Optimization of Diesel and Crude Oil Degradation in a Ghanaian Soil Using Organic Wastes as Amendment

Soil contamination by hydrocarbons poses numerous environmental, health and agricultural problems. The degradation of these pollutants can occur naturally but very slowly. It is therefore generally necessary to stimulate this degradation by different means. Thus, this study aimed to improve the bio-degradation of diesel and crude oil in a Ghanaian soil by biostimulation. For this, the sampled soil was characterized by standard methods and contaminated with diesel and crude oil at a proportion of 1% (w/w). Then, contaminated soil samples were supplemented with biochar-compost, poultry manure or cow dung at the proportion of 10% (w/w). Periodically, fractions of these samples were taken to evaluate the density of hydrocarbon utilizing bacteria (HUB) and the residual quantities of diesel or crude oil. The characteristics of the soil used show the need for supplementation for better degradation of hydrocarbons. The results of the study show that supplementing the soil with organic substrates increases HUB loads in soils contaminated by diesel and crude oil. They also show that the residual quantities of diesel and crude oil are generally significantly lower in supplemented soils (p = 0.048 and p < 0.0001 respectively). In addition, the study shows that degradation was generally greater in soils contaminated by diesel compared to those contaminated by crude oil, especially at the end of the study.

Impacts of chemical fertilizer reduction and organic amendments supplementation on soil nutrient,enzyme activity and heavy metal content

Excessive use of agro-chemicals （such as mineral fertilizers） poses potential risks to soil quality. Application of organic amendments and reduction of inorganic fertilizer are economically feasible and environmentally sound approaches to de- velop sustainable agriculture. This study investigated and evaluated the effects of mineral fertilizer reduction and partial substitution of organic amendment on soil fertility and heavy metal content in a 10-season continually planted vegetable field during 2009-2012. The experiment included four treatments： 100% chemical fertilizer （CF100）, 80% chemical fertilizer （CF80）, 60% chemical fertilizer and 20% organic fertilizer （CF60＋OM20）, and 40% chemical fertilizer and 40% organic fertilizer （CF40＋OM40）. Soil nutrients, enzyme activity and heavy metal content were determined. The results showed that single chemical fertilizer reduction （CF80） had no significant effect on soil organic matter content, soil catalase activity and soil heavy metal content, but slightly reduced soil available N, P, K, and soil urease activity, and significantly reduced soil acid phosphatase activity. Compared with CF100, 40 or 60% reduction of chemical fertilizer supplemented with organic fertilizer （CF60＋OM20, CF40＋OM40） significantly increased soil organic matter, soil catalase activity and urease activity especially in last several seasons, but reduced soil available P, K, and soil acid phosphatase activity. In addition, continu- ous application of organic fertilizer resulted in higher accumulation of Zn, Cd, and Cr in soil in the late stage of experiment, which may induce adverse effects on soil health and food safety.

Soil microbial characteristics and yield response to partial substitution of chemical fertilizer with organic amendments in greenhouse vegetable production

Greenhouse vegetable production has been characterized by high agricultural inputs, high temperatures, and high cropping indexes. As an intensive form of agriculture, nutrient cycling induced by microbial activities in the greenhouses is relatively different from open fields in the same region. However, the responses of soil microbial biomass carbon （MBC） and nitrogen （MBN）, enzyme activities, microbial community composition, and yield to organic amendment are not well understood. Therefore, a 5-year greenhouse tomato （Solanum lycopersicum Mill.）-cucumber （Cucumis sativus L.） rotation experiment was conducted. The field experiment comprised 5 treatments： 4/4CN （CN, nitrogen in chemical fertilizer）, 3/4CN＋1/4MN （MN, nitrogen in pig manure）, 2/4CN＋2/4MN, 2/4CN＋1/4 MN＋1/4 SN （SN, nitrogen in corn straw） and 2/4CN＋2/4SN. The amounts of nitrogen （N）, phosphorus （P2O5）, and potassium （K2O） were equal in the five treatments. Starting with the fourth growing season, the optimal yield was obtained from soil treated with straw. MBC, MBN, phospholipid fatty acid （PLFA） profiles, and enzyme activities were significantly changed by 5 years of substitution with organic amendments. Redundancy analysis showed that MBC accounts for 89.5 and 52.3％ of the total enzyme activity and total community variability, respectively. The activities of phosphomonoesterase, N-acetyl-glucosaminidase, and urease, and the relative abundances of fungi, actinomycetes, and Gram-negative bacteria were significantly and positively related to vegetable yields. Considering the effects of organic amendments on soil microbial characteristics and vegetable yield, 2/4CN＋1/4MN＋1/4SN can improve soil quality and maintain sustainable high yield in greenhouse vegetable production.

Effects of Long-Term Organic Amendments on Soil Organic Carbon in a Paddy Field: A Case Study on Red Soil

Soil organic carbon （SOC） is one of the main carbon reservoirs in the terrestrial ecosystem. It is important to study SOC dynamics and effects of organic carbon amendments in paddy fields because of their vest expansion in south China. A study was carried out to evaluate the relationship between the SOC content and organic carbon input under various organic amendments at a long-term fertilization experiment that was established on a red soil under a double rice cropping system in 1981. The treatments included non-fertilization （CK）, nitrogen-phosphorus-potassium fertilization in early rice only （NPK）, green manure （Astragalus sinicus L.） in early rice only （OM1）, high rate of green manure in early rice only （OM2）, combined green manure in early rice and farmyard manure in late rice （OM3）, combined green manure in early rice, farmyard manure in late rice and rice straw mulching in winter （OM4）, combined green manure in early rice and rice straw mulching in winter （OMS）. Our data showed that the SOC content was the highest under OM3 and OM4, followed by OM1, OM2 and OM5, then NPK fertilization, and the lowest under non-fertilization. However, our analyses in SOC stock indicated a significant difference between OM3 （33.9 t ha^-1） and OM4 （31.8 t ha^-1）, but no difference between NPK fertilization （27 t ha^-1） and nonfertilization （28.1 t ha^-1）. There was a significant linear increase in SOC over time for all treatments, and the slop of linear equation was greater in organic manure treatments （0.276-0.344 g kg-1 yr^-1） than in chemical fertilizer （0.216 g kg^-1 yr^-1） and no fertilizer （0.127 g kg^-1 yr^-1）.

Types of Irrigation Water and Soil Amendment Affect the Growth and Flowering of Petunia x alkinsiana ‘Bravo Pinc’

Water insufficiency is the hampering feature of crop sustainability,especially in arid and semi-arid regions.So,the effectual usage of all water resources especially underground brackish water represents the core priority in Saudi Arabia.The present study aimed to recognize the influence of different types of water irrigation(tap water as a control,salinized well water,and magnetized salinized well water)with or without soil amendments(soil without any amendment as a control,peat-moss,ferrous sulfate,and peat-moss plus ferrous sulfate)on petunia plant growth and flowering as well as ion content.Irrigating Petunia plants with saline well water adversely affected growth and flowering as compared to tap water and magnetized saline well water.Additionally,plants irrigated with magnetized water showed a significant enhancement in all the studied vegetative and flowering growth parameters as compared to those irrigated with salinized well water.Furthermore,mineral contents and survival of Petunia plants irrigated with magnetized well water were higher than those irrigated with tap water.Irrigation with magnetized well water significantly reduced levels of Na+and Cl−ions in leaves of Petunia plants indicating the role of magnetization in alleviating harmful effects of salinity.In conclusion,we recommend the utilization of magnetized saline well water for irrigating Petunia plants either alone or in combination with soil amendments(peat moss plus ferrous sulfate).

Effects of Biochar and Wood Vinegar on Labile Phosphorus Pool in Soda Saline-Alkaline Soil

A pot experiment was conducted to research the effect of biochar and wood vinegar on labile phosphorus fractions in saline-alkali soil.There were eight treatments,including CK(0 kg•hm-2 biochar+0 kg•hm-2 wood vinegar),C1(0.6 t•hm-2 biochar),C2(0.6 t•hm-2 wood vinegar),C3(1.2 t•hm-2 wood vinegar),C4(1.8 t•hm-2 wood vinegar),C5(0.6 t•hm-2 biochar+0.6 t•hm-2 wood vinegar),C6(0.6 t•hm-2 biochar+1.2 t•hm-2 wood vinegar),and C7(0.6 t•hm-2 biochar+1.8 t•hm-2 wood vinegar).The results showed that biochar without wood vinegar and the co-application of biochar and wood vinegar significantly increased soil total phosphorus content.Meanwhile,compared with CK,all of treatments increased resin phosphorus and sodium bicarbonate-extracted inorganic phosphorus(NaHCO3-Pi)contents in saline-alkali soil.Especially,the contents of resin phosphorus and NaHCO3-Pi under C5,C6,and C7 treatments were higher than those of C2,C3,and C4 treatments,respectively,indicating that the increases of labile phosphorus contents under the co-application of biochar and wood vinegar were better than those of the alone application of biochar and wood vinegar.Each treatment increased the proportion of labile phosphorus pool in saline-alkali soil and the proportion of labile phosphorus pool increased with the increase of the amount of wood vinegar.In addition,the application of biochar and wood vinegar increased the 100-grain weight of rice,and C6 treatment had the best effect,increasing the 100-grain weight by 134.35%.Therefore,the application of biochar and wood vinegar in saline-alkali soil could improve the soil phosphorus availability,increase the weight of rice grains,thereby realizing the resource utilization of agricultural waste and the sustainable development of agriculture.

Short-term residual effects of various amendments on organic C and N, and available nutrients in soil under organic crop production

Two 3-year (2008-2010, wheat-pea-barley) field experiments were conducted on certified organic farms near Spalding (Dark Brown Chernozem-Typic Haploboroll) and Star City (Gray Luvisol-Typic Haplocryalf) in northeastern Sas-katchewan, Canada, to determine the residual effects of compost, alfalfa pellets, wood ash, rock phosphate, Penicillium bilaiae, gypsum and MykePro on organic C and N (total organic C [TOC], total organic N [TON], light fraction organic C [LFOC], light fraction organic N [LFON]) and mineralizable N (Nmin) in the 0 - 15 cm soil layer, and ammonium-N, nitrate-N, extractable P, exchangeable K and sulphate-S in the 0 - 15, 15 - 30 and 30 - 60 cm soil layers in autumn 2010. Compared to the unamended control, mass of TOC, TON, LFOC and LFON increased with compost and alfalfa pellets in both soils. However, the increases were much more pronounced for LFOC (by 125% - 133%) or LFON (by 102% - 103%) than TOC (by 19% - 29%) or TON (by 25% - 40%). The Nmin also increased in these two treatments compared to the control, but the increases were much smaller for compost than alfalfa pellets. In general, residual nitrate-N increased with increasing rate of compost and alfalfa pellets in the 0 - 15 and 15 - 30 cm layers in both soils. Extractable P increased with compost and exchangeable K with alfalfa pellets, but only in the 0 - 15 cm soil layer. Sulphate-S increased with compost, but mainly in the 30 - 60 cm soil layer. Soil pH usually increased with compost and more so with wood ash, but no effect of any amendment on ammonium-N. Overall, the quantity of organic C and N, and available nutrients in soil increased with compost and/or alfalfa pellets, but the magnitude varied with amendment and/or soil type. In conclusion, our findings suggest that soil quality and fertility can be improved with these organic amendments, suggesting sustainability of production from organic crops.

Assessing Effects of Crop History and Soil Amendments on Yields of Subsequent Crops

Three field trials were set up to measure the effect of previous crops or soil amendments on the yields of subsequent crops of cereals under a cool temperate maritime climate in arable crop land in the east of Scotland. Winter wheat and winter barley direct drilled into legume and cereal + legume stubble (pre-crop) gave substantial yield boost compared with other pre-crop cereals, but pre-crop effects of oats were similarly great. Restored rotation after continuous barley gave expected yield enhancement to subsequent winter and spring barley but not to subsequent wheat. Some diseases were reduced on restored rotation crops. Slurry effects on yield were generally small but beneficial and compost effects were greater. However, compost had effects on plant developmental speed and was difficult to compare directly with other treatments. NDRE measurements in the restored rotation and soil amendment trials indicated that yield gains were associated with improved crop health as indicated by leaf chlorophyll content. There were no clear cultivar interactions within crop type with treatments effects in any of these trials.

Influence of Organic Amendments on Adsorption, Desorption and Leaching of Methiopyrisulfuron in Soils

Methiopyrisulfuron is a novel sulfonylurea herbicide with good activity for annual broadleaf and gramineal weeds control. Present study was to investigate the effects of organic amendments （including peat （PE）, sewage sludge （SS）, and humic acid （HA）） on adsorption, desorption and leaching of methiopyrisulfuron in soils. The batch equilibration technique was applied for adsorption-desorption experiments and the leaching was tested through soil column simulated experiments under laboratory conditions. The Freundlich model may well describe adsorption-desorption of methiopyrisulfuron on organic amendments, the natural soil, and amended soils. Organic amendments could not only greatly increase the adsorption capacity of methiopyrisulfuron, but also significantly enhance the hysteresis of desorption of methiopyrisulfuron. The correlations between Kf_ads and organic matter content of amended soils were significant, and the correlations between H and soil organic matter in amended soils with PE, SS, and HA were significant too. The results of soil column experiments indicated that organic amendments greatly decreased leaching of methiopyrisulfuron. This study suggested that PE, SS, and HA could greatly influence environmental behavior of methiopyrisulfuron in soils. Use of organic amendments might be an effective management practice for controlling potential pollution of methiopyrisulfuron to environment.

Response of Soil Microbial Properties to Long-Term Application of Organic and Inorganic Amendments in a Tropical Soil (Saria, Burkina Faso)

Soil microbial biomass carbon (MBC), β-glucosidase, acid phosphatase and fluorescein diacetate (FDA) activities and bacterial community structure were assessed in a long-term (26 years) experiment, at physiological stages of sorghum growth, comparing different management methods for organic (manure, straw residues) and inorganic (urea) amendments at the INERA field station in Saria (Burkina Faso). Annual application of manure led to the highest soil microbial biomass and enzyme activities. Investigations indicated that only microbial biomass and β-glucosidase activities were affected during the cropping season. Phosphatase and FDA enzyme activities did not depend on the crop development stages. The application of N fertilizer modified phosphatase and FDA enzyme activities, the activities being higher in soils amended with N fertilizer. The bacterial community structure was analyzed by PCR-denaturing gradient gel electrophoresis (PCR-DGGE) targeting the eubacterial 16S rRNA gene. Cluster analysis of PCR-DGGE patterns showed two major clusters, the first containing the mineral fertilization and straw treatments and the second, the straw + urea, manure and manure + urea treatments. Sorghum grain yields were the highest for manure treatments. In this long-term experiment, applying straw did not produce a better grain yield than that obtained in the un-amended plot.

Fertilization and Soil Ploughing Practices under Changing Physical Environment Lead to Soil Organic Carbon Dynamics under Conservation Agriculture in Rice-Wheat Cropping System: A Scoping Review

Ploughing and fertilization practices in rice-wheat system have deteriorated the soil carbon (C) pools. Conservation agriculture (CA) based management approaches have proven to enhance C sequestration and reverse the loss of soil-organic-carbon (SOC), which further enhances soil fertility. Different fractions of SOC pools react to the alterations in management practices and indicate changes in SOC dynamics as compared to total C in the soil. Higher SOC levels in soil have been observed in case of reduced/no-till (NT) practices than conventional tillage (CT). However, between CT and zero tillage/NT, total SOC stocks diminished with an increase in soil depth, which demonstrated that the benefits of SOC are more pronounced in the topsoil under NT. Soil aggregation provides physical protection to C associated with different-sized particles, thus, the improvement in soil aggregation through CA is an effective way to mitigate soil C loss. Along with less soil disturbance, residual management, suitable crop rotation, rational application of manures and fertilizers, and integrated nutrient management have been found to be effective in not only improving soil C stock but also enhancing the soil health and productivity. Thus, CA can be considered as a potential method in the build-up of SOC of soil in rice-wheat system.

A Soil Quality Index to Evaluate the Vermicompost Amendments Effects on Soil Properites

The aims of this work were 1) to evaluate the changes in soil properties with the application of different amounts of vermicompost (10 and 20 Mg?ha–1), and 2) to construct a soil quality index that allows the evaluation of changes in the most sensitive soil parameters. The study was carried out in a cattle field of General Alvear, Buenos Aires, Argentina. Vermicompost application showed a positive effect on most of the chemical and biological soil properties evaluated, especially with the higher dose (20 Mg?ha–1). There were slight but significant increases in electrical conductivity and soil pH with the higher dose of vermicompost. Physical soil properties were not affected by the vermicompost amendment. The SQI showed a significant increase of soil quality with the vermicompost dose of 20 Mg?ha–1, especially by enhancing the biochemical and biological properties.

Soil Macrofauna Behaviour in the Presence of Pesticides and Organic Amendments

Insects attack vegetable crop, leading to an overuse of pesticides. Organic amendments are recommended to increase soil fertility. The impact of two insecticides, on soil macrofauna under rainfed cultivation of tomato (Lycopersicon esculentum L.) with or without organic amendments was evaluated. The insecticides were Lambda Super (lambda-cyhalothrin) and Dursban (chlorpyrifos ethyl) and organic amendments were compost, pig manure and cattle manure. An experimental device in split-plot with three replicate was installed. Pesticides were applied periodically each week during the experiment. The results have showed that with organic amendments, Lambda super increased the earthworm population compared to the control. Indeed, we found 42 individuals/m2 with compost;1 individuals/m2 with pig manure and 27 individuals/m2 with cattle manure but the control was 0 individuals/m2 in the presence of Lambda super without organic amendment. Similarly, Dursban increased the population of earthworms in the presence of organic amendment with 11, 37 and 91 individuals/m2 respectively for compost, pig manure and cattle manure. Lambda super with compost has led to a total elimination of termites. In the presence of Dursban, a decrease in the number of termites was observed when adding cattle manure (11 individuals/ m2) compared to the control containing only Dursban (21 individuals/m2). Better distribution of macrofauna was obtained with treatment with Dursban and compost (E = 0.99 for earthworms and E = 0.96 for termites). All organic amendments used in our study stimulated earthworm population, but more in the presence of Lambda super or Dursban.

Management of Petroleum Impacted Soil with Phytoremediation and Soil Amendments in Ekpan Delta State, Nigeria

The study is aimed at evaluating the effectiveness of phytoremediation in the management of oil impacted soil in Ekpan communities of Delta state, Nigeria. To do this, the study adopted an experimental research design that involve the use of phytoremediation (carpet grass Axonopus compressus) and nutsedge Cyperus rotundus) in the management of petroleum impacted soil site in Ekpan, This experiment spans for three months periods (one planting season). It involves the treatment of the oil impacted site with different plant species and soil amendments. Laboratory analysis of the soil samples was conducted to determine the effect of phytoremediation and soil amendments on hydrocarbon loss in oil impacted sites. The study revealed that the combined effect of Axonopus sp., Cyperus sp. and oil amendments accounted for 59% reduction in hydrocarbon. However Axonopus sp. and Cyperus sp. accounted for 47% and 48% reduction in hydrocarbon respectively. This shows that though, both plant species can be used successfully as a phytoremediation technique for the reclamation of oil impacted soils, but Axonopus sp. and Cyperus sp. was the most effective when applied with soil amendment (organic and inorganic manure). It is therefore recommended that iindigenous plant species (particularly Axonopus sp. and Cyperus sp.) should be used together with soil amendments in phytoremediation rather than the traditional bioremediation involving the use of microorganism. Oil companies operating in the Niger Delta region of Nigeria are encouraged not only to carry out physical clean-up of oil spills but should also carry out bioremediation to restore the environment back to its natural or near natural state. The methodology adopted in this study could be followed by oil companies to manage oil impacted soils in the Niger-Delta environment in Nigeria and indeed everywhere in the world.

Degradation of Lindane (γ-HCH) in a Mollisol as Effected by Different Soil Amendments

Soil amendments play an important role in management of pesticide residues. In this study, incubation experiment was conducted using the surface (0 - 15 cm) sample of a mollisol supplied with different soil amendments (farmyard manure, cow-dung slurry, pyrite and gypsum) to investigate the effect of amendments on the dissipation of lindane in mollisols. Dissipation of lindane in soil was studied at eight consecutive samplings (0, 1, 3, 5, 7, 10, 15 and 30 d). The results indicated that soil amendments could promote the degradation of lindane in soil. After 30 d of incubation 79% degradation was observed in the untreated soil (without any amendment) whereas, in the case of farmyard manure and cow-dung slurry amended soils, 83% and 91% degradation was observed, respectively. The pyrite and gypsum amendments also enhanced the degradation of lindane in soils, but the effect was less pronounced as compared to the organic amendments. Enhanced degradation in soil treated with organic amendments could be attributed to stimulated microbial activity after the addition of organic amendments. These addition, under different soil management conditions, minimize the persistence of lindane and consequently the risk of leaching and seepage into aquifers.

Soil Moisture Retention on the High Plains of North America via Compost Amendments: A Longitudinal Field Study

Water is a finite but vital resource, and the volume of water used in arid and semi-arid regions must be managed to its fullest and best use. Irrigation water is approximately 37% of the total water used in the United States by volume annually. Thus, this area of water use is critical for local and national water conservation. Irrigation is primarily used to increase soil water content above that which precipitation can supply. Soil structure and associated effects on drainage and evapotranspiration, however, largely control soil water content, no matter the amount of applied water. Therefore, improving soil structure to hold more water decreases the amount of water needed for irrigation, which frees that water for other uses. In this paper, organic compost amendments are studied to determine the change in soil structure and accompanying improvements in soil water content over a 4-year period. A uniform field site was selected for this research in the high plains of South Dakota, where irrigation water was available for crop growth. The test site was divided into two equal area fields;one without compost and a field with compost amendments added to 20 cm depth. Compost was incorporated into the treated field at rates of 5% and 10% by weight. Both fields received the same tillage, seed, fertilizer, weather and irrigation. Weekly to monthly in-situ water content measurements from both fields were recorded at the surface and the depths of 20, 40 and 60 cm from 2017 to 2020. Precipitation and applied irrigation water were recorded at the site. No irrigation occurred in 2019 and 2020, and moisture content was dependent on natural precipitation in those years. Results of water content and soil structure show significant differences in the water contents of the soils with the compost amendments compared to baseline, with higher compost content resulting in higher water contents without the soil becoming over-saturated. These results were consistent at all depths and across all growing seasons. This work demonstrates the efficacy of compost soil amendments in regulating soil moisture, which has profound impacts on crop yields, topsoil erosion losses, carbon sequestration, and water conservation.

Soil inorganic amendments produce safe rice by reducing the transfer of Cd and increasing key amino acids in brown rice

The digestibility of cadmium(Cd)in brown rice is directly related to amino acid metabolism in rice and human health.In our field study,three kinds of alkaline calcium-rich soil inorganic amendments(SIAs)at three dosages were applied to produce safe rice and improve the quality of rice in Cd-contaminated paddy.With the increased application of SIA,Cd content in iron plaque on rice root significantly increased,the transfer of Cd from rice root to grain significantly decreased,and then Cd content in brown rice decreased synchronously.The vitro digestibility of Cd in brown rice was estimated by a physiologically based extraction test.Results showed that more than 70%of Cd in brown rice could be digested by simulated gastrointestinal juice.Based on the total and digestible Cd contents in brown rice to evaluate the health risk,the application of 2.25 ton SIA/ha could produce safe rice in acidic slightly Cd-contaminated paddy soils.The amino acids(AAs)in brown rice were determined by high-performance liquid chromatography.The contents of 5 key AAs(KAAs)that actively respond to environmental changes increased significantly with the increased application of SIA.The structural equation model indicated that KAAs could be affected by the Cd translocation capacity from rice root to grain,and consequently altered the ratio of indigestible Cd in brown rice.The formation of indigestible KAAs-Cd complexes by combining KAAs(phenylalanine,leucine,histidine,glutamine,and asparagine)with Cd in brown rice could be considered a potential mechanism for reducing the digestibility of Cd.

Effects on soil quality of biochar and straw amendment in conjunction with chemical fertilizers

The objective of this study was to evaluate the effects on chemical and microbiological properties of paddy soil of short-term biochar,straw,and chemical fertilizers compared with chemical fertilization alone.Five soil fertilization treatments were evaluated：regular chemical fertilizers（RF）,straw＋regular chemical fertilizers（SRF）,straw biochar＋regular chemical fertilizers（SCRF）,bamboo biochar（BC）＋regular chemical fertilizers（BCRF）,and straw biochar＋70%regular chemical fertilizers（SC＋70%RF）.Their effects were investigated after approximately 1.5 years.The soil p H and cation exchange capacity（CEC）were significantly higher in biochar-treated soils.The soil phosphorous（P）and potassium（K）contents increased with biochar application.The soil Colwell P content was significantly increased with the addition of straw biochar in the treatments of SCRF and SC＋70%RF.The oxygen（O）：carbon（C）ratio doubled in BC picked from the soil.This indicated that BC underwent a significant oxidation process in the soil.The denaturing gradient gel electrophoresis（DGGE）fingerprints of microbial communities differed among the treatments.Soils with added biochar had higher Shannon diversity and species richness indices than soils without biochars.The results suggest that biochar can improve soil fertility.