稻作区灌溉水流传播的杂草种子与稻田土壤杂草种子库的关系

选择典型稻作区,对灌溉水流传播的杂草种子的种类和数量进行取样调查,并与田埂、灌溉水渠周围生境、下茬麦田的杂草群落及稻田土壤杂草种子库进行比较分析,以研究自然条件下灌溉水流传播的杂草种子与土壤杂草种子库及其他生境杂草群落间的相互关系。 有14科21种杂草种子随灌溉水流输入稻田,这些杂草种子主要隶属禾本科、报春花科、藜科、蓼科等。土壤杂草种子库中共检出19科41种杂草种子,含有所有其他生境中杂草的种子。灌溉水流传播的杂草种子与田埂上、灌溉水渠周围生境、下茬麦田杂草群落及稻田土壤种子库的杂草群落间相似性较高,Sorensen指数均在0.5以上。     

稻田土壤多年生杂草种子库研究

对江苏省仪征市连年稻麦两熟轮作稻田土壤多年生杂草种子库中杂草种类、繁殖方式、分布及萌发等特性进行了系统调查研究。结果表明,眼子菜、矮慈姑、野荸荠、水莎草、扁秆藨草等5种多年生杂草种子和块（球）茎主要分布在0~15 cm耕作层内,并以营养繁殖为主。种子萌发主要在土壤表层,块（球）茎萌发在0~15 cm土层内;土壤含水量饱和至薄水层最有利于萌发。同时阐述了种子和块（球）茎的寿命,以及免耕和水旱轮作对稻田多年生杂草种子库的影响,并提出了控制措施。     

稻油轮作田杂草种子库组成及其垂直分布特征

杂草种子库是潜在的杂草群落，对杂草可持续治理具有重要意义。在稻油轮作田杂草种子库中共检测到28种杂草，主要隶属于禾本科、玄参科和菊科，种子库密度达224 550 seed/m2，其中约64％为冬季油菜田杂草种子。从杂草种子库中种子的垂直分布来看，土壤表层的种子密度较高，占整个种子库数量的63.88%，而中层和下层的种子密度较小，其垂直分布主要有3种类型。种子库中优势恶性杂草有菵草Beckmannia syzigachne、异型莎草Cyperus difformis、看麦娘Alopecurus aequalis、稻槎菜Lapsana apogonoides和日本看麦娘Alopecurus japonicus等，随着土层深度的增加，各土层的优势种组成也有差异。通过采取措施调控杂草种子库的规模，有望实现稻油轮作田杂草的可持续治理。     

不同伐藤处理下次生林群落土壤种子库特征及演替趋势

本研究以五指山市受藤本植物危害严重的低海拔次生林群落为研究对象,采用野外植被调查和室内种子萌发试验相结合的方法,对不同伐藤处理下的次生林群落土壤种子库特征、物种多样性及其与林下植被的相似性进行了研究。结果表明:（1）人工除藤可提高研究区土壤种子库种子萌发数量及速度,也可延长其种子萌发天数;（2）不同伐藤处理下的土壤种子库中共出现74种植物,隶属35科67属,其中菊科、茜草科和禾本科植物种出现比例较高,而飞机草在不同伐藤处理下的土壤种子库中均为优势种;不同伐藤处理下的土壤种子库物种生活型组成,均以草本植物占明显优势,人工除藤可使土壤种子库中乔木、灌木等生活型的物种数明显增多;（3）不同伐藤处理下土壤种子库种子密度和物种数均随土层深度的加深呈递减趋势,人工除藤可使研究区2~5、5~10 cm土层土壤中的种子密度明显增加;（4）不同伐藤处理下土壤种子库物种多样性指数均无显著差异,且其土壤种子库与林下植被的相似性系数（0.173~0.302）普遍较低,但随着伐藤年限的延长,土壤种子库与林下植被物种组成的相似性增大,伐藤3年处理的群落显著大于未做处理的对照群落。综上可知,人工除藤可提高研究区土壤种子库的植被恢复潜力及天然更新能力,有助于推动该区域次生林群落的正向恢复演替。     

华南地区大豆田杂草种子库特征与化学防除的研究

针对华南地区大豆田杂草防除问题,采用种子库诱萌法和田间药效试验法,研究田间杂草种子库的预测方法,筛选最佳化学防除方案.结果表明:杂草种子库共有杂草7科10属,主要分布在0～ 10 cm的土层,总出草量为6 861株·m-2.田间实际出草种类为6科9属,实际出草量平均为208株·m-2,占土壤杂草种子库总量的3.03％;6种除草剂都具有良好的防除效果,其中7.5％禾阔灵乳油的防除效果最佳,能有效防除禾本科杂草、莎草科杂草以及阔叶杂草,药后45 d鲜重防效仍达到70.7％～72.4％,可使大豆增产20.5％～ 34.5％.     

马铃薯田杂草综合防除措施浅析

大兴安岭地区地广人稀,耕作粗放,杂草危害十分严重,农田杂草与作物争夺水分、养分、空间和阳光等有限资源,直接影响了马铃薯的产量,因此本文就如何有机地把各项除草措施相配套,使之增强灭草效果,避免灭草效果的削弱进行了探讨。1　农业防除11　轮作由于杂草种子在土壤表层发生量大,危害大,通过轮作改变土壤层的耕作制度,把杂草种子深埋在土壤深层抑制其萌发出苗,同时还可降低伴生性　收稿日期:1999-11-02杂草的密度,改变田间优势杂草群落,促进田间杂草种群数量降低。12　耕翻由于我区种植结构单一造成多年生杂草泛滥,土壤通过多次耕翻后,问…     

稻田以水带氮肥（尿素）深施技术研究

本研究将稻田氮肥施用方法与水分管理结合起来。施肥前对稻田停止灌水晾田数天,尽可能控制土壤处于水不饱和状态,再把氮肥表施,然后立即浅层灌水,让氮肥随水下渗带入土层中,达到氮肥深施的目的,简称为“以水带氮肥深施技术”。研究结果表明,此技术可将表施的60%以上的尿素氮带入土层中,减少了肥料氮素的损失,提高了氮肥的增产效果和氮素利用率,对水稻省肥增产的作用十分显著,可作为氮肥经济合理施用技术之一,在具有排灌条件的稻田中推广应用。     

Characteristics of Soil Seed Banks in Different Eucalyptus urophylla×E.grandis Forest Types

为揭示土壤种子库在桉树人工林可持续经营与物种多样性恢复中的潜在作用,采用野外调查取样和室内模拟试验相结合的方法,研究了不同桉林土壤种子库的物种组成、密度、垂直分布等特征.结果表明:(1)新造桉林和桉萌芽林土壤种子库储量密度分别为9 804、7 356粒/m2,显著高于对照大叶栎杂木林土壤种子库储量密度(3 614粒/m2).(2)新造接林土壤种子库出现物种共15种,分属于9科;桉萌芽林为8种,分属于7科;大叶栎杂木林为16种,分属于11科.不同林型土壤种子库物种组成均以草本为主,灌木次之.(3)种子库垂直分布格局表明,不同类型森林种子主要储存在枯枝落叶层和浅层土壤中.新造桉林和萌芽林土壤种子库具有较高的生态优势度指数,但丰富度指数、Simpson多样性指数、均匀度指数及土壤种子库和地上植物的相似性系数均低于对照.桉树人工林物种多样性的提高需要适度的人为干预和科学的调控措施.     

不同类型桉树人工林土壤种子库特征研究

为揭示土壤种子库在桉树人工林可持续经营与物种多样性恢复中的潜在作用,采用野外调查取样和室内模拟试验相结合的方法,研究了不同桉林土壤种子库的物种组成、密度、垂直分布等特征。结果表明：（1）新造桉林和桉萌芽林土壤种子库储量密度分别为9 804、7 356粒/m2,显著高于对照大叶栎杂木林土壤种子库储量密度（3 614粒/m2）。（2）新造桉林土壤种子库出现物种共15种,分属于9科;桉萌芽林为8种,分属于7科;大叶栎杂木林为16种,分属于11科。不同林型土壤种子库物种组成均以草本为主,灌木次之。（3）种子库垂直分布格局表明,不同类型森林种子主要储存在枯枝落叶层和浅层土壤中。新造桉林和萌芽林土壤种子库具有较高的生态优势度指数,但丰富度指数、Simpson多样性指数、均匀度指数及土壤种子库和地上植物的相似性系数均低于对照。桉树人工林物种多样性的提高需要适度的人为干预和科学的调控措施。     

稻田生态种养对农田生态效应的影响

就近年来国内外稻田生态种养如稻田养禽类(鸡、鸭、鹅)、稻田养鱼类(鱼、鳅、鳝)、稻田养两栖类(鳖、蛙)和稻田养甲壳类(虾、蟹)对水稻群体结构和植株生长、水体环境、稻田土层、稻田杂草和水稻病虫害等方面的农田生态效应进行了概述,旨在为更好地开展稻鱼生态种养的研究与实践提供参考.     

大豆DNA扩增片段长度多态性(AFLP)研究

本文研究ＡＦＬＰ技术在大豆上的应用,在改进大豆种子ＤＮＡ提取方法的基础上,比较同位素与银染检测方法的效果,筛选适宜大于大豆ＡＦＬＰ分析的酶切和引物组合,从而建立了适用于大豆指纹图谱快速鉴定的ＡＦＬＰ操作程序,并对我国野生大豆和栽培大豆代表性材料进行了ＡＦＬＰ分析。     

R5期遮荫对大豆植株体内源激素和酶活性的影响

在Ｒ５期利用人为每天遮荫８小时,连续遮荫１０天,研究了遮荫对生殖生长期大豆叶片蔗糖合成酶（ＳＳ）,蔗糖磷酸合成酶（ＳＰＳ）,谷氨酸合成酶（ＧＳ）活性及叶片和子粒中的四种内源激素含量的影响,结果表明：遮荫明显增加叶片的三种酶活性,提高子粒中ｉＰＡ,ＧＡ和ＡＢＡ的含量,改变叶片中ＧＡ,ｉＰＡ和ＩＡＡ的积累方式。认为酶活性及内源激素的变化是大豆忍耐遮荫不良环境积极生理反应,有助于减少产量和品质损失。     

Weed Seed Bank Dynamics

Summary

Weeds continue to have major impacts on crop production in spite of efforts to eliminate them. Most weed species rely on seed for regeneration and persistence. The species composition and density of weed seed in the soil vary greatly and are closely linked to the cropping history of the land. Altering tillage practices changes patterns of soil disturbance and weed seed depth in the soil, which plays a role in weed species shifts. Crop rotation and weed control practices also impact the weed seed bank in the soil. Information on the weed seed bank should be a useful tool for integrated weed management. Decision aid models are being developed that use information on the composition of the weed seed bank to estimate weed populations, crop yield loss, and to recommend weed control tactics. Understanding weed seed bank dynamics can also be used to guide management practices. Improving and applying our understanding of weed seed and seed bank dynamics is essential to developing improved weed management systems.     

咸宁苎麻产业形势与发展对策

本文阐述了咸宁苎麻产业经营的现状,发展的有利条件,制约因素和进一步发展苎麻产业的构思,以及实现这一构思采取的几项举措:扩大生产规模;加强优质原料基地及龙头企业的建设;提高品牌档次,促进工业带动农业,集科、工、农、贸为一体,走产业经营的发展道路.     

亚麻优异种质创新利用及发展

亚麻种质创新工作采用外源总体DNA导入,Co60-γ射线处理种子、植株以及利用雄性核不育材料进入转育等方法创造新类型、新材料,提供给育种家,培育出一批优异亚麻新品种,促进了亚麻生产的飞速发展.随着新的生物技术和信息技术的突破,对今后种质创新工作进行展望.     

水稻植株防御白背飞虱为害的某些生理反应

 以对白背飞虱具有不同抗性水平的水稻品种(组合) 为材料, 研究了水稻在白背飞虱为害后稻株体内的生理变化。结果表明, 稻株受害后, 感虫品种(TN1和汕优63) 光合作用速率和叶绿素含量下降比抗虫品种(N 22) 明显; 感虫品种超氧化物歧化酶(SOD) 活性增加, 过氧化物酶(POD) 和过氧化氢酶(CAT) 活性下降, 而抗虫品种POD 和SOD 均增加, CAT减少;感虫品种除丙氨酸含量下降外, 其他氨基酸含量均上升, 尤其是天门冬氨酸、苏氨酸、缬氨酸及蛋氨酸等含量增加很快, 抗虫品种中天门冬氨酸、缬氨酸等含量增加也很快, 但苏氨酸、蛋氨酸、丙氨酸的含量显著下降。     

Weed seed bank as affected by crop rotation and disturbance

An experiment was conducted to determine the influence of crop rotations on soil seed bank to provide a comparison between crop fields and non-crop lands. Crop rotations were continuous dryland wheat (Wd), continuous irrigated wheat (Wi), wheat-sugarbeet (WS) and wheat-chickpea (WCh). Nearby pastures (P) and orchards (Or) were also studied for comparison purposes. Estimates of the density of seed banks ranged from 52779 seed m⁻² in P to 9906 seeds m⁻² in Wd. A total of 114 plant species from 24 families were identified from seeds collected from different farms. 33 weed species were at high frequency in weed communities. Crop rotations were dominated by annual weed species, while the weed species dominated in P were mostly not found in any crop rotation. The two weed species Roemeria refracta and Eragrostis cilianensis were frequently present in all the study sites. Amaranthus chlorostachys and Euphorbia esula were more abundant in the areas of moderate to high disturbance. In SW and WS rotations, due to use of grass herbicides and hand weeding, winter annual broadleaves such as Lactuca serriola and Anchusa italica were the prominent species in the seed bank. Results showed that a number of weed species are adapted to a specific crop sequences and disturbance levels. Weed species richness, seed bank abundance and diversity in soil depths are highly dependent on disturbance levels. The current study highlights the importance of agricultural practices including crop sequences or disturbance levels in determining the characteristics of weed populations. This provides useful information to improve methods for maintaining plant population balance.     

Spatial distribution of nutsedge (Cyperus spp. L.) seed bank in rice growth cycle using geostatistics

A field experiment was conducted to investigate the spatial distribution of nutsedge (Cyperus spp L.) seed bank in rice growth cycle using geostatistics in 2010–11. The sampling from seed banks were performed prior to rice farm preparation and after rice harvest; also weeds density was determined in three different dates during the growing season. The results showed that the highest amount of weed population was belonging to nutsedge (Cyperus spp. L.) including Cyperus difformis, C. rotundus and C. esculentus species. Nugget/sill ratios for all variogram models ranged from 15.2 to 46.9%, indicated that there was strong and moderate spatial correlation as spherical and exponential variograms models between weed and seedling nutsedge at all stages of sampling. Visual assessments of the weed growth in these field indicated that the weed exist in patches, but mapping results showed that the size and morphology of these patches varied within field. In the present study, seed bank patchy pattern was roughly in accordance with seedling germination pattern. Generally the provided seed bank maps can be used not only as information database of seedling germination, but also for predicting of seed bank dynamics and weed management programs.     

Multi-Year Evaluation of Model-Based Weed Control Under Variable Crop and Tillage Conditions

Abstract

Selecting effective weed management options requires biological, ecological, and economic information. This study compared model-based to standard-herbicide weed control in a corn (Zea mays L.)/soybean [Glycine max (L.) Merr.] rotation that had a long-term history of different tillage and weed management practices. The model integrates weed population dynamics, herbicide efficacies, and economic information to evaluate preplant incorporated (PPI) or preemergence (PRE) weed control options based on weed seed bank size and postem-ergence (POST) strategies based on weed seedling densities. There were fewer weeds in standard-herbicide compared with model-based treatments. No-tillage had the greatest numbers of weeds 3 out of 4 years. Soybean yield was reduced the first year of the study in several treatments receiving model-based weed control and the third year in all model-based treatments. Corn yields were greatest in reduced tillage. Resuits of using model recommendations to control weeds were mixed, with PRE recommendations being insensitive to a common cocklebur (Xan-thium strumarium L.) infestation. Our conclusions agree with those of others that the nature of the weed pressure may be a prevailing influence on the outcome of using weed control recommendations of bioeconomic models.