加拿大有机农业中的杂草管理

本文介绍了加拿大有机农业生产中防治杂草的各种措施，包括作物轮作、绿肥作物、可持续土壤管理、适度机械耕作等。同时选择合适的播种时间、播种率、行间距为作物创造有利的与杂草竞争的条件。当杂草比较严重时，还可进行机械锄草或火烧。     

计算机杂草识别技术的研究现状

针对不同的杂草种类分别采取光谱分析法，颜色分析法，纹理分析法以及外形分析法来识别的特点，介绍了国外在该领域的研究应用进展，提出了计算机杂草识别技术的意义及在我国的发展前景。     

废弃秸杆变板材

废弃的秸秆、花生壳、杂草，经过加工就可以变成人们喜爱的环保型板材，这是河北省井陉县科技部门，经过两年研制开发出的一项科研新技术。到目前，该县已建成年产2．1万块环保型板材生产企业，年消化秸秆、花生壳、杂草等157万多吨。     

新书介绍

《杂草幼苗识别图册》简要介绍了近300种杂草幼苗的形态特征;根据杂草幼苗的特征,本着简明实用的原则编成农田杂草幼苗分科检索表;附有各科杂草幼苗分种检索表     

农业生态系统中杂草资源的可持续利用

杂草是农业生态系统中对农作物的生长和产量产生重要影响的伴生植物。杂草具有耐不良环境、生长快、繁殖力强等优良特性,是重要的生物资源。可利用杂草的优良基因作为农作物遗传改良的基因供体,利用其有用成分开发中医药,利用植物他感效应进行害虫生物防治,可开发成观赏植物,可作为先锋物种进行生态恢复、改良环境、促进养分循环、保护土壤微生物等。杂草的化学防除是导致杂草资源丧失的重要因素,寻找既利于杂草资源保护又不影响农作物生长的防除途径、杂草资源数据库的创建、杂草资源有益基因的发掘和开发利用,是杂草科学今后应加强的研究方向。     

农药应用对地下水污染的经济损失

农药应用对地下水污染的经济损失提出了使用农药增强生产力和地下水污染危害的经济权衡问题。通过现场试验大豆生产中使用农药控制杂草的损益分析模型，来识别并例证如何选用各种控制杂草的策略，以降低被污染的地下水饮用时对人体健康的危害。该模型包括供水费用、农作物...     

磺酰脲类除草剂的残留分析

磺酰脲类除草剂是一类新型超高效除草剂，大约包括２Ｖ化合物，已被广泛用于禾谷作物防除阔叶杂草以及某些禾本科杂草，该类除草剂在环境中的残留浓度〈１μｇ．ｋｇ＾－１水平。常规的分析方法包括生物鉴定，酶免疫分析，气相色谱法和高效液相色谱法（ＨＰＬＣ）、ＨＰＬＣ／ＭＳ联用后，可以准确测定复杂环境样中磺酰脲类除草剂的痕量残留。     

"超级杂草"伴随着转基因作物而出现

最初的转基因大豆被基因工程业誉为“万金油”。它们能够在有除草剂的环境下生长，从理论上说，这将导致田地里那些不受欢迎的植物(比如杂草)的末日。这也将减少种植费用和除草剂的使用量。然而，多年来转基因技术的反对者们的预言现在已经变成了事实：随着时间的推移，“杂草”与转基因植物一样也具备了耐除草剂的特性。这便意味着必须应用其它除草剂，带来更多的花费。     

基于Subspace集成学习的稻田杂草识别研究

针对稻田苗期杂草识别中单一分类方法存在的不足,提出了一种基于Subspace集成学习的稻田杂草识别方法。先提取杂草图像的颜色、纹理、形状特征作为稻田杂草的识别特征,再通过多个基分类器集合训练得到Subspace集成学习模型。结果表明,当基学习器个数为32和子空间维度为91时,Subspace集成学习模型的准确率达到91.41%,且基于Subspace集成学习算法的识别精度高于SVM和BP神经网络,解决了针对稻田杂草特征单一分类器识别率不高的问题。     

三种田间杂草的镉、铅富集特征研究

选择了三叶鬼针草(Bidens pilosa)、青蒿(Herba Artemisiae Annuae)、飞蓬(Erigeron acer)3种田间杂草进行盆栽试验,其间用不同浓度的镉、铅溶液处理,最后测定杂草根系及地上部镉、铅量。结果表明:3种田间杂草无论是根系,还是地上部,镉、铅量都随处理液浓度增高而增高;3种杂草对镉的富集系数排序为:三叶鬼针草飞蓬青蒿;转移系数排序为:三叶鬼针草青蒿飞蓬;对铅的富集系数排序为:飞蓬青蒿三叶鬼针草;转移系数排序为:飞蓬青蒿三叶鬼针草。研究还表明,3种杂草对于镉的富集系数和转移系数都远大于对铅的富集系数和转移系数,三叶鬼针草是镉的超富集田间杂草。     

生物有机除草剂防除水田杂草试验研究

采用田间试验方法,进行了生物稻壳粉、生物稻草粉2种生物有机除草剂对水田杂草的防效试验。结果表明,2种生物有机除草剂对水田杂草均有不同程度的防效,其中生物稻壳粉防效最好、经济效益最高,生物稻草粉防效和经济效益次之。该试验研究为生产有机水稻提供了新的除草方法。     

基于湿解技术处理木质纤维类废物的研究

运用木质纤维素固体基质半纤维素、纤维素和木质素定量分析程序等分析检测了不同湿解工况下草坪草和杂草主要组分的化学变化。结果表明,在湿解过程中草坪草和杂草中半纤维素、纤维素的相对含量呈减少趋势;木质素类物质经过衍生和小分子缩合后,其相对含量呈增加趋势;湿解最终产物呈弱酸性,可以用来改良碱性土壤。经过湿解处理的有机物料有机质含量丰富并含有大量腐殖酸,随湿解温度升高,腐殖化程度增加。在湿解过程中有机物料的主要化学组分同时受到热、湿、水解等各种作用,最终形成腐殖质。     

可降解有机物湿解实验及产物分析

湿解是环境友好的新型有机废物处理工艺,湿解实验在反应温度450K,反应时间1h的工况下,对杂草和马粪进行湿解,并分析了两种物料的湿解产物。结果表明:杂草和马粪经湿解处理后,分别得到了18.8%和16.3%的原料转化率,有机质转化率均超过了95%,可为土壤提供丰富的有机质;两种湿解液中所含物质基本上均集中在166.7~428.9及1122~1622的两组质荷比范围内,湿解液呈弱酸性,其中奎尼酸、柠檬酸和L-苹果酸含量丰富。     

A methodology for assessing soil quantity and quality in life cycle assessment

Changes resulting from economic activities in the quantity and quality of soil in a system under analysis are important considerations in a life cycle assessment (LCA) study because they affect the safeguard subjects of resources and future agricultural productivity. In the approach proposed here, soil is treated as an ancillary which may leave the system in a form different from that at entry. Relevant factors describing possible changes in the soil include: soil mass, nutrients, weeds and weed seeds, pathogens, nutrients, salts, pH, organic matter, and soil texture and structure. Many of the factors can be included by modelling the effects of infrequent activities benefitting the crop(s) under analysis. Three additional factors require separate assessment: changes in the mass of soil, its organic matter content, and soil compaction. Taken together, these approaches provide an integrated assessment method capable of accounting for the overall impacts of agricultural production on soil.     

三种田间杂草的镉、铅富集特征研究

选择了三叶鬼针草（Bidens pilosa）、青蒿（Herba Artemisiae Annuae）、飞蓬（Erigeron acer）3种田间杂草进行盆栽试验,其间用不同浓度的镉、铅溶液处理,最后测定杂草根系及地上部镉、铅量。结果表明：3种田间杂草无论是根系,还是地上部,镉、铅量都随处理液浓度增高而增高;3种杂草对镉的富集系数排序为：三叶鬼针草〉飞蓬〉青蒿;转移系数排序为：三叶鬼针草〉青蒿〉飞蓬;对铅的富集系数排序为：飞蓬〉青蒿〉三叶鬼针草;转移系数排序为：飞蓬〉青蒿〉三叶鬼针草。研究还表明,3种杂草对于镉的富集系数和转移系数都远大于对铅的富集系数和转移系数,三叶鬼针草是镉的超富集田间杂草。     

Plant species coexistence alleviates the impacts of lead on Zea mays L.

Whether plant coexistence can reduce the impacts of lead (Pb) on crops in agroecosystems has not been well understood. We conducted a factorial experiment to investigate the effects of weeds coexisting with maize (Zea mays L.) on Pb accumulation in maize and soil microbes at two Pb levels (ambient and 300 mg/kg). Elevated Pb tended to increase the Pb concentration in maize and decreased soil microbial activity (indicated by the average well color development, AWCD), functional group diversity, as well as arbuscular mycorrhizal (AM) colonization and vesicle number of maize. Compared to the monoculture, weeds coexisting with maize reduced the Pb concentrations in the root, leaf, sheath and stem of maize at both seedling and mature stages. In maize-weed mixtures, soil microbial activity and functional group diversity tended to increase for both Pb treatments relative to the monoculture. Furthermore, principal component analysis revealed that the soil microbial community structure changed with the introduction of weeds. The highest Pb accumulation in weeds occurred for the elevated Pb treatment in a three species mixture. The results suggest that multiple plant species coexistence could reduce lead accumulation in crop plants and alleviate the negative impacts on soil microbes in polluted land, thereby highlighting the significance of plant diversity in agroecosystems.     

Effect of herbivory by the slug, Mariaella dussumieri, and certain insects on growth and competitive success of two sympatric annual weeds

The effect of plant-eating by the slug, Mariaella dussimieri Gray, and by certain lepidopteran insects and their larvae was studied under field conditions, on the growth of two sympatric annual weeds, Galinsoga ciliata (Raf.) Blake and G. parviflora Cav., in pure and mixed stands. Under the influence of herbivory, both weeds generally produced a greater number of leaves, but the leaf area per plant was drastically reduced. Plant survival and seed output decreased in both weeds due to herbivory, but the effect was more severe in G. parviflora, especially in the mixed stands. Herbivory also reduced the dry matter yield and delayed flowering in G. parviflora. Relatively poor growth of G. parviflora in the mixed stand exposed to herbivory could be attributed to its preferential feeding by the slug and insects which reduced the competitive ability of this weed against G. ciliata.     

Comparison of soil N availability and leaching potential,crop yields and weeds in organic,low-input and conventional farming systems in northern California

Increasing dependence on off-farm inputs including, fertilizers, pesticides and energy for food and fiber production in the United States and elsewhere is of questionable sustainability resulting in environmental degradation and human health risks. The organic (no synthetic fertilizer or pesticide use), and low-input (reduced amount of synthetic fertilizer and pesticide use), farming systems are considered to be an alternative to conventional farming systems, to enhance agricultural sustainability and environmental quality. Soil N availability and leaching potential, crop yields and weeds are important factors related to agricultural sustainability and environmental quality, yet information on long-term farming system effects on these factors, especially in the organic and low-input farming systems is limited. Four farming systems: organic, low-input, conventional (synthetic fertilizer and pesticides applied at recommended rates) 4-year rotation (conv-4) and a conventional 2-year rotation (conv-2) were evaluated for soil mineral N, potentially mineralizable N (PMN), crop yields and weed biomass in irrigated processing tomatoes (Lycopersicon esculentum L.) and corn (Zea mays L.) from 1994 to 1998 in California’s Sacramento Valley. Soil mineral N levels during the cropping season varied by crop, farming system, and the amount and source of N fertilization. The organic and low-input systems showed 112 and 36% greater PMN pools than the conventional systems, respectively. However, N mineralization rates of the conventional systems were 100% greater than in the organic and 28% greater than in the low-input system. Average tomato fruit yield for the 5-year period (1994–1998) was 71.0 Mg ha⁻¹ and average corn grain yield was 11.6 Mg ha⁻¹ and both were not significantly different among farming systems. The organic system had a greater aboveground weed biomass at harvest compared to other systems. The lower potential risk of N leaching from lower N mineralization rates in the organic and low-input farming systems appear to improve agricultural sustainability and environmental quality while maintaining similar crop yields.     

A note on the effects of tropical weed decomposition on seed germination and seedling growth of some agricultural crops

Greenhouse and laboratory experiments were carried out to evaluate the allelopathic effects of Euphorbia heterophylla, Cyperus rotundus and Digitaria sanguinalis on seed germination and seedling growth of tomato, soko (feather cockscomb), pepper and sorghum. Significant reductions in germination and seedling growth of tomato, pepper and sorghum were observed when grown in pots containing increasing quantities of decomposed weeds. Decomposed Euphorbia heterophylla had the least suppressive effect on crop seeds, and soko seeds germinated without significant suppression. Seedling growth of sorghum was severely retarded when allowed to grow in leachates obtained from soil containing decomposed weeds.