertilizers. Therefore, we conducted an incubation experiment using an alkaline soil from Tianjin（p H 8.37–8.43） to evaluate the suppression effect of Trichoderma viride（T. viride） biofertilizer on NH3 volatilization, and compared the differences in microbial community structure among all samples. The results showed that viable T. viride biofertilizer（T） decreased NH3 volatilization by 42.21% compared with conventional fertilizer（（CK）, urea）, while nonviable T. viride biofertilizer（TS） decreased NH3 volatilization by 32.42%. NH3 volatilization was significantly higher in CK and sweet potato starch wastewater（SPSW） treatments during the peak period. T. viride biofertilizer also improved the transfer of ammonium from soil to sweet sorghum. Plant dry weights increased 91.23% and 61.08% for T and TS, respectively, compared to CK. Moreover, T. viride biofertilizer enhanced nitrification by increasing the abundance of ammonium-oxidizing archaea（AOA） and ammonium-oxidizing bacteria（AOB）. The results of high-throughput sequencing indicated that the microbial community structure and composition were significantly changed by the application of T. viride biofertilizer. This study demonstrated the immense potential of T. viride biofertilizer in reducing NH3 volatilization from alkaline soil and simultaneously improving the utilization of fertilizer N by sweet sorghum.