Effects of temperature on Renibacterium salmoninarum infection and transmission potential in Chinook salmon,Oncorhynchus tshawytscha (Walbaum)

Renibacterium salmoninarum is a significant pathogen of salmonids and the causative agent of bacterial kidney disease (BKD). Water temperature affects the replication rate of pathogens and the function of the fish immune system to influence the progression of disease. In addition, rapid shifts in temperature may serve as stressors that reduce host resistance. This study evaluated the effect of shifts in water temperature on established R. salmoninarum infections. We challenged Chinook salmon with R. salmoninarum at 12 °C for 2 weeks and then divided the fish into three temperature groups (8, 12 and 15 °C). Fish in the 8 °C group had significantly higher R. salmoninarum‐specific mortality, kidney R. salmoninarum loads and bacterial shedding rates relative to the fish held at 12 or 15 °C. There was a trend towards suppressed bacterial load and shedding in the 15 °C group, but the results were not significant. Bacterial load was a significant predictor of shedding for the 8 and 12 °C groups but not for the 15 °C group. Overall, our results showed little effect of temperature stress on the progress of infection, but do support the conclusion that cooler water temperatures contribute to infection progression and increased transmission potential in Chinook salmon infected with R. salmoninarum.     

猕猴桃溃疡病防治研究

对猕猴桃细菌性溃疡病防治方法进行研究,结果表明,冬末春初“划道”控制,病斑,夏委彻底刮除治疗病斑,疗效达80％－90％,DTMz等为此病防治的首选药物。     

吉林省玉米施肥效果与肥料利用效率现状研究

【目的】本研究通过收集整理2005~2013年国家测土配方施肥项目在吉林省布置的1110个“3414”田间试验,分析了施用氮、磷、钾肥对玉米产量、经济效益的影响,测算了氮、磷、钾肥的利用效率,目的在于明确当前生产条件下吉林省玉米的施肥效果与肥料利用效率,为肥料的合理施用与配置提供依据。【方法】选取玉米“3414”田间试验的处理1（N₀P₀K₀）、处理2（N₀P₂K₂）、处理4（N₂P₀K₂）、处理6（N₂P₂K₂）和处理8（N₂P₂K₀）,分别记为不施肥（CK）、不施氮（-N）、不施磷（-P）、氮磷钾配施（NPK）和不施钾（-K）处理,研究不同施肥处理下的玉米产量、产值、施肥利润和产投比,比较增施氮、磷、钾肥的增产效应以及不同肥料的农学效率、偏生产力和肥料贡献率。另外,分析不施肥处理（缺素处理）玉米产量与相应肥料贡献率之间的关系,并利用模型进行模拟。【结果】不施肥条件下,当前吉林省玉米的平均产量和产值分别为6.6 t/hm2和1.21×103 yuan/hm2。施肥可显著提高玉米的产量和经济收益,其中以NPK处理的玉米产量和施肥利润最高,平均分别为10.1 t/hm2和5.07×103 yuan/hm2,其后分别为-K处理（8.9 t/hm2、3.27×103 yuan/hm2）、-P处理（8.7 t/hm2、2.83×103 yuan/hm2）和-N处理（7.7 t/hm2、1.39×103 yuan/hm2）。在其他养分施用基础上,增施氮、磷、钾肥可平均分别增产2.36 t/hm2（35.1%）、1.39 t/hm2（18.0%）和1.18 t/hm2（14.9%）,平均施肥利润分别为3.68×103、2.24×103和1.80×103 yuan/hm2。当前生产条件下,吉林省玉米在氮磷钾配施条件下的肥料农学效率、偏生产力和肥料贡献率分别为11.4 kg/kg N、32.8 kg/kg和34.7%,而增施氮、磷、钾肥的平均农学效率分别为14.3 kg/kg N、20.5 kg/kg P₂O₅和17.2 kg/kg K₂O,平均偏生产力分别为61.1、146.4和142.4 kg/kg,平均肥料贡献率分别为23.4%、14.1%和11.9%。分析发现,氮磷钾肥配施（或某一肥料）的肥料贡献率随不施肥处理（或相应缺素处理）玉米产量的提高而显著下降,且关系符合对数函数模型,说明提高基础地力可减少对外源肥料的依赖。【结论】吉林省玉米氮磷钾肥的增产效果和肥料利用率相比全国平均水平较高,但仍需重视氮肥管理以稳产增效,继续大力推广平衡适量施肥理念及相应技术,在实现作物增产的同时提高肥料利用效率并促进土壤培肥。     

Nitrous oxide emission as affected by changes in soil water content and nitrogen fertilization

Nitrous oxide emission was measured in laboratory incubations of an alluvial soil (58% clay, pH 7.4). The soil was amended with 40 mg N kg⁻¹ as NaNO₃ or NH₄Cl, or with NaCl as a control. Each fertilization treatment was adjusted to three different water contents: constant 60% WHC (water-holding capacity), constant 120% WHC, and water content alternating between 60 and 120% WHC. During an 8-day incubation period N₂O emission rates and inorganic nitrogen concentrations in soil (NH₄⁺, NO₂⁻, NO₃⁻) were determined at regular intervals. In the control and after nitrate application small N₂O emission rates occurred with only minor variations over time, and no differences between the water treatments. In contrast, with ammonium application N₂O emission rates were much higher during the first two days of incubation, with peaks in the constant 60% WHC and 120% WHC at day 1 and in the changing-water treatment at day 2, when the first wet period (120% WHC) was completed. This N₂O peak in the changing-water treatment was 4 to 9 times higher than with constant WHC and occurred when both, NH₄⁺ and NO₂⁻ concentrations declined sharply. Thus, this N₂O emission flush can be attributed to nitrifier denitrification. After the second rewetting of the NH₄⁺-amended soil no further N₂O emission peak was observed, being in accordance with small NH₄⁺ and NO₂⁻ concentrations in soil at that time. The unexpectedly small N₂O fluxes in the constant 120% WHC treatment after nitrate application were probably caused by the reduction of N₂O to N₂ under the prevailing conditions. It can be concluded that continuous wetting or flooding of a soil is an effective measure to reduce N₂O emissions immediately after the application of NH₄⁺ fertilizers.     

家畜排泄物综合处理工艺的研究

对我国广大农村家畜排泄物常规处理存在的利弊进行了调查研究,最终揭示出厌氧发酵制沼气、好氧发酵制复混肥的一套符合我国可持续发展、创建和谐社会、节约型社会的家畜粪便处理的科学、实用方法。     

生物有机肥在苦瓜、豆角栽培上的应用研究

对苦瓜、豆角实施新生力生物有机肥应用效果试验,结果表明:施用新生力生物有机肥能显著提高苦瓜、豆角的产量,与施用进口芬兰复合肥相比,平均每公顷增产苦瓜4639.5kg,增产豆角5568.0kg,增幅分别为15.9%和25.1%;同时又能改善苦瓜、豆角的外观和食用品质,增加土壤有机质和速效养分含量,改良土壤,培肥地力。生产上推广应用新生力生物有机肥,对促进生态农业的建设与发展极具意义。     

线辣椒叶面喷施沼液的效应

对线辣椒叶面喷施不同浓度沼液的结果表明,喷施沼液可使可溶性糖有不同程度的提高,以喷施沼液浓度75%的处理为最佳,达到了8.83%;辣椒素含量也显著高于对照;vC含量最高的达到了139.42 mg/100 g;农艺性状较对照有所改善,产量也有不同程度的提高,其中以喷施沼液浓度50%的处理产量最高,干重达到了4 796.40 kg/hm^2,较对照增产25.42%.可见,线辣椒叶面喷施沼液能有效改善其品质并提高产量.     

肥料减施条件下水稻土壤有机碳组分对紫云英—稻草协同利用的响应

研究紫云英与稻草不同利用模式在化肥减量条件下稻田表层土壤有机碳及其活性组分的差异,为合理利用有机物料调控土壤肥力提供参考。采用湖南省南县连续5年(2011—2015年)大田定位试验的方法,研究了减量施肥下洞庭湖地区紫潮泥双季稻田0-20cm表层土壤总有机碳(TOC)、微生物量碳(MBC)、可溶性有机碳(DOC)、易氧化有机碳(EOC)和轻组有机碳(LFOC)对紫云英与稻草不同利用模式的响应。结果表明:与不施肥(CK)相比,单施化肥(F100)TOC、MBC、DOC、EOC和LFOC的含量均有显著上升,增幅分别为12.2%,19.5%,18.6%,11.3%和100.9%。化肥减量20%条件下紫云英与稻草利用模式更有助于有机碳组分的积累,其中晚稻留高桩还田冬种紫云英(F80+HR+A)处理效果最为突出,与CK相比,增幅分别为18.3%,47.2%,24.1%,20.0%和204.0%。减量施肥下紫云英单独利用相比稻草单独还田更益于MBC、DOC与EOC的积累,增幅分别为9.8%,4.0%和0.6%,土壤LFOC则相反,下降了34.8%。敏感指数分析表明土壤有机碳及其活性组分中LFOC对土壤质量变化最为敏感,其次是MBC,二者可作为衡量土壤质量状况的良好指标。F80+HR+A各有机碳组分敏感性均显著高于F100处理。相关性分析表明水稻产量、土壤有机碳及其组分之间均呈极显著相关(p0.01)。综上所述,化肥减量条件下不同紫云英与稻草利用模式对紫潮泥稻田土壤有机碳及其活性组分含量的影响存在明显差异,稻草还田能够显著提高土壤总有机碳和轻组有机碳的含量,紫云英的利用则有利于土壤微生物量碳、可溶性有机碳和易氧化有机碳的积累,而紫云英与稻草协同利用模式,尤其是晚稻留高桩还田冬种紫云英更有助于土壤有机碳及其活性组分的积累。     

不同施氮量对谷子产量和效益的影响

摘要;以赤谷9号、赤谷10号和峰谷12为材料,研究不同的施氮量（O、150、300、450、600kg／hm2）对谷子品种产量的影响。结果表明：从产量和肥料投资的经济效益两方面考虑,3个谷子品种的产量均在施氮量为450kg／hm2时达到最高,得到的经济效益最大。     

沼肥对保护地番茄产量、品质和土壤肥力的影响

采用田间小区试验,研究了沼肥对番茄产量、品质及其土壤肥力的影响。试验结果表明,沼肥可以促进番茄生长发育,提高产量,改善果实品质,增加土壤中有机质、全量养分及速效养分的含量。表现为施用沼肥比不施肥增产88.24%,比等养分的化肥增产7.87%,产量差异达到极显著水平;果实中可溶性固形物、维生素C、糖酸比,比不施肥处理分别增加9.03%、23.69%、13.28%,比化肥处理分别增加12.26%、15.37%、28.49%,土壤耕层有机质、全氮、全磷、碱解氮、速效磷、速效钾与试前本底养分相比分别增加了12.70%、9.52%、7.50%、4.33%、74.77%、17.58%。