Impacts of cadmium addition on the alteration of microbial community and transport of antibiotic resistance genes in oxytetracycline contaminated soil

The large-scale development in livestock feed industry has increased the chances of antibiotics and heavy metals contamination in the soil.The fate of antibiotic resistance genes(ARGs)and microbial community in heavy metals and antibiotic contaminated soil is still unclear.In this study,we investigated the effect of cadmium(Cd)addition on the transport of ARGs,microbial community and human pathogenic bacteria in oxytetracycline(OTC)contaminated soil.Results showed that the addition of OTC significantly increased the abundance of ARGs and intI1 in the soil and lettuce tissues.The addition of Cd to OTC treated soil further increased the abundance and translocation of ARGs and intI1.Moreover,Cd promoted the transfer of potential human pathogenic bacteria(HPB)into lettuce tissues.Compared with O10 treatment,the addition of Cd decreased the concentration of OTC in soil and lettuce tissue,but slightly increased the fresh weight of lettuce tissues.Redundancy analysis indicated that bacterial community succession is a major factor in ARGs variation.Network analysis indicated that the main host bacteria of ARGs were mainly derived from Proteobacteria.Correlation analysis showed that intI1 was significantly correlated with tetG,tetC,sul1,sul2,erm X,and ermQ.Meanwhile,potential HPB(Clostridium,and Burkholderia)was significantly correlated with intI1 and eight ARGs(tetG,tetC,tetW,tetX,sul1,sul2,ermX,and ermQ.).The findings of this study suggest that the addition of heavy metals to agricultural fields must be considered in order to reduce the transfer of ARGs in the soil and crops.

Strategies for improving fertilizer phosphorus use efficiency in Chinese cropping systems

A four-year project,entitled"The mechanisms of fraction transformation and high use efficiency of P fertilizer in Chinese cropping systems"commenced in 2017.The project was established to answer three key questions and looked at 17 cropping systems on ten soils.First,we asked what are the dynamics of transformation,fixation and mobilization of P fertilizers in soil-cropping systems?Second,what are the mechanisms of soil-cropmicrobe interactions by which P fertilizer can be efficiently used?Third,how to manipulate the processes of P use in cropping systems?The targets of this project are(1)to explore the mechanisms of P fixation,the pathways of loss of P availability and the threshold of migration of fertilizer P in the field;(2)to uncover mechanisms by which soil legacy P is mobilized through root physiological and morphological processes and through arbuscular mycorrhizal fungi and P-solubilizing bacteria in rhizosphere and hyphosphere;(3)to estimate the biological potential of crops for high efficiency P absorption and use;(4)to innovate new approaches for improving the efficiency of P fertilizers.The outcomes will provide theoretical support for setting standards for limitation of P fertilizer application rate in the main cropping zones of China.

Greenhouse area detection in Guanzhong Plain,Shaanxi,China:spatio-temporal change and suitability classification

The extensive use of greenhouses has brought soared economic benefits for farming practitioners in China and an overview of the spatio-temporal distribution of greenhouses is of great interest to agricultural practitioners and decision-makers.In this study,Landsat image based greenhouse maps in Guanzhong Plain,Shaanxi,China were made using random forest classification algorithm through visual interpretation on the Google Earth Engine.The 7-year's changes in greenhouse areas were investigated(i.e.2000,2003,2006,2010,2013,2015 and 2019)with yearly overall accuracy more than 90%.The results showed that the total area of greenhouses in Guanzhong Plain demonstrated an increasing trend,from 5.92 km2 in 2000 to 194.42 km2 in 2019 with a considerable growth between 2010 and 2015.The dominant drivers for the increase are largely attributed to the government policy as well as economic profitability.The distribution of greenhouse shifts to central and eastern regions of Guanzhong Plain.Greenhouses preferentially expand to the area near to rural roads,main rivers,and high elevation,with more than 45%greenhouses distributed within 1 km of the county rural road.The principal component analysis based suitability evaluation showed that a total of 38.44%of the area was suitable for greenhouse.