连续施用有机肥对连作花生根际微生物种群和 酶活性的影响

花生连作导致土传病害易发,严重制约其产量和品质。为探讨持续施用有机肥缓解连作花生病害发生的防治机理,大田条件下研究了连续6年施用化肥、普通有机肥和生物有机肥(接种内生菌拟茎点霉B3)后对连作花生根腐病、根际土壤典型微生物种群和酶活的影响。结果表明:与单施化肥相比,持续施用普通有机肥和生物有机肥可有效控制连作花生土传病害发生,荚果产量提高23.8%和47.9%。连续施用普通有机肥和生物有机肥均显著提高根际过氧化氢酶、脱氢酶和酚氧化酶活性,荧光定量PCR进一步测定出连续施用有机肥可显著增加连作花生根际细菌和真菌的数量,说明连续施用有机肥后连作花生根际微生物活性显著提升。连续施用普通有机肥和生物有机肥显著增加了连作花生根际有益微生物种群的数量,其中放线菌增加0.9倍和1.6倍,假单胞菌增加10.9倍和13.1倍,伯克氏菌增加2.6倍和1.9倍,芽孢杆菌增加1.1倍和2.1倍;然而连续施用有机肥对连作花生根际主要致病微生物种群(如镰刀菌属和青枯雷尔氏菌)无明显影响。表明通过持续施用有机肥可有效提高连作花生根际有益微生物种群的数量和土壤酶活性,进而改善连作花生根际微生态环境,增强连作土壤抑病能力,以达到控制连作花生土传病害易发的目的。     

花生连作土壤微生物区系变化研究

通过盆栽试验研究了不同连作年限花生根际及非根际土壤微生物区系变化。结果表明,随着连作年限的增加,花生根际及非根际土壤中的细菌、放线菌数量明显减少,真菌数量明显增加。4个处理根际土壤中细菌数量在整个生育期的变化均为先上升后下降的单峰曲线,不同之处为连作5年在结荚期时达到峰值,其他3个处理峰值出现在花针期。连作1年花生根际土壤中真菌数量动态变化曲线为先上升后下降再上升,峰值出现在花针期。其他3个处理均为先上升后下降的单峰曲线。CK和连作3年根际土壤中放线菌在整个生育期的菌量动态变化曲线较为一致,总体上均呈现先上升后下降的趋势,峰值均出现在结荚期,连作1年和5年的动态变化曲线较为一致,总体均呈现先上升后下降再缓慢上升的趋势,峰值均出现在花针期。     

再植枸杞根际真菌群落对长期连作的响应研究

受枸杞自身种植特点和道地产区土地资源限制,连作障碍已成为制约宁夏枸杞产业可持续发展的主要因素之一,导致严重的经济损失和生态问题。前期研究表明,连作能够显著影响再植枸杞根际土壤细菌的群落结构和多样性,但就连作对真菌群落结构和功能的影响目前仍不清楚。本文利用实时荧光定量PCR和高通量测序技术,研究连作对再植枸杞根际真菌群落丰度及多样性的影响。实时荧光定量PCR分析表明,与对照样地相比,连作显著促进再植枸杞根际及非根际土壤中细菌和真菌的丰度。但连作对真菌的促进作用明显高于细菌,导致细菌/真菌比例失衡,使再植枸杞根际及非根际土壤微生物环境偏向于真菌型。对测序结果的分析发现,所测定样地中枸杞根际及非根际土壤中的优势真菌门分别为子囊菌门、担子菌门、接合菌门、壶菌门及球囊菌门,其中连作地再植枸杞根际子囊菌门的相对丰度较对照样地显著降低,而接合菌门的相对丰度则显著增加(P0.05)。FUNGuild真菌功能预测也证实连作显著抑制再植枸杞根际土壤丛枝菌根真菌的相对丰度(P0.05)。基于距离的冗余分析(db-RDA)结果表明,土壤pH、电导率、硝态氮和有效磷含量是影响枸杞根际土壤真菌群落变化的主要因子(P0.05),而土壤硝态氮和有效磷含量则是解释非根际土壤真菌群落变化的主要因子(P0.05)。这些结果说明长期施用化肥可能是改变连作地再植枸杞根际土壤真菌群落结构及枸杞-真菌互作关系的主要因素之一。这一研究结果为理解枸杞连作障碍的形成机制提供理论基础。     

持续施用生物有机肥对花生产量和根际细菌群落的影响

为了揭示集约化经营制度下施用生物有机肥对花生连作障碍的调控,采集旱地红壤进行了连续5 a的盆栽试验,试验处理包括:花生–玉米轮作、施用化肥的花生连作和施用生物有机肥的花生连作,探究持续施用生物有机肥防控花生连作障碍的根际微生态机制。结果显示,相比于轮作,施用化肥的连作花生产量显著降低;相比于连作花生施用化肥,持续施用生物有机肥可以显著缓解连作花生产量降低的问题,施用有机肥第5季荚果干重提高27%。与施用化肥的连作处理相比,持续施用生物有机肥显著增加了花生根际细菌多样性和丰富度,与轮作花生处理无显著差异;持续施用生物有机肥显著提高了连作花生根际变形菌门和拟杆菌门的相对丰度,降低了厚壁菌门的相对丰度;属水平上,花生根际促生菌Rhizobium,Mesorhizobium和Bradyrhizobium的相对丰度较化肥处理分别提高了295%、89%和40%,而Leifsonia和Burkholderia的相对丰度分别降低了67%和47%。冗余分析进一步发现,土壤有机质和p H是根际细菌群落结构改善的重要理化因素。这表明持续施用生物有机肥可以改良红壤理化环境(如p H和有机质含量),进而优化连作...     

烟蒜轮作与套作对土壤微生物类群数量的影响

采取田间试验方式,以单作烤烟为对照,研究了不同年度和烤烟生育时期烟蒜轮作、烟蒜套作对根际和非根际土壤细菌、真菌、放线菌、解钾菌和解磷菌数量变化的影响。结果表明:随生育时期推进,烟蒜轮作和烟蒜套作处理根际土壤细菌含量高于单作烤烟的趋势越来越明显。2014年,上部叶成熟期烟蒜轮作、烟蒜套作根际土壤细菌数量是单作烤烟的1.41倍和1.24倍。中部叶成熟期和上部叶成熟期,烟蒜轮作处理根际土壤真菌数量最少,但2014年烟蒜轮作和烟蒜套作处理下非根际土壤真菌数量高于单作烤烟处理。烟蒜轮作、烟蒜套作处理根际土壤放线菌数量高于单作烤烟,上部叶成熟期分别是单作烤烟2.01倍和2.93倍(2013年)、1.12倍和1.28倍(2014年)。烟蒜轮作、烟蒜套作处理根际土壤解钾菌和解磷菌含量在烤烟生长发育的中后期显著高于单作烤烟,且非根际土壤的解磷菌含量也呈现相同的趋势。不同年度,烟蒜轮作与烟蒜套作处理烟叶产量和上中等烟率均显著高于单作烤烟处理。烟蒜轮作和烟蒜套作种植模式能改良土壤根际环境微生物结构,维持良好的土壤质量状态。     

轮作与连作对烟田土壤微生物区系及多样性的影响

为探讨轮作与连作对烟田根际土壤微生物群落的影响,采用实验室微生物培养联合微生物高通量测序技术,分析了玉米-烤烟轮作和烟叶连作对烟株根际土壤微生物数量、群落结构及其多样性的影响。研究结果表明,轮作烟田根际土壤中可培养细菌和放线菌数量均高于连作烟田根际土壤,但真菌数量低于连作烟田。土壤高通量测序结果表明,轮作烟田根际土壤真菌和细菌群落多样性均高于连作烟田;在烟株的生长过程中,轮作和连作烟田在旺长期和成熟期微生物群落相似度降低。相较于黑胫病/根腐病/根结线虫发病率较高(36. 67%)的连作烟田来说,轮作烟田发病率较低(0%),进一步分析真菌和细菌群落结构发现,轮作烟田根际土壤中拮抗菌如Sphingomonas (鞘脂单胞菌属)、Pseudomonas (假单胞菌属)、Aspergillus (曲霉属)等相对丰度均高于连作烟田,而连作烟田根腐病病菌Pythium (腐霉属)丰度较高。     

化肥配施有机肥对花生根际细菌群落结构及共存网络的影响

为评估化肥配施有机肥对花生根际细菌群落的影响，田间试验条件下研究了不施肥(CK)、施化学氮磷钾肥(NPK)和化学氮磷钾肥+有机肥配施(NPKM)对花生根际细菌群落多样性、结构和共存网络的影响。结果表明：NPKM处理下花生根际土养分状况明显改善，特别是有效磷的含量，较CK和NPK处理分别提高了5.31倍～12.16倍和3.24倍～6.50倍；而NPK处理下花生根际土养分状况并没有明显提升；Source Tracker分析显示，NPKM处理下根际细菌群落中只有2.1%～5.5%的物种来源于有机肥自身，但其花生根际细菌群落多样性在生育期前期要明显高于CK和NPK处理，而CK和NPK处理下根际细菌群落多样性差异不大；限制性主成分分析(CAP)显示，施肥措施和生育期均对根际细菌群落结构产生了显著影响，NPKM处理下花生根际土中富集了属于根瘤菌目(Rhizobiales)、梭菌目(Clostridiales)和芽孢杆菌目(Bacillales)这一类根际促生菌，根际细菌共存网络结构更加复杂，且网络中重要连接点的比例要也明显高于CK和NPK处理网络。可见，化肥配施有机肥有助于构建一个健康稳定的根际细...     

茅苍术间作对连作花生土壤线虫群落的影响

以连作10年花生的红壤为基质,分别设置花生单作和花生/茅苍术间作处理,于花生成熟期采集单作花生根际土壤、间作处理花生和茅苍术根际土壤,分析土壤线虫的数量、多样性和群落结构,以揭示茅苍术间作对土壤线虫群落的影响及对花生连作障碍的缓解机制。结果表明,与花生单作相比,间作处理花生的株高、主根长、秸秆干重和荚果干重显著增加(p0.05)。茅苍术间作减少了连作花生土壤线虫的总数,显著提高了花生根际土壤食细菌线虫、食真菌线虫和捕食/杂食线虫的相对丰度,降低了植物寄生线虫的相对丰度(p0.05)。与花生单作相比,间作提高了花生根际土壤线虫的Shannon-Wiener多样性指数(H′)和均匀度指数(J),而土壤线虫群落的优势度指数(λ)显著降低。间作处理花生根际土壤线虫的瓦斯乐斯卡指数(WI)和自由生活线虫成熟度指数(MI)显著升高,植物寄生线虫成熟度指数(PPI)显著降低,而线虫通道比(NCR)无显著变化。综合分析得出,茅苍术间作可以提高花生连作土壤线虫多样性、优化土壤线虫群落结构,进而增强有益线虫的生态功能、改善花生连作障碍。     

马铃薯连作栽培对土壤微生物多样性的影响

马铃薯是宁夏回族自治区南部山区重要的粮菜兼用作物,随栽培面积持续扩大,轮作倒茬困难,由此带来的连作障碍问题日渐突出。为探明马铃薯连作障碍机制,分别采集马铃薯正茬、连作1年、6年和10年的根际土壤样本,利用末端标记限制性片段长度多态性(terminal restriction fragment length polymorphism,T-RFLP)技术研究连作栽培对根际土壤微生物多样性的影响,以期揭示马铃薯根际土壤主要菌群动态变化规律及连作障碍的可能原因。结果表明:连作栽培后马铃薯土壤细菌和真菌DNA仍具有较高的T-RFLP多态性,但不同连作年限根际土壤中优势T-RFs片段发生变化,多年连作使某些T-RFs消失;随连作年限增加,根际土细菌Shannon-Wienen指数、Simpson指数和Sorenson指数下降,而真菌Shannon-Wienen指数和Simpson指数上升。菌群分析发现,土壤细菌中以厚壁菌门(Firmicutes)芽孢杆菌纲(Bacilli)和梭菌纲(Clostridia)所占比例最大。连作使细菌和真菌菌群发生变化,芽孢杆菌纲、鞘氨醇纲(Sphingobacteria)等比例下降甚至消失,β-变形菌纲(Beta proteobacteria)和异常球菌纲(Deinococci)比例上升;土壤真菌中座囊菌纲(Dothideomycetes)煤炱目(Capnodiales)随连作年限增加比例下降,粪壳菌纲(Sordariomycetes)肉座菌目(Hypocreales)随连作年限增加比例上升。马铃薯连作使根际土壤中芽孢杆菌属(Bacillus)等有益菌属的细菌减少,罗尔斯通菌属(Ralstonia)等致病菌属的细菌增加。连作导致马铃薯根际土壤细菌多样性水平降低,真菌多样性水平升高,根际土壤微生物多样性存在明显差异,连作破坏了根际土壤微生物群落的平衡,使其根际土壤微生态环境恶化。连作障碍可能是多因素综合互作用的结果,持续的研究有利于做出较合理的解释。     

连作对再植枸杞根际细菌群落多样性和群落结构的影响研究

受枸杞道地产区土地资源等因素限制,连作障碍已成为影响枸杞产业发展的重要原因之一,导致严重的经济损失.研究连作条件下枸杞农田土壤生态系统微生物群落的演替规律对枸杞产业的可持续发展具有重要的理论意义.以宁夏银川市南梁农场连作多年的枸杞地为研究对象,利用Illumina MiSeq测序技术分析了连作对再植枸杞根际/非根际细菌群落的影响.结果表明,连作地显著抑制再植枸杞苗地径的增加,且其土壤pH较对照样地显著降低(p<0.05).测序结果证实,与对照样地相比,连作地再植枸杞根际土壤细菌物种数显著降低(p<0.05),细菌群落α多样性下降(p>0.05).主坐标分析表明,连作和对照样地间枸杞非根际细菌群落结构无明显差异,但连作显著改变再植枸杞根际细菌的群落结构.对细菌群落丰度的统计分析发现,连作地枸杞根际浮霉菌门、非根际假单胞菌门的相对丰度较对照样地显著降低(p<0.05).此外,冗余分析结果表明:枸杞园土壤pH和有效磷含量是影响枸杞非根际土壤细菌群落结构变化的主要因素,分别解释了41.8%和35.4%的群落结构变化(p<0.05),其他土壤因子无统计学意义,但土壤理化因子对再植枸杞根际细菌群落结构变化的影响均未达显著水平.这些结果证实连作能够显著抑制再植枸杞生长、影响再植枸杞根际细菌群落结构和多样性,干扰枸杞与土壤细菌群落间的互作关系.这些研究结果将为解析枸杞连作障碍机制提供理论基础.     

低氮和干旱胁迫对富士和秦冠生长及氮素利用的影响

【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。     

Pasture Vegetation Elemental Analysis by Laser-Induced Breakdown Spectroscopy

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.     

Faculty positions:Center for Agricultural Resources Research,Chinese Academy of Sciences

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,     

Biodiversity and ecogeography of wild Lactuca spp. in some European countries

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.     

Macroinvertebrates in North American tallgrass prairie soils: effects of fire, mowing, and fertilization on density and biomass

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.     

Properties of anaerobically digested and composted municipal solid waste assessed by linking soil mesofauna dynamics and nitrogen modelling

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.     

Faculty positions: Center for Agricultural Resources Research,Chinese Academy of Sciences

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,     

Faculty positions: Center for Agricultural Resources Research,Chinese Academy of Sciences

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,     

Variation in quality parameters between and within 14 Nordic tree fruit and berry species

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.     

Potassium Fixation and Release Characteristics in Rhizosphere and Nonrhizosphere Soils for a Rapeseed–Rice Cropping Sequence

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.