The major features of an infestation by the invasive weed legume gorse (Ulex europaeus) on volcanic soils in Hawaii

Gorse (Ulex europaeus) infestation occupies over 4,000 ha of agriculture and conservation lands on the southeastern slope of Mauna Kea on the Island of Hawaii. The aim of this investigation is to identify ecological features associated with this weed invasion by comparing the gorse-infested areas to the surrounding uninfested areas of this landscape. The soils within the gorse infestation are more acidic, resulting in higher levels of KCl-extractable Al and lower levels of Mehlich III-extractable Ca, Mg, Mn, and Zn. Yet, gorse accumulates higher concentrations of Ca, Zn and, Cu than the kikuyu grass (Pennesitum clandestinum), which is ubiquitous throughout the site. The Ca:Al and Mg:Al molar charge ratios of the soils are lowest within the epicenter of the gorse infestation, while the molar ratios are highest in the gorse apical stem tissues. All gorse plants are nodulated and have higher nitrogen contents than the surrounding kikuyu grass. Furthermore, the δ¹⁵N of the gorse stem tissues approaches 0‰, suggesting that nitrogen is being symbiotically fixed from the atmosphere. Characterization of the Bradyrhizobium isolated from gorse nodules shows similarities and distinctions to Bradyrhizobium isolated from the endemic legume koa (Acacia koa) within the same location. Population densities of the indigenous Bradyrhizobium are higher within the gorse rhizosphere than the kikuyu grass. Soil acidification, nutrient depletion, and symbiotic nitrogen fixation distinguish gorse-infested areas from the surrounding uninfested areas. These observations suggest that gorse has a competitive advantage over kikuyu grass under conditions of soil nutrient deficiency.     

不同化学除草方案对夏播大豆田间杂草的防除效果

研究了北京地区不同化学除草方式:播前土壤处理,播后苗前1处理、播后苗前2、出苗后处理和播后苗前2 苗期5种主要除草方式对夏播大豆田间杂草的防除效果。结果表明:(1)播后苗前 苗期茎叶处理方案对单子叶杂草除草效果最好;(2)播后苗前2处理对双子叶杂草防除效果明显;(3)对于杂草茎叶防治效果,播后苗前2 苗期处理有较显著防效。     

广州地区春季叶菜田杂草群落组成及其特征

于春季利用倒置"W"取样法对广州地区不同种植年限及管理措施的叶菜田进行杂草群落调查。结果表明广州地区叶菜田杂草种类共有35种,属12科,25属。其中马齿苋、牛筋草、稗草、碎米莎草等为主要杂草。种植5年的菜田中以牛筋草 马齿苋 萹蓄等杂草为主;种植10年的菜田中以马齿苋 稗草 碎米莎草等杂草为主;长期种植的菜田以马齿苋 碎米莎草 凹头苋等杂草为主。种植5年的菜田杂草群落的香浓指数和匀度指数最大。在以人工防除为主的控草措施下,菜田中杂草群落物种丰富度指数最小(4.67)。通过聚类分析表明种植年限是影响叶菜田杂草群落结构的最重要因素。     

Patchy weed distribution and site-specific weed control in winter cereals

Site-specific weed control in winter cereals was performed on the same fields every year over a 5-year period (1999–2003). The most common weeds (Apera spica-venti, Galium aparine, Veronica hederifolia, Viola arvensis) were counted by species, at grid points which were georeferenced and the data were analysed spatially. For weed control, weeds were grouped into three classes: grass, broad-leaved weeds (without Galium aparine), and Galium aparine. Based on weed distribution maps generated by the spatial analyses, herbicide application maps were created and site-specific herbicide application was carried out for grouped and or single weed species. This resulted in a significant reduction in herbicide use. Averaging the results for all fields and years, the total field area treated with herbicides was 39% for grass weeds, 44% for broad-leaved weeds (without Galium aparine) and 49% for Galium aparine. Therefore, site-specific weed control has the potential to reduce herbicide use compared to broadcast application, thus giving environmental and economic benefits.     

不同稻田状态下克无踪快速灭茬控草试验

为控明不同稻田状态下克无踪快速除草灭茬的效果，2000年在湖南宁乡进行了克无踪用药量、对水量、施药时天气、增效剂、前作留茬高度等对除草剂清的效果试验。结果表明：克无踪有效用量为3.75L/hm^2左右，视杂草基数适当增减；对水量对灭草和灭稻茬的效果有较大的影响；二甲四氯、乙草胺、碳铵＋氯化钾可不同程度地提高克无踪的控草效果；卵茬高率不同的主要影响稻茬原再生蔸率和再生株数。推荐克无踪施用量，早稻冬泡田为3.00-3.75L/hm^2，早稻冬干田3.75-4.50L/hm^2，晚稻免耕田为3.75L/hm^2，同时加入碳酸氨铵45kg/hm^2和乙草胺450mL/hm^2为增效剂，对水900kg/hm^2于傍晚或清晨喷施，晚稻免耕清茬时，前茬留茬高度不超过4cm杂草枯黄以后应及时灌水淹没杂草或稻茬，以有效控制杂草或稻茬再生。     

Weed Detection Using Canopy Reflection

For site-specific application of herbicides, automatic detection and evaluation of weeds is desirable. Since reflectance of crop, weeds and soil differs in the visual and near infrared wavelengths, there is potential for using reflection measurements at different wavelengths to distinguish between them. Reflectance spectra of crop and weed canopies were used to evaluate the possibilities of weed detection with reflection measurements in laboratory circumstances. Sugarbeet and maize and 7 weed species were included in the measurements. Classification into crop and weeds was possible in laboratory tests, using a limited number of wavelength band ratios. Crop and weed spectra could be separated with more than 97% correct classification. Field measurements of crop and weed reflection were conducted for testing spectral weed detection. Canopy reflection was measured with a line spectrograph in the wavelength range from 480 to 820 nm (visual to near infrared) with ambient light. The discriminant model uses a limited number of narrow wavelength bands. Over 90% of crop and weed spectra can be identified correctly, when the discriminant model is specific to the prevailing light conditions.     

除草剂变量施药技术的研究现状与进展

除草剂的田间大面积均匀喷洒不仅造成了浪费,而且加剧了环境污染,作为精确农业关键技术的除草剂的变量施药能够精确地对准杂草喷洒除草剂,从而有效地减少除草剂用量,降低了农业生产成本、减轻了环境污染压力。文章介绍了基于颜色、形状、纹理、光谱、位置特征的计算机视觉杂草识别技术;给出了变量施药技术的概念和介绍了变量施药技术的国内和国外的研究概况,并探讨了该技术的实施难点和未来研究发展方向。     

海南南红稻田杂草群落物种多样性指数的测定及评价

以株数、盖度、重要值为测定指标，运用物种丰富度指数（S）、Shannon-Wiener指数（H’）、Gini指数（D’）、Pielou均匀度指数（ShannonE,GiniE)以及生态优势度（SN）等指数对南红农场稻田杂草群落进行物种多样性分析，结果表明：重要值作为测定指标，反映多样性水平最合理，Shannon-Wiener指数用来监测调控杂草群落的多样性比较合适。     

宝天曼自然保护区杂木林群落的植物特征分析

宝天曼自然保护区约有高等植物114科、334属、667种及变种，分别占宝天曼自然保护区植物科的51．12％，属的34．33％，种的24．60％；占河南等植物科的5．47％，属的25％和种的14．02％，组成本区杂木林植物的优势科有蔷薇科、菊科、禾本科、豆科等4科，合计199种，占本区被子植物总种数的32．4％，杂木林植物以温带成分为主，兼有一定热带分布类群，它体现了本区植物区系的过渡性、边缘性、多样性和独特性，显示出多方交汇和一定的古老性。本区杂木林群落垂直分布比较明显。     

纸膜覆盖水稻种植技术节水控草的效果

采用再生纸、农用纸和牛皮纸作为水稻种植的覆盖材料，研究了纸膜覆盖在水稻乳芽直播和插秧等不同种植工艺条件下的节水和控制杂草效果。研究结果表明：纸膜覆盖对水稻生产过程中的节水和杂草密度控制有明显的作用，并对保护生态环境和生产有机稻米有重要意义，为纸膜覆盖水稻种植工艺的机械化奠定了农艺基础。