聊城市园林植物线虫种类调查与群体密度消长动态研究

2004～2006年对聊城园林植物线虫病进行了系统调查.采用筛淘-改良贝尔曼漏斗法分离根际土壤或介质中的线虫,通过鉴定共发现植食性线虫11种、腐生线虫3种、捕食性线虫1种,掌握了从春至秋各类线虫种群数量呈增长趋势、群体结构呈多样化发展的规律,确定晚秋是线虫种群数量、种类最为繁盛的时期.     

宁夏枸杞园土壤线虫和微生物群落多样性研究

为了揭示宁夏枸杞园土壤质量变化趋势,以宁夏枸杞之乡——中宁县为研究区,选取不同树龄宁夏枸杞园土壤,分析不同季节、土层和树龄条件下土壤线虫和微生物群落特征变化规律。结果表明,随树龄的增加,枸杞园0~20 cm土壤线虫总数先增加后减少,6 a树龄时达最大值。不同树龄表层土壤均为食细菌线虫所占比例最大(夏季和秋季平均分别为57.23%和61.19%),植物寄生线虫次之;亚表层植物寄生线虫比例显著提高。夏季表层土壤总磷脂脂肪酸(PLFA)和细菌PLFA浓度随树龄呈减小-增大-减小的趋势,9 a树龄各菌群PLFA浓度普遍最大。随树龄的增加,夏季0~20 cm土壤线虫多样性和丰富度指数先增大后减小,但土壤微生物多样性指数、均匀度指数都逐渐减小,线虫和微生物群落优势度指数都逐渐增大;20~40 cm土壤线虫和微生物数量、多样性指数和优势度指数变化趋势一致。土壤EC与微生物总PLFA浓度、细菌PLFA浓度达显著负相关;土壤有机质、全氮、速效磷含量与土壤各线虫数量和微生物浓度相关性普遍达显著或极显著水平。土壤线虫总数、食细菌线虫数量与细菌、真菌和放线菌PLFA浓度均显著或极显著相关。总之,季节、土层和树龄对土壤线虫和微生物群落均有不同程度的影响,但树龄对其影响相对最小;季节、土层和树龄对土壤微生物群落的影响比对土壤线虫群落更显著。在相同季节和土层条件下,土壤微环境质量随着树龄的增加呈现出先改善后退化的趋势。     

土壤高温蒸汽消毒对蕃茄根结线虫的防治效果评价

针对传统化学防治解决土壤连作障碍存在农药残留、食品安全及环境污染等问题,引进一种移动式土壤高温蒸汽消毒机并进行技术可行性分析.通过田间试验及数据分析,使用高温蒸汽处理技术2 h可以显著降低番茄根结线虫数量、有效控制番茄根结线虫的危害.统计结果表明,在高温蒸汽处理后2d,根结线虫的线虫减退率为92.9％;移动式土壤高温蒸...     

离散元模拟振动幅值对玉米种群运动速度的影响

排种器是免耕播种机的重要组成部分,排种盘吸种性能直接影响免耕播种机播种合格率。排种室内种群运动速度对排种盘吸种性能影响较大,而振动是影响种群运动速度的重要因素。为此,应用离散元软件模拟排种室内玉米种群的运动,得到排种盘和搅种轮转速为17.8 r/min,排种室内充种3 750粒,排种器振动频率为1 5 Hz,振动幅值分别为0.5、1、1.5、2、2.5、3、3.5、4 mm时,振动幅值对排种室内种群运动的影响。通过离散元软件后处理模块得到4 s时间内,以0.02 s为间隔所有时间点的玉米种群运动最大速度、最小速度、平均速度和竖直方向玉米种群最大速度、最小速度,由Origin软件得到排种室内玉米种群速度与振动幅值的拟合曲线。模拟结果表明:玉米种群最大速度、最小速度与排种器振动幅值呈二次曲线变化;玉米种群平均速度和竖直方向种群最大速度与排种器振动幅值呈线性关系;振动幅值大于2mm时,竖直方向种群最小速度基本保持不变。本次仿真为室内排种试验振动幅值的选择提供了依据。     

重力辅助充种盘室同步气吸式排种器性能分析

为探究重力辅助对盘室同步气吸式精量排种器充种性能的影响,以盘室同步气吸式精量排种器为载体,对其充种过程进行了受力分析,建立了重力辅助充种受力数学模型,结果表明：型孔充填过程中,待充种子重力在排种盘径向的分量与气流曳力方向一致;已充种子脱离种群过程中,种子重力沿径向分量与压力梯度力方向一致,种子重力对充种有辅助作用。运用EDEM(Engineering discrete element method)软件仿真分析了300、600、900、1200粒种群数量条件下,待充种子对排种盘平均法向力随低、中、高3种不同充种区域变化的影响,仿真结果表明：种群数量300粒时,各区域平均法向力随区域位置的变化不明显,种群数量为600、900、1200粒时,平均法向力随区域位置的变化规律一致,此时种群数量对充种效果影响可忽略。对仿真结果进行试验验证的结果表明,盘室同步气吸式精量排种器台架试验3个区域漏充率由大到小为：低位、中位、高位。通过盘室同步气吸式精量排种器重力辅助充种和无重力辅助充种对比试验表明：重力辅助充种下,排种器作业风压3~5.5kPa时,合格指数均高于94%;无重力辅助充种情况下,排种器作业风压6kPa才开始满足国标需要,重力辅助充种显著降低了排种器作业风压需求,提高了作业质量。     

宁夏荒漠草原带酸枣种群年龄结构与数量动态分析

酸枣(Ziziphus jujuba var. spinosa)属于鼠李科枣属植物,耐旱、耐盐碱和耐瘠薄,在宁夏中北部地区具有很好的生态功能。其药用价值及经济价值也很高,但目前对于野生酸枣在半干旱地区的种群动态的研究很少。为明晰该地区酸枣种群动态变化,挖掘其生态价值,本文以宁夏红寺堡区酸枣林为研究对象,通过设置样地,对酸枣基径进行测定、处理,研究该酸枣种群的年龄结构、静态生命表及存活曲线,运用时间序列模型预测了种群数量动态。结果发现:该种群年龄结构呈宽底"金字塔"型,幼龄植株储备丰富;存活曲线均趋于Deevey II型,死亡率一直居高不下,第3径级达到死亡率峰值;该种群在2、4、6各龄级时间后,个体数均呈现小幅度的增加趋势,该种群基本达到稳定阶段。     

土壤电处理技术防治黄瓜土壤根结线虫试验

以辽宁省大连市炮台镇黄瓜种植区为对象，研究了土壤电处理对土壤中造成土壤连作障碍的根结线虫杀灭情况。结果表明，延长通电时间可以有效提高电处理杀灭土壤中根结线虫的效果，延长通电时间至6 min，土壤中和根际的根结线虫数量已趋近于零，且经过电处理后的黄瓜每株数量和产量均有提升。      

利用元胞自动机建立两种害虫竞争预测模型

本文基于Lotka-Volterra模型中的参数,结合元胞自动机,模拟粮食中的主要害虫玉米象和谷蠹同时存在的情况下种群的发展趋势。两物种之间的种间竞争属于资源利用型竞争,通过试验得出了2个种群的初始数量是决定种群竞争胜利与否的重要参数的结论。通过害虫预测模型,可以帮助我们了解粮食中害虫的分布情况,并有效地控制和消除掉害虫。     

基于离散元的排种器振动对大粒径作物种群的影响

排种器工作效果受种群运动情况的影响较大,而振动则直接影响种群运动。为此,运用离散元软件模拟排种室内大豆种群(充种2 600粒左右)的运动,在排种盘转速为54r/min、排种器整体振动频率为14Hz情况下,振幅分别为0、1、2、3、4、5mm时,分析了振幅对排种室内种群运动的影响。通过软件后处理模块得到2~5s稳定状态内若干时间点的种群平均速度和种群所受压力。利用ORIGIN软件得到种群速度和受力同振幅的拟合曲线,结果表明:种群平均速度随排种器振幅增大而提高,种群所受压力随振幅增加而先降低后升高。本次仿真试验为室内排种试验振幅的选择提供了可靠依据。     

基于EDEM软件的玉米育种排种器改进与充种性能试验

基于EDEM软件,以种腔自净型排种器为研究对象,对带凹槽排种盘扰动种群的过程进行了仿真分析,考察了种群平均法向力、种群距排种盘平均距离和种群运动平均速度3个指标,分析对比了带凹槽排种盘及无凹槽排种盘对种群离散程度的影响。仿真结果表明,在种子量较少的情况下,带凹槽排种盘可有效增强种群的离散程度,降低种子在被吸孔吸附前受到的种群内摩擦力,提高吸附率。台架试验验证了仿真分析的推论,通过在排种盘上设置凹槽的改进方式,加强排种盘对种群的扰动就可以在一定程度上提高排种盘吸孔吸附种子的能力,降低漏充率,使排种器的漏播率满足国标要求。     

A model of the life cycle of sheep nematodes and the epidemiology of nematodiasis in sheep

A computer model (NEMAT) of the life cycle of sheep nematodes and of the epidemiology of nematodiasis in sheep was constructed. Its purpose is to predict the development of nematodiasis in weaner sheep and to determine optimum nematode control programmes. It has been developed for use in western Victoria, Australia, but it should also be of use in other localities.NEMAT simulates the growth of perennial ryegrass (Lolium perenne) and subterranean clover (Trifolium subterraneum) pasture and weaner sheep and the development of populations of the sheep nematodes Ostertagia spp. and Trichostrongylus spp. The development and death rate parameters of the free-living stages of these nematodes were estimated by a direct search optimisation procedure specifically developed for this study. The death rates of the parasitic stages of Ostertagia spp. were determined in a field experiment and expressed as a function of the rate of infection and the time of exposure to infection. Other probability density functions and deterministic functions needed to complete the quantification of the sheep-nematode system were derived from published reports or personal communications.NEMAT was validated against data from two independent field experiments carried out in western Victoria. Predicted serial measurements of pasture availability, liveweights, total nematode counts, nematode eggs per gram of faeces and numbers of infective nematode larvae per hectare were compared with those actually observed. The predicted and observed measurements were subjectively similar and could not be differentiated statistically by spectral analysis.NEMAT was then used to evaluate some nematode control programmes in western Victoria. Using observed weather data, it simulated the continuous development of nematode populations during 1957–1976 on pastures set stocked on the 1st of January each year with recently drenched weaner sheep.If sheep were drenched in only one month of the year, the effect of this drench on liveweights and woolweights at the end of the year was greatest if it was given in February. There was a progressive decline in final liveweights and woolweights if it was given in subsequent months to December. If sheep were drenched in February and given a second drench in any one of the remaining months of the year, the effects of this second drench on final liveweights and woolweights was greatest if it was given at the autumn break. A drench in February and a drench and shift to ‘clean’ pasture (<10⁴ nematode larvae per hectare) in July were always sufficient to limit the mean yearly effects of nematodiasis to 1 kg in liveweight and 0·1 kg in woolweight. When such a shift was not possible, a drench in February, another at the autumn break and 0–5 drenches in winter and spring were required to attain similar productivity. The number and timing of these drenches after the autumn break depended on the daily effects of weather on the nematode population and could be determined only by a model of the sheep-nematode system such as NEMAT.     

Population dynamics and crop yield effects of nematodes and white mold in peanuts,cotton and velvet beans

Dynamic population equations for the root-knot nematode (Meloidogyne arenaria), Southern blight (`white mold') fungus (Sclerotium rolfsii), and microbivorous nematodes in peanuts, cotton, and the Alabama velvet bean were statistically estimated with replicated experimental data from Headland, AL, USA. The level of microbivorous nematodes the previous crop year was found to suppress the root-knot nematode and white mold in peanuts the following crop year in monoculture peanut production and in peanuts after velvet beans. Statistical results showed that both the root-knot nematode and white mold had a negative effect on peanut yield, while microbivorous nematodes had a positive effect on peanut and cotton yields. Scientific knowledge of these organisms does not fully explain the results, but the statistical results strongly suggest that these relationships exist. On the basis of statistical results for peanuts, each white mold occurrence (in a 60-ft row) cost $21.41, each root-knot nematode (in 100-cm³ soil sample) cost $0.41, and each microbivorous nematode (in 100-cm³ soil sample) had a benefit of $0.11. In cotton production, microbivorous nematodes had a benefit of $0.13.     

Exploring the scope for improving biocontrol of black vine weevil,Otiorhynchus sulcatus,with Heterorhabditis spp. at low temperatures: A simulation study

Control success with heterorhabditid nematodes varies with nematode species, isolate, production and storage conditions, and environmental conditions after application. These factors affect nematode behaviour. A model was developed that simulates movement of a nematode population in space and time from the moment of application on a sand column until penetration into a host. It was used to identify, (1) which nematode traits can best be used for improvement, and (2) what is the most promising strategy of improvement. The sensitivity of simulated control success of Heterorhabditis spp. against larvae of the black vine weevil, Otiorhynchus sulcatus, at low temperatures, to changes in nematode behavioural parameters was quantified and related to genetic or environmental variation found in the nematodes. Parameters characterizing nematode movement had little influence on simulated control success. Parameters characterizing aggregation and arrestment had a large effect on control, but there is no variation in Heterorhabditis for these traits. Parameters characterizing penetration had a moderate effect on control. The most promising option to enhance control by Heterorhabditis in this system would be to raise the proportion infectious nematodes of an isolate up to its genetic maximum, by improving production and storage conditions. Variation in biocontrol would be reduced, resulting in a more reliable product.     

Optimal rotation of peanuts and cotton to manage soil-borne organisms

Damage from the root-knot nematode (Meloidogyne arenaria) and Southern blight (white mold) fungus (Sclerotium rolfsii) are principal yield-limiting factors in the production of peanuts (Arachis hypogaea) in the USA. Both are widespread in the southeastern USA and yield losses caused by them can be severe. Both organisms can be suppressed by pesticides, but both can also be suppressed by rotation with cotton and certain other crops. This article presents a stochastic dynamic programming model that maximizes the expected present value of profit over a multi-year planning horizon with production of peanuts and cotton, accounting for: (1) the stochastic population dynamics of the peanut root-knot nematode, Southern blight fungus, and beneficial microbivorous nematodes; (2) the stochastic market prices for cotton and peanuts; and (3) land use in each of the previous 2 years. Expected profit from this seven-state variable dynamic programming model is compared to expected profit for monoculture peanuts, monoculture cotton, three fixed rotations, and a myopic, but flexible, rotation. Comparison of expected returns for these decision models indicates that an information-based strategy—the optimal dynamic strategy or the myopic strategy—is better than any of the fixed rotations. The myopic strategy results in expected profits almost as high as the optimal strategy for this particular problem. Since a myopic strategy is much more easily computed and more easily explained to producers, it has much more promise for adoption than difficult-to-understand results from a stochastic dynamic programming model.     

秸秆还田方式对旱地玉米产量和水分利用效率的影响

基于中国北方干旱地区18年的长期秸秆还田田间定位试验,开展了不同秸秆还田方式及施肥时期对春玉米产量及水分利用效率影响的比较研究.结果表明:与春施肥对应处理相比,不同方式秸秆还田秋施肥具有显著增产效果,18年累计增产玉米籽粒9.71～15.58 t/hm2,增产率为8.33％～16.19％;同时,玉米生育期耗水量减少,土壤贮水量增加,水分利用效率明显提高.4种不同秸秆还田方式对春玉米18年总产量、总水分利用效率的贡献从大到小依次为:秸秆过腹还田、秸秆覆盖还田、秸秆粉碎直接还田、秸秆未还田.不同的降水年型,对各处理玉米产量和水分利用也存在较大影响.正常年型玉米产量最高,偏旱年型玉米水分利用效率最高.秸秆覆盖还田秋施肥对偏旱年份的增产及水分利用效率提高的效果尤为突出.     

温室番茄对微小流量滴灌埋深与灌水量的响应

试验采用番茄品种为“中研998”,于2017年3-7月在中国农业大学通州实验站春秋大棚中进行.试验共6个处理,3个灌水梯度(以田持的85%,75%,65%计)与2个痕量带埋深梯度(15,30 cm).研究结果表明:埋深与灌水下限对番茄植株株高茎粗的影响规律性不强;深埋处理更有利于植株茎干物质积累,浅埋更有利于叶干物质积累,说明浅埋处理植株蒸腾量更大;埋深与灌水下限对根干重的影响规律性不强;深埋更有利于提高果实产量、氮素表观利用率与肥料偏生产力,浅埋更有利于提高水分利用效率;灌水下限越低,果实产量、水分利用效率、氮素表观利用率与肥料偏生产力越高.因此根据本试验研究的各项指标综合得出埋深为30 cm、灌水下限为65%田持时最适宜此种试验条件下温室番茄的生长.     

Modeling the alfalfa stem nematode in irrigated alfalfa

An alfalfa growth simulation model, modified to incorporate the impact of the alfalfa stem nematode and include an economic analysis component, is reported. The modified model was calibrated for Colorado growing conditions and used to evaluate nematode control measures and determine the optimal time for alfalfa replacement when fields are infested with the alfalfa stem nematode. The results indicate that planting nematode-resistant varieties increases returns from nematode-infested alfalfa fields. Nematode control activities implemented at the proper time can extend the economic life of an alfalfa stand. Planting a non-host crop in the fifth year of production also increases returns.     

秋灌定额对越冬期土壤水盐运移分布的影响

通过盐渍化冻融土壤秋灌试验,研究了不同秋灌定额下越冬期间土壤含水率、盐分的变化情况。结果表明,秋灌定额为150～200 mm时,春播期土壤含水率基本适宜。秋灌定额对土壤盐分的动态影响较大,秋灌能够起到冲洗压盐的作用。但是秋灌定额不宜过大,秋灌前不实施耕作措施更有利于储水保墒。     

沿海地区萝卜根结线虫病的防治

沿海地区是我国萝卜主产区之一,但日益严重的根结线虫病害导致萝卜减产、品质下降。介绍了萝卜根结线虫病的识别方法以及防治方法,包括农业防治、物理防治、化学防治和生物肥防治等,以减少根结线虫病的危害。