施氮量对小麦氮磷钾养分吸收利用和产量的影响

高产条件下研究了不同施氮量对小麦植株氮、磷、钾养分吸收利用及籽粒产量的影响.结果表明,适量施氮可促进小麦植株对氮素的吸收与积累,较高的施氮量不利于起身期之后的氮素积累,致使成熟期小麦氮素积累量未能显著提高;与不施氮肥相比,施氮显著提高植株磷素积累量;随施氮量增加,植株磷素积累量增加不显著;施氮量增加促进小麦生育前期对钾素的吸收积累,在生育后期降低植株钾素的流失.随施氮量增加,籽粒氮素含量呈先增后降的趋势,氮素向籽粒的分配比例趋于降低,植株氮素利用效率无显著变化,氮素收获指数下降;不同施氮处理之间籽粒磷素含量和钾素含量无显著差异,施氮量增加,营养器官钾素含量、钾素积累量和钾素向叶片的分配比例均呈增加趋势;同时,磷素和钾素利用效率降低;不同施氮处理间,植株磷素、钾素收获指数无显著差异.籽粒产量随施氮量增加呈先增加后降低的趋势,以施氮195 kg/hm2的处理籽粒产量最高.     

不同土壤肥力条件下施氮量对小麦氮肥利用和土壤硝态氮含量的影响

在土壤肥力不同的两块高产田上,利用15N示踪技术,研究了高产条件下施氮量对冬小麦氮肥吸收利用、籽粒产量和品质的影响,及小麦生育期间土壤硝态氮含量的变化.结果表明：1.成熟期小麦植株积累的氮素73.32%～87.27%来自土壤,4.51%～9.40%来自基施氮肥,8.22%～17.28%来自追施氮肥;随施氮量增加,植株吸收的土壤氮量减少,吸收的肥料氮量和氮肥在土壤中的残留量显著增加,小麦对肥料氮的吸收率显著降低;小麦对基施氮肥的吸收量、吸收率和基施氮肥在土壤中的残留量、残留率均显著小于追施氮肥,基施氮肥的损失量和损失率显著大于追施氮肥;较高土壤肥力条件下,植株吸收更多的土壤氮素,吸收的肥料氮量较少,土壤中残留的肥料氮量和肥料氮的损失量较高,不同地块肥料氮吸收、残留和损失的差异主要表现在基施氮肥上.2.当施氮量为105 kg/hm2时,收获后0～100cm土体内未发现硝态氮大量累积,随施氮量增加,0～100cm土体内硝态氮含量显著增加;施氮量大于195 kg/hm^2时,小麦生育期间硝态氮呈明显的下移趋势,土壤肥力较高地块,硝态氮下移较早,下移层次深.3.随施氮量增加,小麦氮素吸收效率和氮素利用效率降低,适量施氮有利于提高成熟期小麦植株氮素积累量、籽粒产量和蛋白质含量;施氮量过高籽粒产量和蛋白质含量不再显著增加,甚至降低;较高土壤肥力条件下,获得最高籽粒产量和蛋白质含量所需施氮量较低.     

灌溉方式和施氮量对棉田氮肥利用率及损失的影响

在田间条件下,研究不同灌溉方式(滴灌和漫灌)和不同施氮水平(0、240、360、480kg N·hm-2)对棉田氮肥利用率及损失的影响,并定量分析了氮肥被植株吸收、土壤硝态氮残留,以及氨挥发、硝态氮淋溶损失、硝化反硝化损失等氮素循环转化途径.结果表明:滴灌棉花籽棉产量、植株吸氮量和氮肥利用率均显著大于漫灌.漫灌土壤硝态氮残留量显著高于滴灌;在不同施氮量处理中滴灌土壤氨挥发损失量占肥料氮施用量的比例为0.06％～0.14％,且显著高于漫灌;滴灌和漫灌硝态氮淋溶损失量占肥料氮施用量的比例分别为4.4％和8.8％,与漫灌相比,滴灌能显著降低淋溶水中硝态氮淋失量;滴灌和漫灌肥料氮的硝化-反硝化损失量分别占肥料氮施用量的17.9％和16.8％.硝态氮淋溶和硝化-反硝化损失是新疆棉田氮素损失的主要途径.     

施氮和肥料添加剂对水稻产量、氮素吸收转运及利用的影响

在苏南太湖地区开展田间试验,研究了施氮和肥料添加剂对水稻产量、氮素吸收转运及利用的影响.结果表明:施氮对水稻产量、各生育时期植株累积吸氮量、阶段氮累积量和花后氮素转运量具有显著的促进作用(P＜0.01),当施氮量高于200 kg·hm-2时,增施氮肥的增产效应不显著(P＞0.05);花后氮素转运率和氮肥利用率均随施氮量的增加而降低.施用肥料添加剂可进一步提高水稻产量、累积吸氮量、花后氮素转运量和氮肥利用率,且该效应在高施氮量( ≥200 kg·hm-2)条件下表现更明显.本试验条件下不施用肥料添加剂时,施氮150kg·hm-2可同时获得较高的产量和氮肥利用率.     

水氮耦合对冬小麦氮肥吸收及土壤硝态氮残留淋溶的影响

在高肥力条件下,大田试验采用裂区设计,主区为不同灌水频次(0～3次),裂区为不同施氮量(0～240 kg/hm2),结合15N微区示踪技术,研究了水氮耦合对冬小麦氮肥的吸收利用及生育后期土壤硝态氮累积迁移的影响.结果表明,在一定氮肥水平下,不灌水处理的氮肥利用率高于各灌水处理,各灌水处理的氮肥利用率随灌水次数增加呈上升趋势;增加灌水次数,氮肥耕层残留量和残留率显著降低,氮肥损失量和损失率则明显增加.在一定的灌溉水平上,随施氮量(0～240 kg/hm2)增加,植株总吸氮量、氮肥吸收量、氮肥耕层残留量、氮肥损失量以及损失率均呈上升趋势,而氮肥利用率和耕层残留率呈下降趋势.氮肥水平一定时,在灌0至灌2水范围内,籽粒产量随灌水次数增加呈上升趋势,灌3水处理中施氮处理(N168、N240)的籽粒产量较灌2水处理显著降低;灌水生产效率随灌水次数增加显著下降.在一定灌溉水平上,施氮量由168 kg/hm2增至240 kg/hm2,氮素收获指数和氮肥生产效率显著降低,各灌水处理的生物产量、籽粒产量和籽粒蛋白质含量均无显著变化,不灌水处理的生物产量、籽粒产量显著降低.灌水促进了施氮处理(N168,N240)中土壤硝态氮向下迁移,从开花到收获0～100 cm土层中部分硝态氮迁移到了100～200 cm土层.灌水次数是导致收获期0～100 cm土层残留NO-3-N累积量变化的主导因素;水氮互作效应是决定收获期100～200 cm土层残留NO-3-N累积量变化的主导因素,且灌水效应大于施氮效应.     

稻油轮作下秸秆还田配施化肥对作物产量及肥料利用率的影响

水稻-油菜轮作集约化耕作导致土壤肥力下降,而秸秆还田是培肥土壤肥力的主要途径之一。通过水稻-油菜轮作田间长期定位试验,设置了秸秆不还田的不施氮肥(CK)和农民习惯处理(FPP),3个秸秆还田配施化肥处理(SF1、SF2、SF3),每年水稻秸秆以3000kg·hm~(-2)的量还田,SF1、SF2、SF3配施氮、磷、钾肥量依次增加,分析了水稻和油菜产量、养分积累利用及平衡状况。结果表明:不同施肥处理,水稻和油菜籽粒产量表现出相似的格局,即SF3SF2SF1FPP,但SF2与SF3产量差异不显著;与FPP比较,秸秆还田配施化肥处理周年平均产量增加了17.5%～28.6%,水稻和油菜氮、磷、钾积累量随施肥量的增加而增加,水稻氮、磷、钾积累量平均增加了21.7%、17.7%、14.0%,油菜则分别增加了22.4%、19.6%、51.8%,秸秆还田与增施钾肥使油菜钾积累量增幅最高;同样,秸秆还田配施化肥处理提高了水稻和油菜的氮肥偏生产力和农学利用率,其中氮肥偏生产力分别增加了8.1%～31.1%和4.2%～29.3%,以SF2增幅最高,但降低了磷肥和钾肥偏生产力;养分平衡计算显示,秸秆还田配施化肥处理水稻磷、钾亏缺,油菜氮、磷、钾盈余超出可接受范围。在水稻-油菜轮作体系中,秸秆还田配施化肥可以提高作物产量和养分积累量,增加氮肥利用率,大量磷、钾肥的投入及秸秆还田提供的养分造成了油菜养分盈余和肥料利用率下降,需进一步调整优化秸秆还田下化学肥料的投入量,使生产系统中养分循环利用更加合理和持续。     

氮肥运筹对晚播冬小麦氮素和干物质积累与转运的影响

氮素平衡对干物质积累与分配的影响是农业生态系统研究的重要内容,在保障产量前提下减少氮肥施用量可减少环境污染与温室气体排放。以晚播冬小麦为研究对象,设置4个施氮量水平:0 kg/hm2(N0)、168.75 kg/hm2(N1)、225 kg/hm2(N2)、281.25 kg/hm2(N3),每个施氮量水平下设置2个追氮时期处理:拔节期(S1)、拔节期+开花期(S2),研究了氮肥运筹对晚播冬小麦氮素和干物质积累与转运及氮肥利用率的影响。结果表明:拔节期追施氮肥(S1)条件下,在225 kg/hm2(N2)基础上增施25%氮肥(N3)对开花期氮素积累总量和营养器官氮素转运量无显著影响;拔节期+开花期追施氮肥(S2)条件下,随施氮量增加,开花期氮素积累总量和花后营养器官氮素转运量升高;S2较S1显著提高成熟期籽粒及营养器官氮素积累量、花后籽粒氮素积累量及其对籽粒氮素积累的贡献率。同一施氮量条件下,S2较S1提高了成熟期的干物质积累量、开花至成熟阶段干物质积累强度和花后籽粒干物质积累量。同一追氮时期条件下,籽粒产量N2与N3无显著差异,氮肥偏生产力随施氮量增加而降低;同一施氮量条件下,S2较S1提高了晚播冬小麦的籽粒产量和氮肥吸收利用率。拔节期+开花期追施氮肥,总施氮量225kg/hm2为有利于实现晚播冬小麦高产和高效的最优氮肥运筹模式。     

减量施氮对玉米-大豆套作体系土壤氮素残留和氮肥损失的影响

通过田间试验,研究了玉米单作、大豆单作、玉米-豆套作3种种植模式和不施氮、减量施氮(180 kg N·hm^-2)、常量施氮(240 kg N·hm^-2)3种施氮水平对玉米和大豆植株氮素吸收、土壤氮素残留和氮肥损失的影响.结果表明: 玉米-豆套作体系下,施氮提高了玉米土壤中残留的NO₃^--N、NH₄⁺-N含量,但在大豆土壤中则降低.与单作相比,玉米套作的土壤氮素残留量增加,氮肥损失量降低,大豆套作的土壤氮素残留量和氮肥损失量均降低.减量施氮处理下,玉米-豆套作系统的氮肥残留率、损失率和氨挥发损失率分别比玉米单作低17.7%、21.5%和0.4%,比大豆单作高2.0%、19.8%和0.1%.与常量施氮相比,减量施氮降低了玉米-豆套作系统的氮肥残留量、残留率、损失量和损失率,同时还降低了由氨挥发所引起的氮肥损失,其中氮肥残留率、损失率和氨挥发损失率分别降低12.0%、15.4%和1.2%.     

施氮对关中还田玉米秸秆腐解和养分释放特征的影响

在陕西关中平原的冬小麦-夏玉米轮作区,采用尼龙网袋田间填埋与¹⁵N同位素标记玉米秸秆相结合的方法,设置不施氮和施氮200 kg·hm^-2两个处理,研究施氮对小麦生长期内还田玉米秸秆腐解的影响以及腐解过程中秸秆碳、氮、磷、钾的养分释放.结果表明: 从小麦播种到越冬期,施用氮肥对秸秆碳和干物质分解无显著影响,但可促进秸秆中磷的释放,抑制氮和钾的释放.灌浆到成熟期,氮肥对秸秆腐解及其N、P、K养分的释放无显著影响,但秸秆碳的释放显著增加.不同生育期,玉米秸秆碳的释放与干物质分解变化趋势一致,C/N逐渐下降.种植一季小麦后,秸秆干物质累计腐解率不足50%;秸秆碳释放率为47.9%～51.1%,不施氮和施氮处理的秸秆C/N分别由32.2降低到20.2和17.9.小麦收获时,秸秆氮、磷、钾均为净释放,氮释放量为7.2～9.4 kg·hm^-2,占秸秆氮的12.7%～16.6%;磷释放量为1.29～1.44 kg·hm^-2,占29.0%～32.4%;钾的释放量大、释放快,越冬前超过80%,成熟时释放量为51.8～52.5 kg·hm^-2,占90.5%～91.7%.在秸秆还田条件下,应考虑秸秆归还的钾,减少小麦钾肥用量,适量补充氮、磷.     

长期氮磷钾肥配施对贵州黄壤玉米产量和土壤养分可持续性的影响

为明确长期氮磷钾肥配施下贵州典型黄壤玉米产量、氮磷钾肥增产效应及土壤养分的演变特征,利用国家贵阳黄壤肥力与肥效长期定位试验,研究氮磷钾平衡施肥(NPK)与缺素施肥(N、NK、NP、PK)对玉米相对产量、氮磷钾肥增产贡献率及土壤氮磷钾素养分可持续性指数等的影响.结果表明: 氮磷钾平衡施肥有显著增产效果,玉米相对产量均值为:NPK>NP>NK>PK>CK;氮、磷、钾肥增产贡献率和农学利用率均为氮肥>磷肥>钾肥,施肥依存度为氮、磷、钾肥配施>氮肥>磷肥>钾肥,但缺磷处理(NK)玉米相对产量以每年1.4%的速度极显著下降,磷肥贡献率和依存度则以每年2.3%和1.4%的速度极显著上升,最终磷肥对玉米生产的影响逐渐与氮肥持平;缺磷处理土壤pH值和有机质含量均最低,而缺氮处理则较高;施用化学磷肥可提高黄壤磷素可持续性指数,但氮肥和钾肥对黄壤氮素和钾素可持续性指数无显著影响.综上,平衡施肥是贵州典型黄壤地区玉米高产的重要保障,其中磷肥与氮肥同等重要,但长期单施化肥尤其是缺磷处理不利于黄壤养分的可持续利用.     

烤烟烟叶中N,K营养及N,K平衡的初步研究

研究了滇中地区烤烟中部叶片旺长期（移栽后６０－６５ｄ）Ｎ、Ｋ营养及Ｎ、Ｋ平衡。结果表明：⑴烟叶一般Ｎ含量为２．５％－４％,Ｋ含量为１％－３％,Ｎ／Ｋ比为２．５－３．５。⑵烟叶Ｎ含量＞４％,就有Ｎ过剩的症状产生。⑶烟叶Ｎ含量＜２．５％,Ｋ含量＜１％,就表现出Ｎ、Ｋ缺乏症状。⑷烟叶Ｎ／Ｋ比失调,过高或过低,都会影响烟株正常生长。     

Aggregation of gelsolin wild-type and G167K/R,N184K,and D187N/Y mutant peptides and inhibition

Molecular and Cellular Biochemistry - Gelsolin, an actin-binding protein, is localized intra- and extracellularly in the bloodstream and throughout the body. Gelsolin amyloidosis is a disease...     

Effect of N,K, and P fertilization,N source,and clipping on potential tetany hazard of bromegrass

Summary The objective of this field study was to determine early-season effects of N source, N, K, and P fertilization, and clipping (to simulate grazing) on potential tetany hazard of bromegrass (Bromus inermis L.) as indicated by the chemical composition of its forage. Tetany is a metabolic disorder of ruminants resulting from forage with low Mg availability. Chemical components considered in the forage were inorganic cations, organic acids, aconitate, and per cent total N/per cent total water soluble carbohydrate (N/TWSC). Differences between the sum (in meq/kg) of inorganic cations (Mg, Ca, K, and Na) and inorganic anions (Cl, NO₃, H₂PO₄, and SO₄) in forage were defined as the concentration of organic acids (C-A). Soil was Parshall fsl, a Pachic Haploboroll. Yields and chemical composition of oven-dried forage from previously unclipped and reclipped plots were determined at 3-week intervals beginning May 22 and June 12, respectively. A water budget was determined using soil-water and rainfall data.Forage yields were increased 2- to 3-fold by N fertilization with the NO₃-N source generally outyielding the NH₄-N source. A slight additional yield response to that obtained with N alone was obtained with K+P fertilization but not with K or P alone with or without N. Much less total forage was removed from reclipped plots than from unclipped plots. Forage Mg content was decreased only slightly by K or NH₄-N fertilization. Soil analysis indicated that high NH₄-N levels were present at the May 22 harvest. Magnesium and Ca concentrations were only slightly affected by N fertilization; however, K, K/(Ca+Mg), total N, C-A, and aconitate were increased. Reclipping increased Mg, N, K, N/TWSC, C-A, and aconitate. Estimates of blood-plasma Mg concentrations were obtained by using the data for plant N, K, and Mg. These estimates did not indicate increased tetany hazard as a result of reclipping, but did indicate increased tetany hazard from N fertilization. Forage C-A and aconitate concentrations were decreased by fertilization with KCl which seemed to have been caused by the increased Cl concentrations in the forage. Estimates of quantities of Mg, arriving at the root surfaces from the soil by mass flow, far exceeded amounts of Mg in the forage. Mass flow seemed to be the principal mechanism by which Mg and Ca arrived at root surfaces but this mechanism was much less important for K.This study indicated an increased potential tetany hazard resulting primarily from N fertilization with either NH₄-N or NO₃-N sources. However, the potential for increased forage and livestock-carrying capacity with N fertilization is very large. Therefore, management practices corroborated by livestock data are vitally needed to minimize tetany hazard while increasing bromegrass yields by N fertilization.Contribution from Soil, Water, and Air Sciences, North Central and Northeastern Regions, ARS-USDA.Follett, Power, and Grunes are soil scientists and Kleinis a biological laboratory technician. Follett is now National Program Staff Scientist, ARS, BARC-West, Beltsville, MD 20705. Power and Klein are at the USDA Northern Great Plains Research Center, Mandan, ND 58554, as formerly was Follett. Grunes is at the U.S. Plant, Soil and Nutrition Laboratory, Ithaca, NY 14853.     

The Effect of I155T,K156Q,K156E and N186K Mutations in Hemagglutinin on the Virulence and Reproduction of Influenza A/H5N1 Viruses

Molecular Biology - The continued circulation of influenza A virus subtype H5 may cause the emergence of new potential pandemic virus variants, which can be transmitted from person to person. The...     

农林生态系统中营养元素N、P、K流动的网络分析

对农林业系统沙兰杨-小麦-玉米群落类型中N、P、K流动网络分析表明,系统中N、P、K的循环指数分别为0.071、0.039、0.139,均小于传统的循环系数(CC等于回归量/吸收量),而在群落中的总滞留时间分别为22.41、79.72、26.57a.     

羊草草地枯枝落叶中N、P、K变化动态

On Aneurolepidium chinease grassland, the amounts of N, P and Ktransferred from deadplants into the litters are respectively 0.7227, 0.1137 and 0.4974g·m^-2·yr^-1.After oneyear, the loss rates of them are respectively 59.71, 73.21 and 83.26%.Under imbalancestate, the input of these three elements is larger than their output, being at accumulationstage, while under stable state, their contents in litters are respectively 1.1859, 0.1565 and 0.5963g·m^-2.     

N,N'-dicyclohexylcarbodiimide-sensitive K+-dependent ATPase activity in Escherichia coli

ATPase activity sensitive to N,N'-dicyclohexylcarbodiimide and dependent on K+ content in medium is observed only in anaerobically grown Escherichia coli and as the analysis of mutants with defects in different subunits of (F0F1) H+-ATPase and in potassium transport shows only under the structural integrity of both F0F1 and K+-ionophore (the Trk system). The obtained results confirm the data on the H+/K+-exchange and indicate that the F0F1 and Trk systems in anaerobically grown bacteria unite into the same membrane supercomplex inside which the direct energy transfer occurs without a mediation of delta-mu H+.