中国原油污染区重金属空间分布模式及其潜在来源研究

Twenty-two soil samples were collected at the subregional scale （50 km2） around Gudao Town, a typical oil-producing region of the Shengli Oilfield in the Yellow River Delta, China to determine the spatial distribution patterns and potential sources of heavy metals in soils of crude oil-polluted regions. The concentrations of total petroleum hydrocaxbons （TPHs） and heavy metals as well as other soil properties were determined and the enrichment factor values were calculated for the heavy metals measured. Principal component analysis （PCA） and cluster analysis （CA） were used to estimate potential sources contributing to the concentrations of heavy metals in the soils. The results revealed that the soils were slightly alkaline （pH = 7.33-8.05） and high in salinity （1.43-41.30 g kg-1）, TPHs （0.51 28.40 g kg-1） and organic matter （1.74-31.50 g kg-1）. The mean concentrations of the measured heavy metals Cu, Zn, Pb, Cd, Cr, Ni and V were 18.4, 78.2, 20.8, 0.19, 56.6, 26.3 and 62.1 mg kg-1, respectively. Although the concentrations of all the metals measured in this study were not high enough to exceed the national control standards, there was a significant enrichment of Cd in the study area and Zn and Ni were in the category of deficiency to minimal enrichment. The spatial distribution patterns of Cu, Cr, Ni and V were similar and partially affected by oil exploitation and petroleum hydrocarbon spills. Potential sources of Cr, Ni, V and Cu in the soils were both natural sources and petroleum hydrocarbon spills, while Zn, Pb and Cd were probably from anthropogenic sources such as farming activities and traffic.     

Effects of different N sources on N nutrient and microbial distribution across soybean rhizosphere

Abstract

Nitrogen is the most important nutrient for plant growth. In the present study, investigations were carried out on the effects of sodium nitrate, ammonium sulfate, urea, and two types of controlled-release coated urea (LP-40 and LP-70) fertilizers on the NO₃ ^?-N, NH₄ ⁺-N concentrations, and microbial numbers as well as pH distribution across the rhizosphere of soybean (Glycine max L. Merrill, var. Heinong 35). The study was conducted on a typical black soil using a rhizobox system. The results showed that NO₃ ^?-N was the main source of nitrogen, which was deficient in the rhizosphere in the treatments of ammonium sulfate, urea, LP-40, and LP-70, but accumulated considerably in the sodium nitrate treatment. The NH₄ ⁺-N concentration slightly increased in the rhizosphere in the ammonium sulfate treatment, and decreased in the rhizosphere when the other four kinds of N fertilizers were supplied. In an the treatments, bacterial and fungal numbers were highest in the central compartment (C.C.) of the rhizoboxes where the soybean root system was confined, but the rhizosphere width estimated from the increase in the microbial abundance differed among different N fertilizers. The experimental results also indicated that the fungal composition in the C.C. was less diverse than in other parts of the rhizobox compartments, and that the majority of fungal groups was represented by Penicillium spp., suggesting that the microbial distribution across the soybean rhizosphere differed both quantitatively and qualitatively.     

Long-term tillage effects on the distribution patterns of microbial biomass and activities within soil aggregates

The effects of tillage on the interaction between soil structure and microbial biomass vary spatially and temporally for different soil types and cropping systems. We assessed the relationship between soil structure induced by tillage and soil microbial activity at the level of soil aggregates. To this aim, organic C (OC), microbial biomass C (MBC) and soil respiration were measured in water-stable aggregates (WSA) of different sizes from a subtropical rice soil under two tillage systems: conventional tillage (CT) and a combination of ridge with no-tillage (RNT). Soil (0–20 cm) was fractionated into six different aggregate sizes (> 4.76, 4.76–2.0, 2.0–1.0, 1.0–0.25, 0.25–0.053, and < 0.053 mm in diameter). Soil OC, MBC, respiration rate, and metabolic quotient were heterogeneously distributed among soil aggregates while the patterns of aggregate-size distribution were similar among properties, regardless of tillage system. The content of OC within WSA followed the sequence: medium-aggregates (1.0–0.25 mm and 1.0–2.0 mm) > macro-aggregates (4.76–2.0 mm) > micro-aggregates (0.25–0.053 mm) > large aggregates (> 4.76 mm) > silt + clay fractions (< 0.053 mm). The highest levels of MBC were associated with the 1.0–2.0 mm aggregate size class. Significant differences in respiration rates were also observed among different sizes of WSA, and the highest respiration rate was associated with 1.0–2.0 mm aggregates. The C_mic/C_org was greatest for the large-macroaggregates regardless of tillage regimes. This ratio decreased with aggregate size to 1.0–0.25 mm. Soil metabolic quotient (qCO₂) ranged from 3.6 to 17.7 mg CO₂ g^− 1 MBC h^− 1. The distribution pattern of soil microbial biomass and activity was governed by aggregate size, whereas the tillage effect was not significant at the aggregate scale. Tillage regimes that contribute to greater aggregation, such as RNT, also improved soil microbial activity. Soil OC, MBC and respiration rate were at their highest levels for 1.0–2.0 mm aggregates, suggesting a higher biological activity at this aggregate size for the present ecosystem.     

Effects of different application methods of selenite and selenate on selenium distribution within wheat

Abstract

The objective of this sand culture experiment was to determine how fertilization methods (i.e., fertigation rates of 0.5, 1, and 2?mg Se·pot^?1, foliar rates of 5, 10, and 20?mg Se· L^?1) and fertilizer type (i.e., selenate or selenite) affected wheat Se concentrations. The results showed that the fertigation and foliar treatments both increased wheat Se content. In the fertigation and foliar treatment total Se content of wheat was greatest in the selenate treatments. In the fertigation treatment, the Selenite had mainly accumulated in the roots, while the Selenate was majority transported to shoot. In the foliar treatment, we found that most of Se was transported to grain. In addition, the organic Se concentration was the most than other Se fractions. In conclusion, selenate was more effective than selenite in both the fertigated and the foliar application treatments. And the foliar application was better than fertigation.     

Formation and distribution of methylmercury in sediments at a mariculture site: a mesocosm study

Purpose

The aim of the present study was to investigate the differences of methylmercury (MeHg) formation and distribution between mariculture (aquaculture) sediments (MS) and reference sediments (RS) collected from a site in Hong Kong.

Materials and methods

The MS and RS samples were split into four batches, three of which were spiked with HgCl₂ aqueous solution to a concentration of 0.8, ,2 and 8 mg k g^?1 in sediment samples SP1, SP2, and SP3, respectively, while the rest served as a control batch (referred to as C).

Results and discussion

The results showed that the highly Hg-polluted sediment produced greater amounts of MeHg. During the culture period, MeHg concentrations in sediments decreased over time. The decreasing percentage increased in the order of SP3?<?SP2?<?SP1, which might be due to the inhibition of MeHg degradation by high Hg concentrations. The mean value of MeHg concentrations and %MeHg of the total Hg (THg) in MS was significantly lower than those in RS, possibly due to the complexation of Hg with organic ligands, leading to lower Hg bioavailability for methylation bacteria. The distribution coefficient of THg (K_dT) was relatively high in MS compared to RS, indicating that the former had a greater number of binding sites for Hg adsorption.

Conclusions

Methylmercury formation was inhibited in MS, probably due to increased complexation of Hg²⁺ with organic matter and adsorption of Hg to MS. Furthermore, the mean value of K_dT in MS was relatively high when compared to RS, which illustrates that MS sediments have more binding sites than RS for adsorption of Hg.     

幼果期富士苹果树体各器官钙定量分析

对幼果期矮化富士苹果树体各器官及其皮层、木质部的生物量、钙含量和钙累积量进行了研究。结果表明，单株干重为10．21kg，皮层和木质部干重分别为2．14和7．07kg，骨干枝干重为各器官之首；各器官钙含量差异显著，根系平均钙含量高于地上部多数器官，中央干皮层钙含量最高；单株钙累积量为76．67g，皮层和木质部钙累积量分别为52．44和13．83g，直径1．0-5．0cm根的钙累积量最高。     

Natural strontium isotope composition as a tracer of weathering patterns and of exchangeable calcium sources in acid leached soils developed on loess of central Belgium

The natural Sr isotope composition of acid leached soils developed on loess, under beech forest, in central Belgium was used as a tracer of soil forming processes, in conjunction with physico‐chemical and quantitative mineralogical investigations. Attention was focused on weathering and exchange processes, with special emphasis on the origin of the current soil exchangeable fraction and the influence of the atmospheric deposition and biological cycling on the calcium exchangeable pool (Sr acts as a proxy for Ca). The determination of ⁸⁷Sr/⁸⁶Sr ratios was made on the bulk soil, on the clay‐ and silt‐size soil separates, on 0.1 m HCl extracts, on the labile pool, on the soil solution and on the bulk precipitation. The acid leached soil profiles are characterized by a sequence of weathering processes that is highlighted by both mineralogical and isotopic changes. From the calcareous unweathered loess (pH 7.5) to the uppermost soil horizons (pH < 4.0) the evolution of the ⁸⁷Sr/⁸⁶Sr isotope ratio clearly reflects: (i) the selective weathering of Ca‐plagioclase (small ⁸⁷Sr/⁸⁶Sr ratio) and the increasing proportion of resistant K‐ and Rb‐rich minerals (large ⁸⁷Sr/⁸⁶Sr ratio) in the uppermost soil horizons; and (ii) a downward translocation of clay minerals with a large isotopic ratio, a physical breakdown of muscovite and a non‐congruent chemical weathering of K‐feldspar. The influence of organic restitutions or atmospheric deposition is not significant. The comparison between the Sr isotopic signature of the soil solution, and the exchangeable and HCl‐extractible soil fractions provides information about cation exchange efficiency, soil–water interaction and the origin of the exchangeable pool.     

Potassium and calcium distribution patterns along the leaf insertion gradient of bean plants grown in nutrient solutions

Potassium and calcium distribution patterns along the leaf insertion gradient of bean plants (Phaseolus vulgaris L. cv Tacarigua) were analyzed in plants grown in different K and Ca concentrations in the nutrient solution. The plants were sampled at the early flowering stage and the leaves analyzed following the helix or genetic spiral which follows leaves in the order of their origin at the shoot tip. Different canopy profiles for K and Ca showed that “critical concentration limits”; could be established for K but not for Ca, due perhaps to the non‐phloem mobile nature of this element. Besides, sampling procedures based on a “representative”; leaf (or leaves) were compared to those based on the sampling of the whole canopy in order to obtain reference nutrient concentration values.     

不同管理方式对小麦氮素吸收、分配及去向的影响

【目的】随着氮肥在农业生产中的广泛应用,已有许多通过不同施氮水平调控,分析作物养分吸收,提高氮素利用率的相关研究,但是关于高产体系下作物花前花后氮素利用、转移规律的研究相对较少。本文探讨传统（CT）和优化（YH）两种栽培体系对冬小麦氮素吸收、分配及去向的影响。分析高产条件下化肥氮的作物吸收土壤残留损失的新变化,解析小麦花前花后氮素利用、转移规律,探讨肥料氮、土壤氮与作物氮之间的关系。【方法】在传统和优化两种栽培体系定位试验中设置15N 微区,采用将15N 标记的尿素表施的方法,通过测定植株、土壤样品分析氮素利用特征。新鲜土壤 NH+4-N和NO-3-N 含量采用TRACCS 2000型流动分析仪测定。15N土壤及植物全氮用美国THERMO finnigan 公司的稳定同位素质谱仪Delta plusXP 测定。【结果】在该试验条件下,优化管理小麦籽粒产量和吸氮量均显著高于传统处理,分别比传统管理高35%和34%。优化管理15N利用率比传统管理高,差异达显著水平。小麦各器官中氮素的累积量及向籽粒中的转移量均表现为来自土壤氮高于来自肥料中的氮,说明土壤氮是小麦生长的主要氮源。传统管理籽粒氮素大部分来源于花前累积,转运氮的贡献率为81.65%,优化管理为62.14%。优化管理土壤硝态氮及15N含量显著低于传统管理;开花期传统管理土壤表层硝态氮及15N大量累积;收获后4060 cm土层15N 出现累积峰,氮肥随水向下运移。两种管理方式的小麦当季化肥去向均表现为土壤残留作物吸收损失;传统管理土壤氮肥残留率高达 69.33%,优化管理较低,为39.17%。【结论】在优化栽培体系中冬小麦施氮量为139 kg/hm2 时,小麦籽粒产量达到高产且氮肥高效利用。合理调控氮素投入量以及适度的水分胁迫可以实现水氮高效前提下的作物高产。     

The effect of calcium spray on leaf and bract distortion,bound:unbound calcium ratio,and calcium distribution in two poinsettia cultivars

To determine if direct Ca sprays could affect the distribution and binding of Ca in the leaves and the severity of leaf/bract distortion in two varieties of poinsettia (Euphorbia pulcherimma Willd.), we applied either 100 mg.l^‐1 or 400 mg.1^‐1 of Ca either one time or weekly to leaves of distortion‐ susceptible ('V‐14 Glory') and nonsusceptible ('Annette Hegg Dark Red,’ AHDR) cultivars. Only weekly spraying with 400 mg.l^‐1 Ca reduced distortion in V‐14 plants, compared to controls or AHDR plants. Both bound and unbound Ca concentrations were higher in AHDR leaves than in V‐14 leaves, but these differences were not correlated with distortion severity. EDX analysis demonstrated that distorted regions of V‐14 leaves and bracts had lower Ca concentrations than did undistorted regions or AHDR leaves; weekly spraying with 400 mg.l^‐1 Ca produced relatively uniform leaf Ca distribution in V‐14 leaves. Localized Ca deficiencies appear to produce the bract/leaf distortion in ‘V‐14 Glory’ plants, and these deficiencies can be partially overcome by weekly Ca spray applications.     

The effect of calcium spray on leaf and bract distortion,bound:Unbound calcium ratio,and calcium distribution in two poinsettia cultivars

To deteimine if direct Ca sprays could affect the distribution and binding of Ca in the leaves and the severity of leaf/bract distortion in two varieties of poinsettia (Euphorbia pulcherimma Willd.), we applied either 100 mg.l^‐1 or 400 mg.l^‐1 of Ca either one time or weekly to leaves of distortion‐ susceptible ('V‐14 Glory') and nonsusceptible ('Annette Hegg Dark Red,’ AHDR) cultivars. Only weekly spraying with 400 mg.l^‐1 Ca reduced distortion in V‐14 plants, compared to controls or AHDR plants. Both bound and unbound Ca concentrations were higher in AHDR leaves than in V‐14 leaves, but these differences were not correlated with distortion severity. EDX analysis demonstrated that distorted regions of V‐14 leaves and bracts had lower Ca concentrations than did undistorted regions or AHDR leaves; weekly spraying with 400 mg.r¹ Ca produced relatively uniform leaf Ca distribution in V‐14 leaves. Localized Ca deficiencies appear to produce the bract/leaf distortion in ‘V‐14 Glory plants, and these deficiencies can be partially overcome by weekly Ca spray applications.     

不同利用方式的苏打盐渍土剖面盐分组成及分布特征

通过野外调查、采样和室内分析,研究了松嫩平原不同利用方式的苏打盐渍土剖面形态特征及可溶盐含量与组成在土壤剖面中的变化。结果表明,土壤的利用方式不同,土壤剖面腐殖质层厚度、耕层和腐殖质层的有机质含量等有明显差异。在围栏草原、旱田、新水田及老水田4个剖面中,土壤可溶盐总量、pH与ESP均是在剖面中部最高,上部和下部较低;可溶盐组成均以K++Na+和HCO 3-、CO23-为主。表明草原围栏、旱田及水田利用均有抑制苏打盐分表聚的作用。放牧草原剖面的可溶盐含量自下向上逐渐增多,盐分表聚非常显著。开垦20余年的水田剖面中,表层土壤的可溶盐总量、pH和ESP值分别降至0.21%、7.56和9.1%,表明苏打盐碱地种稻较草原和旱田利用更有利于土壤脱盐脱碱。     

不同管理方式对夏玉米氮素吸收、分配及去向的影响

【目的】本文利用15N同位素示踪技术探讨传统(CT)和优化(YH)两种管理方式对夏玉米氮素吸收、分配及去向的影响。分析目标产量下化肥氮的变化,解析夏玉米花前、花后氮素利用及转移规律,探讨肥料氮、土壤氮与作物氮之间的关系,为该地区夏玉米的科学合理施氮提供合理依据。【方法】在传统和优化两种管理方式定位试验中设置15N微区,采用将15N标记的尿素表施的方法,分析植株和土壤样品。新鲜土壤用1 mol/L KCl浸提,滤液用TRACCS 2000型流动分析仪测定土壤的NH+4-N和NO-3-N含量。15N标记的土壤和植物全氮的测定用烘干样(过0.15 mm筛),然后用美国THERMO finnigan公司生产的稳定同位素质谱仪DeltaplusXP进行测定。【结果】在该试验条件下,优化方式下夏玉米籽粒产量和总吸氮量显著高于传统方式,分别增加12%和10%。作物收获后,优化方式的15N吸收量及利用率显著高于传统方式,利用率分别为20.81%、32.54%。夏玉米各器官中氮素的积累量和向籽粒中的转移量土壤氮显著高于肥料氮,传统方式籽粒中氮素的57.73%、优化方式籽粒中氮素的45.15%来自各器官的转移,近一半的氮素是在花后积累的,基施高氮对作物生长作用不大。开花期土壤表层硝态氮含量传统方式显著高于优化方式,收获后有所降低,而土壤深层含量明显增加,有向下淋洗的趋势。夏玉米收获后,传统方式各土层的原子百分超均高于优化方式,而且在20—40 cm处出现了明显的15N累积峰,与开花期相比,40 cm以下土层的原子百分超明显增大,氮肥随水向下淋洗强烈。夏玉米收获后传统方式土壤氮素残留率高达56.18%,表现为土壤残留损失作物吸收;优化方式则表现为土壤残留作物吸收损失。【结论】在优化方式中夏玉米施氮量为N 185 kg/hm2时,玉米达到高产水平且氮肥的利用率高。适当减少施氮量及增加后期追肥次数可实现夏玉米的高产和肥料的高效利用。     

不同来源氮素在烤烟体内的累积分配及对烟叶品质的影响

通过在云南省玉溪市赵桅村6组烟田（A）和赵桅实验基地（B）进行的大田15N示踪试验,研究了在不施氮和施氮90 kg/hm2条件下,水稻土烤烟干物质累积特征、肥料氮和土壤氮的吸收和分配及肥料氮和土壤氮对烟叶品质的影响。结果表明,施氮能显著提高烟株干物重,增加烟株吸氮量,但在生育后期施氮与不施氮处理,烟株均存在干物质和氮素累积过多问题。施氮90 kg/hm2情况下,烟株整个生育期中吸收的氮素主要来自于土壤氮,而且烟株吸收的土壤氮及其占总吸氮量的比例随生育期延长和烟叶着生部位的升高显著增加;到采收结束时,两试验田烟株吸收的土壤氮占总吸氮量的比例分别达69%和74%。不同施氮水平烟叶品质差异较大,不施氮处理各部位烟叶总氮和烟碱含量均偏低,糖碱比不协调;施氮处理各部位烟叶总氮含量均在适宜范围内,但由于烟株生育后期土壤供氮较多,上部烟叶存在烟碱含量偏高的问题。选择有机质含量适宜的土壤,控制烟株生育后期土壤供氮量,对降低上部烟叶总氮和烟碱含量,提高我国烟叶整体质量至关重要。     

Spatial variability of infiltration patterns related to site characteristics in a semi-arid watershed

Preferential flow may strongly affect hydrology at different scales. Measurement of preferential flow however remains very difficult. Tracer-infiltration profiles are often used to measure the degree of preferential flow at plot scale. These experiments are time-consuming, costly and destructive. As a result existing dye-tracer studies are often based on a limited number of profiles. The aim of this study is therefore to select a limited number of soil and landscape characteristics with high predictive value for the degree of preferential flow. 18 rainfall simulations with a dye-tracer and additional site measurements such as soil type, vegetation type and soil physical parameters were performed in a 1 km² catchment in the Dehesa (Extremadura, Spain). A stepwise multiple regression procedure was used to select variables with a high predictive value for the degree of preferential flow.     

Root distribution patterns of white yam (Dioscorea rotundata Poir.): a field study

Abstract

The productivity of white yam (Dioscorea rotundata Poir) must increase to sustainably meet the demand of the increasing populations in the developing world where this is a staple crop. Although this could be achieved through the use of mineral fertilizers, reports indicate limited effects of these inputs on tuber yield. We hypothesized (i) that D. rotundata has a small and shallow root system and (ii) that this root system does not respond to mineral fertilizer application. Two field experiments were conducted in Côte d'Ivoire in year 1 and in year 2 to test these hypotheses. In the first field experiment we measured biomass production, as well as root density during plant growth in fertilized and unfertilized plots while in the second experiment, we analysed the distribution pattern of roots in horizontal and vertical root profiles in fertilized plots. The root system of D. rotundata consisted of seminal, adventitious and tubercular roots. Only the adventitious roots remained alive until the end of the growth cycle. The root length density was very low with a maximum of 0.25 cm cm^?3. No roots were observed in the 15–30 cm horizon at 50 cm from the plant's crown. The horizontal and vertical root maps revealed that roots were mostly distributed in clumps, and there was a good correlation between the two methods of root sampling for this species. Fertilizer application had no significant effect on plant biomass, fresh tuber yield or on root growth. However, thinner and longer roots and higher tuber yields were observed in year 1 than in year 2. The different weather conditions and more specifically the higher soil temperature might explain the results obtained in year 1. Therefore, it could be recommended to farmers not to fertilize D. rotundata.     

High sodium/calcium ratios in alkaline Wimmera soils: The role of magnesium and a hypothesis for their development

Sodium calcium ratios are often sufficiently high to limit root growth and result from lower calcium rather than high sodium, and was the focus of this study. A simple model of complex ion formation by magnesium and carbonate was derived, which adequately explained the relationship between pH, calcium, and magnesium, particularly the typical supersaturation of calcium with respect to calcium carbonate. Concentrations of magnesium and calcium declined when excess bicarbonate was applied, and the frequency of adverse sodium/calcium ratios increased. Calcium and magnesium declined proportionately until low concentrations when the proportion of calcium increased. Increased carbonate concentrations could depress calcium and magnesium concentrations to low levels with magnesium being buried in calcium carbonate and unable to redissolve once carbonate levels return to normal. Magnesium soil amendment may be the key to addressing adverse sodium calcium ratios. Plant selection for tolerance to adverse sodium calcium ratios is warranted.     

经济发达区不同土壤利用方式下重金属的时空分布及预测

土壤利用方式的改变可能导致重金属的积累,并威胁食品安全。本文以长江三角洲经济发达的典型地区张家港市为例,评价了土壤利用由稻麦轮作转变为蔬菜种植对该市土壤中Cd、As、Cr、Cu时空分布的影响;并预测了目前条件下,蔬菜种植面积的扩大和种植年限的增加对重金属在土壤中的积累趋势及污染潜力。结果表明,在蔬菜种植过程中,土壤中As含量变化不明显;Cd、Cr和Cu的含量有不断累积的趋势,一定面积的土壤超过了土壤环境质量一级限值(背景值);如果按目前的蔬菜种植扩大和重金属积累的趋势发展,未来10年,将有2.4%面积的土壤Cu超过土壤环境二级限值,20年后,Cd亦出现超标现象(约0.7%面积),有可能对蔬菜品质产生影响。因此,对今后蔬菜种植管理过程中引起的土壤重金属积累及潜在污染问题应该得到充分的重视。     

高粱在不同氮源处理下分泌生物硝化抑制剂的差异

高粱根系能分泌抑制土壤亚硝化细菌的物质,称为生物硝化抑制剂.在铵态氮存在时,这类物质会大量分泌,而以硝态氮为氮源时则分泌很少.目前还不清楚,这是因为不同氮素代谢的差异所引起的,还是根系吸收铵态氮后根际酸化影响了硝化作用.因此本研究通过砂培试验,用铵硝营养处理高粱根系,并且控制pH,最后收集根系分泌物,利用一种荧光标记的亚硝酸细菌来测定高粱分泌的硝化抑制剂活性,计算其分泌速率.结果发现,铵态氮是导致根系大量分泌硝化抑制剂的主要原因,并且在根际pH＜6时,硝化抑制剂的活性与分泌速率随着根系分泌氢离子数量的增加而增强.研究表明,铵态氮营养下高粱根系分泌生物硝化抑制剂高于硝态氮营养可能是高粱根系保护根际铵氧化,提高氮素利用率的一个重要生理机制.     

不同灌溉方式对温室嫁接黄瓜根系分布影响的研究

采用土柱模拟试验和大田调查相结合的方法,研究了不同灌溉方式下温室嫁接黄瓜根系分布特征,结果表明：膜下暗灌和滴水灌溉温室黄瓜根系干重最大值分别出现在黄瓜定植后180d和210d,黄瓜拔蔓时根系干重后者较前者高29．0％。黄瓜不同发育时期根系垂直分布特征有明显差异,在初瓜期前,0．20cm根系干重前者明显高于后者,20cm以下根系干重二者无明显差异;结瓜盛期以后,0～20cm根系干重二者差异不明显,20cm以下根系干重后者显著高于前者。膜下暗灌和滴水灌溉黄瓜根系水平分布在0．15cm。分别占总根干重的96．6％、94．2％。随着黄瓜生长发育的推进,膜下暗灌内侧根系分布数量逐渐下降,结瓜期以前内侧根系占植株根系总数量的61．1％,中后期占15．6％;而滴灌黄瓜全发育期,内外侧根系分布数量比较均衡。说明灌水方式对温室嫁接黄瓜根系分布特征有显著影响。