The effect of non-inversion tillage and light availability on dispersal and spatial growth of Cynodon dactylon     

A C Guglielmini  & E H Satorre 《Weed Research》2004,44(5):366-374

The invasive ability of Cynodon dactylon is dependent on self dispersal and on cultivation practices. Tillage can seriously change patch biomass and spatial structure, spreading vegetative propagules of the weed. The objectives of this study were: (i) to quantify the effect on non‐inversion tillage on dispersal, establishment and colonization of C. dactylon and (ii) to propose a simple model considering soil cultivation effects and light availability on spatial growth of weed patches. Two experiments were carried out, exploring different soils and environmental conditions. Spatial distribution of vegetative units differed when tillage was conducted with different non‐inversion implements and could be described by simple functions. A minimum patch biomass seems necessary before vegetative structures are vulnerable to movement by cultivation. Only a small proportion of the biomass dispersed from original patches was able to establish. However, simulation showed that the area colonized by C. dactylon mostly increased by means of tillage dispersal, both with and without crop competition, in one growing cycle. It appears sensible to consider changing cultivation practices to reduce weed dispersal and to use crop competition for light to create unsuitable habitats limiting weed colonization.  相似文献   

Critical periods for weed control in cotton in Turkey     

B Bukun 《Weed Research》2004,44(5):404-412

Field studies were conducted over 4 years in south‐eastern Turkey in 1999–2002 to establish the critical period for weed control (CPWC). This is the period in the crop growth cycle during which weeds must be controlled to prevent unacceptable yield losses. A quantitative series of treatments of both increasing duration of weed interference and of the weed‐free period were applied. The beginning and end of CPWC were based on 5% acceptable yield loss levels which were determined by fitting logistic and Gompertz equations to relative yield data representing increasing duration of weed interference and weed‐free period, estimated as growing degree days (GDD). Total weed dry weight increased with increasing time prior to weed removal. Cotton heights were reduced by prolonged delays in weed removal in all treatments in all 4 years. The beginning of CPWC ranged from 100 to 159 GDD, and the end from 1006 to 1174 GDD, depending on the weed species present and their densities. Practical implications of this study are that herbicides (pre‐emergence residual or post‐emergence), or other weed control methods should be used in Turkey to eliminate weeds from 1–2 weeks post‐crop emergence up to 11–12 weeks. Such an approach would keep yield loss levels below 5%.  相似文献   

松嫩平原优势种羊草与其主要伴生种芦苇空间分布格局分析   总被引：6，自引：0，他引：6  

巴雷  王德利  高莹 《草业学报》2005,14(5):111-116

芦苇是松嫩草地优势种羊草的主要伴生种,两者常常形成物种组成比较单一的混生群落或者与其他物种组成羊草 杂类草群落.选择羊草 芦苇混生群落,羊草群落和芦苇群落的交错区进行羊草、芦苇单物种格局分析.结果表明,1)混生群落和交错区中,羊草和芦苇均是以集聚分布的形式存在;2)羊草在混生群落中的格局强度小于交错区中的格局强度,芦苇在2种类型群落中的格局强度没有显著差异;3)除了考虑物种的生物学特性以外,混生群落种内、种间竞争也是影响羊草集聚分布和格局强度的主要因素,交错区中,环境异质性和种间竞争是影响集聚分布和格局强度的重要因子;4)芦苇在混生群落和交错区中格局强度没有明显差异,由此可以判定芦苇的空间分布格局形成主要受植物本身生物学特性的影响.  相似文献   

基于加权Voronoi图的林木竞争指数   总被引：4，自引：2，他引：2  

李际平  房晓娜  封尧  孙华  曹小玉  赵春燕  李建军 《北京林业大学学报》2015,37(3):61-68

以福寿山林场25年生的杉木生态公益林为研究对象,通过分析林木竞争指数与胸径生长因子的相关关系,得出二者为负相关,从而确定加权Voronoi图的权重为胸径倒数(W),借助Arcgis软件里的加权Voronoi图工具,通过加权Voronoi图的方法来确定竞争单元,提出基于加权Voronoi图的W_V_Hegyi竞争指数,最后将W_V_Hegyi竞争指数与Hegyi、V_Hegyi竞争指数进行对比分析,结果表明:1) 3种竞争指数与胸径相关性强弱排序为:W_V_HegyiV_HegyiHegyi;2) 3种竞争指数与胸径服从幂函数关系,曲线拟合度排序为:W_V_HegyiV_HegyiHegyi;3) 样地竞争指数平均值排序均为:V_HegyiW_V_HegyiHegyi。通过以上比较分析证明,W_V_Hegyi竞争指数比Hegyi、V_Hegyi竞争指数能更准确地反映林木间的竞争关系。   相似文献   

基于协同理论产业融合的食用菌电子商务系统构建     

赵郁园 《中国食用菌》2020,(2):190-192

基于企业战略协同理论,对食用菌企业协同战略的必要性进行了讨论,介绍了几种食用菌电子商务的模式。在竞争日益激烈的电子商务领域,食用菌行业的电子商务模式也需要战略上的协同与合作,企业在竞争与合作之间要张弛有度、合理控制彼此间的关系,保持自身的核心竞争力,实现合作共赢。  相似文献   

Early interspecific dynamics,dry matter production and nitrogen use in Kernza (Thinopyrum intermedium) – alfalfa (Medicago sativa L.) mixed intercropping     

Shoujiao Li  Ana Barreiro  Erik Steen Jensen  Yingjun Zhang 《Acta Agriculturae Scandinavica, Section B - Plant Soil Science》2020,70(2):165-175

ABSTRACT

The global interest in growing perennial grain crops such as intermediate wheatgrass (Thinopyrum intermedium) (Kernza) for production of food and feed is increasing. Intercropping Kernza with legumes may be a sustainable way of supplying nitrogen to soil and associated intercrop. We determined the competitive interactions between intercropped Kernza (K) and alfalfa (Medicago sativa L.) (A) under three inorganic nitrogen (N) rates N0, N1, N2 (0, 200, 400 kg ha^?1) and five species relative frequencies (SRF) (100%K:0%A, 75%K:25%A, 50%K:50%A, 25%K:75%A and 0% K:100%A) in mixed intercrops (MI) in a greenhouse pot experiment. After 11 weeks of growth. Kernza dry matter yield (DM) and N accumulated (NACC) were low, but alfalfa DM and NACC high at 0 kg N ha^?1. 200 and 400 kg N ha^?1 fertiliser application increased the competitive ability (CA) of Kernza and reduced the CA of alfalfa. SRF had large impacts on alfalfa DM, NACC and NFIX only at 0 kg N ha^?1 fertiliser, and insignificant impacts on Kernza at all N fertiliser levels, indicating that adjustment of SRF may not be an effective way to modulate the interspecific competition of Kernza. Further research on the other factors that influence the interspecific competition are warranted.  相似文献   

防御信号途径在B型烟粉虱取食烟草诱导抗蚜防御中的作用     

徐亚楠  孙夏  赵海朋  薛明 《中国农学通报》2020,36(36):93-99

B型烟粉虱取食能够诱导烟草产生对烟蚜的抗性反应,为了明确水杨酸和茉莉酸防御信号途径与烟粉虱诱导抗蚜防御之间的关系,采用生化分析、实时定量PCR、蚜虫生物活性测定等方法比较了烟粉虱若虫取食对烟草水杨酸、茉莉酸含量、通路下游防御基因表达水平的影响及外源水杨酸、茉莉酸对烟蚜生长发育的影响。结果显示：烟粉虱侵染能够显著激活水杨酸防御途径,在取食15天后,水杨酸水平较对照升高1.40倍,水杨酸下游防御基因PR-1a及PR-2a分别较对照升高3.22和0.74倍;然而烟粉虱侵染后烟草叶片茉莉酸含量与对照相比无显著变化,JA下游防御基因PI-II和TPI的转录水平分别较对照降低73.91%和56.73%。生测结果显示,外源施用水杨酸对烟蚜的存活率和相对平均生长率具有显著不利影响。烟草叶片施用1 mmol/L水杨酸后,蚜虫的存活率及相对生长率分别较对照降低43.2%和11.54%;然而喷施茉莉酸甲酯对蚜虫的生长发育无不利影响。上述结果表明,水杨酸介导的防御应答在B型烟粉虱取食诱导烟草的抗蚜防御中起重要作用。  相似文献   

高职组电子产品设计与制作项目技能大赛的备赛策略探究     

周平 《湖南农机》2016,(3):142-143

近年来，随着职业教育的不断发展，越来越多的高职院校开始加大对学生实践能力的提升，学校根据自身的特色制定出一系列的专业技能比赛机制并不断地将这种方式进行延伸，将参加省市级，甚至国家级技能大赛作为展示学校和学生优势的一个重要的形式，电子产品设计与制作项目技能大赛更是新阶段较为常见的技能大赛。文章主要针对电子产品设计与制作项目技能大赛的备赛策略进行一定的探究。  相似文献   

涉农专业青年教师以竞赛为平台的专业成长有效途径研究     

张左悦  熊亚琴 《农业网络信息》2014,(12):162-163

在信息技术飞速发展的当今社会,对教育工作者提出了越来越高的要求。在专业教师队伍中,青年教师已逐渐成为主体,而想要将这支年轻的队伍打造成一支中坚力量,成为师资队伍建设的重心,也是当今教育资源建设的一项重要任务。本文以涉农专业青年教师为研究的出发点和立足点,通过搭建各种竞赛平台,研究促进青年教师的专业成长的有效途径。  相似文献   

Changes in the herbicide sensitivity and competitive ability of Abutilon theophrasti over 28 years: Implications for hormesis and weed evolution     

Sandra R. Ethridge  Saket Chandra  Anna M. Locke  Wesley J. Everman  David L. Jordan  Micheal D.K. Owen  Ramon G. Leon 《Pest management science》2023,79(10):4048-4056

BACKGROUND

The potential of weed species to respond to selection forces affecting the evolution of weedy traits such as competitive ability is poorly understood. This research characterized evolutionary growth changes in a single Abutilon theophrasti Medik. population comparing multiple generations collected from 1988 to 2016. A competition study was performed to understand changes in competitive ability, and a herbicide dose–response study was carried out to assess changes in sensitivity to acetolactate synthase-inhibiting herbicides and glyphosate over time.

RESULTS

When grown in monoculture, A. theophrasti biomass production per plant increased steadily across year-lines while leaf number decreased. In replacement experiments, A. theophrasti plants from newer year-lines were more competitive and produced more biomass and leaf area than the oldest year-line. No clear differences in sensitivity to imazamox were observed among year-lines. However, starting in 1995, this A. theophrasti population exhibited a progressive increase in growth in response to a sublethal dose of glyphosate (52 g a.e. ha⁻¹), with the 2009 and 2016 year-lines having more than 50% higher biomass than the nontreated control.

CONCLUSION

This study demonstrates that weeds can rapidly evolve increased competitive ability. Furthermore, the results indicate the possibility of changes in glyphosate hormesis over time. These results highlight the importance of the role that rapid (i.e., subdecadal) evolution of growth traits might have on the sustainability of weed management strategies. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.  相似文献