Control of Fusarium wilt disease of cucumber plants with the application of a bioorganic fertilizer

Two field experiments were conducted to evaluate the effect of organic fertilizer application either with or without antagonistic bacteria (Bacillus subtilis SQR-5 and Paenibacillus polymyxa SQR-21) on the control of Fusarium oxysporum f. sp. Cucumerinum J. H. Owen wilt disease in cucumber. The incidence of Fusarium wilt disease was 5.3–13.5% for cucumber plants treated with bioorganic fertilizer, while it was 30.3–51% in controls (only with organic fertilizer). Higher yields and lower disease incidences were observed in the dry season when compared with the wet season for both types of organic fertilizer treatments. Biolog analysis showed a significant change in soil bacterial composition and activity after bioorganic fertilizer application. The numbers of colony-forming units of F. oxysporum f. sp. Cucumerinum J. H. Owen for bioorganic-fertilizer-treated soils were significantly decreased compared with control. Scanning electron micrographs of cucumber basal stems showed a presence of mycelia-like mini strands accompanied by an amorphous substance within the xylem vessels. This amorphous substance and mini strands were richer in calcium and phosphorus but had low carbon and oxygen than the living mycelia. Reverse-phase high-pressure liquid chromatography and mass spectroscopic analysis showed that the antagonistic bacteria produced the antifungal compounds fusaricidin A, B, C, and D with molecular weights of 883.5, 897.5, 947.5, and 961.5 Da, respectively. The application of bioorganic fertilizer has a great potential for the control of F. oxysporum wilt disease in cucumber plants.     

Bioorganic fertilizer maintains a more stable soil microbiome than chemical fertilizer for monocropping

Understanding the responses of soil microbiome composition to various farming practices is important for selecting suitable managements to maintain soil functions. In this study, the influences of heavy chemical fertilizer application (CF) and reduced chemical fertilizer supplemented with organic (OF) or bioorganic fertilizer (BF, BF = OF + Trichoderma) on composition of soil microbiome were investigated for monocropping cucumber systems using a five-season continuous pot experiment. The MiSeq sequencing data indicated that the CF treatment resulted in the lowest fungal diversity and the BF treatment resulted in a relatively higher one close to the initial soil (CK). The BF and OF treatments had similar impacts on the composition of bacterial community, and the CF treatment significantly reduced bacterial diversity. Although both OF and BF treatments had better plant growth responses, they had less disturbance on the composition of fungal community relative to the CF treatment. The BF treatment is more predictable than the other treatments for postponing fungal diversity as the inoculated fungal species significantly (p < 0.05) affected the fungal community. In conclusion, the combination of bioorganic fertilizers with reduced chemical fertilizer application can maintain a diverse soil microbiome in cucumber monocropping.     

Assessment of cowpea and groundnut contributions to soil fertility and succeeding sorghum yields in the Guinean savannah zone of Burkina Faso (West Africa)

Atmospheric biological nitrogen fixation (BNF) by cowpea (Vigna unguiculata) and groundnut (Arachis hypogea) was evaluated using a 2-year (2000–2001) experiment with different fertilizer treatments. The ¹⁵N isotopic dilution method with a nonfixing cowpea as test reference crop was used. The effects of the two legumes on soil N availability and succeeding sorghum (Sorghum bicolor) yields were measured. Groundnut was found to fix 8 to 23 kg N ha-1 and the percentage of N derived from the atmosphere varied from 27 to 34%. Cowpea fixed 50 to 115 kg N ha⁻¹ and the percentage of N derived from the atmosphere varied from 52 to 56%. Compared to mineral NPK fertilizer alone, legumes fixed more N from the atmosphere when dolomite or manure was associated with mineral fertilizers. Compared to soluble phosphate, phosphate rock increased BNF by cowpea. Significant correlation (p<0.05, R ²=0.94) was observed between total N yields of legumes and total N derived from the atmosphere. Compared to monocropping of sorghum, the soils of cowpea–sorghum and groundnut–sorghum rotations increased soil mineral N from 15 and 22 kg N ha⁻¹, respectively. Cowpea–sorghum and groundnut–sorghum rotations doubled N uptake and increased succeeding sorghum yields by 290 and 310%, respectively. Results suggested that, despite their ability to fix atmospheric nitrogen, N containing fertilizers (NPK) are recommended for the two legumes. The applications of NPK associated with dolomite or cattle manure or NK fertilizer associated with phosphate rock were the better recommendations that improved BNF, legumes, and succeeding sorghum yields.     

生物质炭与化肥配施对连作黄瓜产量及肥料利用率的影响

在如皋农科所进行黄瓜大棚试验,设置按常规施肥(计为100％,F)、减肥10％(F-10％)和减肥20％(F-20％)3个施肥水平,每个施肥水平下设置生物质炭添加量为0 t/hm2(CK)、5 t/hm2(C1)、10 t/hm2(C2)、20 t/hm2(C3)、30 t/hm2(C4)和40 t/hm2(C5)6个处...     

根际促生菌Bacillus subtilisY-IVI在香草兰上的应用效果研究

【目的】香草兰为多年生热带经济作物,随着种植年限的增加,植株长势弱,土壤有益微生物减少,土壤微生物区系失衡,严重制约了香草兰产业的可持续发展。枯草芽孢杆菌作为一种根际促生菌,被广泛应用于促进作物生长,改善土壤微生物环境。本文将枯草芽孢杆菌Y-IVI接种在有机肥上,生产了生物有机肥,并就该生物有机肥对香草兰生长的影响进行了研究。【方法】采用温室盆栽试验,调查施用根际促生菌枯草芽孢杆菌(Bacillus subtilis)Y-IVI及其经固体发酵制得的微生物有机肥料(Y-IVI:3×108cfu/g)后,香草兰植株地上部及根系的生长状况,采用选择性培养基方法研究了Y-IVI在香草兰根际土壤中的定殖能力及对香草兰根茎腐病致病菌-尖孢镰刀菌数量的影响。【结果】施用Y-IVI及BIO 4个月后,香草兰根际土壤Y-IVI数量仍可达到106cfu/g土,二者无显著差异,在处理OF和对照中未检测到菌株Y-IVI。施用生物有机肥香草兰地上部干重和根系干重均显著高于对照,分别增加了63.1%和59.4%,与不接种Y-IVI的有机肥处理(OF)相比,地上部干重显著提高了43.2%,根系干重提高了18%,差异不显著;施用Y-IVI菌液的处理植株地上部干重和根系干重均高于对照,但无显著性差异;处理BIO根系直径、根系表面积和总体积与对照相比分别增加了41.9%、88.9%和80.4%,均显著高于对照,总根长与对照差异不显著;处理BIO根系表面积和总体积与有机肥处理OF相比分别显著增加了41.9%和30.8%,根系直径与OF相比增加了10.1%,差异不显著;处理Y-IVI根系直径与对照相比显著增加了25.5%,但根系表面积和总体积与对照差异不显著;与对照相比,施用BIO及Y-IVI的处理根际土壤尖孢镰刀菌数量分别明显降低了52.2%和41.8%,施用有机肥OF的处理降低了10%,差异不显著。【结论】Y-IVI可稳定定殖于香草兰根际土壤对其生长起有益作用,含促生菌Y-IVI的生物有机肥料比单独使用促生菌菌液可以更有效地减少根际土壤中尖孢镰刀菌数量,降低连作生物障碍。施用生物有机肥料比施用化肥和有机肥更有效地促进香草兰地上部及根系生长,因此,施用由根际促生菌枯草芽孢杆菌(Bacillus subtilis)Y-IVI制得的生物有机肥是解决香草兰连作生物障碍和提高收益的有效手段。     

Effects of Garlic Bulb Aqueous Extract on Cucumber Seedlings,Soil Microbial Counts,and Enzyme Activities

The effects of the aqueous extract of garlic bulbs on cucumber seed germination, seedling growth, soil microbial counts, and soil enzyme activities were investigated using a bioassay test and a pot experiment. Garlic bulb extracts impacted cucumber seed germination and seedling growth but had no significant effects at low concentration. Polyphenol oxidase, saccharase, urease, and catalase activities were increased significantly at all concentrations of aqueous extract tested in the soil. Bacterial counts were increased by garlic bulb extract and trends of actinomycete counts were the same as for bacterial counts. Fungal counts were significantly depressed with increasing concentration of garlic bulb extract. Polyphenol oxidase activity showed significant positive correlations with catalase, saccharase, and urease activities and counts of actinomycetes and a significant negative correlation with fungal counts. The results indicate that garlic may be effective in reducing some obstacles of continuous cropping through its potential effects in appropriate culture systems.     

不同施肥措施对洞庭湖区旱地肥力及作物产量的影响

应用长期定位试验方法,研究了洞庭湖区非粮食作物棉花-油菜轮作下,农民习惯施肥(TF)、配方施肥(NPK)及有机肥和化肥不同配比模式[有机肥来源氮占配方肥总氮量的50%(50%OM)、30%(30%OM)和10%(10%OM)]的作物产量和土壤养分的变化,以期为相应作物种植制度下的合理施肥提供参考。研究结果表明:在本试验施肥量及有机无机肥配比下,有机肥和化肥配施显著提高了棉花和油菜的产量,且以50%OM处理产量最高,各处理产量的顺序为50%OM30%OM10%OMNPKTFCK(不施肥对照);当有机氮施用量占总氮量的50%时(50%OM处理),棉花和油菜产量分别比NPK处理高24.52%、29.57%,比习惯施肥(TF)处理分别高46.03%和49.07%。同时,施用有机肥各处理作物产量的年际变化均不到20%,明显小于NPK、TF和CK处理,即施用有机肥不仅能促进旱地作物高产,同时也能保证其稳产。有机肥与化肥配施能增加土壤有机质、全氮、碱解氮和速效钾含量,且以50%OM处理效果最好,与试验前比较的增加幅度分别达57.5%、38.2%、65.1%和48.1%;土壤有效磷含量有随施入磷素量的增加而增加趋势;而CK处理土壤有机质和养分含量则均呈逐年下降的趋势。各处理土壤有机质和养分含量(Y)随试验年限(X)的变化均可用方程式Y=a X+b来表示。在洞庭湖区肥力较高的旱地土壤中,合理的有机肥和化肥施用比例对保障非粮作物高产稳产和耕地地力提升尤为重要,且本试验条件下当有机肥来源氮占总施氮量的50%时能获得最佳效果。     

<Emphasis Type="Italic">Bacillus subtilis</Emphasis> SQR 9 can control <Emphasis Type="Italic">Fusarium</Emphasis> wilt in cucumber by colonizing plant roots

Fusarium wilt is one of the major constraints on cucumber production worldwide. Several strategies have been used to control the causative pathogen, Fusarium oxysporum f. sp. cucumerinum J. H. Owen, including soil solarization, fungicide seed treatment and biological control. In this study, F. oxysporum f. sp. cucumerinum was successfully controlled by a newly isolated strain, Bacillus subtilis SQR 9, in vitro and in vivo. Greenhouse experiments were carried out to evaluate the effect of inoculation and solid fermentation of organic fertilizer with B. subtilis SQR 9, hereby defined as bio-organic fertilizer (BIO), on the control of Fusarium wilt. In comparison with the control, the wilt incidence was significantly reduced (49–61% reduction) by application of BIO. The rhizosphere population of F. oxysporum f. sp. cucumerinum, as detected both by selective plating and realtime PCR, was significantly lower in BIO-treated plants than the control. The localization of bacterial cells, pattern of colonization and survival of B. subtilis SQR 9 in the rhizsosphere of cucumber, was examined by fluorescent microscopy and explored following recovery of the green fluorescent protein (gfp)-labeled SQR 9 with the new gfp-marked shuttle vector pHAPII through selective plating. The preferential sites of the labeled strain were the differentiation and elongation zone, root hair and the lateral root junctions. The population of the strain was 10⁶ cfu/g root in rhizoplane. These results indicate that the strain was able to survive well in the rhizosphere of cucumber, suppressed growth of F. oxysporum in the rhizosphere of cucumber and protected the host from the pathogen.     

黄瓜与西芹间作土壤细菌多样性及其对黄瓜枯萎病发生的影响

本试验以黄瓜与西芹间作种植模式为处理,黄瓜单作和西芹单作种植模式为对照,利用Illumina公司Miseq平台对上述不同处理土壤进行16S rDNA细菌群落多样性高通量测序分析和田间接种黄瓜枯萎病菌,探讨黄瓜与西芹间作模式土壤细菌的多样性及其对田间黄瓜枯萎病发生的影响。16S rDNA测序结果表明,黄瓜与西芹间作土壤的细菌物种总数最多,群落多样性水平最高,与对照相比显著提高了土壤细菌observed species指数、Shannon指数和Chao1指数(P0.05);Beta多样性聚类分析表明,黄瓜与西芹间作土壤的环境群落物种与黄瓜单作和西芹单作有一定差异性。在门分类水平上,共检测到45个菌门,其中变形菌门占明显优势,其次为酸杆菌门和放线菌门等;黄瓜与西芹间作土壤细菌种类所占比例最高,达98.63%。在属水平上,共检测到428类菌属,GP6、GP16、GP4、芽单胞菌属、节细菌属5属的丰度值较大;黄瓜与西芹间作土壤的节细菌属分布比例最高,红游动菌属、鞘氨醇单胞菌属和芽球菌属丰度值较大,为黄瓜与西芹间作土壤细菌明显优势菌属。田间接种黄瓜枯萎病菌试验结果表明,采用上述3种不同种植模式土壤种植黄瓜,在黄瓜苗期接种黄瓜枯萎病菌,黄瓜与西芹间作处理的黄瓜枯萎病的田间发病率较西芹单作和黄瓜单作分别降低57.03%~63.54%和66.95%~72.15%。因此,黄瓜与西芹间作增加了土壤细菌群落多样性,降低了黄瓜枯萎病的发病率,对后茬黄瓜土传病害防控具有一定科学指导意义。     

Influence of mineral and organic fertilizers on soil organic carbon pools

Abstract

The influence of farmyard manure (FYM) and equivalent mineral NPK application on organic matter content, hot water extractable carbon (HWC), microbial biomass C (C_mic), and grain yields in a long-term field experiment was assessed after 40 years in Hungary. The unfertilized plot, FYM fertilized plots and plots fertilized with equivalent NPK fertilizer contained 0.99%, 1.13% and 1.05% total organic carbon (TOC) respectively. Compared to the unfertilized plot, FYM application resulted in 8.2% higher TOC than equivalent NPK fertilization. The highest TOC was only 1.21%, much lower than expected for a soil containing 21.3% of clay. The quantity of HWC varied depending on the type of fertilization: Compared to control, FYM treatments lead to 29% more HWC than mineral fertilization (FYM: 328 mg kg^?1; NPK: 264 mg kg^?1). The impact of FYM and equivalent NPK fertilizer on C_mic was contrary. FYM and NPK resulted in 304 and 423 mg kg^?1 C_mic, respectively. The difference was 119 mg kg^?1; 42% as compared to the unfertilized plot. Despite the higher HWC content, FYM treatments lead to significantly less (35%) grain yields than equivalent NPK doses; C_mic content showed closer correlation to grain yields.     

土壤消毒结合施用生物有机肥对西瓜病土改良效果的影响

选取西瓜枯萎病发病严重的大棚,设置5个处理:对照、棉隆熏蒸、棉隆熏蒸后种植西瓜过程中施用不同次数生物有机肥,研究棉隆消毒土壤及配合不同生物有机肥施用次数对土壤理化和生物学性质及西瓜枯萎病发病率的影响。结果表明:棉隆熏蒸土壤后,施用生物有机肥虽未减缓尖孢镰刀菌增长速率、降低西瓜枯萎病发病率,但显著增加了土壤细菌和真菌数量,改变了细菌和真菌群落结构。此外,施用生物有机肥会降低土壤pH,过量施用会导致土壤NO–3累积、盐分增加。从改良土壤微生物群落结构和避免NO–3累积及土壤盐渍化加重角度出发,种植西瓜过程中生物有机肥最佳施用方式为移栽时施用1次+种植过程中追施1～2次。     

低肥力土壤施用氮磷钾肥影响柏木家系根系发育和养分吸收对钙肥的响应

  【目的】  探讨柏木(Cupressus funebris Endl)家系在不同养分条件下根系发育和营养吸收对钙添加的响应,为提高柏木苗木质量和林木生产力及造林地选择提供理论依据。  【方法】  以柏木5个家系的1年生幼苗为材料,分别在施3 g/kg NPK肥和未施NPK肥两小区内,设置施CaSO₄ 0、3和6 g/kg (依次记为Ca₀、Ca₃和Ca₆) 3 个水平,分析柏木家系生长与根系形态及氮磷钙吸收量对钙肥添加的响应。  【结果】  在施 3 g/kg NPK肥的小区中,添加钙对柏木的苗高、干物质量积累和氮磷吸收量影响不显著,抑制了D2和D3径级根系的发育;柏木钙吸收量在Ca₆处理下最高,比Ca₀处理提高73.86%;柏木苗高、干物质量及氮磷钙素的吸收量在家系间差异显著,T2家系表现最好。在未施NPK肥的小区中,Ca₃处理明显提高了柏木的苗高、根干物质量和茎干物质量,增加了磷和钙的吸收量,分别比Ca₀处理高出9.15%、19.85%、16.67%、27.46%和44.02%;Ca₆处理提高了钙吸收量,比Ca₀处理高出39.95%,但抑制柏木幼苗苗高和D1~D4径级根系的发育。不论施NPK肥与否,家系与钙处理对柏木的株高和根干物质量存在着显著的互作效应。  【结论】  在低肥力土壤上,施用氮磷钾肥会降低钙肥对柏木苗生长和养分吸收的影响,应选择优良家系进行育苗造林,不需要增加钙肥;在不施用氮磷钾肥时,应添加少量钙肥(CaSO₄ 3 g/kg),以促进苗木对钙和磷的吸收。     

Soil nutrient dynamics,growth and yield of green maize and vegetable cowpea with organic-based fertilization

The growth and yield performance of green maize (Zea mays), followed by a late-season vegetable cowpea (Vigna unguiculata), was assessed with two rates of three different types of organic-based fertilizers (OBFs) fortified with an inorganic nutrient source. There was also an inorganic fertilizer treatment of NPK 20–10–10 applied at 300 kg ha^?1 and a no-fertilizer control treatment. Maize growth was affected by fertilizer type and rate. Organic fertilizer, applied at 5 t ha^?1, 3 weeks before maize released enough nutrients to have comparable growth as inorganic fertilizer. Applying the OBF at 2.5 t ha^?1 was inadequate to give comparable growth. Application of fortified OBF with total nitrogen content higher than 2.4% N at 5.0 t ha^?1 gave maize grain yields comparable with NPK fertilizer. Cowpea yields following early-season maize were highest with DPW + NPK. They were significantly lower with 2.5 t ha^?1 of the OBFs. Application of the IAR&T-OBF (OBF made by Institute of Agricultural Research and Training) and decomposed poultry waste (DPW) + NPK at 5.0 t ha^?1 gave comparable seed yields significantly higher than OYO-OBF (OBF made by Oyo State Government of Nigeria). NPK fertilizer application supported early-season maize cultivation, but it was not adequate to support the following cowpea. OBF should have nitrogen content up to 2.4% and applied at 5.0 t ha^?1 to support an early-season maize cultivation with a late-season cowpea.     

Suppression of tomato hornworm (Manduca quinquemaculata) and cucumber beetles (Acalymma vittatum and Diabotrica undecimpunctata) populations and damage by vermicomposts

The effects of food waste vermicompost on populations of adult striped cucumber beetles (Acalymma vittatum) and spotted cucumber beetles (Diabotrica undecimpunctata) on cucumbers and larval hornworms on tomatoes (Manduca quinquemaculata) were evaluated in both greenhouse and field experiments as well as damage caused. In the field, cucumber and tomato plants were grown, with two different application rates (1.25 and 2.5 t ha⁻¹) of food waste vermicompost or inorganic fertilizer, in a complete randomized block design field experiment. All treatments were balanced for NPK. Field cucumber beetle populations were suppressed significantly on cucumber plants treated with food waste vermicompost at both application rates, compared with those on plants treated only with inorganic fertilizer. In the greenhouse, cucumber and tomato plants were grown in a soil-less medium MetroMix 360 (MM360) substituted with 0%, 20% or 40% food waste vermicompost, and exposed to standardized pest attacks in nylon mesh cages. In the greenhouse, both the 20% and 40% vermicompost substitution rates decreased damage by cucumber beetles to cucumber foliage and hornworms to tomato foliage significantly.     

Effects of microbial inoculations on soil chemical,biochemical and microbial biomass carbon of cassava (Manihot esculenta Crantz) growing Vertisols

Cassava is an important subsidiary food in the tropics. In Tamil Nadu, India, microbial cultures were used to eradicate the tuberous root rot of cassava. Hence, an experiment was conducted for two consecutive years to test the effects of coinoculation of microbes on soil properties. The surface soil from the experimental site was analysed for soil available nutrients, soil enzyme activities and microbial biomass carbon. The treatment of Azospirillum with Trichoderma at the 50% recommended N:P₂O₅:K₂O (NPK) rate (50:25:50 kg ha^?1) significantly increased soil available nitrogen (142.81 kg ha^?1) by 72.66% over uninoculated control. There was a significant increase in available phosphorus in soil by the inoculation of AM (arbuscular mycorrhizal) fungi with Trichoderma at the 50% recommended NPK rate (41.04 kg ha^?1) compared to other treatments. The application of Pseudomonas fluorescens with Trichoderma at the 50% recommended NPK rate significantly increased available iron (19.34 µg g^?1) in soil. The treatment of Azospirillum with Trichoderma increased urease enzyme activity at the recommended NPK rate (816.32 μg urea hydrolyzed g^?1 soil h^?1). Soil application of all cultures at the 50% recommended NPK rate significantly increased dehydrogenase activity (88.63 μg TPF g^?1 soil) and β-glucosidase activity (48.82 μg PNP g^?1 soil) in soil. Inoculation of Trichoderma alone at the 50% recommended NPK rate significantly increased microbial biomass carbon (3748.85 μg g^?1 soil). Thus, the microbial inoculations significantly increased soil available nutrient contents, enzyme activities such as urease, dehydrogenase and β-glucosidase activity and microbial biomass carbon by reducing the amount of the required fertilizer.     

稻草覆盖对坡地红壤培肥及作物增产的效果

研究了坡地红壤连续5年采用稻草覆盖措施对土壤肥力和作物产量的影响。结果表明,“稻草+化肥氮磷”(“Straw+NP”)处理的土壤有机碳和全氮、磷分别比不施肥(CK)的提高42.9%和17.4%、44.2%,有机碳和全氮的增幅约是纯化肥(NPK)处理的2倍。与CK和NPK处理的相比,“Straw+NP”处理能明显提高微生物生物量碳、氮、磷和溶解性有机碳、氮以及Olsen-P含量,差异达到显著(P<0.05)或极显著(P<0.01)水平。在等养分施用量的条件下,“Straw+NP”处理能显著提高油菜和甘薯的产量。因此,稻草易地覆盖是一种有效培肥坡地红壤和增加作物产量的途径。     

<Emphasis Type="Italic">p</Emphasis>-Coumaric can alter the composition of cucumber rhizosphere microbial communities and induce negative plant-microbial interactions

Phenolics from root exudates or decaying residues are usually referred as autotoxins of several plant species. However, how phenolics affect soil microbial communities and their functional significances are poorly understood. Rhizosphere bacterial and fungal communities from cucumber (Cucumis sativus L.) seedlings treated with p-coumaric acid, an autotoxin of cucumber, were analyzed by high-throughput sequencing of 16S rRNA gene and internal transcribed spacer amplicons. Then, feedback effects of the rhizosphere biota on cucumber seedlings were evaluated by inoculating non-sterilized and sterilized rhizosphere soils to sterilized background soils. p-Coumaric acid decreased the bacterial diversity of rhizosphere but increased fungal diversity and altered the compositions of both the bacterial and fungal communities. p-Coumaric acid increased the relative abundances of microbial taxa with phenol-degrading capability (such as Chaetomium, Humicola, and Mortierella spp.) and microbial taxa which contained plant pathogens (such as Fusarium spp.). However, p-coumaric acid inhibited the relative abundances of Lysobacter, Haliangium, and Gymnoascus spp., whose species can have pathogen-antagonistic and/or plant-growth-promoting effects. The positive effect of cucumber rhizosphere microbiota on cucumber seedling growth was reduced by p-coumaric acid. Overall, our results showed that, besides its direct phytotoxicity, p-coumaric acid can inhibit cucumber seedling growth through generating negative plant-soil microbial interactions.     

Microbial composition and diversity of an upland red soil under long-term fertilization treatments as revealed by culture-dependent and culture-independent approaches

Background, aim, and scope  Fertilization is an important agricultural practice for increasing crop yields. In order to maintain the soil sustainability, it is important to monitor the effects of fertilizer applications on the shifts of soil microorganisms, which control the cycling of many nutrients in the soil. Here, culture-dependent and culture-independent approaches were used to analyze the soil bacterial and fungal quantities and community structure under seven fertilization treatments, including Control, Manure, Return (harvested peanut straw was returned to the plot), and chemical fertilizers of NPK, NP, NK, and PK. The objective of this study was to examine the effects on soil microbial composition and diversity of long-term organic and chemical fertilizer regimes in a Chinese upland red soil. Materials and methods  Soil samples were collected from a long-term experiment station at Yingtan (28°15′N, 116°55′E), Jiangxi Province of China. The soil samples (0–20 cm) from four individual plots per treatment were collected. The total numbers of culturable bacteria and fungi were determined as colony forming units (CFUs) and selected colonies were identified on agar plates by dilution plate methods. Moreover, soil DNAs were extracted and bacterial 16S rRNA genes and fungal 18S rRNA genes were polymerase chain reaction amplified, and then analyzed by denaturing gradient gel electrophoresis (DGGE), cloning, and sequencing. Results  The organic fertilizers, especially manure, induced the least culturable bacterial CFUs, but the highest bacterial diversity ascertained by DGGE banding patterns. Chemical fertilizers, on the other hand, had less effect on the bacterial composition and diversity, with the NK treatment having the lowest CFUs. For the fungal community, the manure treatment had the largest CFUs but much fewer DGGE bands, also with the NK treatment having the lowest CFUs. The conventional identification of representative bacterial and fungal genera showed that long-term fertilization treatments resulted in differences in soil microbial composition and diversity. In particular, 42.4% of the identified bacterial isolates were classified into members of Arthrobacter. For fungi, Aspergillus, Penicillium, and Mucor were the most prevalent three genera, which accounted for 46.6% of the total identified fungi. The long-term fertilization treatments resulted in different bacterial and fungal compositions ascertained by the culture-dependent and also the culture-independent approaches. Discussion  It was evident that more representative fungal genera appeared in organic treatments than other treatments, indicating that culturable fungi were more sensitive to organic than to chemical fertilizers. A very notable finding was that fungal CFUs appeared maximal in organic manure treatments. This was quite different from the bacterial CFUs in the manure, indicating that bacteria and fungi responded differently to the fertilization. Similar to bacteria, the minimum fungal CFUs were also observed in the NK treatment. This result provided evidence that phosphorus could be a key factor for microorganisms in the soil. Thus, despite the fact that culture-dependent techniques are not ideal for studies of the composition of natural microbial communities when used alone, they provide one of the more useful means of understanding the growth habit, development, and potential function of microorganisms from soil habitats. A combination of culture-dependent and culture-independent approaches is likely to reveal more complete information regarding the composition of soil microbial communities. Conclusions  Long-term fertilization had great effects on the soil bacterial and fungal communities. Organic fertilizer applications induced the least culturable bacterial CFUs but the highest bacterial diversity, while chemical fertilizer applications had less impact on soil bacterial community. The largest fungal CFUs were obtained, but much lower diversity was detected in the manure treatment. The lowest bacterial and also fungal CFUs were observed in the NK treatment. The long-term fertilization treatments resulted in different bacterial and fungal compositions ascertained by the culture-dependent and also the culture-independent approaches. Phosphorus fertilizer could be considered as a key factor to control the microbial CFUs and diversity in this Chinese upland red soil. Recommendations and perspectives  Soil fungi seem to be a more sensitive indicator of soil fertility than soil bacteria. Since the major limitation of molecular methods in soil microbial studies is the lack of discrimination between the living and dead, or active and dormant microorganisms, both culture-dependent and culture-independent methods should be used to appropriately characterize soil microbial diversity.     

The effect of starter fertilizers on cotton production in legume residues

Abstract

Field and greenhouse studies were conducted to identify starter fertilizers which would enhance cotton seedling survival, growth, and yield in legume residues. Field studies were initiated in the fall of 1982 on a Norfolk sandy loam (Typic Paleudult) in the Upper Coastal Plain of Alabama. Winter annual legumes, crimson clover (Trifolium incarnatum L.) and hairy vetch (Vicia villosa Roth) were established as whole plots along with a winter fallow area. Split plot treatments consisted of O, N, P, K, NP, NK, and NPK starter fertilizers. The cotton (Gossypium hirsutum L.) was planted with a conservation tillage planting unit with in‐row subsoilers. The starter fertilizers were applied deep (8 to 10 inches) in the subsoil track. Greenhouse studies were also conducted with soil from whole plot areas top dressed with corresponding legume tissue at a rate of .9 g tissue/500 g soil. Seedlings in the greenhouse were rated for disease and emergence, and dry weights were recorded.

Cotton populations in field studies were lower in legume mulched than fallow soils in 1984. Application of starter fertilizers generally increased harvest populations, particularly the NK combination. In 1983, cotton growth was greater in vetch than other soils, but responses to starter fertilizers varied with analyses and years. Seed cotton yields were consistently high with P starter, although P did not always improve cotton stands and growth. When averaged across years and cover crops, yields were 3151, 3031, 2865, 2790, 2753, 2741, 2512, and 2364 for P, NP, P, NP, K, NPK, N and O, starter treatments respectively.

Greenhouse studies indicated that starter fertilizer improved cotton emergence in legume soils, but decreased emergence in fallow soils. Disease ratings of emerged seedlings were more severe when starter fertilizer was used than when it was not used. Thus, starter fertilizer increased emergence and survival, despite high disease ratings. Cotton seedling growth generally increased when poor emergence reduced cotton seedling competition.     

施肥方式对冬小麦—夏玉米轮作土壤N_2O排放的影响

氧化亚氮(N_2O)是一种重要的农田温室气体,本研究利用紫色土长期施肥试验平台,采用静态箱/气相色谱法对紫色土旱作农田冬小麦—夏玉米轮作系统的N_2O排放进行了定位观测(2012年11月至2013年9月),研究单施氮肥(N)、常规氮磷钾肥(NPK)、猪厩肥(OM)、猪厩肥配施氮磷钾肥(OMNPK)和秸秆还田配施氮磷钾肥(ICRNPK)等施肥方式对紫色土N_2O排放特征的影响;不施肥(NF)作为对照计算排放系数,以探寻紫色土地区可操作性强、环境友好的施肥方式。结果表明,所有施肥方式的N_2O排放均呈现双峰排放,峰值出现在施肥初期;玉米季N_2O排放峰值显著高于小麦季(p0.05)。在相同的施氮水平(小麦季130 kg hm~(~(-2)),玉米季150 kg hm~(~(-2)))下,施肥方式对N_2O排放和作物产量均有显著影响(p0.05)。N、OM、NPK、OMNPK和ICRNPK处理的土壤N_2O周年累积排放量分别为1.93、1.96、1.12、1.50和0.79 kg hm~(~(-2)),排放系数分别为0.62%、0.63%、0.33%、0.47%和0.21%,全年作物产量分别为4.35、11.95、8.39、9.77、10.93 t hm~(~(-2))。施用猪厩肥显著增加N_2O排放量,而秸秆还田在保证作物产量的同时显著降低N_2O排放量,可作为紫色土地区环境友好的施肥方式。土壤无机氮(NO_3~--N和NH_4~+-N)是N_2O排放的主要限制因子。因此,在施氮水平相同时,施肥方式对紫色土活性氮含量的影响导致N_2O排放差异显著,是土壤N_2O排放差异的根本原因。土壤孔隙充水率也是影响N_2O排放的重要环境因子,并且其对N_2O排放的影响存在阈值效应。