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1.
不同种植年限覆膜滴灌盐碱地土壤盐分离子分布特征   总被引:33,自引:11,他引:22  
为了研究长期覆膜滴灌对土壤化学性质的影响,该文通过时空转化的方法研究了覆膜滴灌种植春玉米1a和2a的盐碱地土壤盐分及盐分离子在0~150 cm土壤削面上的分布特征,同时以试验地附近未种植的盐碱荒地作为对照.结果表明,覆膜滴灌条件下,当滴头下方20 cm处土壤基质势为-10 kPa时,0~40 cm土层土壤盐分含量、各种盐分离子含量、土壤pH值、Cl-/SO24和钠吸附比(SAR)随滴灌种植年限增加向降低.这表明根区土壤环境随种植年限增加逐渐变好,有利于作物生长.与盐碱荒地相比,滴灌种植以后40 cm以下土层Cl-含量、Na 含量、Cl-/SO24、钠吸附比(SAR)均增加了.  相似文献   

2.
窦超银  康跃虎 《土壤》2010,42(4):630-638
采用时空替代的研究方法,研究地下水浅埋区重度盐碱地不同滴灌种植年限(0、1、2、3年)对土壤盐分及不同盐分离子分布的影响,旨在为采用覆膜滴灌技术进行盐碱地改良提供理论依据。试验结果表明滴灌种植枸杞第1年,土壤盐分变化主要为自上而下被淋洗,种植2年和3年土壤年内盐分含量和分布变化相似,盐分主要分布在土壤表层,且在枸杞生育期结束时,剖面土壤含盐量都低于年初水平;土壤溶液电导率(EC1:5)与主要离子之间都具有极显著的相关关系,其中Cl-和Na+与EC1:5关系最为紧密;HCO3-与EC1:5负相关,相关性随着种植年限的增加而减小;Cl-、Mg2+、Ca2+、Na+在盐分组成中的荷载随种植年限增加而增大;回归分析表明Cl-和EC1:5之间具有线性关系,SO42-与EC1:5之间具有对数关系,EC1:5可以通过Cl-和SO42-表达;利用咸水覆膜滴灌并没有根本改变土壤类型,但在距滴头水平距离0~30cm范围内土壤含盐量从13.1g/kg降低到4~6g/kg,由盐土脱盐演化为重度盐化土。因此,采用覆膜滴灌技术明显降低了作物根区盐分含量,改善了作物根系生长的土壤环境条件。  相似文献   

3.
通过田间试验研究覆膜滴灌条件下不同灌溉制度对土壤盐分分布的影响。试验通过控制滴头正下方20 cm处的土壤基质势下限进行灌溉,共设5个水平的土壤基质势处理:-5 kPa(S1)、-10 kPa(S2)、-15 kPa(S3)、-20 kPa(S4)和-25kPa(S5),每个处理重复3次,按随机区组布置。结果表明:不同土壤基质势控制对盐渍土中盐分分布有显著影响,不同土壤盐分离子的分布各不相同。其中Na+与Cl-容易被淋洗,两个生长季后,各处理土壤中Na+与Cl-含量有显著降低,并且土壤基质势控制越高淋洗效果越好。SO42-与HCO3-的淋洗效果主要受离子浓度影响,第一年淋洗效果较第二年明显。Mg2+与Ca2+不易随水移动,各处理无明显差异。经过两个生长季的灌溉淋洗,各处理土壤SAR值与全盐含量均有显著降低,根区内SAR值与全盐含量的降低幅度均在50%以上。研究结果对内陆干旱区盐碱地水盐调控和灌溉制度的制定具有理论意义和应用价值。  相似文献   

4.
苏打碱化土壤盐分离子与相关性分析   总被引:1,自引:0,他引:1  
选取典型苏打碱化土壤剖面,分析了0~200cm深度主要盐分离子(Ca2+、Mg2+、Na+、K+、CO32-、HCO3-、Cl-和SO42-)的垂直分布规律。对各离子之间的相关性进行了统计分析。结果表明,测试土样离子以Na+和HCO3-离子为主,其剖面分布规律是表层含量较低,在80cm左右逐渐增至最大值,其后离子含量随深度而降低,至160cm以下则又随深度而增加,即在整个土壤剖面上大致呈倒"S"曲线分布。CO32-、HCO3-、Cl-与Na+,CO32-、HCO3-与Cl-之间均是相关系数大于0.80的极显著相关;除K+离子外,其它7个离子间均具有显著相关性,这表明该苏打碱化土壤盐分离子组成具有复杂性的特点。  相似文献   

5.
不同能源作物对土壤剖面盐分离子迁移的影响   总被引:1,自引:0,他引:1  
为了筛选耐盐能源作物、挖掘利用盐渍土资源、促进农业可持续发展。以甘肃白银市东大沟盐渍化土壤作为研究对象,在大田试验条件采用对比研究的方法探讨种植四翅滨藜(Atriplex canescens)、油菜籽(Brassica napus)、甜高粱(Sorghum bicolor(L.)Moench)、荻(Triarrherca sacchariflora)、柳枝稷(Panicum virgatum)5种不同能源作物对土壤剖面盐分及其离子(HCO3-、Cl-、SO42-、K+、Na+、Ca2+、Mg2+)迁移的影响。结果表明:在盐渍化土壤,种植柳枝稷、四翅滨藜能明显减少土壤剖面0—100cm土层盐分、Cl-、Na+、Ca2+、Mg2+的含量,脱盐的同时会导致HCO3-在土壤剖面0—100cm土层累积。种植油菜可以抑制0—50cm土层盐分的累积。种植荻可以抑制50—100cm土层盐分、0—100cm土层HCO3-、60—100cm土层SO42-的累积。种植柳枝稷可明显减少土壤剖面0—100cm土层K+的含量。研究发现四翅滨藜、柳枝稷两处理的电导率均与其他处理之间达显著水平(P0.05),荻与其他处理之间水溶性Na+含量均达显著水平(P0.05),柳枝稷与其他处理之间HCO3-含量均达极显著水平(P0.01)。  相似文献   

6.
黄河三角洲土壤盐渍化与地下水特征关系研究   总被引:14,自引:0,他引:14  
为研究黄河三角洲表层土壤盐分含量与地下水特征的关系,对研究区内土壤盐分含量及地下水进行原位监测,分析土壤盐渍化和地下水特征,并运用灰色关联分析法对地下水埋深、电导率、p H和主要离子含量的关系进行定量分析。结果表明:土壤表层盐分含量均值为3.90~6.31 g kg-1,表层以下土壤盐分含量均值为2.54~3.44 g kg-1,属于中度及以上盐渍化程度;地下水埋深平均值为1.16~1.71 m,普遍较浅;地下水阴离子以Cl-为主,阳离子以Na+为主,两者分别占阴、阳离子总量的比例约为65%。关联分析表明,不同地下水特征指标与土壤表层盐分含量的密切程度不同,同一特征指标与土壤表层盐分含量的密切程度在不同时期间差异显著,总体而言,土壤表层积盐与地下水电导率、Na+、Cl-的关系较为密切,与p H、CO32-和HCO3-之间的关系较弱。在防治土壤盐渍化中,应当加强对地下水电导率、Na+、Cl-的控制与管理。  相似文献   

7.
基于高光谱特征的盐渍化土壤不同土层盐分离子含量预测   总被引:5,自引:3,他引:2  
为了利用高光谱技术准确预测不同土层土壤盐渍化程度,该研究以宁夏银北地区不同层次土壤为研究对象,以土壤实测光谱数据和室内盐渍化指标测定数据为基本信息源,系统分析不同类型盐渍化土壤光谱特征,确定与土壤pH值、电导率(electricconductivity,EC)和可溶性盐分离子相关性最强的反射率转换方式,筛选0~5 cm和0~20 cm土层盐分指标敏感波段,然后建立并验证不同土层不同土壤盐分指标的预测模型。结果表明:研究区不同类型、不同盐渍化程度土壤光谱特征曲线变化趋势相似,盐土光谱反射率最高,轻度硫酸盐型土壤反射率最低。在所有盐分指标中,单波段反射率与0~5 cm土壤SO42-的相关性最强(相关系数为0.910 4);反射率与CO32-、HCO3-、Cl-含量相关性不显著。土壤单波段反射率与0~20 cm土层SO42-的平均相关系数比0~5 cm土层降低了0.232 2,但Cl-、K+、HCO3-和EC的相关系数都有所增大。反射率通过不同方式转换后,敏感波段与各盐分的相关性有不同程度的增强,尤其是一阶微分和连续统去除后一阶微分转换。在0~5 cm土层反射率经过平滑后一阶微分转换后与土壤pH值、SO42-、K+、Mg2+相关性最强;反射率经平滑后连续统去除一阶微分转换与土壤EC、CO32-、HCO3-、Cl-、Na+、Ca2+的相关性最强。0~20 cm土层中,平滑后连续统去除一阶微分与土壤pH值、Cl-相关性最强,平滑后倒数对数一阶微分与EC、HCO3-、SO42-、Na+、Ca2+的相关性最强,而平滑后一阶微分与CO32-、K+、Mg2+相关性最强。不同土层相同盐分指标敏感波段不同。利用偏最小二乘回归建立的预测模型中,0~5 cm和0~20 cm敏感波段对10个盐分指标预测平均决定系数分别为0.820 8和0.890 7,其中0~5 cm敏感波段对SO42-的预测模型决定系数达0.967 6。采用逐步回归与偏最小二乘回归相比模型引入敏感波段减少,但R2降低。验证结果表明模型对0~20 cm土层SO42-和CO32-的预测能力不及0~5 cm;但对其他8个盐分离子的预测能力明显高于0~5 cm。研究结果可以为该地区土壤的盐渍化信息预测及植物格局配置提供科学依据。  相似文献   

8.
伊犁河流域土壤盐分与地下水关系的关联分析   总被引:1,自引:0,他引:1  
《土壤通报》2013,(3):561-566
根据2009年伊犁河流域土壤盐分与地下水条件的监测和取样分析资料,运用灰色关联分析法,对伊犁河流域3月、6月、9月与11月的土壤盐分与地下水埋深、矿化度、电导率、pH值与主要离子进行了关联分析。分析研究表明:研究区表层土壤盐分平均含量为1.37 g kg-1,属于轻度盐渍化土壤。地下水矿化度平均值为2.50 g L-1,属于微咸水。在关联排序中,地下水埋深、矿化度、电导率、SO42-、Cl-、Mg2+、Na+与土壤盐分变化的关联性较强;地下水pH、K+与Ca2+与土壤盐分变化的关联度低,均小于0.321;地下水Mg2+含量与土壤盐分关联度最高,为0.606。灌溉对地下水pH、矿化度、电导率、Mg2+、Cl-离子变化的影响不大,而对地下水埋深、Na+、SO42-、K+与Ca2+离子变化的影响较明显。为了防止土壤次生盐渍化,应该加强对地下水中Mg2+、Na+与Cl-离子的控制与管理。  相似文献   

9.
芦苇对盐碱地盐分富集及改良效应的影响   总被引:5,自引:0,他引:5  
利用自制模拟试验装置研究芦苇不同生长阶段内盐碱土pH、电导率、离子(Ca2+、Mg2+、SO24-、CO23-、HCO3-、Na+、Cl-)含量的变化和芦苇含盐量的变化,以及芦苇生长阶段过后腐烂成腐殖质对盐碱土pH、电导率、有机质含量的影响,揭示了处于生长阶段的芦苇具有富集盐分的能力以及生长阶段过后的芦苇腐烂成腐殖质对盐碱土具有改良作用。结果表明:(1)在芦苇不同生长阶段内盐碱土pH和电导率都呈现降低趋势。土壤pH平均值由9.22降低到8.79;电导率平均值由0.96mS/cm降低到0.43mS/cm。芦苇成熟期-枯黄期,土壤电导率降低趋势平缓,基本达到稳定状态。(2)在芦苇各生长阶段土壤离子含量都缓慢降低,其中HCO3-、Cl-、SO24-、Ca2+含量变化幅度比较大。成熟期-枯黄期,土壤各离子含量降低趋势平缓,基本达到稳定状态。(3)不同生长阶段芦苇吸收盐分是不同的。展叶期-成熟期,芦苇吸收盐分量逐渐增加,成熟期达到最大值。但成熟期-枯黄期,芦苇吸收盐分逐渐减少,说明芦苇富集盐分的能力主要集中在展叶期-成熟期阶段,而成熟期-枯黄期,富集盐分的能力减弱;在不同生长阶段,芦苇的根、茎含盐量缓慢增长,叶含盐量增长速度较快,且叶含盐量比根、茎大。(4)芦苇生长阶段过后腐烂成腐殖质,通过9次取土样分析表明腐殖质能够提高土壤有机质含量。且对土壤pH、电导率也起到了降低的效果。总之,生长阶段芦苇对盐碱土盐分降低具有显著作用,同时生长阶段过后芦苇枯萎腐烂成腐殖质对盐碱土盐分降低和有机质含量提高也同样具有一定的效果。  相似文献   

10.
半干旱盐渍化地区果园土壤盐分离子相关性研究   总被引:9,自引:2,他引:7  
郭全恩  王益权  郭天文  刘军  南丽丽 《土壤》2009,41(4):664-669
以甘肃省秦安县兴国镇郑川村果园土壤为研究对象,利用统计分析的方法对500个土样盐分离子含量的相关性进行了研究.结果表明:该研究区土壤阴离子主要是HCO3-、SO42-,阳离子主要是Na+.CO32- 与HCO3-、Mg2+ 之间存在着显著的负相关,与Na+ 之间存在着极显著的正相关;HCO3- 与Cl- 之间存在着极显著的负相关,与Mg2+ 之间存在着极显著的正相关;Cl- 与SO42-、Ca2+、Mg2+、Na+ 之间存在着显著的正相关,其中与Ca2+、Na+ 之间存在着极显著的正相关;SO42- 与Ca2+、Mg2+、Na+ 之间存在着极显著的正相关;Ca2+ 与K+ 之间存在着极显著的正相关,与Na+ 之间存在着显著的负相关;Mg2+ 与K+ 之间存在着显著的负相关;K+ 与Na+ 之间存在着极显著的负相关.通过对盐分离子的聚类分析发现,Cl-、Mg2+、CO32-、Ca2+、K+ 和HCO3- 在该区土壤中有着相似或相近的运移特征.对相关分析和偏相关分析这两种分析方法所得结果进行了对比分析,它们之间存在着明显的差异,偏相关分析能进一步消除由于其他变量的影响,因而能够更加准确地刻化多元变量其中的两个变量之间的相关性.  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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