Management of newly established field margins on nutrient-rich soil to reduce weed spread and seed rain into adjacent crops

We studied the effect of different ways to establish and to maintain unfertilised field margins on the development of potential weeds and seed dispersal into adjacent crops. Plant communities in field margins either developed spontaneously or were sown with different seed mixtures of grasses and forbs. Margins were mown twice a year and the cuttings were either removed or left in situ. Three years after establishment, the importance of the unsown rhizomatous species Elytrigia repens and Urtica dioica was significantly higher in the unsown community or when cuttings were not removed after mowing. Seed dispersal from the margin into adjacent crops was important in the unsown community during the first year after establishment. Between 82% and 99% of the seeds were disseminated within 4 m from the margin strip. Overall risk of contaminating the adjacent crop with weeds originating from the field margin strip was concentrated within a few metres of the crop edge. In order to minimise the dissemination of weed species and invasion by noxious vegetatively propagated weeds on nutrient‐rich land, it is recommended that field margins are established by sowing and cuttings removed after each cut.     

基于参考机的单机等面积暂态稳定分析

提出了相对参考机的单机稳定裕度评估方法.研究了单一机组功角曲线的表达方式，将多机系统中单机功角曲线表达为本机相对参考机转子角度的函数，提出了基于泰勒级数的功角曲线预测拟合方法.提出了稳定裕度的预测评估方法与事后评估方法，比较了事后评估与预测评估所得稳定裕度的差异.SGEAC方法在判别系统是否稳定时没有任何假设，不需要进行动态二群的识别.实例验证了所提方法的有效性.     

沿江双季稻北缘区晚稻适宜品种类型及高产群体特征

研究沿江双季稻北缘区晚季籼稻和粳稻产量差异,明确适宜类型品种及高产形成机制。试验于2018—2019年在安徽庐江进行,以当地常规种植的17个籼稻和17个粳稻优质品种(系)为研究对象,比较和分析籼稻和粳稻在产量及构成、物质积累和生育进程方面的差异。结果表明,粳稻与籼稻总体上产量水平相当,但粳稻产量限制因子少,安全齐穗性有优势,具有更高的产量稳产性和生态安全性。高产粳稻主要是通过增加移栽–抽穗期干重来增加总干物质积累,以提高总颖花量和产量。不同穗型粳稻品种生育前中期不同阶段的干物质积累对总颖花量的影响差异较大,其中大穗型(每穗粒数102.3～112.0)和小穗型粳稻(每穗粒数52.0～99.7)干物质优势积累期分别为移栽–穗分化期和穗分化期–抽穗期,与总颖花量的相关系数达到0.709和0.829。进一步分析发现,大穗型粳稻品种移栽–穗分化期干物质积累受穗分化期分蘖数显著影响,而小穗型粳稻品种穗分化–抽穗期干物质积累由抽穗期分蘖数和单茎干重共同影响。综上所述,本研究认为粳稻是沿江双季稻北缘区适宜的双季晚稻品种类型,高产粳稻群体颖花量为33.8×10~3～41.0×10~3 m^–2<...     

近期中国农产品贸易特点与展望

近期中国农产品贸易保持较快增长,进口增速反弹,出口基本平稳,贸易逆差扩大。谷物、油籽、乳制品等进口大幅增加,棉花、食糖、植物油等进口下降,但仍保持高位,水产品、蔬菜、水果等优势农产品出口小幅增加。进口大幅增加的主要原因是国内需求强劲增长和国内外农产品价差扩大。预计2014年中国大宗农产品进口将保持较高水平,需要妥善应对进口压力。     

黄土丘陵沟壑区沟沿线边缘植被特征初步研究

 通过对黄土丘陵沟壑区安塞纸坊沟沟沿线边缘植被特征的调查,共发现隶属26科的66个物种,其中豆科、禾本科和菊科物种分别占19.70%1、5.15%和13.64%;物种中出现最多的是多年生草本,其次依次是1年生草本、灌木、小灌木、乔木、藤本和小乔木,其中灌乔物种多为主要物种且多为当地优势灌木虎榛子和酸枣等,指示着研究区植被恢复的方向;调查植物种基本包含了陕北黄土高原森林草原带次生演替各个阶段的主要植物种,是研究区次生演替的一个缩影;从沟沿线边缘植被的分布看,灌木远多于草本,其中以灌木为主的沟沿线区段植被的宽度、盖度均比以草本为主的沟沿线区段大,沟沿线防蚀效益较好。     

改进的内模PD参数整定及其在水

PID控制是一种广泛应用的工业控制算法，但由于其控制参数整定的复杂性，因而其应用常常受到一定的限制[1，2]。为了更有效地解决这一问题，在内模参数整定的基础上,提出了用系统频域参数配置的方法来对过程某些变化较大的参数进行估计，并用过程估算的参数来对内模PID参数进行整定，同时把它应用于水轮机调节系统的控制，仿真结果显示了良好的控制效果,尤其是对模型失配严重的系统其效果更加显著。     

Evaluating the merits of climate smart technologies under smallholder agriculture in Malawi

The merits of three climate smart agriculture (CSA) technologies implemented by farmers were assessed in Machinga district of Malawi with respect to their soil quality and maize yield effects. Data were collected from farms implementing the three CSA technologies, namely conservation agriculture (CA), maize–pigeonpea (Maize-PP) intercrops and a local organic and inorganic soil amendment known as Mbeya fertilization (Mbeya-fert), from 2018 to 2019. With respect to resilience and adaptation, particulate organic matter, soil organic carbon (SOC), N, P, K, Ca and Mg all significantly improved while bulk densities were lowered under the three CSA systems. Higher annual biomass inputs and improved water infiltration from the Maize-PP intercrops were observed. With respect to productivity, CA and Mbeya-fert improved maize yields by 51 and 19%, respectively, compared to conventional farmer practices. With regard to climate change mitigation, increases in measured SOC in the top 20 cm depth compared to the conventional farmer practices amounted to 6.5, 12 and 10.5 t C ha⁻¹ for CA, Mbeya-fert, and Maize-PP intercrops, respectively, over a period of 2–6 years. This suggests higher potential for carbon sequestration from CSA technologies. Furthermore, use of drought tolerant varieties, timely weeding and optimum plant populations, increased productivity. Improved gross margins from CSA practices were also apparent. Thus, employing these CSA technologies could enable farmers to be more resilient, productive and adapt better to climate change shocks leading to improved food security and livelihoods.     

油桐北缘产区优树选择及其主要性状描述

为推进油桐产业的快速和规模化发展,解决北缘地区油桐良种缺乏的问题,2011年以来,在对安徽大别山区的桐城和金寨等地的油桐种质资源调查的基础上,开展油桐优良单株选择工作,经初选、复选和决选,最终选择出5株油桐优良单株。所选5个优株雌雄花比例均在1:10以内,属于典型的少花花序类型;丛果性除"金寨2号"稍弱外,其他4株丛果性均较强,果大皮薄,光滑整齐,粒饱仁满,种仁含油率均在50%以上,2年的年均鲜果产量在1.25 kg·m-2以上,各项指标均达到了我国油桐优树的选择标准。以上油桐优树的选出为北缘地带发展油桐提供了良种培育的基础。     

板栗新病害褐缘叶枯病及病原鉴定

板栗(Castanea mollissima)在山东省是一重要的干果树种.自2004年起,山东泰安、济南、潍坊、临沂等地相继发生一种新的叶部病害,板栗感病后,叶片上产生褐色的斑点,随后病斑迅速扩大,呈不规则大面积干枯,9月中、下旬开始大量落叶,10月中、下旬二次发芽抽稍,新发枝稍冬季枯死,极易诱发板栗疫病,引起树木整株死亡.近年来,该病逐年加重.2006年对泰安市徂徕山林场600hm2板栗林调查,发病率为100%,800余株10～15年生板栗树死亡,2007年死亡9000余株,减产近12万kg.为控制该病害的危害,生产上迫切需要确诊出该病害及病原,2006-2009年,笔者对该病害进行了系统的研究,旨在为研究病害的发生发展规律和防治措施的制定提供理论依据.     

芦荟胶囊通便作用的实验研究

目的研究芦荟胶囊润肠通便的作用。方法通过结扎大鼠回肠模型,观察动物肠道水分的分泌及家兔在体肠肌收缩幅度及频率。结果芦荟胶囊可明显促进大鼠肠道水分的分泌,增强家兔在体肠肌收缩幅度及频率。结论芦荟胶囊具有很好的润肠功能及排便功能。