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1.
为从微生态角度探索接种AM真菌对铅污染根际土壤微生物群落代谢特征的影响,以摩西管柄囊霉(Funneliformis mosseae)和幼套近明囊霉(Claroideoglomus etunicatum)为接种菌剂,在温室盆栽条件下以Pb4+含量为0 mg·kg-1、200 mg·kg-1、400 mg·kg-1和800 mg·kg-1土壤种植龙葵(Solanum nigrum)10周后采集根际土壤,采用Biolog微平板法测定龙葵根际土壤微生物群落的代谢变化。结果表明:1)微生物平均代谢活性(AWCD)随铅浓度增加呈降—升—降趋势;接种AM真菌显著提高了铅胁迫下根际土壤微生物的AWCD值,仅中浓度(400 mg·kg-1)下未达显著差异。2)中浓度铅处理能显著提高根际土壤微生物对糖类及其衍生物、氨基酸类、脂肪酸和脂类及代谢产物类四大类碳源底物利用能力;接种AM真菌,高浓度(800 mg·kg-1)铅处理显著提高了根际土壤微生物对氨基酸类底物的利用能力。3)铅胁迫下接种AM真菌提高了根际土壤微生物多样性指数,在中浓度下丰富度指数、Shannon-Wiener多样性指数、Simpson优势度指数均达显著水平。4)主成分分析显示,代谢产物类在PC1和PC2中种类最多,分别为6种和4种;糖类及其衍生物在PC3中种类最多(5种)。5)在铅胁迫和接种AM真菌共同作用下,微生物碳源利用主要受铅浓度调节,并且二者对微生物碳源利用具有显著交互效应。综上可知,接种AM真菌能够提高铅胁迫下龙葵根际土壤微生物多样性指数,增强根际土壤微生物对碳源底物的利用能力。该研究为进一步探究AM真菌强化植物联合修复技术提供了依据。  相似文献   

2.
长期氮肥施用对农田黑土NLFA与PLFA特性的影响   总被引:3,自引:0,他引:3  
以不施肥与休闲处理为对照,通过对土壤微生物磷脂脂肪酸(PLFA)、中性磷脂脂肪酸(NLFA)、NLFA/PLFA比值及各菌群特定PLFA比值的测定,研究不同氮肥处理条件下东北黑土微生物群落变化规律.PLFA测定结果表明,氮磷配施能促进土壤微生物生长;氮磷钾配施未表现出促进土壤微生物生长的作用;单施氮肥处理因有效磷等养分过度消耗而抑制真菌生长.不同菌群之间PLFA比值表明,真菌较细菌更能适应养分贫瘠条件,而氮肥与磷肥的施入则能促进细菌生物量增加.不同氮肥处理NLFA含量及个别NLFA/PLFA比值存在较大差异,可用来说明土壤微生物生理状态和土壤养分水平.  相似文献   

3.
为揭示冬麦免耕覆盖栽培管理措施对土壤丛枝菌根真菌多样性的影响,以农田土壤生态系统为研究对象,利用Illumina MiSeq平台通过高通量测序的方法,对连续免耕覆盖栽培及有机肥管理下冬麦土壤丛枝菌根真菌群落组成及其与土壤环境因子间的相互关系进行研究。结果表明,丛枝菌根(AM)真菌在97%相似度下共获得4 515个AM真菌的操作分类单元(OTUs),分属于1门3纲4目8科10属155种。不同处理中,类球囊霉属(Paraglomus),球囊霉属(Glomus)和近明球囊霉(Claroideoglomus)为优势属,受农业综合管理措施中有机肥施用、免耕覆盖因子的影响,近明球囊霉、有隔球囊霉属相对丰度在不同处理间存在显著差异(P<0.05)。与耕作、不覆盖相比,免耕、覆盖措施提高了AM真菌多样性指数,但降低了AM真菌属的丰富度;与无肥条件相比,有机肥施用提高了AM真菌丰富度指数,但降低了AM真菌多样性指数。多元分析结果表明,土壤全磷及速效磷含量是影响AM真菌群落组成中优势属丰度变化的主要因素。免耕覆盖、有机栽培改变了土壤AM真菌的多样性及丰富度,土壤中丰度较低的AM真菌菌属更容易受到有机肥施用的影响;有机肥与免耕、覆盖管理的交互作用对AM真菌近明球囊霉属相对丰度有显著影响(P<0.05)。AM真菌群落对耕作覆盖、有机肥施用管理活动的响应受到农业综合管理活动及其相关因素交互作用的影响。本研究结果为合理农作物免耕覆盖、有机栽培管理提供了理论依据。  相似文献   

4.
发酵床养猪是一种新型的养殖技术,可有效缓解养猪的环境污染问题,微生物在其中起关键作用。为明确养猪发酵床发酵过程微生物群落的变化规律,为发酵床的科学管理提供依据,本研究采用磷脂脂肪酸生物标记(phospholipid fatty acids,PLFA)法分析养猪发酵床不同发酵等级垫料的微生物群落结构特征。采用色差法将垫料分为3个发酵程度等级:1级、2级和3级,采集不同发酵等级表层(0~15 cm)和里层(30~45 cm)垫料样本,测定各样本的PLFA。结果表明,共检测到61种PLFA,发酵2级垫料的PLFA种类最多,发酵3级垫料的PLFA种类最少。在各垫料中,PLFA分布量均表现为细菌 > 真菌 > 放线菌。指示细菌、真菌、放线菌、革兰氏阳性细菌(G+)、革兰氏阴性细菌(G-)的PLFA及总PLFA在各发酵等级表层垫料的分布量均显著大于其在里层垫料的分布量,最大值出现在发酵1级表层垫料中。与对照(未发酵垫料)相比,发酵垫料总PLFA含量均显著增加(P<0.05)。发酵3级表层垫料的真菌/细菌值最大,发酵2级表层垫料的G+/G-值最大。多样性分析表明,Shannon指数和Pielou指数最大值出现在发酵2级垫料中,而Simpson指数最大值出现在发酵3级表层垫料中。聚类分析表明,当欧氏距离为233.15时,可将不同发酵等级垫料聚为3个类群,同一发酵级别的垫料聚在相同类群中;主成分分析表明,发酵1级表层和里层垫料单独归一类群,其他发酵等级垫料和对照垫料归另一类群中。综上,不同发酵等级垫料的微生物种群结构不同,发酵1级表层垫料微生物分布量最大,发酵2级垫料的微生物种类最多,相同发酵级别表层和里层垫料微生物群落结构相似。  相似文献   

5.
长期施肥对农田黑土微生物活力与群落结构的影响   总被引:6,自引:0,他引:6  
白震  张明  闫颖  李维福  张旭东 《土壤学报》2009,46(1):107-116
以黑土长期肥料定位站CK、N、P、NP、MN(有机肥+氮)、MP(有机肥+磷)、MNP(有机肥+氮+磷)等处理为供试土样,研究氮、磷及有机肥不同配施条件下土壤基本理化性质、磷脂脂肪酸(PLFA)、中性磷脂脂肪酸(NLFA)、酸(碱)性磷酸酶、微生物量碳或氮(SMB-C或N)等变化规律。结果表明,26年有机肥-化肥配施明显提高土壤有机质(OM)、总氮(TN)以及速效氮、磷、钾等养分含量,其SMB-C或N、SMB-C/OM比值、磷酸酶活力以及各菌群PLFA含量显著高于CK和各化肥处理。长期N处理微生物活力明显低于CK,而P处理对微生物活力与结构影响最小。NLFA在各菌体相对含量与活体生物标识物变化趋势相反,表明养分充足的有机肥处理中各菌群休眠体或贮存物质积累有限。PLFA、NLFA与NLFA/PLFA主成分分析表明,有机肥与化肥处理微生物群落结构显著不同。个别PLFA或NLFA载荷值分析表明,真菌C18∶2ω6,9受有机肥施用影响显著;而G+菌iC15∶0、iC17∶0、iC16∶0等更易受化肥施用影响。与PLFA或NLFA相比,NLFA/PLFA比值PC分析能更有效地区分不同施肥处理。  相似文献   

6.
为探究长期秸秆覆盖对免耕区作物产量、土壤氮素组分及微生物群落特征的影响,以稻–麦定位免耕试验为研究对象,选取了其中免耕且秸秆移除和免耕且秸秆覆盖2个处理,于试验开展第12年(2018年)小麦收获后,统计分析近五年产量数据,并采集各处理0~5、5~10、10~20、20~30 cm的土壤样品,测定土壤全氮及活性氮组分,利用磷脂脂肪酸(PLFA)方法表征土壤微生物群落。结果表明:(1)秸秆覆盖显著提高了小麦产量(增幅为6.49%),对水稻产量影响不显著。(2)秸秆覆盖对土壤氮组分的影响略有差异:它显著提高了土壤0~5 cm全氮、硝态氮和铵态氮以及0~10 cm颗粒有机氮、0~5 cm和10~20 cm可溶性有机氮含量,对微生物生物量氮无显著影响;它提高了0~5 cm和10~20 cm可溶性有机氮占全氮的比例,对其他组分占全氮比例无显著影响。(3)秸秆覆盖显著提高了土壤微生物总PLFA和细菌PLFA丰度,对真菌PLFA和放线菌PLFA无影响,降低了土壤真菌/细菌比;微生物生物量氮、土壤全氮、颗粒有机碳/颗粒有机氮比是显著影响土壤微生物群落组成的关键土壤环境因子。(4)无论秸秆覆盖与否,土壤全...  相似文献   

7.
长期种植毛竹林土壤丛枝菌根真菌群落演变趋势   总被引:1,自引:0,他引:1  
为揭示长期种植毛竹林土壤丛枝菌根(Arbuscular mycorrhizae, AM)真菌群落演变特征,通过磷脂脂肪酸(Phospholipid fatty acid, PLFA)和Illumina Miseq测序平台研究了AM真菌生物量及群落结构的演变趋势。结果表明,长期种植毛竹林土壤养分含量总体呈下降趋势,球囊霉素相关土壤蛋白(Glomalin-related soil protein, GRSP)含量及AM真菌生物量也显著降低(p<0.05),其中易提取态球囊霉素相关土壤蛋白含量与有机质、速效钾、碱解氮显著正相关(p<0.05),而AM真菌菌丝生物量(16:1ω5 PLFA)与碱解氮极显著正相关(p<0.01)。长期种植毛竹林显著降低了土壤2~0.25 mm大团聚体比例(p<0.05),且与AM真菌菌丝生物量极显著正相关(p<0.01)。测序结果表明,毛竹林土壤AM真菌以球囊霉属(Glomus)为优势种群,其次是无梗囊霉属(Acaulospora),长期种植毛竹后土壤球囊霉属相对丰度显著增加而无梗囊霉属显著降低(p<0.05)。非度量多维尺度转换排序(NMDS)分析显示,对照马尾松林与不同种植年限毛竹林土壤AM真菌群落显著区分(p=0.001),土壤含水量(p=0.005)、有效磷(p=0.014)、碱解氮(p=0.001)对AM真菌群落结构变异具有重要贡献。长期种植毛竹显著降低了AM真菌生物量、球囊霉素相关土壤蛋白含量以及2~0.25 mm大团聚体比例,并改变了AM真菌群落结构,不利于土壤碳固存和维持生态系统稳定。  相似文献   

8.
不同施肥和耕作制度下土壤微生物多样性研究进展   总被引:15,自引:3,他引:15  
本文主要介绍了运用Biolog GN、磷脂脂肪酸(PLFA)、核酸分析法进行土壤微生物群落分析的优缺点,综述了施肥、耕作两种农业措施对土壤微生物多样性影响的研究进展。指出不同施肥处理对微生物影响效果不同,合理施用有机肥有利于维持土壤微生物的多样性及活性;由于受其他环境因素(如土壤类型、农作制度、残茬量等)的影响,不同耕作措施对土壤微生物多样性影响有差异,但是大多试验结果显示免耕、少耕能增加微生物多样性和生物量,保持系统的稳定性。文章还指出了目前研究中存在的问题,并对今后的研究方向做了展望。  相似文献   

9.
长期不同施肥条件下红壤性水稻土微生物群落结构的变化   总被引:10,自引:2,他引:10  
以位于江西省红壤研究所内长期定位试验的水稻土(始于1981年)为研究对象,运用磷脂脂肪酸(phospholipid fatty acid,PLFA)和BIOLOG分析技术研究了不施肥(CK)、单施化肥(NPK)及有机肥与化肥混施(NPKM)三种施肥方式对土壤微生物群落结构的影响。结果表明:长期施化肥和有机肥与化肥混施处理的PLFA总量均高于未施肥处理,两者分别较未施肥处理高91%和309%;PLFA主成分分析(PCA)显示施肥促进了土壤微生物群落结构的变化,其中NPKM处理增加了革兰氏阴性细菌(G-细菌)、真菌、放线菌和原生动物的数量,NPK处理增加了革兰氏阳性细菌(G+细菌)的数量,不施肥处理较施肥处理提高了真菌/细菌比例,CK和NPK处理的微生物群落结构更为相似;各施肥处理间土壤的AWCD值(平均每孔颜色变化率,average well color development,AWCD)表明,NPKM处理能够促进土壤微生物群落对碳源的利用能力,进而增加土壤中微生物的整体活性,而NPK处理减弱了土壤微生物的活性。代谢功能多样性分析同时表明,NPKM处理增加了微生物群落的多样性,而NPK处理使土壤微生物的多样性降低;土壤PLFA与土壤养分的相关性分析显示,土壤总PLFA量与土壤有机质和全氮呈极显著相关(p0.01),与速效养分相关性不大。  相似文献   

10.
采用室内恒温培养方法,研究了不同施肥处理对水稻长期肥料试验中不施肥区(CK)和全肥区(NPK)土壤酶活性及微生物群落结构的变化。结果表明,施肥处理(单施化肥、施猪粪和施秸杆)可以显著提高土壤的微生物量碳以及脲酶、酸性磷酸酶的活性,施用有机肥的效果明显大于单施化肥; 有机肥在无肥区(CK)的施用效果与在全肥区(NPK)的效果接近。PLFA分析表明,施肥使无肥区(CK)土壤微生物群落结构发生了显著的变化,施用有机肥显著增加了土壤微生物群落结构的多样性。与不施肥和单施化肥相比,施有机肥主要增加了细菌和真菌的特征脂肪酸如不饱和脂肪酸、环状脂肪酸cy19∶0等的相对含量,而降低了放线菌标记性脂肪酸10Me18∶0的相对含量。  相似文献   

11.
【目的】以富士(Fuji)、 秦冠(Qinguan)嫁接在平邑甜茶(Malus hupehensis Rehd.)上的当年生盆栽苗为试验材料,采用砂培方法,研究了缺氮胁迫和干旱对富士和秦冠生长情况、 光合参数、 植株各部位氮磷钾含量及氮素利用效率的影响,分析比较了低氮干旱条件下富士和秦冠生长及氮素利用的差异,以期为果树生产高效肥水利用提供理论指导。【方法】试验共设四个处理: 正常氮正常水(ZZ)、 低氮正常水(DZ)、 正常氮干旱(ZG)、 低氮干旱(DG)。氮素和水分均设置两个水平,分别为正常氮(6 mmol/L NO-3-N)、 低氮(0.3 mmol/LNO-3-N)、 正常供水(保持盆中砂子相对含水量为饱和含水量的80%~85%)、 干旱处理(保持盆中砂子相对含水量为饱和含水量的60%~65%)。【结果】富士和秦冠的生物量(茎和叶)、 株高茎粗等生长指标以及光合速率、 气孔导度、 蒸腾速率均为正常氮正常水(ZZ)>低氮正常水(DZ)>正常氮干旱(ZG)>低氮干旱(DG),并且相对应处理下秦冠的以上指标均高于富士;正常供水下,缺氮处理使富士、 秦冠的根冠比比正常氮处理均有所增加,富士提高了2.05%,秦冠提高了22.40%。富士和秦冠的氮、 磷、 钾含量均表现出正常氮正常水(ZZ)>低氮正常水(DZ)>正常氮干旱(ZG)>低氮干旱(DG); 氮、 钾元素含量在植株各部位的分布顺序依次是叶>根>茎,磷元素则是根>叶>茎;光合氮素利用效率(PNUE)和氮素利用效率表现为秦冠处理之间差异极显著,富士处理之间差异不显著;秦冠的PNUE和NUE明显高于富士,在低氮正常水(DZ)处理下,秦冠氮肥利用率比富士高42.07%,在低氮干旱(DG)处理下高64.14%;低氮胁迫下富士和秦冠的NUE显著提高,并且秦冠提高的幅度高于富士。【结论】施用氮肥能够显著提高富士与秦冠的干物质量,同等水肥条件下,秦冠生长优于富士;水分亏缺会减少叶片对氮的吸收,干旱条件下适度增施氮肥,可提高果树的抗旱能力;低氮干旱胁迫下秦冠的生长指标、 光合指标及氮素利用效率指标均优于富士,表现出较强的抗低氮干旱胁迫的能力。  相似文献   

12.
Laser-induced breakdown spectroscopy (LIBS) is a new technique for the analysis of plant material. This study investigates the application of LIBS to pasture-based plant samples. The LIBS measurements were obtained from pelletized pasture samples (100 samples) that had been also analyzed by inductively coupled plasma–optical emission spectroscopy (ICP-OES) following microwave digestion for calibration and comparison purposes. Comparisons for elements sodium (Na), potassium (K), magnesium (Mg), calcium (Ca), manganese (Mn), iron (Fe), copper (Cu), zinc (Zn), boron (B), phosphorus (P), and sulfur (S) showed that LIBS could be used for almost all the standard profile total elements with concentrations down to low mg/kg levels (observed error of Na: 0.024 percent, K: 0.18 percent, Mg: 0.016 percent, Ca: 0.073 percent, P: 0.017 percent, Mn: 31 mg/kg, Fe: 150 mg/kg, Zn: 6.6 mg/kg, and B: 1.1 mg/kg). Elemental analysis at less than mg/kg levels was not possible using LIBS. The elements S and Cu were particularly difficult to analyze with reliability using LIBS at the concentration levels found in the plant samples. Replacing microwave digestion and subsequent ICP analysis with a direct analysis of dried plant samples using LIBS has the potential to improve the productivity and reduce the cost of testing.  相似文献   

13.
正The Center for Agricultural Resources Research(CARR),the Institute of Genetics and Developmental Biology(IGDB),Chinese Academy of Sciences,invites applicants for several research group leader positions.CARR is one of the research organizations in Chinese Academy of Sciences(CAS).We seek nominations and applications from individuals who have expertise and a record of accomplishment in research areas related to ecology,agro-hydrology,  相似文献   

14.
Staff members of the Department of Botany of Palacký University in Olomouc and Gene Bank Department – Workplace Olomouc, Research Institute of Crop Production in Prague, Czech Republic, conducted an expedition in seven European countries (Austria, Czech Republic, France, Germany, Italy, the Netherlands, Switzerland) in August/September 1999 to collect wild Lactuca spp. germplasm and study its geographic distribution, ecology and biodiversity. During the mission, more than 600 locations were visited resulting in the collection of 602 seed samples (accessions) of wild Lactuca species and 13 seed samples of related genera (Chondrilla and Mycelis). Lactuca serriola f. serriola, L. serriola f. integrifolia, L. saligna and L. viminea subsp. chondrilliflora were prevalent in southern Europe (Italy, France), however, only L. serriola was common in central and western Europe (Austria, Czech Republic, Germany, Netherlands, Switzerland). The greatest diversity of Lactuca species was found in France, where also the most seed samples (165) were collected. The most characteristic habitats with a high density of Lactuca spp. populations were observed along roads and highways, grassy ditches, ruderal communities, and dust-heaps. Natural infections by powdery mildew (Erysiphe cichoracearum) and downy mildew (Bremia lactucae) on some wild Lactuca spp. were observed. Recent observations concerning the geographic distribution, population structure, habitats, and natural occurrence of diseases of Lactuca spp. are discussed. This assemblage of genetic resources of Lactuca spp. can serve as the basis of future studies of species diversification, spatial population structure, plant microevolution, domestication processes, and genetic variability of host-parasite interactions.  相似文献   

15.
The responses of tallgrass prairie plant communities and ecosystem processes to fire and grazing are well characterized. However, responses of invertebrate consumer groups, and particularly soil-dwelling organisms, to these disturbances are not well known. At Konza Prairie Biological Station, we sampled soil macroinvertebrates in 1994 and 1999 as part of a long-term experiment designed to examine the effects and interactions of annual fire, mowing, and fertilization (N and P) on prairie soil communities and processes. For nearly all taxa, in both years, responses were characterized by significant treatment interactions, but some general patterns were evident. Introduced European earthworms (Aporrectodea spp. and Octolasion spp.) were most abundant in plots where fire was excluded, and the proportion of the total earthworm community consisting of introduced earthworms was greater in unburned, unmowed, and fertilized plots. Nymphs of two Cicada genera were collected (Cicadetta spp. and Tibicen spp.). Cicadetta nymphs were more abundant in burned plots, but mowing reduced their abundance. Tibicen nymphs were collected almost exclusively from unburned plots. Treatment effects on herbivorous beetle larvae (Scarabaeidae, Elateridae, and Curculionidae) were variable, but nutrient additions (N or P) usually resulted in greater densities, whereas mowing usually resulted in lower densities. Our results suggest that departures from historical disturbance regimes (i.e. frequent fire and grazing) may render soils more susceptible to increased numbers of European earthworms, and that interactions between fire, aboveground biomass removal, and vegetation responses affect the structure and composition of invertebrate communities in tallgrass prairie soils.  相似文献   

16.
We have studied the effect of anaerobically digested (ADMSW) and composted municipal solid waste (CMSW) on mineralization and foodweb dynamics to verify the hypothesis that ADMSW would immobilize N right after addition to soil in contrast to addition with CMSW. Another hypothesis was that the mesofauna (enchytraeids and microarthropods) would stimulate N release from the decomposer community. We measured excretion of -N and urea-N from the mesofauna and hypothesized that enchytraeids would release urea. ADMSW and CMSW were amended to pots with sandy loam and barley. The pots were divided into treatments with or without mesofauna. Mesofauna, plant N and biomass, soil N and ergosterol (fungal biomass) were measured over a 113-day period of four equidistant samplings. Soil respiration, N mineralization and N release by the mesofauna were modelled from concurrent studies. ADMSW- and CMSW-treated soils initially (<20 days) immobilized N. The amendments did not increase plant growth substantially, and this was probably due to N-limitation in the early stages of plant growth. Enchytraeid abundance was about three times higher in ADMSW- than CMSW-treated soils, indicating that ADMSW contained more labile compounds, bacteria, and microfauna. The mesofauna did not affect N-content, but the cumulated -N excreted by the mesofauna was estimated to be substantial and about one-fifth of total plant N in ADMSW. An explanation for this discrepancy might be that in the absence of the mesofauna, other members of the detrivore and microbivore community performed the mesofauna’s function. Neither enchytraeids nor microarthropods excreted urea.  相似文献   

17.
正The Center for Agricultural Resources Research(CARR),the Institute of Genetics and Developmental Biology(IGDB),Chinese Academy of Sciences,invites applicants for several research group leader positions.CARR is one of the research organizations in Chinese Academy of Sciences(CAS).We seek nominations and applications from individuals who have expertise and a record of accomplishment in research areas related to ecology,agro-hydrology,  相似文献   

18.
正The Center for Agricultural Resources Research(CARR),the Institute of Genetics and Developmental Biology(IGDB),Chinese Academy of Sciences,invites applicants for several research group leader positions.CARR is one of the research organizations in Chinese Academy of Sciences(CAS).We seek nominations and applications from individuals who have expertise and a record of accomplishment in research areas related to ecology,agro-hydrology,  相似文献   

19.
Abstract

A 3-year study was carried out to investigate quality parameters in 14 tree fruit and berry species grown in southern Norway. The species were blueberry, apple, aronia, sour cherry, sweet cherry, red raspberry, strawberry, blackcurrant, gooseberry, red currant and elderberry, harvested along with wild bilberry, cloudberry and lingonberry. Significant differences between species were identified for all quality parameters. The coefficient of variation between species was lowest for pH (12.5%), dry matter (18.9%) and soluble solids (25.3%), followed by titratable acids (59.3%), total phenolics (83.8%), antioxidant capacity FRAP (85.7%) and antiradical power by the DPPH-assay (97.8%), total monomeric anthocyanins (132%) and ascorbic acid (137%). Average coefficient of variation within species were lower and ranged from 4 (pH) to 62% (ascorbic acid). Only the FRAP values were significantly affected by harvesting year with lower levels in 2004 than in 2005 and 2006. There were significant interactions between species and harvesting year for dry matter, soluble solids, pH, ascorbic acid and FRAP. The results indicate generic ranges in composition within species independent upon growing location and climate, and the composition of the tree fruits and berries is not likely to deviate from these ranges. It is concluded that desirable composition of tree fruits and berries and their products should primarily be achieved by selection among species rather than searching fors broadened variation within individual species.  相似文献   

20.
Potassium (K) fixation and release in soil are important factors in the long-term sustainability of a cropping system. Changes in K concentration and characteristics of K fixation and release in rhizosphere and nonrhizosphere soils in the rapeseed (Brassica napus L.)–rice (Oryza sativa L.) rotation were investigated using a rhizobox system. The concentrations of different forms of K in both rhizosphere and nonrhizosphere soils decreased with plants compared to without plants, regardless of K fertilizer application. Potassium uptake by crops mainly came from the rhizosphere soil. In the treatment without K fertilizer (–K), the main form of K supplied by the soil to the crops was 1.0 mol L?1 nitric acid (HNO3) nonextractable K, followed by nonexchangeable K, and then exchangeable K. In the treatment with K fertilizer (+K), the main K forms supplied by the soil to the crops were exchangeable K and nonexchangeable K. The amount and rate of K fixation after one cycle of the rapeseed–rice rotation was greater in rhizosphere soil than in nonrhizosphere soil. The amount and rate of K fixation of soil in the +K treatment were significantly less than in the –K treatment. The cumulative amounts of K released with 1.0 mol L?1 ammonium acetate (NH4OAc) and 1.0 mol L?1 HNO3 extraction increased with the increasing numbers of extractions, but the K-releasing power of soil by successive extraction decreased gradually and finally became almost constant. The release of K was less in rhizosphere soil than in nonrhizosphere soil. The release of K in the +K treatment was similar to that in the –K treatment in rhizosphere soil, but the K release in nonrhizosphere soil was greater with the +K than the –K treatment. Overall, the information obtained in this study will be helpful in formulating more precise K fertilizer recommendations for certain soils.  相似文献   

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