北方耕地和蔬菜保护地土壤磷素状况研究

以北方一般耕地和蔬菜保护地为供试土壤 ,研究了不同种植条件下土壤磷素状况 ,蔬菜保护地土壤磷素的空间分布特性。结果表明 ,蔬菜保护地土壤全磷、无机磷、有机磷、Olsen-P的平均含量是一般耕地土壤的 2.7～14.0倍 ,土壤Olsen P占全磷的比率 ,Ca₂-P ,Ca₈-P ,Al-P占土壤无机磷的比率显著高于一般耕地土壤。蔬菜保护地土壤各形态磷素主要积累在 0～20cm土层 ,并随土层深度的增加各形态磷素的含量逐渐降低 ,各土层Olsen-P ,Ca₂-P ,Ca₈-P ,Al-P含量降低幅度明显高于Fe-P ,O-P ,Ca₁₀-P含量的降低值     

不同磷源对设施菜田土壤速效磷及其淋溶阈值的影响

土壤中磷的移动性不仅取决于磷的数量且与磷肥形态有关。了解不同磷源（有机肥和化肥）对设施菜田土壤磷素的影响对于指导科学施肥和面源污染防治至关重要。本文选取河北省饶阳县3种不同磷含量的农田土壤（未种植过蔬菜的土壤、种植蔬菜30年的塑料大棚土壤和种植蔬菜4年的日光温室土壤）为研究对象,采用室内培养试验和数学模型模拟方法研究有机无机磷源对设施菜田土壤磷素的影响,确定无机肥和有机肥源土壤磷素淋溶的环境阈值。结果表明添加有机肥和无机磷肥都会显著增加3种不同种植年限设施菜田土壤速效磷（Olsen-P）和氯化钙磷（CaCl₂-P）含量,但增加速度不同。对于未种植过蔬菜的低磷对照土壤,磷投入量高于50 mg·kg^-1（干土）后,无机肥比有机肥显著提高了土壤Olsen-P含量。对于已种植蔬菜30年的塑料大棚土壤,高磷投入时[300 mg·kg^-1（干土）和600 mg·kg^-1（干土）],无机肥比有机肥显著提高了土壤Olsen-P含量,低于此磷投入量时有机肥和无机肥处理之间没有显著差异。3种不同农田土壤CaCl₂-P的含量所有处理均表现出无机肥显著高于有机肥处理,尤其是在高磷量[>300 mg·kg^-1（干土）]投入时表现更加明显。两段式线性模拟结果表明,设施菜田土壤有机肥源磷素和无机肥源磷素淋溶阈值分别为87.8 mg·kg^-1和198.7 mg·kg^-1。随着土壤Olsen-P的增加,添加无机肥源磷对设施菜田土壤CaCl₂-P含量的增加速率是有机肥源磷的两倍。因此,建议在河北省高磷设施菜田应减少无机磷肥的投入,特别是土壤速效磷高于198.7 mg·kg^-1的设施菜田应禁止使用化学磷肥和有机肥,在土壤速效磷低于198.7 mg·kg^-1的设施菜田应加大有机肥适度替代无机肥技术的推广。     

石灰性土壤无机磷的形态分布及其有效性

本文应用蒋柏藩和顾益初(1989)提出的石灰性土壤无机磷的分级方法,对我国北方主要的石灰性土类进行了无机磷形态分级的研究,并对其有效性作出了初步评价。供试的甘肃、陕西和河南的16种土壤的无机磷形态的分布情况为:Ca₂-P平均占无机磷总量的1.34%,Ca-P占9.91%,Al-P占4.27%,Fe-P占4.40%,O-P占10.9%,Ca₁₀-P占69.1%。生物试验的结果表明:Ca₂-P型的磷酸盐是最有效的,也是作物磷素营养的主要来源;Ca₈-P、Al-P和Fe-P可以作为缓效磷源;Ca₁₀-P和O-P只是一种潜在磷源。本研究为石灰性土壤无机磷的研究和磷肥的合理施用提供了理论依据。     

种植年限对设施菜田土壤剖面磷素累积特征的影响

以山东寿光集约化设施菜田为研究对象,分析了不同种植年限设施菜田土壤磷素投入和土壤磷素累积的差异,比较不同种植年限土壤剖面中无机磷、有机磷、Olsen-P和CaCl2-P含量的变化特征。结果表明：磷素过量积累是设施菜田的显著特征,主要由于有机肥以粪肥投入为主,复合肥中P素比例偏高,收获作物带走量仅占磷素投入的7.2%;随着种植年限增加,P素累积现象明显,过量的磷素盈余导致了土壤剖面中不同形态磷含量的上升,其中以无机磷尤其明显;用来表征土壤有效磷指标的Olsen-P与CaCl2-P有显著的相关性,研究区域中当土壤（Olsen-P）达到80.7mg·kg-1时,土壤CaCl2-P开始显著升高,增大了设施菜田磷素淋溶风险。     

不同种植年限黑土型蔬菜保护地磷素状况的研究

采用石灰性土壤无机磷形态分级方法,对不同种植年限的蔬菜保护地0～60cm土层土壤磷素形态及其含量特征与差异进行了研究.结果表明:哈尔滨市蔬菜保护地土壤磷素处于大量积累状态,其中全磷、速效磷、有机磷、Ca2-P、Ca8-P、Al-P、Fe-P、O-P、Ca10-P在0~20era土层积累较多,且随土层深度的增加各形态磷的...     

不同年限温室土壤磷素变化分析

温室大量施肥引起土壤磷素水平极高,为明确温室土壤磷素变化特点,以露地土壤为CK,选择种植模式相近、种植年限不同的温室土壤,通过相关分析和通径分析,阐明各形态磷素变化特点及其与有效磷的关系。结果表明:土壤各形态磷素均随种植年限的延长而增加,以Ca_8-P和Ca_(10)-P的含量最高。各年限温室土壤Ca_2-P、Ca_8-P和Al-P均显著高于露地CK,第10年和第14年无显著差异;温室土壤Ca_(10)-P和O-P只在第14年时与CK有显著差异。同年限温室间的极差随年限延长而逐渐加大。温室土壤有效磷、全磷和无机磷总量均显著高于CK,有效磷第10年最高达420.00 mg kg~(-1),无机磷占全磷的百分比保持相对稳定。相关分析和通径分析表明,Ca_2-P和Ca_8-P对土壤有效磷的直接影响和综合影响均呈正相关,而A1-P和Fe-P对有效磷综合影响呈正相关,但直接影响为负相关,这可能与温室土壤p H降低使Fe和Al大量溶解而和磷发生沉淀反应有关。     

北方耕地和蔬菜保护地土壤磷素状况研究

以北方一般耕地和蔬菜保护地为供试土壤 ,研究了不同种植条件下土壤磷素状况 ,蔬菜保护地土壤磷素的空间分布特性。结果表明 ,蔬菜保护地土壤全磷、无机磷、有机磷、Olsen-P的平均含量是一般耕地土壤的 2.7～14.0倍 ,土壤Olsen P占全磷的比率 ,Ca2-P ,Ca8-P ,Al-P占土壤无机磷的比率显著高于一般耕地土壤。蔬菜保护地土壤各形态磷素主要积累在 0～20cm土层 ,并随土层深度的增加各形态磷素的含量逐渐降低 ,各土层Olsen-P ,Ca2-P ,Ca8-P ,Al-P含量降低幅度明显高于Fe-P ,O-P ,Ca10-P含量的降低值     

制种玉米连作恒量施磷对灌漠土与潮土中磷素利用的影响

[目的]研究恒量外源磷施用对玉米种子生产的影响,为合理施磷提供依据。[方法]通过大田定位与实验室分析相结合,选用河西走廊石灰性潮土及灌漠土定位施肥。[结果]制种玉米连作8a,恒量磷二铵525kg/(hm^2·a)施用,除无机态二钙磷(Ca_2-P)外,2种不同土类总磷(T-P)、速效性磷(Av-P)、总无机磷(T-IP)、总有机磷(T-OP),以及其他各分级无机、有机磷组分均显著增加。无机磷占全磷总量65.2%~70.2%,有机磷占全磷总量6.5%~11.4%。无机磷中十钙磷(Ca₁₀-P)>八钙磷(Ca8-P)>铝磷(Al-P)>铁磷(Fe-P)>闭蓄态磷(O-P)。有机磷中活性有机磷(MLO-P)>高稳性(HRO-P)>中稳性有机磷(MROP)>活性有机磷(LO-P)。随连作年限增加,灌漠土Ca₁₀-P在连作第5a达到最大,Al-P,O-P均持续增加;潮土Ca₁₀-P持续增加,Fe-P,O-P在连作第5a达到最大,磷增加量为3.94%~37.28%。0—60cm土层,两种土类无机磷各组分含量均呈现由表层至下层递减特点,但不同分级磷在不同土层所占比例不同,Ca₁₀-P,Al-P,O-P,MRO-P底聚,Ca_2-P,HRO-P表聚,制种玉米连作生产8a,磷肥最大表观利用率为4.89%,磷素活化系数<2%,外源磷肥以174.3kg/(hm^2·a)残余在土壤中。[结论]制种玉米连作,总磷转化率低,磷素移动缓慢,大部分以溶解性较低的磷素形态在土壤表层积累,但随连作年限增加,土壤对磷素的固持及转化率下降,表现底聚趋势,对生态环境健康存在极大风险,应减量或停止施磷。潮土磷肥施用应采取更加合理措施。     

不同温室蔬菜种植模式下土壤磷素形态分布与转化

采用蒋柏藩-顾益初无机磷分级浸提法,研究了15a长期有机、综合和常规种植3种温室蔬菜生产体系下石灰性土壤磷形态分布及转化特征。结果表明:种植模式及施肥年限对土壤有机磷含量和各形态无机磷含量均有显著影响,且交互作用显著。随着施肥时间延长,3种种植模式土壤有机磷含量与无机磷形态Ca_2-P、Ca_8-P、Fe-P含量不断升高,Al-P、O-P、Ca_(10)-P含量呈现不规则变动,差异较小;有机模式土壤有机磷含量与无机磷形态Ca_2-P、Ca_8-P、Fe-P含量均高于常规和综合模式,O-P、Ca_(10)-P含量略小于常规和综合模式。在各磷素占比中,中等活性磷源(Ca_8-P、Fe-P、Al-P)潜在磷源(O-P、Ca10-P)有效磷源(Ca_2-P)。表层土中有机磷占全磷的8%～23%,亚表层土中有机磷占全磷的6%～13%。有机模式促进了无机磷各形态之间、有机磷和无机磷形态之间的转化过程,0～20 cm土层的磷素转化比20～40 cm更活跃。     

石灰性土壤无机磷有效性的研究

本文概要地介绍了作者推荐的关于石灰性土壤无机磷分级体系的建立依据,并将该分级体系中的Ca₂-P、Ca₈-P和Ca₁₀-P与张守敬的土壤无机磷分级体系进行了比较。根据对土壤中无机磷形态的分析,以及系列的生物试验结果,对石灰性土壤中不同形态无机磷的有效性进行了初步评价。     

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,     

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.     

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.     

Electron donor and pH relationships for biologically enhanced dissolution of chlorinated solvent DNAPL in groundwater

Biologically enhanced dissolution offers a method to speed removal of chlorinated solvent dense non-aqueous-phase liquid (DNAPL) sources such as tetrachloroethene (PCE) and trichoroethene (TCE) from aquifers. Bioremediation is accomplished by adding an electron donor to the source zone where fermentation to intermediates leading to acetic acid and hydrogen results. The hydrogen and possibly acetic acid are used by dehalogenating bacteria to convert PCE and TCE to ethene and hydrochloric acid. Reductive dehalogenation is thus an acid forming process, and sufficient alkalinity must be present to maintain a near neutral pH. The bicarbonate alkalinity required to maintain pH above 6.5 is a function of the electron donor: 800 mg/L of bicarbonate alkalinity is sufficient to achieve about 1.2 mM TCE dechlorination with glucose, 1.7 mM with lactate, and a much higher 3.3 mM with formate. Laboratory studies indicate that in mixed culture, formate can be used as an electron donor for complete conversion to ethene, contrary to pure cultures studies indicating it cannot. Various strategies can be used to add electron donor to an aquifer for DNAPL dehalogenation while minimizing pH problems and excessive electron donor usage, including use of injection-extraction wells, dual recirculation wells, and nested injection-extraction wells.     

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.     

Increase in auxiliary photoprotective photosynthetic pigments in wheat seedlings induced by Azospirillum brasilense

Inoculation of wheat seedlings with the plant growth-promoting bacterium Azospirillum brasilense Cd was immobilized in alginate microbeads and, without applying any stress, significantly increased the quantity of several photosynthetic pigments, such as chlorophyll a, chlorophyll b, and the auxiliary photoprotective pigments violaxanthin, zeaxanthin, antheroxanthin, lutein, neoxanthin, and β-carotene. This resulted in greener plants with no apparent visible stress. After monitoring the quantity of photosynthetic pigments for 4 weeks, we observed that inoculated plants had higher quantities of pigments in shoot and stem. The greatest difference in the quantity of all pigments between inoculated and noninoculated plants occurred in the first week of growth. Regardless of treatment, the quantity of pigments in stems was three to four times less than the quantity of these pigments in shoots. Application of Azospirillum, either as liquid inoculant or as alginate microbeads, did not alter the positive effect of the bacteria on pigment production or the positive response of the plants towards A. brasilense Cd inoculation.     

In-situ enrichment and analysis of atrazine-degrading microbial communities using atrazine-containing porous beads

We examined the community composition of microbes that colonized atrazine-containing beads buried in agricultural soils that differed in atrazine treatment history. Bacterial abundance was 5-40-fold greater in atrazine-fortified beads. In beads containing 20 mg atrazine kg⁻¹ buried in soil with a history of atrazine application (conditioned soil), the abundance of Actinobacteria increased approximately 80-fold whereas in control soil, Actinobacteria were enriched only 10-fold and the gamma-Proteobacteria and Planctomycetes increased by 60- and 25-fold, respectively. The gamma-Proteobacteria were enriched by 120- and 230-fold in beads containing 200 mg atrazine kg⁻¹ in conditioned and control soil, respectively. The results demonstrate that BioSep^® beads are a suitable matrix for recruiting a diverse subset of the bacterial community involved in atrazine degradation.