豫东潮土区大蒜氮磷钾推荐施肥研究

通过大蒜氮肥用量和丰缺指标多点田间试验研究,采用Excel进行统计分析,建立不同氮肥用量与产量的效应函数,推荐大蒜氮肥用量369.9 kg/hm2;以土壤中速效磷、速效钾养分的测定值及其相对产量拟合回归方程,再以相对产量的55%、75%、80%、90%划分土壤养分丰缺指标,同时结合大蒜的目标产量,进行磷、钾施肥量的推荐,分别为200、300 kg/hm2。     

基于GIS和丰缺指标法的区域施肥管理体系的构建

  【目的】  采用GIS定位和养分丰缺指标相结合的方法,研究西辽河平原耕地土壤碱解氮、有效磷、速效钾的空间分布特点,建立直观、精准的推荐施肥系统。  【方法】  西辽河平原包括科尔沁区、开鲁县、奈曼旗、科尔沁左翼后旗、科尔沁左翼中旗。以该区域的15421个土壤测试数据和143个玉米“3414试验”数据为基础,运用GIS方法计算耕地土壤碱解氮、有效磷、速效钾的空间插值结果,结合土壤丰缺指标,将西辽河平原耕地土壤碱解氮、有效磷、速效钾养分分区,确定不同土壤氮磷钾养分组合下的施肥量,并制作玉米氮磷钾分区施肥图。  【结果】  西辽河平原耕地土壤养分空间分布不均,大部分土壤碱解氮含量较低,有效磷、速效钾含量中等。耕地土壤有效氮、磷、钾养分含量呈低氮–中磷–中钾 (碱解氮 ≤ 69.5 mg/kg、有效磷4.18～10.40 mg/kg、速效钾90.3～152.5 mg/kg)、中氮–中磷–中钾 (碱解氮69.5～107.9 mg/kg、有效磷4.18～10.40 mg/kg、速效钾90.3～152.5 mg/kg)、中氮–中磷–高钾 (碱解氮69.5～107.9 mg/kg、有效磷4.18～10.40 mg/kg、速效钾 > 152.5 mg/kg) 的面积占比分别为42.4%、14.1%、13.5%。土壤碱解氮、有效磷、速效钾含量 (x) 与经济最佳施肥量 (y) 之间存在较好的对数关系,氮施肥模型y = –102.5ln(x) + 617.22,磷施肥模型y = –36.11ln(x) + 174.1,钾施肥模型为y = –25.89ln(x) + 180.96。不同土壤养分组合种植玉米所需的经济最佳N–P₂O₅–K₂O用量 (kg/hm2) 组合分别为202–110–58、168–107–57、164–102–47。  【结论】  土壤碱解氮、有效磷、速效钾含量与相对产量存在较好的对数函数关系。西辽河灌区土壤有效氮磷钾丰缺指标的划分以75%和85%作为相对产量的分级区间较为合适。在土壤有效氮磷钾养分大数据的支撑下,采用GIS和丰缺指标法相结合的方法,可以准确快捷地构建区域施肥管理体系。     

黑龙江省典型黑土区玉米优化施肥——以双城为例

为明确黑龙江省玉米主产区土壤养分限制因子,充分发挥土壤及肥料的增产潜力,达到玉米的高产高效,通过双城市5年的田间小区对比试验,研究了玉米对不同肥料的产量响应及肥料效应。结果表明,不施氮磷钾锌硫肥均降低玉米产量,不施氮肥、不施磷肥、不施钾肥、不施锌肥、不施硫肥的各减素处理较推荐施肥处理平均减产分别为27.7%、18.4%、17.6%、7.8%和9.7%。氮磷钾合理配施显著提高玉米产量、养分吸收、农学效率和肥料利用率。与农民习惯施肥处理相比,优化施肥处理玉米平均增产12.6%,增加氮磷钾养分吸收量分别为13.4 kg·hm-2、9.0 kg·hm-2和12.4 kg·hm-2;增加氮磷钾农学效率分别为6.5 kg·kg-1、17.5 kg·kg-1、7.0 kg·kg-1;提高氮磷钾肥利用率分别为8.1%、13.4%和9.5%。影响双城市玉米产量的主要土壤养分限制因子是氮,其次是钾和磷,潜在因子是锌和硫。与优化施肥相比,该地区玉米生产农民习惯施肥中,氮施用量略有不足,磷肥用量过高,钾肥用量过低,生产中应适当增加钾肥用量,否则长期种植玉米易造成土壤钾素的亏缺。图3,表5,参20。     

基于养分专家系统的西北旱地冬小麦推荐施肥效应研究

  【目的】   本研究调查了养分专家系统 (Nutrient Expert, NE) 推荐施肥在西北旱地冬小麦生产上的应用效果,以明确该方法在西北旱地小麦推荐施肥中的可行性。   【方法】   在陕西渭北旱塬两年共布置15个田间试验,所有试验均设置两个处理:养分专家系统推荐施肥 (NE) 和农户习惯施肥 (FP)。在小麦成熟期采集小麦样品和0—100 cm土层土壤样品,测定植株氮磷钾养分含量和土壤硝态氮含量,调查分析小麦产量及其构成要素、经济效益和肥料偏生产力。   【结果】   NE推荐的N施用量平均为158 kg/hm2,较FP处理 (N 192 kg/hm2) 减少了18%;P₂O₅施用量平均为62 kg/hm2,较FP处理 (134 kg/hm2) 减少了54%;而K₂O用量为40 kg/hm2,较FP处理 (28 kg/hm2) 增加了43%。NE处理的冬小麦平均籽粒产量为5171 kg/hm2,与FP处理 (5111 kg/hm2) 籽粒产量接近,经济效益提高了7.8%,氮肥偏生产力提高25.1%,磷肥偏生产力提高了139.8%。与FP相比,NE处理的土壤0—100 cm土层硝态氮残留量无显著差异。   【结论】   相比农户习惯施肥,基于养分专家系统推荐的施肥方案减少了18%的氮肥和54%的磷肥用量,增加了43%的钾肥用量,冬小麦产量保持稳定,氮肥和磷肥的偏生产力和经济效益均显著提升,具有较好的化肥减施和增收效果,可在旱地冬小麦生产中推广应用。     

近14年北方冬小麦肥料产量效应变化及优化施肥方案

  【目的】  通过分析近14年来北方冬小麦肥料产量效应的多点试验数据,明确北方冬小麦产量变化特征及肥料产量效应,为该区冬小麦养分管理和合理施肥提供科学依据。  【方法】  通过我国北方冬小麦区2002—2016年96个定位监测试验,研究小麦地力产量和肥料农学效率变化趋势;通过120个田间肥料效应的检验试验,研究不同时段和不同施肥水平时氮、磷、钾在冬小麦上的产量效应;以肥料农学效率变化和施肥产量效应为依据,通过24个田间试验对习惯施用的复合肥配方进行田间校验,提出相应的节肥增效建议。  【结果】  1) 2002—2016年间,北方冬小麦区的土壤供肥能力呈逐渐增加的趋势,其平均地力产量自2002年的4721 kg/hm2增加到2016年的5828 kg/hm2,年均增加1.6%。施肥能显著增加小麦产量,但施肥增产率从2005年后呈下降趋势,由2005年的30.9%下降至2016年的20.2%。2) 2002—2016年,肥料的农学效率呈下降趋势,由2002年的9.0 kg/kg下降至2010年的6.7 kg/kg,2010年后维持在6.3～6.7 kg/kg。3) 基于不同时段氮、磷、钾在冬小麦上的产量效应函数计算出经济施肥量,其中2002—2006年间,最高产量的N、P₂O₅、K₂O施用量分别为180.5、107.4、55.9 kg/hm2;经济最佳用量分别为167.8、102.5、53.7 kg/hm2;经济合理用量 (R = 0.1) 分别为155.5、99.9、52.8 kg/hm2;2012—2016年间,最高产量的N、P₂O₅、K₂O施用量分别为184.3、125.1、52.4 kg/hm2;经济最佳用量分别为171.7、118.5、48.6 kg/hm2;经济合理用量分别为159.2、114.9、47.0 kg/hm2;优化复合肥N–P₂O₅–K₂O配方为16–20–8,比常规原配方减少氮磷钾总用量的12.0%。  【结论】  从2002年到2016年,北方冬小麦区土壤地力产量逐渐提高,虽然施肥仍有显著增产效果,但增产率和农学效率呈逐渐降低的趋势,2016年施肥增产率为20.2%,肥料农学效率维持在6.5 kg/kg。北方冬小麦N–P₂O₅–K₂O优化配方为16–20–8,推荐施肥方案为:基肥该配方肥600 kg/hm2,追施氮69 kg/hm2。     

基于GIS和测土配方数据的晋北县域春玉米专用肥配方筛选

为改善当前施肥过高或过低等问题,促进区域合理施肥,该研究依据测土配方施肥项目田间试验数据和土样分析数据,以应县为研究区域,遵循"氮肥总量控制,分期调控及磷、钾恒量监控"的技术原理,利用地理信息系统(geographic information system,GIS)技术开展县域春玉米专用肥配方筛选研究。采用肥料效应函数法对测土配方施肥项目田间试验数据进行模拟分析,确定研究区域平均适宜施氮用量为200 kg/hm2,其中80 kg/hm2氮素作为播种前基肥,120 kg/hm2作为大喇叭口期追肥。综合利用养分丰缺指标法、肥料效应函数法建立磷、钾养分丰缺指标及磷、钾肥的推荐施肥指标体系。基于GIS技术形成区域土壤养分分布图、氮磷钾养分推荐用量图,制定区域氮磷钾养分配方图,并筛选出适合县域推广的春玉米专用肥大配方。结果表明,应县氮磷钾养分空间变异特征明显,形成的11个专用肥配方经筛选后最优春玉米专用肥配方为20-17-8(为专用肥氮磷钾养分含量比例,即N-P2O5-K2O,专用肥总养分45%)、17-19-9和21-12-12。该研究将GIS技术和测土配方施肥技术有机结合,促进了测土配方施肥项目结果推广应用,为县域春玉米养分资源高效利用提供了参考。     

福建甘薯氮磷钾施肥指标研究

根据近年来在甘薯主产区完成的118个氮磷钾肥效田间试验结果,建立甘薯氮磷钾施肥指标体系,包括甘薯施肥效应和土壤肥力分级、土壤速效氮磷钾丰缺指标、不同产量水平的氮磷钾最佳用量和比例、土测值与最佳施肥量关系式以及施肥时期和施肥方法等5个方面内容。结果表明,土壤对甘薯产量的平均贡献率为62.5%,氮磷钾平均增产效果是N>K>P,均达显著水平;土壤碱解氮、Olsen-P和速效钾的高产临界指标分别为176 mg kg-1、17 mg kg-1和106 mg kg-1;平均经济施肥量是N165kg hm-2、P2O5 63 kg hm-2、K2O 204 kg hm-2,比例为1∶0.38∶1.24,但不同土壤肥力等级的推荐施肥量存在较大差异;土壤速效氮磷钾土测值与最佳施肥量之间满足指数模型,该式实现了根据土测值预测具体地块推荐施肥量的目的。研究结果为福建甘薯高效施肥提供了科学依据。     

潮土区麦田土壤有效磷施肥指标及小麦施磷推荐-基于ASI法的土壤养分丰缺指标

运用ASI法测定的潮土区小麦土壤有效磷含量分别与不施磷小麦相对产量呈显著正相关关系。根据小麦相对产量<50%,50%～65%,65%～75%,75%～95%和>95%对应的土壤有效磷指标,可以得出潮土区土壤有效磷"极低"指标为<7 mg/L,"低"指标为7～12 mg/L,"中"指标为12～18 mg/L,"较高"指标为18～38mg/L,"高"指标为>38 mg/L。据此建立的麦田土壤养分丰缺指标推荐施磷量:土壤有效磷含量小于7 mg/L,推荐磷肥用量为135 kg/hm2;土壤有效磷含量在7～12 mg/L之间时,磷肥用量推荐为105 kg/hm2;土壤有效磷含量在12～18 mg/L之间时,磷肥用量推荐为90 kg/hm2;土壤有效磷含量在18～38 mg/L之间时,磷肥用量推荐为60 kg/hm2;土壤有效磷含量大于38 mg/L,建议不施或者少施磷肥。     

甘肃中部灌区春小麦土壤氮磷钾 养分丰缺指标及施肥指标研究

在甘肃中部引黄灌区及井灌区连续多年多点对春小麦氮磷钾土壤养分丰缺指标开展田间试验研究,建立本地灌区春小麦土壤有效养分与缺素区相对产量及氮磷钾最佳施肥量之间的函数模型,确定土壤氮、磷、钾养分丰缺指标和推荐施肥指标。结果表明:现阶段当地灌区小麦相对产量50%(极低)、50%～60%(低)、60%～70%(较低)、70%～80%(中)、80%～90%(较高)、90%(高)6个肥力等级的土壤氮、磷、钾养分丰缺指标划分为全氮0.35、0.35～0.5、0.5～0.8、0.8～1.3、1.3～2.0、2.0 g/kg;有效磷(P)5、5～10、10～15、15～25、25～45、45 mg/kg;速效钾(K)65、65～90、90～130、130～185、185～265、265mg/kg。在正常年份降水及灌溉条件下,对应推荐施N量分别为285、255～285、235～255、200～235、170～200、170 kg/hm~2,施P_2O_5量分别为140、110～140、95～110、85～95、65～85、65 kg/hm2;施K2O量分别为70、65～70、45～65、35～45、25～35、25 kg/hm2。试验研究表明,当地灌区土壤氮素养分仍处于低水平;磷素养分处于中等水平;而钾素养分与以往相比有所下降,但依然处于中等较丰富水平。生产中春小麦应当合理增施氮肥,适度施用磷肥,适当增施钾肥。     

湘南地区杂交早稻施肥技术指标体系研究

选择自然环境条件基本相同的区域,建立作物施肥指标体系是测土配方施肥的重要研究课题。基于此,全面分析了"3414"试验中的基础地力产量、目标产量、肥料当季利用率、土壤养分校正系数及磷钾丰缺指标等测土配方施肥技术参数,并利用推荐施肥模型求得最佳产量与最佳施肥量,按照目标产量定氮、丰缺指标定磷钾的基本思路,建立不同肥力等级、不同产量水平条件下氮肥推荐用量检索表和不同土壤有效磷、速效钾丰缺级别下的磷、钾肥推荐用量检索表,进一步丰富和完善了湘南地区早稻施肥指标体系,并为农民、规模种植主体及基层农技推广者提供了技术支撑。     

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.