Microbial Responses of Soil Fertility to Depth of Tillage and Incorporation of Straw in a Haplic Chernozem in Northeast China

Straw is widely incorporated into soil worldwide,but most studies have concentrated on the effects of straw mulching or incorporation with topsoil.To determine the effect of depth of straw incorporation on bacterial and fungal communities,we established a field experiment in a region in Northeast China with Haplic Chernozems using four treatments:conventional tillage(CT,tillage to a depth of 15 cm with no straw incorporation),straw incorporation with conventional tillage(SCT,tillage to a depth of 15 cm),inversion tillage(IT,tillage to a depth of 35 cm)and straw incorporation with inversion tillage(SIT,tillage to a depth of 35 cm).The soils were managed by inversion to a depth of 15 or 35 cm after harvest.The results show that soil organic carbon content was significantly higher and pH and bulk density were significantly lower in the 15–35 cm layer in IT and SIT than CT and SCT.Fungal abundance was higher with straw incorporation,but fungal diversity was lower in the 0–15 cm layer in SCT and SIT than in CT and IT.Path length in the bacterial network was shorter and connectivity was higher in CT+SCT than in IT+SIT,leading to a more complex ecosystem,and the fungal network had opposite patterns.The key taxa in the phylum Actinobacteriota and Ascomycota in the microbial networks changed dramatically at the genus level following inversion tillage with straw amendment,which may increase bacterial network resistance to environmental disturbances and unstable fungal networks,resulting in large changes in the fungal community involved in the decomposition of recalcitrant straw-derived C and the more efficient acquisition of limiting resources.

Assessment of the ecological state of haplic chernozem contaminated by oil,fuel oil and gasoline after remediation

The intensive use of petroleum hydrocarbon products has made them priority environmental pollutants.When petroleum hydrocarbons enter the soil,a change in physical,chemical,and biological properties is observed.The natural restoration of oil-contaminated soils is a lengthy process;therefore,remediation is often required.The aim of this study is to assess the change in the ecological state of haplic chernozem soil contaminated with oil,fuel oil,and gasoline after remediation.The indicators of soil biological activity,such as phytotoxicity(germination,length of shoots and roots),the activity of oxidoreductase enzymes(catalase and dehydrogenases),and the total number of bacteria were studied.The effects of nitroammophoska fertilizer,sodium humate,biochar,and the biofertilizer“Baikal EM-1”on the ecological state of soils contaminated with oil,fuel oil,and gasoline were studied.Pollution with oil,fuel oil,and gasoline decreased the values of all biological indicators.The most sensitive indicator was the length of radish roots in soils polluted with oil,gasoline,and fuel oil after remediation with nitroammophoska and Baikal EM-1 addition.The length of roots was the most sensitive indicator when remediation was performed with biochar and sodium humate added to soil contaminated with oil and gasoline,and with contamination of haplic chernozem soil with fuel oil,the total number of bacteria was the most sensitive indicator.The most effective ameliorant to phytotoxicity indicators for oil pollution was a 1 D dose of biochar,for fuel oil it was 1 D biochar and 2 D sodium humate,and for gasoline it was a 2 D dose of biochar and Baikal EM-1.All ameliorants at most of the studied doses increased dehydrogenase activity,but increased catalase activity only in some cases.An increase in the total number of bacteria in oil-contaminated soils was promoted by biochar and nitroammophoska at a dose of 2 D.Nitroammophoska was the most effective in ameliorant in soils contaminated with fuel oil;in soils polluted with gasoline,all doses of ameliorant increased the number of bacteria equally.The stimulating effect of ameliorants on biological activity of oil-contaminated haplic chernozem were in the following sequence:nitroammophoska>biochar>sodium humate>Baikal EM-1.The 2 D biochar dose was most effective.The stimulation of biological indicators by ameliorants when soil was contaminated with fuel oil were in the following sequence:biochar>Baikal EM-1>sodium humate>nitroammophoska.The same sequence of ameliorant stimulation was observed in soil polluted with gasoline.The results of this study can be used to biodiagnose the ecological state of oil-contaminated soils after remediation.

Trends and rates of holocene soil evolution in the North Caucasian Piedmont

In the piedmont of the North Caucasus a 3500 yr B.P. steppe was replaced by forest asclimate became moister. Steppe Chernozems were preserved under high (up to 8 m) burial mounds(kurgans) constructed about 5000 yr B.P. On natural landsurfaces surrounding the kurgans,Chernozems evolved to Luvisols. On the kurgans made of loess and Chernozem soil, matureLuvisols formed during the forest stage. On the kurgans covered with artificial limestone paving,the Luvisol profile is less developed. Migration and transformation of substances occur throughoutthe whole kurgan pile. These include fissures and earthworm channels filled with clay-humusmaterial or secondary carbonates, gleyed mottles, iron oxides, and neoformed gypsum. Theseprocesses cause diagenetic transformation of buried Chernozems even at depth.

Nutrient cycling and greenhouse gas emissions from soil amended with biochar-manure mixtures

Integrating biochar into cattle diets has recently emerged as a potential management practice for improving on-farm productivity.Yet,information concerning the cycling of biochar-manure mixtures is scarce.A 70-d incubation experiment was conducted within two surface(0–15 cm)Mollisols with contrasting textures,i.e.,sandy clay loam(Raymond)and clayey(Lethbridge),to evaluate the effects of biochar(3 Mg ha^(-1))on cumulative greenhouse gas(GHG)emissions and related fertility attributes in the presence or absence of cattle manure(120 Mg ha^(-1)).Five treatments were included:i)non-amended soil(control,CK),ii)soil amended with pinewood biochar(B),iii)soil amended with beef cattle manure(M)(manure from cattle on a control diet),iv)soil amended with biochar-manure(BM)(manure from cattle on a control diet,with pinewood biochar added at 20 g kg^(-1)of diet dry matter),and v)soil amended with B and M at the aforementioned rates(B+M).A total of 40 soil columns were prepared and incubated at 21℃and 60%–80%water-holding capacity.On average,total CO_(2)fluxes increased by 2.2-and 3.8-fold under manure treatments(i.e.,M,BM,and B+M),within Raymond and Lethbridge soils,respectively,relative to CK and B.Similarly,total CH4 fluxes were the highest(P<0.05)in Raymond soil under B+M and BM relative to CK and B,and in Lethbridge soil under M and BM relative to CK and B.In Lethbridge soil,application of BM increased cumulative N_(2)O emissions by 1.8-fold relative to CK.After 70-d incubation,amendment with BM increased(P<0.05)PO_4-P and NO_3-N+NH_4-N availability in Raymond and Lethbridge soils compared with B.A similar pattern was observed for water-extractable organic carbon in both soils,with BM augmenting(P<0.05)the occurrence of labile carbon over CK and B.It can be concluded that biochar,manure,and/or biochar-manure have contrasting short-term effects on the biogeochemistry of Mollisols.At relatively low application rates,biochar does not necessarily counterbalance manure-derived inputs.Although BM did not mitigate the flux of GHGs over M,biochar-manure has the potential to recycle soil nutrients in semiarid drylands.

Fractionation and fixation of rare earth elements in soils:Effect of spiking with lanthanum,cerium,and neodymium chlorides

Industrial and agricultural activities lead to the release of rare earth elements(REEs)in wastewater and aquatic ecosystems,and their accumulation in soils.However,the behavior of REEs in soils remains somewhat unclear.In the present work the fractionation and fixation of REEs in soddy-podzolic and chernozem soils spiked with La,Ce,and Nd chlorides were studied using dynamic(continuous flow)extraction,which allows natural conditions to be mimicked and artefacts to be minimised.The eluents applied are aimed to dissolve exchangeable,specifically sorbed,bound to Mn oxides,bound to metal-organic complexes,and bound to amorphous and poorly ordered Fe/Al oxides fractions extractable by 0.05 mol/L Ca(NO_(3))2,0.43 mol/L CH_(3)COOH,0.1 mol/L NH_(2)OH·HCl,0.1 mol/L K_(4)P_(2)O_(7) at pH 11,and 0.1 mol/L(NH4)_(2)C_(2)O_(4) at pH 3.2,respectively.It is found that the fixations of added La,Ce,and Nd in the form of metal-organic complexes is predominant for both types of soils:35%-38%in soddy-podzolic soil and 50%-79%in chernozem.The fixation of added elements in the first three fractions(exchangeable,specifically sorbed,and bound to Mn oxides)is significant for soddy-podzolic soil(5%-25%).For chernozem,the relative contents of added Ce and Nd in these fractions are nearly negligible.Only the content of exchangeable La is notable,about 5%.Adding any of three elements(La,Ce,or Nd)at the level of100 mg/kg to an initial sample results in changing the fractionation and bioaccessibility of other REEs present in soil.Their contents increase in the first three fractions and decrease in fifth(oxalate extractable)fraction for both soddy-podzolic soil and chernozem.The main difference is the behavior of REEs in pyrophosphate extractable fraction.For soddy-podzolic soil,adding La,Ce,or Nd results in decreasing the contents of other REEs associated with organic matter.For chernozem,on the contrary,the contents of REEs in the form of metal-organic complexes slightly increase.These processes may be attributed to competitive binding of elements and soil properties;they must be taken into account when assessing the environmental risks of soil pollution with REEs.