Performance of Medicago sativa under dryland conditions on the eastern Highveld

Abstract

Increased livestock numbers and improved animal performance based on dryland lucerne pastures requiring little or no nitrogenous fertilizer have been demonstrated to be feasible on the eastern Highveld. With large scale planting of lucerne‐based pasture (25% of arable land) 350 to 500% more sheep products can be delivered at a lower cost. When lucerne is included in crop rotations the production cost of grain can also be reduced. The increased usage of lucerne‐based pastures, especially for sheep and dairy enterprises, will also reduce the pressure on natural pasture and improve the conservation of vegetation, soil and water resources.     

河西地区豆禾混播草地生产性能对刈割高度与施肥的响应

刈割和施肥是豆禾混播草地生产过程中极为重要的田间管理措施，合理的留茬高度和氮磷配施模式可以有效提高混播草地的生产性能。为探究不同留茬高度和施肥模式对多年生豆禾混播草地产量与品质的影响，在河西走廊地区以紫花苜蓿、无芒雀麦和长穗偃麦草1∶1∶1建植的第3年豆禾混播草地为试验对象，利用裂区试验设计，以留茬高度为主区，设置5 cm（A₁）、8 cm（A₂）、11 cm（A₃）3个留茬高度，施肥模式为副区，设置不施肥CK（B₁）、单施磷肥：150 kg P₂O₅·hm^-2（B₂）、低氮高磷：75 kg N·hm^-2+225 kg P₂O₅·hm^-2（B₃）、氮磷平衡：150 kg N·hm^-2+150 kg P₂O₅·hm^-2（B₄）、单施氮肥：150 kg N·hm^-2（B₅）、高氮低磷：225 kg N·hm^-2+75 kg P₂O₅·hm^-2（B₆）6个施肥模式，在混播草地中豆科牧草初花期进行刈割，施肥方式为第1茬刈割后追施。结果表明：以A₃B₃（11 cm留茬高度和75 kg N·hm^-2+225 kg P₂O₅·hm^-2的施肥模式）处理组合全年产量最高（19626 kg·hm^-2）；A₂B₂（8 cm留茬高度和150 kg P₂O₅·hm^-2的施肥模式）处理组合全年产量最低（14342 kg·hm^-2）。提高留茬高度会在一定程度上降低紫花苜蓿整体品质，提高禾本科牧草整体品质。增施氮肥的同时减施磷肥可有效提高牧草粗蛋白含量和相对饲用价值（RFV），施用量过高会使牧草粗蛋白含量和相对饲用价值下降，最合理的氮磷配施模式为150 kg N·hm^-2+150 kg P₂O₅·hm^-2。综合产量和品质的结果来看，适当的磷肥施用量可以显著提高牧草营养品质。利用TOPSIS综合评价模型对混播草地产量及各混播组分营养品质进行整体评价后得出：8 cm的留茬高度以及施150 kg N·hm^-2+150 kg P₂O₅·hm^-2的氮磷为适宜在河西走廊地区紫花苜蓿+无芒雀麦+长穗偃麦草混播草地利用的留茬高度与施肥模式的组合。     

小麦品种混种对条锈病控制效果及产量影响的研究

通过对不同小麦品种按不同比例混种,研究品种多样性控制小麦条锈病的田间效果,以期为利用品种多样性防治小麦条锈病提供理论依据。本研究利用甘肃省甘谷县和北京市上庄镇当地对条锈病具不同抗性的小麦品种,按照不同混种比例布局了25个混种处理和7个单种处理,比较了品种混种对条锈病的控制效果和对小麦产量的影响,以相对抗病性指数(RRI)把品种抗性加以分类,并以相对混种效果参数(REM)比较各混种处理的效果。结果表明,不同小麦品种混种对小麦条锈病有较好的控制效果,混种处理相对于感病品种单种病情指数平均下降30.5;混种对小麦的增产效果比较明显。在25个小麦品种混种处理中,有14个处理有增产效果(REM>1),占56%,在甘谷试验地抗病(R)品种和高感(HS)品种按质量比5∶1混种时相对感病品种单种处理抗病增产效果最好,而在上庄试验地,高抗(HR)、中感(MS)和感病(S)按质量比1∶1∶1混种时相对感病品种单种处理抗病增产效果最好。品种混种作为综合治理小麦条锈病的措施之一,具有一定的推广应用价值。     

Intercropping reduces Mycosphaerella pinodes severity and delays upward progress on the pea plant

Mycosphaerella pinodes is a serious pea disease of worldwide distribution. The increasing interest of sustainable tools for disease control, together with the lack of sufficient levels of genetic resistance has brought our interest in the use of intercropping as a tool for management of this disease. Effect of intercropping on M. pinodes severity was studied in field experiments performed in Spain and Tunisia, in which a susceptible pea cultivar was grown as monocrop and as two species mixed intercrop with either faba bean, barley, oat, triticale or wheat. Disease was significantly reduced in terms of both percent of diseased tissue per plant and vertical progress of lesions when pea was intercropped. Faba bean and triticale intercropped with pea showed the highest suppressive ability with above 60% of disease reduction. Oat, barley and wheat showed low to moderate M. pinodes suppressive effects. Suppressive effects can be ascribed to a combined reduction of host biomass, altered microclimate and physical barrier to spore dispersal.     

Effects of Silane Coupling Agent on Road Performances of Composite Asphalt Mixtures

Aiming at the influence of mastics to aggregate adhesion on the performances of asphalt mixtures, three modeling techniques were adopted to prepare composite asphalt mixtures specimens. The influences of silane coupling agent on their road performances were studied and coupling mechanism was analyzed with Infrared Spectroscopy (IR) and Scanning Electron Microscope (SEM). The results indicated that the road performances at 7 day and 28 day curing age increased in the beginning and then decreased with the increase of silane coupling agent dosages. The road performances, such as freeze thaw splitting strength ratio, Marshall stability and compression modulus would be enhanced 10%~30% at 0.6% in asphalt emulsion mass. There was Si O Si chemical bond on interface between mastics and modified granite aggregate by Si O chemical bond of silane coupling agent. Surface of cement asphalt emulsion mastics was rough and its structure was dense. The cement asphalt emulsion mastics can be adhered to granite aggregate surface and mastics to aggregate interface structure is improved with silane coupling agent addition.     

3种植物提取物复配对小菜蛾的联合毒力作用

采用浸虫法,测定了3种具有杀虫活性的植物野西瓜苗、牛皮消和茜草乙醇提取物两两复配对小菜蛾的室内联合毒力作用,并筛选了药剂的最佳复配比例。结果表明,野西瓜苗与牛皮消复配具有增效作用,质量比为2:1时,共毒系数(CTC)为160.87,增效作用最为显著;野西瓜苗与茜草复配,对小菜蛾表现为相加作用;茜草与牛皮消复配表现出拮抗作用。     

Resistance, epidemiology and sustainable management of Rhynchosporium secalis populations on barley

Rhynchosporium secalis is one of the most destructive pathogens of barley worldwide, causing yield decreases of up to 40% and reduced grain quality. Rhynchosporium is a polycyclic disease. Primary inoculum includes conidia produced on crop debris, infected seeds and possibly ascospores, although these have not yet been identified. Secondary disease spread is primarily by splash dispersal of conidia produced on infected leaves, which may be symptomless early in the growing season. Host resistance to R. secalis is mediated by both 'major' or host-specific genes (complete resistance) and 'minor' genes of smaller, generally additive effects (partial resistance). Crop growth stage and plant or canopy architecture can modify the expression of resistance. Resistance genes are distributed unevenly across the barley genome, with most being clustered on the short arms of chromosomes 1H, 3H, 6H and 7H, or in the centromeric region or on the long arm of chromosome 3H. Strategies used to manage rhynchosporium epidemics include cultivar resistance and fungicides, and also cultural practices such as crop rotation, cultivar mixtures and manipulation of sowing date, sowing rate or fertiliser rate. However, the high genetic variability of R. secalis can result in rapid adaptation of pathogen populations to render some of these control strategies ineffective when they are used alone. Sustainable control of rhynchosporium needs to integrate major-gene-mediated resistance, partial resistance and other strategies such as customized fungicide programmes, species or cultivar rotation, resistance gene deployment, clean seed and cultivar mixtures.     

棉铃虫幼虫中栓锥感器对肌醇和糖类的电生理反应

利用电生理学技术,以多食性的棉铃虫为研究对象,测定幼虫下颚中栓锥感器对7种糖和肌醇及其混合物的味觉电生理反应,分析不同物质诱导中栓锥感器内对应的味觉感受细胞及不同物质之间诱导昆虫电生理反应的交互作用.结果表明:(1)棉铃虫幼虫下颚中栓锥感器对肌醇、果糖、木糖、阿拉伯糖,葡萄糖、麦芽糖、海藻糖和鼠李糖的单一物质都有明显的...     

滴灌专用有机无机复混肥对番茄产量与品质的影响

为评价滴灌专用有机无机复混肥对番茄生长发育、产量与品质的影响,在温室条件下,研究了滴灌专用有机无机复混液体肥与2 种常规施肥方法对番茄产量与品质形成的影响。结果表明,滴灌有机无机复混肥套餐液体肥,显著增加了番茄植株高度和茎干粗度,比传统漫灌肥料表施模式产量增加了19.53%,Vc 和可溶性固形物分别提高了13.39%、17.85%,硝酸盐含量降低40.06%。说明滴灌有机无机复混肥套餐液体肥可以促进番茄生长发育,显著提高番茄产量和改善果实品质。     

Towards bioremediation of toxic unresolved complex mixtures of hydrocarbons: identification of bacteria capable of rapid degradation of alkyltetralins

Background, aim and scope  Unresolved complex mixtures (UCMs) of aromatic hydrocarbons are widespread, but often overlooked, environmental contaminants. Since UCMs are generally rather resistant to bacterial degradation, bioremediation of UCM-contaminated sites by bacteria is a challenging goal. Branched chain alkyltetralins are amongst the individual classes of components of aromatic UCMs which have been identified in hydrocarbon-contaminated sediments and a number of synthetic alkyltetralins have proved toxic in laboratory studies. Thus, alkyltetralins should perhaps be amongst the targets for UCM bioremediation strategies. The slow degradation of several alkyltetralins by a microbial consortium has been reported previously; however, the bacteria involved remain unidentified and no single strain capable of alkyltetralin biodegradation has been isolated. The present project therefore aimed to enrich and identify bacterial consortia and single strains of bacteria from a naturally hydrocarbon-contaminated site (Whitley Bay, UK), which were capable of the degradation of two synthetic alkyltetralins (6-cyclohexyltetralin (CHT) and 1-(3’-methylbutyl)-7-cyclohexyltetralin (MBCHT)). Materials and methods  Bacteria were enriched from sediment collected from Whitley Bay, UK by culturing with CHT and MBCHT for a period of 4 months. Biodegradation experiments were then established and degradation of model compounds monitored by gas chromatography–mass spectrometry. Internal standards allowed the generation of quantitative data. 16S rRNA gene clone libraries were constructed from individual enrichments to allow assessment of microbial community structure. Selective media containing MBCHT were used to isolate single bacterial strains. These strains were then tested in liquid culture for their ability to degrade MBCHT. Results  The consortia obtained through enrichment culture were able to degrade 87% of CHT and 76% of MBCHT after only 46 days compared with abiotic controls. The 16S ribosomal RNA gene clone libraries of these bacteria were dominated by sequences of Rhodococcus spp. Using selective media, a strain of Rhodococcus was then isolated that was also able to biodegrade 63% of MBCHT in only 21 days. Discussion  The present report describes the isolation of a single bacterial strain able to degrade the resistant MBCHT. Although significant losses of MBCHT were observed, putative metabolites were not detectable. Rhodococcus sp. have been reported previously to be able to biodegrade a range of hydrocarbon compounds. Recommendations and perspectives  Due to their environmental persistence and toxicity, aromatic UCMs require bioremediation. The culturing and identification of such bacteria capable of rapid degradation of alkyltetralins may be an important step toward the development of bioremediation strategies for sites contaminated with toxic UCMs.