Dynamic changes in soil chemical properties and microbial community structure in response to different nitrogen fertilizers in an acidified celery soil

To determine the effects of different kinds of nitrogen fertilizer,especially high-efficiency slowrelease fertilizers,on soil pH,nitrogen(N)and microbial community structures in an acidic celery soil,four treatments(CK,no N fertilizer;NR,urea;PE,calcium cyanamide fertilizer;and SK,controlled-release N fertilizer)were applied,and soil pH,total soil N,inorganic N,and soil microbial biomass C were analyzed.Phospholipid fatty acids(PLFAs)were extracted and detected using the MIDI Sherlock microbial identification system.The PE treatment significantly improved soil pH,from 4.80 to>6.00,during the whole growth period of the celery,and resulted in the highest celery yield among the four treatments.After 14 d application of calcium cyanamide,the soil nitrate content significantly decreased,but the ammonium content significantly increased.The PE treatment also significantly increased soil microbial biomass C during the whole celery growth period.Canonical variate analysis of the PLFA data indicated that the soil microbial community structure in the CK treatment was significantly different from those in the N applied treatments after 49 d fertilization.However,there was a significant difference(P<0.05)in soil microbial community structure between the PE treatment and the other three treatments at the end of the experiment.Calcium cyanamide is a good choice for farmers to use on acidic celery land because it supplies sufficient N,and increases soil pH,microbial biomass and the yield of celery.

Improved rhizoremediation for decabromodiphenyl ether(BDE-209)in E-waste contaminated soils

An experiment was conducted to improve rhizoremediation for decabromodiphenyl ether(BDE-209)contaminated soil from typical E-waste dismantling areas.Plants of ryegrass(Lolium perenne L.)and rice(Oryza sativa L.)were cultivated in aged-contaminated(initial concentration of 346.3μg BDE-209·kg^(-1))and freshly-spiked(initial concentration of 3127μg BDE-209·kg^(-1))soils,coupling with the agricultural modification strategies of compost addition and/or arbuscular mycorrhizal fungi(AMF)infection,respectively.60 days’growth of ryegrass significantly facilitated the dissipation of BDE-209,with the most effective in its rhizosphere in treatment inoculated with AMF;the BDE-209 dissipation rates achieved 51.9% and 22.8% in rhizosphere,and 43.5% and 19.8% in non-rhizosphere,for aged-contaminated and freshlyspiked soils,respectively.120 days’growth of rice with simultaneous inoculation of AMF and addition of compost was the most effective in facilitating BDE-209 dissipation in agedcontaminated soil,with the removal rates of 53.3% and 48.1% in rhizosphere and nonrhizosphere soils respectively;while for freshly-spiked soils,the most effective removal was achieved by compost addition only,with the BDE-209 dissipation rates of 27.9% and 26.6% in rhizosphere and non-rhizosphere soils,respectively.High throughput sequencing analysis of rhizosphere soil DNA showed that responses in microbial communities and their structure differed with plant species,soil pollution dose,AMF inoculation and/or compost addition.Actinomycetales,Xanthomonadales,Burkholderiales,Sphingomonadales,Clostridiales,Cytophagales,Gemmatimonadales and Saprospirales were the sensitive responders and even possibly potential functional microbial groups during the facilitated removal of BDE-209 in soils.This study illustrates an effective rhizoremediation pattern for removal of BDE-209 in pollution soils,through successive cultivation of rice and followed by ryegrass,with rice growth coupled with AMF inoculation and compost addition,while ryegrass growth coupled with AMF inoculation only.