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1.
温室透光覆盖材料透光特性的测试 总被引：7，自引：4，他引：3
透光特性是温室透光覆盖材料的一个重要指标,其数值的表达却因测试方法的不同而有所差异.该文介绍了透光覆盖材料太阳辐射透过率的测试及计算方法,选用聚乙烯塑料膜(PE)、浮法玻璃、聚碳酸酯双层中空板(PC)三种典型的覆盖材料进行了测试,计算了国际照明委员会(CIE)规定的标准C、标准A和标准D65三种光源下,在可见光与PAR波段范围内,基于4种权重系数下的覆盖材料透光率和光合有效辐射(PAR)透过率.结果表明,PE薄膜几乎不受影响,浮法玻璃相差2%左右,聚碳酸酯双层中空板差异达2%～3.7%. 相似文献
2.
基于覆盖层能量平衡法的园艺设施覆盖材料传热系数理论解析与验证 总被引：2，自引：1，他引：2
该文提出了一种园艺设施覆盖材料传热分析以及传热系数的理论计算方法，即覆盖层能量平衡法。该方法通过覆盖层辐射传热和对流换热的能量平衡，建立全面反映覆盖材料传热各主要影响因素的传热模型，得出了传热系数的理论解析计算方法，可根据覆盖材料的红外辐射发射率、反射率和透过率等热物理特性和保温比、角系数等与覆盖层构造相关的参数以及设施内外气温、天空辐射温度、植物与室内地面温度、室外风速等工作环境条件，定量分析覆盖层的传热，得出传热系数的理论计算值。 相似文献
3.
温室用聚碳酸酯中空板辐射透过特性初步研究 总被引：1，自引：2，他引：1
聚碳酸酯中空板质量轻、保温好、抗冲击、寿命长，在温室中得到了广泛的应用。但由于其透光性能比玻璃的差，有时造成种植者生产受损，甚至与材料生产企业发生纠纷。为了分析和了解这种材料的辐射透过性能，该文对聚碳酸酯(PC)中空板辐射透过率进行了测定和计算，并以玻璃为参照，分析了聚碳酸酯中空板对紫外线、可见光和红外线的透过率，结果表明聚碳酸酯中空板基本不透过紫外线，在可见光范围内的透光率较玻璃约低10%，在2～5 μm红外线波段的辐射透过率仅为玻璃的40%左右，在5～25 μm波段有两个小峰值透过率波段，但透过率都低于5%，虽较玻璃差，但从总量值上看仍然具有非常优异的保温性能。 相似文献
4.
几种日光温室外保温覆盖材料的保温性能 总被引：2，自引：2，他引：2
文章采用绝热模型箱方法，测定了目前生产上几种日光温室外保温材料覆盖材料的传热系数Ｋ值，并进行了室外实验。以ＰＶＣ和ＰＥ薄膜为固定膜，分别加益５种材料，在室内、室 外实验中都得到相同的保温性能顺序：草苫〉复合保温被〉双层〉ＰＥ物理发泡片材〉灰色无防〉瓦楞状泡沫板，还得出Ｋ值与风速、辐射高度相关。文章认为复合保温被、双层ＰＥ发泡片材经改进后可以作为草苫的替代覆盖物。 相似文献
5.
农用塑料薄膜光质辐射透过性能 总被引：1，自引：1，他引：0
为了分析和了解农用塑料薄膜的光辐射透过性能,该文采用VARIAN Cary-50紫外/可见光光度计和岛津FT-IR 8700 远红外光谱仪,分别扫描分析材料,得到针对不同光质波段的透过率,结果表明：①紫外区段,聚氯乙烯（PVC）通透能力最低,聚乙烯（PE）较高,乙烯-醋酸乙烯共聚物（EVA）次之;②PAR区段中,该文根据扫描结果分析计算各波段的透过面积比发现,PVC在蓝光区较为充沛,PE在黄绿光区最为丰富,红光和远红光通过计算R/FR值得出,新膜R/FR值较一致,但是百天后PVC膜下降幅度最大达到0.076,PE和EVA下降值都在0.050。③远红外光区PVC膜拥有优异的阻隔能力,PE次之,EVA较差。 相似文献
6.
传热系数Ｋ值是表示保温材料保温性能的重要参数，本文探讨了测定温室保温覆盖材料传热系数的原理和方法，并设计了绝热模型箱，利用稳态传热理论成功地测定了Ｋ值。在无风和不受净辐射影响下，测定的０．０７ｍｍ的ＰＶＣ和ＰＥ薄膜的Ｋ值分别是６．４４Ｗ／ｍ＾２·Ｃ和７．０４Ｗ／ｍ＾２·Ｃ，此值与有关报导一致。 相似文献
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9.
日光温室保温被传热的理论解析及验证 总被引：2，自引：7，他引：2
为掌握日光温室保温被的传热及其保温特性,该文运用传热学理论,建立了模拟辐射、对流以及导热等形式的传热方程,在此基础上构建了日光温室保温被这类厚型覆盖材料的传热理论模型,编制了计算机程序。该模型通过对保温被内、外表面与环境间的有效辐射、投射辐射的分析,来确定辐射换热量;根据能量平衡的原理,建立了保温被表面通过对流传热、辐射传热的传热量与内部传热量之间的关系。所建立的计算方法与程序可根据覆盖材料的红外辐射特性、导热系数、覆盖层的构造参数及工作环境等条件,定量分析保温被覆盖层的传热,计算其传热量及传热系数值。试验测试结果表明,保温被的传热量及传热系数的理论计算值与试验测定值较为一致,该文的方法为保温被一类厚型覆盖材料提供了保温性定量分析评价的理论手段。 相似文献
10.
为了避免日光温室中卷式卷帘机械在工作时损坏前屋面覆盖层薄膜，通常会在卷帘机下方铺垫一条固定保温被。日间，这条保温被会遮挡进入日光温室的太阳光线并在室内形成阴影。针对固定保温被对室内光热环境分布和作物产量的影响，该研究对固定保温被下方的光照、温度和作物的产量进行测试，同时利用太阳直射辐射理论提出固定保温被阴影宽度的计算方法。结果表明，在试验期间固定保温被正下方的光照强度平均值为198 μmol/(m2·s)，距离固定保温被4.0～5.0 m位置处的光照强度是固定保温被正下方的2.0倍以上。日间，固定保温被正下方的空气温度、墙面温度和土壤温度相比于固定保温被两侧最大降低2.2、5.8和2.3 ℃。夜间，墙面温度和土壤温度最大降低1.2和1.3 ℃。固定保温被正下方单垄番茄相比于其他垄平均减产36.2%，植株茎粗平均减小2.0～4.0 mm。不同地理位置和不同方位角的日光温室受到固定保温被遮阴在室内形成的阴影宽度范围为11.0～14.0 m。该研究定量分析了使用中卷式卷帘机械的日光温室中固定保温被对室内光热环境和作物产量的影响。 相似文献
11.
低氮和干旱胁迫对富士和秦冠生长及氮素利用的影响 总被引：2，自引：2，他引：0
【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.
Kyle Devey Michael Mucalo Gordon Rajendram Joseph Lane 《Communications in Soil Science and Plant Analysis》2015,46(4):72-80
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.
《中国生态农业学报》2014,(8)
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.
M.A. Callaham Jr. J.M. BlairT.C. Todd D.J. KitchenM.R. Whiles 《Soil biology & biochemistry》2003,35(8):1079-1093
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
15.
I.L. Boyd 《Biological conservation》2010,143(7):1664-1674
“Wicked” problems are those that are complex and that change when solutions are applied. Many conflicts in conservation fall into this category. The study approached the problem of how to constrain the apparent wickedness of a problem in the conservation management of a species by using simple empirical indicators to carry out iterative assessment of the risk to a population and to document how this risk evolves in relation to the addition of new data and the implementation of management actions. Effects of high levels of uncertainty within data and also concerning population structure were examined through stochastic simulation and by exploration of scenarios. Historical trends in the example used, the Steller sea lion, showed rapid declines in abundance in some regions during the 1980s. The current total population is 130,000-150,000 Steller sea lions through Alaska and British Columbia and this number has been stable since about 1990 in spite of regional differences in population dynamics. Regional differences in the sequence of changes in the number of pups and non-pups, suggested that an internal re-distribution of juveniles could have happened between 1980 and 1990. Current productivity also appears close to the long-term mean. Stochastic population projection using various scenarios showed that, based upon this history, the risk of extinction for the population has declined and is below reasonable thresholds for considering the population to be endangered. The trends in risk suggest that management actions taken since 1990 have probably been effective. Consequently, the conservation management objectives for the Steller sea lion are probably being met. The approach provides a mechanism, based upon experience and scenario analysis, for exploring future policy options and may help to constrain the debate amongst stakeholders about the cost-benefit trade-offs associated with different options. 相似文献
16.
Soil-profile distribution of primary and secondary plant-available nutrients under conventional and no tillage 总被引：1，自引：0，他引：1
Nutrient distributions under no tillage (NT) compared with conventional disk-and-bed tillage (CT) management in the warm, humid region of the southeastern USA need to be assessed so that future placement, quantity, and type of fertilizers can be altered, if necessary, to efficiently match crop demands. We determined soil-profile distributions of pH, N, P, S, K, Ca, Mg, Na, Zn, Fe, Mn, and Cu to a depth of 0.9 m at the end of 8.5 years of continuous CT and NT management on a Weswood silty clay loam (fine, mixed, thermic Fluventic Ustochrept) in southcentral Texas. Most dramatic changes occurred within the 0–0.05 m depth, where soil under NT had lower pH, Fe, and Cu than under CT, but greater P, K, Zn, and Mn. Greater P and K under NT than under CT also occurred below the till-zone (0.15–0.3 m). At a depth of 0–0.3 m, soil under NT contained greater amounts of extractable P, K, Zn, Fe, Mn, and Cu than under CT. Nitrogen fertilization had little effect on nutrient distributions, except resulting in greater extractable K at 0–0.05 m and greater nitrate at 0–0.15 m. Few changes in soil-profile distributions were observed for extractable S, Ca, Mg, and Na. Long-term continuous use of NT on this fine-textured, high-fertility (except for N) soil had no apparent adverse effects on nutrient distributions relative to CT, but enhanced conservation and availability of P, K, Zn, Fe, Mn, and Cu near the soil surface where crop roots proliferate. 相似文献
17.
Grete Skrede Berit Karoline Martinsen Anne-Berit Wold Stein-Erik Birkeland Kjersti Aaby 《Acta Agriculturae Scandinavica, Section B - Plant Soil Science》2013,63(3):193-208
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
18.
《Communications in Soil Science and Plant Analysis》2012,43(7):865-877
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
19.
Electron donor and pH relationships for biologically enhanced dissolution of chlorinated solvent DNAPL in groundwater 总被引：3，自引：0，他引：3
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. 相似文献
20.
Yoav Bashan Bernardo Salazar Ma. Esther Puente Macario Bacilio Robert Linderman 《Biology and Fertility of Soils》2009,45(6):585-594
To evaluate the feasibility of long-term desert reforestation technology of mixed vegetation, cardon cactus (Pachycereus pringlei) seedlings from indoor and outdoor nurseries were planted in the field adjacent to one seedling of potential legume nurse
trees: mesquite amargo (Prosopis articulata), yellow palo verde (Parkinsonia microphylla), and blue palo verde (Parkinsonia florida). Some of the planting holes were also supplemented with common dairy compost. Additionally, the combinations of legume tree–cactus
were inoculated with either a consortium of desert arbuscular mycorrhizal (AM) fungi, plant growth promoting bacteria (PGPB;
the diazotroph Azospirillum brasilense Cd, and the phosphate solubilizer Paenibacillus sp.), or a mixture of all. The field experiments were evaluated periodically during 30 months for survival and growth. Cardons
reared in an outdoor screen house survived better in the field than those reared in a controlled growth chamber and hardened
later outdoors. Association with any legume nurse tree increased survival and enhanced growth of untreated cardons. For cardons
growing alone, application of either compost, AM fungi, and all the treatments combined increased survival. For these plants,
no treatment affected plant growth during the first 3 months after transplanting. Later, all treatments, except for AM fungi,
enhanced plant growth. However, only 2 years after transplanting the enhanced growth effect of AM fungi was also significant.
In the presence of the legume nurse trees, transient positive effects on cardon growth were recorded. General evaluation after
30 months of cultivation showed that the treatments positively affected cardon growth when growing alone or in combination
only with mesquite amargo but not with the other two legume trees. This study proposes that young legume trees have the capacity
to enhance survival and growth of cardon cactus, depending on the legume cactus combination. Additional treatments such as
compost or PGPB can either amplify the effect or else attenuate it. 相似文献