共查询到20条相似文献，搜索用时 93 毫秒
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近年来,随着种植结构的调整,耕作制度的改革,我县旱地棉田的比重越来越大,目前已占全县总棉田面积的3/4左右,旱地棉田土壤肥力中等,耕性和光热资源良好,适宜植棉。1旱地棉花的生育特点旱地棉花由于无水浇条件或水浇条件差,生长期间基本上靠雨养,形成了不同于水浇地棉花的生育规律。从调查资料看,株高70～75cm,单株果节数30个左右,有效蕾期和有效花期比肥水地短1/4左右,总生殖量少1/3。成铃集中在第1～8果枝上,单株结铃率不稳定。三桃分布以伏桃和早秋桃为主,但年际间变幅大,因雨量分布而异。苗蕾期较肥水地生长缓慢,但开花以后,生长速度加快… 相似文献
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山西是北方麦区典型的干旱省份,旱地小麦面积比例较大,旱地小麦生产对山西省小麦生产起着至关重要的作用。为了选育抗旱性、丰产性、稳产适应性等方面具有突破性的小麦品种,提出了现阶段的育种目标,并分析了当前山西省生产条件下旱地小麦育种的5个发展趋势以及存在的分歧。 相似文献
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为了充分发挥土地资源优势、提高胡麻产量、增加经济效益,静宁县种子管理站经试验、示范,总结出一套旱地胡麻丰产栽培技术。详细介绍了旱地胡麻丰产栽培技术的要点。 相似文献
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我国南方大部分旱地没有灌溉条件，靠降雨维持旱地农作物生长，特别是广西地区更为严重，不少秋季作物因干旱收获减少，甚至无收，严重制约了当地种植业的发展。为探索旱地作物高产栽培技术，广西不少地方采用玉米、棉花套种，利用棉花耐高温、抗干旱、根系发达、生活力强、适应性广的特点，玉米、棉花都获得了较好的收成，该模式技术要求粗放，容易管护，经济效益好，农户容易接受。 相似文献
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旱地棉花产量构成因素的通径分析 总被引：7，自引：0，他引：7
研讨了旱地棉花产量与其构成因素间的相互关系及各产量因子对皮棉产量相对重要性和决定作用。结果表明，旱地棉田在干旱和雨涝两种不同条件下，其参数显然不同。一般在干旱条件下，皮棉产量与亩铃数关系密切，在主要产量因素中，亩铃数对皮棉产量的相对重要性最大，决定程序也最高；而在雨涝条件下，皮棉产量与衣分相关关系密切，在主要产量因素中，衣分对皮棉产量的贡献最大，决定程序也最高。通过研究，提出了适应不同条件的棉花育 相似文献
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Joseph Tokosh 《Growth and change》2019,50(1):403-423
This study analyzes three national department store chains in order to identify the factors most associated with their store closures. A binary logistic regression revealed some consistencies and differences in the associations. Larger stores are less likely to close for all three chains. Macy's and Sears stores are less likely to close in large malls (than freestanding stores) and if they are located in the West. J.C. Penney stores in the west are also less likely to close than in other regions, but stores in large shopping centers are more likely to close than freestanding stores. Store age was only significant for J.C. Penney stores, and indicated that older stores are more likely to close. Implications for retail managers and city economic vitality are mentioned and future research possibilities are discussed. 相似文献
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J. C. s'Jacob 《Euphytica》1952,1(3):219-230
Summary In breeding new varieties it will be necessary in most cases to test the degree of resistance of the material by means of artificial infection. After discussing with plant breeders and phytopathologists the question of the research on disease resistance now being done in the Netherlands the Department of Research on Disease Resistance of the Institute for Phytopathological Research at Wageningen have found that the methods mentioned in addendum I are reliable enough to be used by the breeders themselves, though with the aid of the Department.The methods applied in special institutes because they are too complicated for the breeders, are mentioned in addendum II; they are wart-disease testing in potatoes, virus testing in strawberries and raspberries.Under III are treated the methods that are as yet not sufliciently developed to be applied successfully either by institutes or by breeders, and which are now being investigated in the Netherlands. 相似文献
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M. Pérez de la Vega 《Euphytica》1996,92(1-2):27-38
Summary Genetic adaptation implies the shaping of population and species gene pools in response to environmental challenges. The two components of the abiotic land environment are climate and soil, both of which determine much of the evolutionary adaptedness of plants as, besides representing a set of surrounding physical, chemical and sometimes limiting traits, they determine the availability of nutrients and energy, of which they are the immediate source. Ecogeographical distribution of species and ecotypes and different physiological mechanisms and developmental patterns are good evidence of plant adaptedness to soil and climate. However, it is not always easy to determine the underlying genetics of adaptive processes, because 1) environmental factors to which the plants are responding are not always evident and are sometimes too complex, 2) several genes may be involved in the response to a given environmental factor, and 3) the same gene/s may be involved in different adaptive responses. In particular, data on Avena species and temperature as a key environmental factor will be used to illustrate some examples of climatic and edaphic adaptedness. Temperature affects the genetic evolution and geographical distribution of all organisms, and a great deal of evidence indicates that species and populations are genetically adapted to different temperature regimes. Isozymes and other molecular markers have helped in the understanding of the genetic basis of adaptedness. There are many examples of correlation between isozyme and DNA-marker variation and environmental differences. For many population geneticists, isozyme markers are just genetic markers with little or no direct involvement in adaptation. However, metabolic processes are controlled by enzymes, influenced by the environment and used to react in response to it. Evidence that isozymes, and perhaps other molecular polymorphisms, are directly involved in adaptedness will be also presented. Molecular genetic analyses at gene and population levels are opening the ways to a better understanding of plant genetic adaptation. 相似文献
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G. A. Thijn 《Euphytica》1956,5(1):55-62
7. Summary The maintenance and assessment of potato seedlings in 5 consecutive years of trial are described.In the first year single tubers from each plant in a progeny are planted in single rows across the drills (fig. 2). After selection the haulms are killed and 6 tubers per approved seedling are kept.In the second year the unit is 6 tubers per seedling and the seedlings are grouped according to the progeny to which they belong. A standard variety is planted after each group of 9 seedlings. Tubers are harvested towards the end of August and kept in air-cooled stores.In the third year, 18 tubers are planted in 3 drills of 6 plants. 6 tubers of each seedling are planted in a virus-infested area.In the fourth year, seedlings in plots of 36 tubers are compared with nearly all the potato varieties cultivated in the Netherlands. Haulms are not destroyed but elsewhere 40-tuber plots are laid down for seed production.In the fifth year the method of trial is similar to that of the fourth year but in addition seedlings are included in the trials described by Mr J. A. Hogen Esch (Euphytica 2, 1953: 211–233). 相似文献
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Asima Yanty Siahaan Tanya Jakimow Yumasdaleni Aida Fitria Harahap 《Asia Pacific viewpoint》2024,65(1):28-39
Women are under-represented in Indonesian legislatures, and those women who are elected are disproportionately from ‘elite’ backgrounds. This research sought to understand the conditions for women to succeed in politics in conditions of patriarchy and clientelist politics. Research in North Sumatera, Indonesia, revealed that many women did not make the conscious decision not to enter politics, but rather found that they had not established the required preconditions earlier enough in life. Patriarchal social norms and a transactional political culture frustrate women's ability to acquire these conditions, yet they are also subject to change. Interviews with women elected representatives and women who had never contested an election revealed three sites that are critical to women either acquiring the preconditions to contest elections, or frustrating that pathway: the household, the ‘community’ and religious/ethnic associations. We demonstrate how women's actions in these sites transform the conditions to make them more conducive to women's political participation. 相似文献
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科学理解农药最大残留限量的概念 总被引：10，自引：0，他引：10
农药在作物及食品生产中的有益作用已为世界所公认,但是食品中残留微量农药是否对人体健康有危害仍是目前人们关注的焦点。允许的农药残留不应该对人体健康产生影响,因为任何农药在可以使用前必须经过一个包括科学的风险评估在内的农药登记管理程序的评审。最大残留限量（MRLs）是指在优良农业措施（GAP）下使用某农药可能产生的在食物中的最高残留浓度（单位为mg/kg, 指每公斤商品中残留农药的毫克数）,其数值必须是毒理学上可以接受的。MRLs的主要作用是来检验食品生产过程是否严格执行GAP,以及帮助经农药处理的农产品在国际贸易中正常进行进出口活动。MRLs不是一个绝对的安全限量,即接触残留超标的食品并不一定肯定意味着对健康有危害。但是MRLs也经常作为食品安全管理的第一道防线,成为保障人类健康最初级的预警机制。MRLs是各国政府和联合国食品法典委员会设定的,这些设定的标准被应用于国际贸易中。 相似文献
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通过PCR、细菌培养鉴定和血涂片镜检对20例以高热为特征的疑似蓝耳病病例进行病原检测诊断,并根据病因提出综合防治措施.发现蓝耳病（PRRS）阳性率100%,圆环病毒病（PCV-2）阳性率40%,伪狂犬（PRV）阳性率40%,非典型性猪瘟（CSFV）阳性率10%,猪流感（SI）及猪传染性胸膜肺炎（APP）均为阴性,附红细胞体阳性率90%,并有少量细菌感染.结果表明我市猪高热病为高致病性蓝耳病,发病猪并分别不同程度地混合或继发感染了其他病原体,病原一般3～5种,病原多样化导致病情复杂化,增加了诊断和治疗难度,所以本病宜采取综合防治. 相似文献
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川南地区引种桃品种的需冷量研究 总被引：1，自引：1，他引：0
采用室内测定与田间栽培相结合,研究了92个桃品种的需冷量;研究了川南不同海拔高度地区0~7.2℃的有效低温量。结果表明：（1）供试品种之间需冷量差异较大,介于400~1300h之间,多数介于650~950h;花芽需冷量400~1300h,叶芽需冷量400~600h,同一品种花芽需冷量高于叶芽。（2）2003年12月至2004年2月果树休眠期间,川南海拔300m（李庄）地区有效低温量508h,海拔450m（南广）地区有效低温量748h,海拔650m（屏山富荣）地区有效低温量980h。 相似文献
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基于欧氏距离理论的农业可持续发展评价方法与实证研究 总被引：1，自引：0，他引：1
基于欧氏标准化距离理论,构建了农业可持续发展评价理论体系与评价指标框架,包括评价函数、评价等级、评级指标、佳态系统与原点系统等。选取甘肃镇原县、宁夏吴忠市和山东桓台县2000-2012年数据作为实证案例,并在评价指标框架下构建评价指标体系,对3个不同类型的农业系统进行了验证性评价。结果表明：甘肃镇原县ASDI(可持续发展指数)范围[0.70,0.83],呈上升趋势,处于中持续与高持续状态;宁夏吴忠市ASDI范围[0.40,0.77],呈波动较大,6年处于非持续、其余年份主要处于中持续状态;山东桓台县ASDI [0.53,0.71],大部分年份小于0.6,处于不可持续状态。欧氏距离法评价结果与农业系统实际情况接近,分别代表了3类农业生态系统。甘肃镇原在有机废弃物(秸秆与畜禽粪便)还田利用、人均粮食、高职教育、人均收入、饮用水安全、农药施用与基尼系数等方面接近佳态系统,仅在氮磷施用上稍微超标,属物质良性循环类型;宁夏吴忠由于在作物单产、有机废弃物还田与人均粮食等方面接近佳态,但在施肥量、水体污染与土壤有机质等方面远离佳态,因而ASDI有较大波动,属传统与集约化并存类型;山东桓台水肥药投入水平较高,农业面源污染负荷大,导致地表水、地下水氮磷超标引起ASDI较低,属典型的集约化类型。 相似文献