Macronutrient accumulation in wheat crop (Triticum aestivum L.) with Azospirillum brasilense associated with nitrogen doses and sources

Abstract

New studies are needed to optimize the nitrogen (N) amount that can be applied to utilize the Azospirillum brasilense benefits. In addition, information regarding the interaction between the urease inhibitor and biological nitrogen fixation (BNF) and how they affect the macronutrients accumulation are also needed. We evaluate the effect of N sources and doses associated with A. brasilense regarding the macronutrients accumulation in straw and grains and wheat grain yield in tropical conditions. A randomized block experimental design was used with four replications in a 2?×?5?×?2 factorial arrangement as follows: two N sources (urea and urea with urease enzyme inhibitor NBPT; five N doses (0, 50, 100, 150, and 200?kg ha^?1) applied in topdressing; with and without A. brasilense inoculation. We found that an increase in N doses positively influenced the accumulation of macronutrients in straw and grains and the wheat grain yield. N sources have similar effects. Inoculation with A. brasilense increased accumulation of Mg and S in straw and P, Ca, and Mg in grains, regardless of the N dose. The inoculation with A. brasilense associated with 140?kg ha^?1 of N increased wheat grain yield. The inoculation can contribute in a more sustainable way to wheat nutrition and optimizing N fertilization.     

Composition,distribution and sources of polycyclic aromatic hydrocarbons in sediments of the western harbour of alexandria,egypt

Aim and Background  Little data are available on the levels of polycyclic aromatic hydrocarbons (PAHs) in the sediments of the Mediterranean Sea Coast of Egypt in general and the Alexandria coastal zone in particular. It was therefore deemed necessary to set up a monitoring programme to determine the current concentrations of PAHs in bottom sediments, and to identify any area where high concentrations of these potential hazardous contaminants were present in the Western Harbour of Alexandria. Methods  The composition, distribution and the source of PAHs in surficial sediments of the harbour were investigated. To document the spatial PAH input, surficial sediment samples from 23 locations throughout the harbour were analysed. as]Results and Discussion The total PAH load determined in the surficial sediment samples ranged from 8 to 131150 ng g¹ dry wt, generally with most of the samples having total concentrations of PAHs greater than 5000 ng g¹ dry weight. The highest concentration of total PAHs was recorded in sediments of the inner harbour. Ratio values of specific compounds such as phenanthrene to anthracene, fluoranthrene to pyrene, methyl-phen-anthrene to phenanthrene, methyl-dibenzothiophenes to dibenzothiophenes, alkylated to non-alkylated and high molecular weight to low molecular weight PAH, were calculated to evaluate the possible source of PAH contamination in the harbour sediments. Conclusions  Two main sources of PAH in the study area have been found: pyrolytic and petrogenic. Interferences of rather petrogenic and pyrolytic PAH contaminations were noticed for most samples. The dominant sources of PAH appear to be the combustion processes through run-off, industrial and sewage discharges, and atmospheric input. The concentrations of PAHs were generally above levels expected to cause adverse biological effects. Recommendations and outlook  Information from this study and any other relevant studies should be useful in designing future strategies for environmental protection and management of the harbour.     

外来入侵种加拿大一枝黄花及其伴生植物光合特性研究

使用LCA4光合蒸腾测定系统测定外来入侵杂草加拿大一枝黄花(Solidago canadensis)及其16种伴生杂草的光合作用指标.结果发现:①加拿大一枝黄花实测最大净光合速率为19.22μmol CO2·m-2.s-1,低于一年蓬(Erigeron annuus)、野塘蒿(Conyza bonariensis)和小飞蓬(Conyza canadensis)3种外来入侵杂草,但是高于马缨丹(Lantana camara)、空心莲子草(Alternanthera philoxeroides)、北美车前(Plantago virginica)和苦苣菜(Sonchus oleraceus)等外来入侵杂草;②该外来种在五月下旬净光合速率的日进程与空心莲子草相似,有较弱的光合午休现象;③加拿大一枝黄花的光补偿点为48.36μmol·m-2·s-1,表明是一种喜阳性杂草;④在中等光强(300～400 μmol·m-2·s-1)和强光(1300～1800 μmol·m-2·s-1)照射下,加拿大一枝黄花位于植株中部叶片的净光合速率最高,处于弱光(15～45 μmol·m-2·s-1)下,植株基部叶片的净光合速率较高,反映出基部叶片比中上部叶片具有较低的光补偿点;⑤与阴生环境中的植株相比,阳生环境中的加拿大一枝黄花株高、叶数增加较快,净光合速率相对较高.加拿大一枝黄花植株通过提高叶绿素总含量来适应阴生环境;⑥阳生环境下,与加拿大一枝黄花植株净光合速率关系最大的环境因子依次为叶面光合有效辐射、蒸腾速率和叶面温度,而在阴生环境下,与该种净光合速率关系最大的环境因子依次为叶面光合有效辐射、空气相对湿度、蒸腾速率和气孔导度.     

不结球白菜抗病育种的研究 Ⅳ不结球白菜抗芜菁花叶病、霜霉病及黑斑病的多抗性鉴定及筛选

选取８４份经芜菁花叶病毒（ＴｕＭＶ）、霜霉病菌［Ｐｅｒｏｎｏｓｐｏｒａｐａｒａｓｉｔｉｃａ（Ｐｅｒｓ．）Ｆｒ．］、黑斑病菌［Ａｌｔｅｒｎａｒｉａｂｒａｓｉｃａｅ（Ｂｅｒｋ）Ｓａｃ．］单抗鉴定后筛选出的自交系，于１９９２～１９９３年对其进行上述３种病害苗期人工诱发接种多抗性联合鉴定，获得２１份三抗材料。经鉴定，确认为三抗抗源材料。探讨了多抗性联合鉴定的技术与方法。     

林木昆虫演变为重大害虫的主要环境因子

综述了有关林木害虫产生的环境机制，主要包括大气污染、干旱、全球气候变化、外来有害生物的入侵、害虫自身生物学特性与森林经营模式的影响等，以便为害虫的综合防治提供基础理论资料。同时提出今后研究方向：树种、害虫、天敌和生存环境4者关系开展研究，特别调控森林生态系统的主体一植被的时空结构；同时协调运用与环境和其他有益物种的生存和发展和谐的各类措施，将害虫控制在不成灾水平，并在时空上达到可持续控制的效果。表2参33     

液体深层培养贵州绿僵菌分生孢子的研究

本文对贵州绿僵菌液体深层培养的研究表明，不同氮源对生长量、液生芽孢子和液生分生孢子产孢量影响显著．不同碳源对生长量和液生芽孢子产孢量影响显著，但对液生分生孢子产量无明显影响．同时试验还表明，液生分生孢子的形成与培养液的碳氮比、pH以及通气量有关．     

地源热泵技术在中国温室设施中的应用探讨

当前在中国温室设施中应用和推广地源热泵技术尚存在诸多不利因素,大大限制了该项技术在设施农业领域中的发展。为探寻合理的解决途径,对地源热泵空调系统的关键技术和其在中国的发展概况进行了相关的阐述和分析,并以中国农业大学上庄实验站已经建成使用的地下水式温室地源热泵空调系统为实例,介绍该系统的组成、工作流程、性能参数和使用情况,探讨温室地源热泵空调系统在推广和使用中可能出现的投资较高,长时间运行性能不稳定等问题,分析其原因并提出相应的对策建议。     

海南岛外来人侵危险性动植物名录(二)

根据查阅相关文献报道及实地调查结果,总结了截止目前入侵海南岛并对其生态环境造成危害的的外来动物共21种,简要介绍其发源地、分类地位、分布及危害。     

茶树生态系中的立体污染链与阻控

 运用农业立体污染的新概念，针对茶树和茶叶本身的特点，剖析了来自土壤、水源、空气中性质各异的污染物，包括农药残留、铅、氟、铝、硝酸盐、多环芳烃（PAHs）、多氯代二苯并二恶英/呋喃（PCDD/PCDF）等，在水-土、土-气、土-植物等不同相或界面间的相互交换和迁移特性。论述了茶园生态系中的立体污染链以及污染物对不同界面的偏嗜性和界面间转移的时空特征，分析了中国茶叶生产中的立体污染问题。在对茶叶中几种污染物安全性风险评价的基础上，从清洁化生产角度，讨论了不同界面间污染源的控制和污染链防阻技术和应用，探讨了未来创新研究的重点领域。     

提高农民信息网络意识推动农业信息化建设

本文通过对农村信息网络建设及现状的认识和分析，提出了加速农村信息网络建设的一些措施和方法，并着重就农民利用网络信息的心理提出了很多个人见解。