不同种植年限菜场叶菜田恶性杂草马齿苋土壤种子库的研究

采用恒温保湿培养法分别对种植1年、6年、8年和10年的菜场叶菜田马齿苋土壤种子库进行了研究。结果表明：随着菜场种植年限的增加,马齿苋土壤种子库种子密度不断升高,与不同年限菜场田间马齿苋种群发生量的调查结果一致。对马齿苋土壤种子库0~20 cm土层的垂直分布进行研究,结果显示,马齿苋土壤种子库的种子密度随着土壤垂直深度的增加呈现逐渐减少的趋势,其中马齿苋种子在0~15 cm范围分布最多,种子密度占整个分布层的90.8%以上;15~20 cm土层的马齿苋种子数量较少,低于9.2%。对上述不同种植年限菜场叶菜田马齿苋土壤种子库的年动态变化研究结果表明,3月和12月马齿苋土壤种子库种子密度较高,6月和9月相对较低,与马齿苋田间发生量的年动态变化相反。     

油-棉连作棉田油菜秸秆覆盖对棉田杂草发生及土壤杂草种子库的动态影响

在安徽省沿江棉区开展了油菜秸秆覆盖对棉田杂草发生、棉花生长及土壤杂草种子库影响的研究。结果表明：随着油菜秸秆覆盖量的增加,对棉田杂草的抑制效果增强。与未覆盖秸秆且不除草处理相比较,7000 kg/hm²秸秆覆盖量处理棉花单株铃数和子棉产量显著提高。7000 kg/hm²秸秆覆盖量处理在覆盖后30、60、120天逐步减少0~20 cm土层杂草种子库密度,与全程除草剂处理较一致;随着覆盖量减少,对0~20 cm土层杂草种子库密度的降低幅度减小。全程除草剂处理降低0~5 cm土层杂草种子库多样性,而油菜秸秆覆盖则可能增加0~5 cm土层的杂草种子库多样性。3500 kg/hm²覆盖量+秸秆覆盖30天后喷施除草剂处理的抑草效果和增产效果与全程除草剂处理较一致。因此,在安徽省沿江棉区油-棉连作棉田推荐使用3500 kg/hm²油菜秸秆覆盖量+秸秆覆盖30天后喷施除草剂。     

天然沙冬青土壤种子库特征研究

通过野外样方调查、种子鉴定及种子发芽等相结合的方式,对天然沙冬青种群种子库进行研究,以期揭示天然沙冬青土壤种子库特征及与种群更新之间的关系。研究结果显示,天然沙冬青种群土壤种子库比较丰富,平均密度为11粒/m2;种子主要存在于土壤表层,在有结皮存在的情况下,种子才有可能存在于0~2 cm土层中,以下土层没有种子;沙冬青种子发芽率与土壤种子库呈负相关,种子库丰富的地方,种子的发芽率较低,这一对矛盾造成幼苗数量的稀少,进而影响天然沙冬青种群的自然更新。     

拉萨市青稞田杂草发生情况调查

采集拉萨市4个县13个乡的青稞田土样，通过室内诱萌方法，研究青稞田杂草的发生情况。结果表明：拉萨市青稞田常见杂草分属于12个科，26个种，多为一年生杂草。主要危害杂草为禾本科杂草，有早熟禾、狗尾草、无芒稗等；从土壤分层培养结果来看，表现为：0~10 cm土层杂草出苗量要高于10~20 cm土层杂草出苗量。该研究将为拉萨市青稞田的杂草有效防治提供科学依据。     

土层深度对龙葵出苗及生长的影响

为了解杂草种子库中不同土层深度对龙葵生长发育的影响,采用室内随机区组设计,选择2、4、6、8 cm 4个水平的土层深度进行盆栽试验。试验结果表明,土层深度对龙葵种子的出苗率有显著性影响,其影响曲线呈抛物线形。龙葵种子最适深度为2~4 cm,出苗数占所有土层出苗的85%以上;当土层深度6 cm时,龙葵种子则基本不能出苗。不同土层深度的龙葵种子出苗后,其株高、地上部鲜重、地下部鲜重均有显著性差异。随着土层深度的增加,龙葵种子生长发育受到的影响也随之增加。     

麦-油轮作区油菜田土壤杂草种子库研究

麦-油轮作区油菜田杂草种子主要分布在0～15cm的耕层土壤中,青海川水地区以藜为主、脑山地区又以藜、遏蓝菜、鼬瓣花等杂草组成了该地区油菜田土壤种子库.通过调查各地土壤中优势杂草种子的出苗规律.得出在杂草防除上:川水地区着重防治藜,脑山地区在有效控制藜的同时,还应防治遏蓝菜和鼬瓣花等杂草.     

桉树人工林土壤种子库研究

为了了解桉树人工林土壤种子库的物种组成、密度、垂直分布等特征,以2年生桉树人工林为研究对象,相邻的大叶栎人工林作对照,取其土壤,通过室内种子萌发的方法,研究桉树人工林土壤种子库分布特征。结果表明：（1）各土壤层种子萌发的规律基本一致,大约从第7天开始进入种子萌发高峰期,第19天萌发高峰期基本结束,随后进入缓慢萌发期,至最后停止萌发;（2）桉树人工林土壤种子库储量较大,种子密度为9804粒/m2（对照为3614粒/m2）,共计物种15种,分属于9科,其中禾本科的弓果黍为优势种,种子密度为8849粒/m2,占土壤种子库总量90.26%;（3）种子库垂直分布格局显示,80%以上的种子储存在枯枝落叶层和0~5 cm的土壤中。2年生桉树人工林土壤种子库的种子密度大于大叶栎人工林,其组成以草本为主,灌木次之,种子多集中在枯枝落叶层和浅层土壤中。     

黔中玉米耕地土壤杂草种子库季节动态

对黔中玉米耕地土壤进行种子萌发试验,结果表明:玉米地杂草种子库共有44个物种出现,隶属16科40属。4个季节单位面积的种子萌发量Ⅰ季度8 609粒/m2>Ⅲ季度8 045粒/m2>Ⅱ季度6 491粒/m2>Ⅳ季度2 698粒/m2。狗尾草和水田碎米荠为上半年库中优势物种,下半年优势物种则为波斯婆婆纳。整体上随土壤层次的增加种子库存量相对减少,冬季活力种子萌发量最少;就物种多样性而言,种子库Shannon-W iener指数和Simpson指数均表现为Ⅱ>Ⅰ>Ⅲ>Ⅳ。     

推迟拔节水及其灌水量对小麦耗水量和耗水来源及农田蒸散量的影响

于2007-2008和2008-2009小麦生长季, 以高产中筋冬小麦品种济麦22为材料, 采用测墒补灌的方法, 研究推迟拔节水及不同灌水水平对冬小麦耗水量、耗水来源、单位土地面积上旗叶叶面积和蒸腾速率、株间蒸发量、籽粒产量及水分利用效率的影响。结果表明, 测墒补灌后0~140 cm土层能够达到目标含水量。相同补灌时期, 随补灌水平的提高, 拔节至开花阶段日耗水量增大, 0~120 cm土层贮水消耗量减小, 生育期总灌水量和田间耗水量增加, 土壤贮水消耗量先增加后减小, 土壤贮水消耗量和降水量占田间耗水量的比例降低。相同补灌水平, 由拔节期推迟至拔节后10 d补灌则麦田日耗水量减小, 挑旗期日耗水量增大, 拔节至开花阶段80~120 cm土层土壤贮水消耗量增加, 生育期总灌水量和田间耗水量亦增加, 降水量、灌水量和土壤贮水消耗量占田间耗水量的比例不变; 灌浆初期单位土地面积上旗叶叶面积和蒸腾速率降低, 株间蒸发量增加; 公顷穗数降低, 穗粒数、千粒重、籽粒产量、水分利用效率和灌水生产效率增加。本试验条件下, 在拔节后10 d补灌至0~140 cm土层平均土壤相对含水量为75%, 开花期补灌至70% (2007-2008年度)是兼顾节水、高产的最优处理。     

黄土高原丘陵沟壑区不同土地利用模式对土壤机械组成和速效养分影响分析

通过对黄土高原丘陵沟壑区不同土地利用模式土壤机械组成和速效养分的测定,论述黄土高原丘陵沟壑区不同土地利用模式对土壤机械组成和速效养分的影响。结果表明：草地的在两个土层速效养分含量差别不大,而其他土地利用模式0-20cm土层的速效养分含量均高于20-40cm土层。关中土壤的速效养分明显高于黄土高原丘陵沟壑区,草地的速效养分都低于其它土地利用模式。黄土高原丘陵沟壑区土壤机械组成分布大致为：粉粒>细砂粒>粗砂粒≈粘粒。速效养分只与0-20cm的粘粒含量承显著正相关。     

AlomySys: Modelling black-grass (Alopecurus myosuroides Huds.) germination and emergence,in interaction with seed characteristics,tillage and soil climate: I. Construction

Models quantifying the effects of agricultural practices on weed emergence, in interaction with the soil, are necessary to evaluate and design cropping systems. In the present study, such a model was developed for black-grass (Alopecurus myosuroides Huds.), a harmful weed frequently found in rotations consisting mostly of winter crops. The model AlomySys was based on sub-models predicting (a) soil environment (climate, structure) resulting from the cropping system and weather, (b) vertical soil seed distribution after tillage, depending on the tool, the characteristics of the tillage implement and the soil structure; and (c) seed mortality, dormancy, germination and pre-emergent growth depending on soil environment, seed depth, characteristics and past history. Seed movements during tillage depend on the tool used, its characteristics, soil structure and on the initial position of the seed. Seed mortality increases with seed age; seed dormancy depends on seed age, seed depth, the conditions in which the seeds were produced and the past moisture and dryness conditions undergone by the seeds; germination is triggered by rain or tillage and driven by hydro-thermal time; pre-emergent shoot elongation depends on seed weight, on the conditions in which the seeds were produced and increases with thermal time; pre-emergent seedling mortality increases with soil dryness, clod size and seed depth. The sub-models were based either on existing models, or developed with literature data or additional experiments. Simulations were carried out to show how weed emergence can be reduced by adapting tillage mode and date to previous crop history.     

Assessing innovative sowing patterns for integrated weed management with a 3D crop:weed competition model

Weed dynamics models are needed to design innovative weed management strategies. Here, we developed a 3D individual-based model called FlorSys predicting growth and development of annual weeds and crops as a function of daily weather and cropping practices: (1) crop emergence is driven by temperature, and emerged plants are placed onto the 3D field map, depending on sowing pattern, density, and emergence rate; plants are described as cylinders with their leaf area distributed according to height; (2) weed emergence is predicted by an existing submodel, emerged weed seedlings are placed randomly; (3) plant phenology depends on temperature; (4) a previously developed submodel predicts available light in each voxel of the canopy; after emergence, plant growth is driven by temperature; when shaded, biomass accumulation results from the difference between photosynthesis and respiration; shading causes etiolation; (5) frost reduces biomass and destroys plants, (6) at plant maturity, the newly produced seeds are added to the soil seed bank. The model was used to test different sowing scenarios in an oilseed rape/winter wheat/winter barley rotation with sixteen weed annuals, showing that (1) crop yield loss was negatively correlated to weed biomass averaged over the cropping season; (2) weed biomass was decreased by scenarios allowing early and homogenous crop canopy closure (e.g. reduced interrows, increased sowing density, associated or undersown crops), increased summer fatal weed seed germination (e.g. delayed sowing) or, to a lesser degree, cleaner fields at cash crop sowing (e.g. sowing a temporary cover crop for “catching” nitrogen); (3) the scenario effect depended on weed species (e.g. climbing species were little affected by increased crop competition), and the result thus varied with the initial weed community (e.g. communities dominated by small weed species were hindered by the faster emergence of broadcast-sown crops whereas taller species profited by the more frequent gap canopies); (4) the effect on weed biomass of sowing scenarios applied to one year was still visible up to ten years later, and the beneficial effect during the test year could be followed by detrimental effects later (e.g. the changed tillage dates accompanying catch crops reduced weed emergence in the immediately following cash crop but increased seed survival and thus infestation of the subsequent crops). This simulation showed FlorSys to predict realistic potential crop yields, and the simulated impact of crop scenarios was consistent with literature reports.     

The Influence of Johnsongrass Infestation and Nitrogen Rates on Grain Sorghum

Gram sorghum [ Sorghum bicolor (L.) Moench] is grown on marginal land and johnsongrass [Sorghum haiepense (L.) Pers] is the most common and hard to control weed in this crop. The agronomic performance of gram sorghum at different nitrogen (N) and johnsongrass infestation levels in the field has not been adequately investigated. Therefore, research was conducted on a Decatur silty clay loam soil (Rhodic Paleudult) to determine the influence of N rates (0, 40, 80 and 120 kg ha^-1) and johnsongrass infestation levels (0, 2, 4, 6 and 8 plants per 5 m crop row) on the growth and yield of grain sorghum (cv. GK522G) and johnsongrass. Increase in N rates increased seed weight, seed yield and percent protein in grain sorghum as well as dry matter and percent protein of johnsongrass. The increase in johnsongrass infestation (from 0 to 8 plants per 5 m crop row) significantly decreased the performance of grain sorghum and johnsongrass at all the N rates. The results suggest that 40 kg N ha^-1 with up to 2 johnsongrass plants per 5 m crop row or 80 kg N ha^-1 with up to 4 johnsongrass plants per 5 m crop row produced grain sorghum yields equivalent to absence of johnsongrass in the crop.     

Weed seeds in exogenous organic matter and their contribution to weed dynamics in cropping systems. A simulation approach

Nitrogen fertilizers are crucial for ensuring crop production. Mineral nitrogen fertilizer are often complemented or replaced (e.g. in organic agriculture) by exogenous organic matter (EOM) to limit environmental impacts of mineral fertilization (e.g. reduced carbon storage, nitrate leaching to groundwater, biodiversity erosion). EOM can though cause new problems as it comprises pest propagules, particularly weed seeds. The objective of the present work was to evaluate the impact of EOM on grass–weed dynamics, combining EOM analyses and model simulations. The first step analyzed seven EOM types for their chemical properties (e.g. nitrogen, carbon) and weed seed contents (using germination tests). The tested EOMs were of agricultural or urban origin (e.g. co-compost of green waste and sewage sludge or organic fraction of municipal waste). The most infested EOMs were composted farmyard manure and cattle slurry while fresh manure contained few weed seeds. Urban and green waste composts were nearly seed-free. In total, nineteen weed species and one crop species (Triticum aestivum) were identified with cattle slurry comprising the highest species number (thirteen). Weeds were mostly grass species (Lolium sp., Bromus sterilis, Echinochloa crus-galli, Festuca sp., Poa annua), except for Trifolium sp. In the second step, an existing model (AlomySys) which quantifies the effects of cropping systems on the dynamics of an autumnal grass weed similar to Lolium sp. was amended to account for EOM applications, considering both weed seed addition to the native soil seed bank and additional nitrogen. Finally, the amended model was used to simulate the effects on grass–weed dynamics of applying composted farmyard manure, using the observed EOM characteristics. Simulations focused on a small number of factors potentially interacting with EOM, i.e. EOM application frequency and seed content, tillage strategies, mineral nitrogen fertilization, and initial weed infestation. These simulations showed that for autumnal grass–weed species, adding weed seeds via EOM only increased multi-year weed infestation if fields were initially weed-free or if the simulated weed species was highly dormant in summer. Conversely, the additional EOM nitrogen reduced the fitness of the newly produced grass–weed seeds by affecting their dormancy and germination pattern, having more of them emerge in summer and thus unable to flower. Burying manure by mouldboard ploughing decreased or even cancelled the EOM effect.     

Analyse der Ertrags- und Unkrautverteilung in Ackerschlägen mit einem Geo-Informations-System (GIS)

Analysis of the yield and weed distribution in arable fields in a Geo Information System (GIS)
The variation in yield was assessed and mapped in cereals, maize, sunflower and faba beans at Dikopshof Research Station of the University of Bonn from 1998 to 2000 using a CERES 2 yield sensor (RDS^® Company, Minchin-hampton, UK). The calculated yields differed on average by 4–12 % from weighed grain yields depending on the crop and the grain moisture. The yield maps were georeferenced with a Geo Information System and compared to soil and aerial maps, field data and maps of the weed, nutrient and organic matter distributions to identify reasons for the yield variation. In two of the three fields studied, a strong correlation amongst grain yield, soil quality and relief map was found. In another field that was originally separated into two sections with different crop rotations, the distributions of grain yield, phosphorus, potassium and organic matter were still influenced by the former cropping system. On the basis of the results of this study, recommendations were made for site-specific crop management. In addition, the results of this study contribute to elucidation of the complex influences of soil and management on the grain yield.     

Management of Broomrape (Orobanche spp.) – A review

Broomrapes ( Orobanche spp.) are phanerogamic holoparasites that subsist upon the roots of many important crops thus causing considerable yield losses, especially in the drier and warmer areas of Europe, Africa and Asia.
The major principles of reducing the seed bank and controlling the weed in the germination and parasitic/ reproductive phases are critically reviewed. Practices to control broomrape include physical methods (weeding, soil tillage, flooding, irrigation, solarization, flaming), chemical methods (soil fumigation, herbicide application, use of germination stimulants) and biological methods (use of resistant or tolerant varieties, cropping systems with trap and catch crops, intercropping, biological control with insects or fungi). Cultural practices which help to avoid germination, infection or strong reproduction of the weed or improve the crop's tolerance should be optimized.
However, no single cheap method can control the weed, so integrated management practices are required. Integrated control strategies are site- and cropping-system specific but have in common that measures are taken to kill part of the seed bank, induce the conditioned seeds to germinate in the absence of the commercial crop, kill emerging Orobanche shoots before seed set during growth of the commercial crop and further reduce or avoid damage to the commercial crop.     

Annual Medicago as a Smother Crop in Soybean

Use of conservation tillage and narrow row spacing in soybean [Glycine max (L.) Merr.] production has led to increased use of herbicides for weed control. Some producers are seeking alternative weed control methods, such as smother crops, that would reduce dependence on chemical weed control. A successful smother crop must compete strongly with weeds but minimally with the crop. In four environments, we intercropped three annual Medicago spp. (medics) with soybean to test their utility as a smother crop for weed control. Annual medics were intercropped with soybean at rates of 0, 85, 258, or 775 seeds m^?2, and the intercrops were grown with and without weed control. Increasing medic seeding rate decreased weed yields but also reduced soybean herbage and grain yields. For the weed‐controlled treatment, average soybean grain yields declined 7 kg ha^?1 for every 10 seeds m^?2 increase in medic seeding rate. Soybean grain yield was lower when grown with Medicago scutellata L. cv. Sava than when grown with Medicago polymorpha L. cv. Santiago or Medicago lupilina L. cv. George. Soybean grain yield was negatively related (r=?81) to medic herbage production. In the autumn following soybean harvest, medic residue ranged from 200 to 3700 kg ha^?1 depending on the location and seeding rate. Medics provided residue for soil protection, suppressed weeds, but also reduced soybean yields.     

Photocontrol of Weeds

The reduction of weed emergence resulting from night‐time tillage in worldwide conducted field trials was very variable. The efficacy of night‐time tillage ranged from a reduction of weed ground cover of 97.5 % to an increase in weed seedling emergence of 80 % compared with daytime tillage. In most of the field trials, the reduction in the weed density as a result of night‐time tillage was <30 %. Important factors affecting this variation were: (1) the different light sensitivity of weed species, (2) the different light sensitivity of populations within the same species, (3) the dormancy status of the seeds, (4) the seasonal and short‐term variation of light sensitivity of seeds, (5) the variation of soil water content and (6) the type of soil tillage implement used. Less important were the small light intensity during night‐time tillage which cannot be excluded, and the penetration of light into the soil the days following night‐time tillage. The influence of different environmental factors on the effect of photocontrol of weeds is rather unclear because there are presumably complex interactions between environmental factors and the light‐dependent germination of weed seeds under field conditions. However, some field trials indicate that dry soil conditions reduce the efficacy of photocontrol of weeds. Several trials in the literature suggest that photocontrol of weeds during daytime using implements with a light‐proof cover was as effective as night‐time tillage. This review summarizes the results in research of photocontrol of weeds (soil cultivation in darkness), particularly those derived from field trials. Moreover, important factors are discussed, which might influence the effect of photocontrol of weeds.     

不同耕播期对杂草控制及土壤残留农药的影响

【研究目的】为了控制农田杂草,加速土壤残留农药降解,生产无公害农产品是非常重要的。【方法】对于残效农药长期使用的地区,可以采用连续2~3年秋收浅耕、翌年春播时早浅耕晚播种或直接晚耕播种三种措施,来研究杂草的控制效果。通过取样测量作物幼根长和鲜重,分析这三种措施对土壤残留农药的削减程度。【结果】研究结果表明：氟乐灵在油菜田长期使用时,土壤残留农药抑制下茬青稞幼根生长,幼根较对照株缩短3.0~3.1cm/株,鲜重量减少0.19~0.20g/株;甲磺隆在青稞田长期使用时,下茬油菜幼根较对照株缩短1.9~2.0cm/株,鲜重量减少0.13~0.14g/株;秋收后及时浅耕可将落入地表的杂草种子全耙入0~10cm耕层内;翌年春播早浅耕可诱发土壤表层的杂草种子提前萌发出苗,10d后耕种,能防除40%左右的杂草株数;较正常播种期推迟10d后直接晚耕播种,可防除30%左右杂草株数;苗期或后期拔（捋）出残余杂草种子时,除草效果理想,对下茬作物幼苗生长发育及产量无任何不良影响。【结论】在长残效农药长期使用地区进行2~3年秋收浅耕及不同耕播期加人工锄草,能有效控制农田杂草的危害,不污染农田土壤和生活环境,且加速对土壤残留农药的降解。