不同作用因子下有机无机配施添加DMPP对氮素转化的影响

研究不同作用因子下有机无机配施模式添加DMPP(3,4-二甲基毗唑磷酸盐)对土壤氮素形态转化的影响,为田间氮素管理和高效利用提供科学依据.采用好气恒温土壤培养试验,研究施肥用量、水分条件、环境温度、土壤类型等不同作用因子,对有机无机氮肥配施模式添加DMPP土壤氮素形态转化的影响.结果表明,60 d时,高用量有机无机配施处理比常规有机无机处理铵态氮含量提高89倍,硝态氮减少57.8％;与湿润培养相比,淹水条件下有机无机配施模式添加DMPP,60 d内土壤铵态氮含量持续增加,硝化进程受抑制更显著;60 d时15℃处理铵态氮含量较25℃处理高56倍,硝态氮含量低18倍;60 d时红壤中铵态氮含量分别是小粉土和青紫泥的30倍与31倍,而硝态氮含量仅为二者的55.7％与33.6％.25℃时青紫泥、小粉士和红壤中有机无机配施模式添加DMPP最佳抑制效果在30～ 40 d,有效作用时间可达60 d.DMPP能够明显增加有机无机配施模式土壤中铵态氮含量,有效延长铵态氮在土壤中停留的时间,使硝态氮含量长期维持在较低水平.高施肥水平有机无机配施模式下DMPP的抑制效果更突出.低温环境有利于DMPP对硝化进程的抑制.不同作用因子下,有机无机配施模式添加DMPP对氮素转化影响的深层作用机理值得进一步研究.     

尿素与缓释尿素配施添加DMPP对砂姜黑土氮素转化的影响

研究尿素与缓释尿素配施添加硝化抑制剂3,4-二甲基吡唑磷酸（DMPP）对砂姜黑土氮素转化的影响，为田间速效与缓释氮的合理配施提供理论依据。采用室内恒温、恒湿培养试验方法，试验设不施肥（CK）、单施尿素（N）、单施缓释尿素（S）、60%尿素+40%缓释尿素（NS）、尿素+DMPP（ND）、缓释尿素+DMPP（SD）、60%尿素+40%缓释尿素+DMPP（NSD）共七个处理，通过测定不同处理土壤中不同形态氮素含量，探究添加DMPP在单施尿素、单施缓释尿素及尿素与缓释尿素配施上对土壤氮素转化的不同影响。ND处理在培养第1~35 d内铵态氮含量均显著高于N处理（P<0.05），并有效延缓了铵态氮向硝态氮转化的时间。SD处理较之S处理在显著提高土壤中铵态氮含量的同时（P<0.05），也能有效抑制硝化作用，其硝化抑制有效作用时间在49 d左右，并且在此期间内能降低表观硝化率，提高硝化抑制率。与NS处理相比，NSD处理不仅能够显著提高土壤铵态氮含量（P<0.05），使铵态氮半衰期延长至18.6 d，硝化抑制率显著提高（P<0.05），表观硝化作用有效抑制时间延长了32 d左右。综合分析表明，尿素与缓释尿素配施添加DMPP在抑制氨氧化作用中效果明显，显著提高硝化抑制率（P<0.05），降低表观硝化率，有效延长了铵态氮在土壤中停留的时间，该措施为有效阻控农田氮素损失提供了科学依据。     

几种硝化抑制剂和包硫尿素(SCU)对土壤N素形态和小麦产量的影响

采用土壤盆栽法,研究了双氰胺(DCD)、硫脲(THU)和硫脲甲醛树脂(TFR)以及包硫尿素(SCU)对土壤氮素形态和小麦产量的影响。试验共设不施氮(CK)、单施尿素、包硫尿素(SCU)、以及尿素分别与DCD、THA、TUF的3个浓度梯度(分别按尿素用量的0.5%、1%、2%)配合施用共12个处理。结果表明:随添加浓度的增加,硝化抑制作用逐渐增强,高剂量硝化抑制剂显著降低土壤NO-3-N含量,在2%添加浓度下,DCD、THU、TFR的土壤NO-3-N浓度分别比单施尿素降低29%、22%和14%,对土壤表观硝化率的抑制强度也是2%DCD2%THU2%TFR;SCU处理与2%DCD作用强度接近,且在施用早期就体现抑制效果,并在追肥后第74 d土壤表观硝化率显著低于使用硝化抑制剂的处理(P0.05);硝化抑制剂和SCU都可以使土壤NH+4-N含量稳定在较高的水平,抑制剂用量越多,土壤NH+4-N含量越高;与单施尿素相比,尿素+DCD模式,均可提高小麦产量,且在0.5%、1%、2%添加浓度,都达到显著水平(P0.05);THU在1.0%和2.0%添加浓度,小麦产量显著高于单施尿素,但增产效果次于DCD。总体上,包硫尿素(SCU)比硝化抑制剂在控释氮素方面效果更持久,而3种硝化抑制剂中,在控制土壤NH+4-N转化、土壤硝化抑制方面,DCD和THU优于TFR;作为外源添加物的抑制剂长期应用可能对土壤环境造成潜在的危害,不同硝化抑制在土壤中的形态归趋和长期作用还有待进一步研究。     

DMPP与尿素配施对新疆沙砾土壤氮素转化和葡萄叶片光合的影响

研究尿素与硝化抑制剂3,4-二甲基吡唑磷酸盐(DMPP)混施对新疆沙砾土壤氮素转化及葡萄叶片光合的影响,以期为DMPP科学应用提供理论依据。以葡萄品种“赤霞珠”为供试作物,试验设不施肥、单施尿素以及在尿素中分别添加0.5%、1%、3%、5%的DMPP(含氮量的0.5%、1%、3%、5%),共6个处理,探讨不同浓度DMPP与尿素混施对土壤中NH4+-N、NO^3--N、硝化抑制率、pH值以及叶片SPAD值、净光合速率和胞间CO₂浓度等指标的影响。结果表明:施入尿素使土壤中NH4+-N含量增幅达150 mg/kg以上;与单施尿素相比,添加不同浓度的DMPP不仅可以延缓NH4+-N下降趋势,还能有效降低土壤中NO^3--N上升的趋势,但DMPP在0.5%～5%浓度范围内未发生明显的剂量效应,其中添加1%DMPP作用效果最显著;不同浓度的DMPP对土壤的硝化抑制率也不相同,1%DMPP在第14 d的抑制效果可达到49.60%;与不施肥相比,施入尿素可显著提高叶片净光合速率和SPAD值;利用主成分分析提取出的4个主成分可涵盖原始信息的84.146%,其中1%DMPP处理得分最高。综上所述,尿素与DMPP混施可显著抑制NH4+-N向NO^3--N转化,提高硝化抑制率,降低表观硝化率,使土壤中保持较高水平的NH4+-N含量,同时还可显著提高叶片净光合速率。不同浓度DMPP处理间有一定的显著差异,从经济效益和应用效果综合考虑,新疆沙砾土中以1%DMPP与尿素配施效果最佳。     

硝化抑制剂对毛竹林土壤N_2O排放和氨氧化微生物的影响

为了探索硝化抑制剂在毛竹生产中的施用技术,通过培养试验研究3,4-二甲基吡唑磷酸盐(DMPP)和双氰胺(DCD)两种硝化抑制剂对毛竹林施用尿素后土壤N2O排放、氮素转化和相关氨氧化细菌(AOB)、氨氧化古菌(AOA)群落结构和丰度的影响。试验设(1)对照(CK)、(2)单施尿素(Urea)、(3)尿素+1%DMPP(DMPP占总N的1%,下同);(4)尿素+1.5%DMPP;(5)尿素+10%DCD;(6)尿素+15%DCD等6个处理,测定N2O的排放动态以及气体排放转折点时的土壤特征指标。结果表明:与单施尿素相比,160 d的时间内两种DMPP用量处理的土壤N2O累积排放减排幅度均为54%,而10%DCD和15%DCD处理的土壤分别减少28%和41%。DMPP和DCD处理50 d和90 d时土壤的NH4+-N含量均显著高于(p0.05)单施尿素处理,而NO3--N含量和表观硝化率则恰好相反,但两种抑制剂间无差异。DMPP处理的AOB群落结构的变化从10 d开始显现,至50 d和90 d时仍保持明显的抑制状态,而DCD处理则至90 d时抑制作用基本消失。单施尿素AOB功能基因(amo A)的丰度均显著高于硝化抑制剂处理(90 d时尿素+10%DCD处理除外);在整个培养期内,尿素和对照土壤的AOA群落结构相似,硝化抑制剂反而增加了AOA功能基因的丰度,表明硝化抑制剂对AOA丰度无明显抑制作用。即两种硝化抑制剂主要通过抑制AOB起作用;调节土壤p H至中性范围,并在1%DMPP施用条件下,硝化抑制剂的抑制效果最显著。     

硫酸铵与DMPP配施对石灰性褐土氮素转化及N2O、CO2排放的影响

为合理利用工业副产硫酸铵,探究3,4—二甲基吡唑磷酸盐(DMPP)配施硫酸铵对石灰性褐土中氮素转化及N_2O和CO_2排放的影响。通过室内培养试验,研究不同剂量DMPP与硫酸铵配施后,石灰性褐土中铵态氮(NH_4~+-N)含量、硝态氮(NO_3~--N)含量、土壤pH、N_2O和CO_2排放通量和累计排放量的动态变化,并进行了相关性分析。结果表明:单施硫酸铵的ASN处理在培养的前15天硝化作用强烈,第15天时,土壤NH_4~+-N含量降低了477.28 mg/kg, NO_3~--N含量增高了177.03 mg/kg。添加DMPP可以明显抑制硫酸铵NH_4~+-N向NO_3~--N转化。培养30天后,0.75%～1.75%剂量的DMPP处理的土壤NO_3~--N含量低于ASN处理174.02～177.00 mg/kg,硝化抑制率为94.92%～95.30%,且在0.75%～1.75%浓度范围内未表现出明显的剂量差异效应。各剂量DMPP在试验期间的硝化抑制效果表现较好,其作用时长为30天以上。培养30天时,与空白CKII处理相比,单施硫酸铵T1处理的N_2O和CO_2的累计排放量分别显著增加了975.3%,126.66%(P0.05),而添加了DMPP的T2处理相较于单施硫酸铵T1处理,N_2O和CO_2累计排放量分别显著降低了76.8%,6.22%(P0.05)。相关性分析表明,CO_2排放通量与N_2O排放通量呈正相关关系,土壤pH与N_2O、CO_2排放通量呈负相关关系。硫酸铵与0.75%DMPP配合施用在一定程度上可以抑制土壤酸化,同时短期内可以显著降低N_2O和CO_2累计排放量(P0.05)。     

尿素与有机肥配施对棕红壤氮素转化的影响

为了解析尿素配施有机肥对土壤氮库活动的影响,通过室内恒温培养试验研究尿素(225kg N·hm~(-2))分别与低量(30 t·hm~(-2))、中量(60 t·hm~(-2))及高量(120、150 t·hm~(-2))有机肥配施条件下棕红壤有机氮库、无机氮库的动态变化。结果表明,配施有机肥土壤的有机氮含量较单施尿素增加16.3%~85.6%。中、高量配施显著提高土壤氮素矿化速率(p0.05),加剧无机氮转化强度,与单施尿素相比,无机氮最大矿化量增加52.9~246.0 mg·kg~(-1),有效矿化持续时间延长5 d,转化量增大2.3倍~8.7倍;配施有机肥提高土壤氨化强度,加快铵态氮(NH_4~+-N)转化速率。与单施尿素相比,配施有机肥处理NH_4~+-N含量峰值增加2.6~42.6 mg·kg~(-1),平均氨化速率提高7.8 mg·kg~(-1)·d~(-1),转化速率增加1.4倍~8.8倍。一定量配施有机肥(30~120 t·hm~(-2))对土壤的硝化过程无显著影响,但过高量配施有机肥(150 t·hm~(-2)),强化土壤硝化作用,硝化速率较单施尿素提高4.2倍,引起土壤硝态氮(NO-3-N)大量累积。氮素表观平衡结果表明,中、高量配施有机肥显著增加培养体系氮素表观损失,60、90和120 t·hm~(-2)处理氮素损失量分别较单施尿素增加2.2倍、2.8倍和2.3倍,占总输入氮的27.5%~34.5%,其中,NH_4~+-N转化损失是体系氮表观损失的主要途径。本研究结果为棕红壤合理培肥提供了理论依据。     

用于黑土的稳定性氯化铵的适宜硝化抑制剂和氮肥增效剂组合

【目的】本文研究添加不同种类硝化抑制剂的高效稳定性氯化铵氮肥在黑土中的施用效果，旨在筛选出适合旱作黑土的高效稳定性氯化铵态氮肥。【方法】在氯化铵中分别添加硝化抑制剂3,4-二甲基吡唑磷酸盐 (DMPP)、双氰胺 (DCD)、2-氯-6-三甲基吡啶 (Nitrapyrin，CP)、氨保护剂 (N-GD) 和1种氮肥增效剂 (HFJ) 及其组合，制成9种稳定性氯化铵氮肥。以不施氮肥 (CK) 和施普通氯化铵 (CK-N) 为对照，以9种稳定性氯化铵为处理进行了等氮量盆栽试验。在玉米苗期、大喇叭口期、灌浆期和成熟期测定了土壤中铵态氮和硝态氮含量，在玉米成熟期测定植株生物量、籽粒产量和氮素含量，计算铵态氮肥的表观硝化率、硝化抑制率、氮肥农学效率、氮肥偏生产力。【结果】1) 与CK-N处理相比，9个处理均显著提高玉米的产量，HFJ的效果均为最显著，可增加玉米籽粒产量3.99倍，提高氮肥吸收利用率4.98倍，显著高于8个硝化抑制剂处理 (P < 0.05)。CP + DMPP和CP + DCD处理提高玉米籽粒产量1.90～2.11倍，两个处理之间无显著差异；CP + DMPP玉米生物量显著高于CP处理，而与DMPP和DCD处理无显著差异；CP + DMPP玉米氮肥吸收利用率显著高于CP和DMPP处理，显著提高3.71倍 (P < 0.05)；2) CP + DMPP和CP + DCD土壤中铵态氮含量提高2.09～2.42倍，且显著高于CP、DMPP和DCD处理 (P < 0.05)，而硝态氮含量和土壤表观硝化率均显著降低24%和66%～68%，与CP和DCD处理存在显著差异 (P < 0.05)；苗期CP + DMPP和CP + DCD硝化抑制率高达23.9%～24.3%，显著高于CP和DCD (P < 0.05)。【结论】在黑土中，氯化铵中添加硝化抑制剂组合的硝化抑制率显著高于添加单一抑制剂，能够有效减缓土壤中铵态氮向硝态氮的转化，减少土壤中氮素损失，降低环境污染。CP + DMPP组合玉米的氮肥吸收利用率显著高于CP + DCD组合。氮肥增效剂HFJ显著增加玉米的氮素吸收量，提高氮肥利用率，从而使玉米获得高产并获得较高的收获指数和经济系数。因此，综合考虑产量和抑制硝化作用等因素，黑土区氯化铵作为玉米生产用氮肥时，建议首选添加氮肥增效剂HFJ来保证作物的高产和氮肥高利用率，也可以添加硝化抑制剂组合CP + DMPP，或者CP + DCD制备稳定性氯化铵来提高氯化铵的增产效果和氮肥利用率，减少氮素损失，降低环境污染。     

3,4-二甲基吡唑磷酸盐对菜地土壤氮素形态转化的影响

采用小粉土和青紫泥两种典型土壤种植青菜,研究了尿素添加3,4-二甲基吡唑磷酸盐(DMPP)硝化抑制剂对土壤氮素迁移转化和青菜生长效应的影响。结果表明,DMPP抑制剂施入土壤具有显著的氨氧化抑制作用,60 d内使小粉土和青紫泥土壤中铵态氮平均含量分别提高52.7%和57.5%,硝态氮平均含量分别降低58.3%和65.9%。土壤铵态氮浓度增加,硝态氮浓度降低,有效延缓蔬菜地土壤铵态氮向硝态氮的转化,提高氮素的利用率。同时,尿素添加DMPP抑制剂能促进青菜生长,使小粉土和青紫泥土壤中青菜产量分别增加26.1%和29.8%,硝酸盐含量分别降低22.2%和26.9%,明显改善蔬菜品质。     

脲酶/硝化抑制剂对尿素氮在白浆土中转化的影响

采用室内恒温培养方法,研究了脲酶抑制剂（NBPT）、硝化抑制剂（DMPP）及其协同对尿素氮在三江平原白浆土中转化作用效果。研究表明,在白浆土中NBPT有效作用时间小于13 d,作用时间较在棕壤和黑土中短;对土壤中铵态氮、硝态氮及表观硝化率影响与普通尿素基本一致。NBPT与DMPP组合缓释尿素施入4-7 d,能够有效抑制脲酶活性,减缓尿素水解;只添加DMPP与添加NBPT与DMPP协同作用对抑制铵态氮硝化作用效果相同,二者能保持土壤中NH4+-N高含量时间超过80 d。DMPP作用时间可达80 d以上,能有效抑制NH4+-N向NO3--N的转化;在第80 d,土壤中仍有54.58%～56.85%的氮以铵态氮形式存在,表观硝化率只有50%左右。DMPP抑制硝化作用效果十分显著,因此,在白浆土中施用添加NBPT缓释尿素、DMPP缓释尿素、NBPT与DMPP缓释尿素时,应首选添加1%DMPP的缓释尿素肥料。     

Soil-profile distribution of primary and secondary plant-available nutrients under conventional and no tillage

Nutrient distributions under no tillage (NT) compared with conventional disk-and-bed tillage (CT) management in the warm, humid region of the southeastern USA need to be assessed so that future placement, quantity, and type of fertilizers can be altered, if necessary, to efficiently match crop demands. We determined soil-profile distributions of pH, N, P, S, K, Ca, Mg, Na, Zn, Fe, Mn, and Cu to a depth of 0.9 m at the end of 8.5 years of continuous CT and NT management on a Weswood silty clay loam (fine, mixed, thermic Fluventic Ustochrept) in southcentral Texas. Most dramatic changes occurred within the 0–0.05 m depth, where soil under NT had lower pH, Fe, and Cu than under CT, but greater P, K, Zn, and Mn. Greater P and K under NT than under CT also occurred below the till-zone (0.15–0.3 m). At a depth of 0–0.3 m, soil under NT contained greater amounts of extractable P, K, Zn, Fe, Mn, and Cu than under CT. Nitrogen fertilization had little effect on nutrient distributions, except resulting in greater extractable K at 0–0.05 m and greater nitrate at 0–0.15 m. Few changes in soil-profile distributions were observed for extractable S, Ca, Mg, and Na. Long-term continuous use of NT on this fine-textured, high-fertility (except for N) soil had no apparent adverse effects on nutrient distributions relative to CT, but enhanced conservation and availability of P, K, Zn, Fe, Mn, and Cu near the soil surface where crop roots proliferate.     

Assessing the effectiveness of conservation measures: Resolving the “wicked” problem of the Steller sea lion

“Wicked” problems are those that are complex and that change when solutions are applied. Many conflicts in conservation fall into this category. The study approached the problem of how to constrain the apparent wickedness of a problem in the conservation management of a species by using simple empirical indicators to carry out iterative assessment of the risk to a population and to document how this risk evolves in relation to the addition of new data and the implementation of management actions. Effects of high levels of uncertainty within data and also concerning population structure were examined through stochastic simulation and by exploration of scenarios. Historical trends in the example used, the Steller sea lion, showed rapid declines in abundance in some regions during the 1980s. The current total population is 130,000-150,000 Steller sea lions through Alaska and British Columbia and this number has been stable since about 1990 in spite of regional differences in population dynamics. Regional differences in the sequence of changes in the number of pups and non-pups, suggested that an internal re-distribution of juveniles could have happened between 1980 and 1990. Current productivity also appears close to the long-term mean. Stochastic population projection using various scenarios showed that, based upon this history, the risk of extinction for the population has declined and is below reasonable thresholds for considering the population to be endangered. The trends in risk suggest that management actions taken since 1990 have probably been effective. Consequently, the conservation management objectives for the Steller sea lion are probably being met. The approach provides a mechanism, based upon experience and scenario analysis, for exploring future policy options and may help to constrain the debate amongst stakeholders about the cost-benefit trade-offs associated with different options.     

Enhanced establishment and growth of giant cardon cactus in an eroded field in the Sonoran Desert using native legume trees as nurse plants aided by plant growth-promoting microorganisms and compost

To evaluate the feasibility of long-term desert reforestation technology of mixed vegetation, cardon cactus (Pachycereus pringlei) seedlings from indoor and outdoor nurseries were planted in the field adjacent to one seedling of potential legume nurse trees: mesquite amargo (Prosopis articulata), yellow palo verde (Parkinsonia microphylla), and blue palo verde (Parkinsonia florida). Some of the planting holes were also supplemented with common dairy compost. Additionally, the combinations of legume tree–cactus were inoculated with either a consortium of desert arbuscular mycorrhizal (AM) fungi, plant growth promoting bacteria (PGPB; the diazotroph Azospirillum brasilense Cd, and the phosphate solubilizer Paenibacillus sp.), or a mixture of all. The field experiments were evaluated periodically during 30 months for survival and growth. Cardons reared in an outdoor screen house survived better in the field than those reared in a controlled growth chamber and hardened later outdoors. Association with any legume nurse tree increased survival and enhanced growth of untreated cardons. For cardons growing alone, application of either compost, AM fungi, and all the treatments combined increased survival. For these plants, no treatment affected plant growth during the first 3 months after transplanting. Later, all treatments, except for AM fungi, enhanced plant growth. However, only 2 years after transplanting the enhanced growth effect of AM fungi was also significant. In the presence of the legume nurse trees, transient positive effects on cardon growth were recorded. General evaluation after 30 months of cultivation showed that the treatments positively affected cardon growth when growing alone or in combination only with mesquite amargo but not with the other two legume trees. This study proposes that young legume trees have the capacity to enhance survival and growth of cardon cactus, depending on the legume cactus combination. Additional treatments such as compost or PGPB can either amplify the effect or else attenuate it.     

Karyotypic and genome size variation in Cajanus cajan (L.) Millsp. (pigeonpea) and some wild relatives

Detailed karyotypes and 4C DNA amounts have been studied in five cultivars of Cajanus cajan and 20 species belonging to Cajanus, Rhynchosia, Dunbaria, Flemingia and Paracalyx. C. cajan shows intraspecific variability and its karyotype is most similar to that of C. cajanifolius (sect. Cajanus) in the morphology and number of satellite chromosomes and the lack of any correlation between chromosome size within the complement and asymmetry. Karyotypes of C. lineatus and C. sericeus belonging to sect. Atylia are similar with respect to maximum r-index and the ratio of longest and shortest chromosomes in their respective complements. C. acutifolius (sect. Frutocosa) is distinct in having a very low ratio (1.44) between the longest and the shortest chromosomes, while in C. albicans, C. goensis, C. scarabaeoides (sect. Cantharospermum) there is no chromosome pair with r-index >2.0. C. mollis and C. volubilis (sect. Volubilis) show similarity with regard to ratio between the longest and the shortest chromosomes and a distinct chromosome pair with an arm ratio of 2.7 and C. platycarpus is distinct (sect. Rhynchosoides) in having the smallest ratio (1.36) between the longest and the shortest chromosomes. 4C DNA amounts in Cajanus and Rhynchosia vary between 3.28 pg to 11.69 pg and 4.92 pg to 11.13 pg respectively, while in Dunbaria, Flemingia and Paracalyx these vary between 4.70 and 7:06 pg. In the genus Cajanus karyotypic features and 4C DNA amounts agree with the sectional classification and bring out a close relationship between C. cajan and C. cajanifolius. This is supported by studies based on seed protein patterns, isozyme analysis, trypsin and chymotrypsin inhibitor patterns, RFLP and RAPD data and crossability relationships. A clear relation between DNA amount and abnormalities effecting the extent of pairing and recombination in interspecific hybrids shows the importance of this study in developing future breeding programme involving C. cajan and its wild relatives that are of potential value.     

Effect of some fungicide seed treatments on the survival of Bradyrhizobium japonicum and on the nodulation and yield of soybean [Glycine max. (L) Merr.]

Several commercial fungicide seed treatments were evaluated for their possible effect on the survival of Bradyrhizobium japonicum on seeds and on the nodulation and yield of soybeans in a greenhouse and a field experiment. quinolate Pro (carbendazim and oxine copper), Vitavax 200FF (carboxin and thiram), and Monceren (pencycuron) had a small effect or no effect on the survival of B. japonicum and on the nodulation and yield of soybeans. They can thus be considered compatible with soybean seed inoculation. Germipro UFB (carbendazim and iprodione), Apron 35J (metalaxyl), and Tachigaren (hymexazol) decreased B. japonicum survival and the nodulation and yield of soybeans and thus cannot be considered compatible with soybean seed inoculation.     

Einfluss der düngungsmethoden auf die entwicklung von zuckerrübenkrankheiten

Während neunjähriger (1994-2002) Untersuchungen in der Versuchsanstalt Ba?cyny (Fahlerde, Fall-Gleyboden, ausgebildet aus leichtem Lehmboden) wurde der Befall mit Krankheiten an der Zuckerrübe in Abhängigkeit von der Düngungsmethode bewertet. Folgende Methoden wurden angewendet: A - Mineraldünger, B - Stalldung und Mineraldünger, C - Stroh-, Gründung und Mineraldünger, D - Kompostdünger und Biopräparate (ökologische Düngung). Auf den Objekten A, B, C wurden bei konstanter Phosphor-Kalium-Düngung die Stickstoffgaben von 0 bis 180 kg.ha^?1 differenziert. Auf dem ökologischen Objekt D ohne Mineraldünger wurden statt Stickstoff die Biopräparate P₅₀₀ und P₅₀₁ verabreicht. Der geringste Befall von Krankheiten wurde an der Zuckerrübe auf jenem Objekt festgestellt, das mit Kompost und den Biopräparaten gedüngt worden war. Im Rahmen der konventionellen Düngungsmethoden wurde allgemein die höchste Intensität der Krankheiten an der mit Stroh, Gründung und Mineraldünger gedüngten Zuckerrübe beobachtet. Ausnahmen von dieser Regel bildete das Vorkommen von echtem Mehltau und Keimlingsfäule. Auf den Objekten A, B, C nahm die Intensität der Krankheiten mit der Steigerung der Stickstoffgabe zu. Auch die auf Objekt D verabreichten Biopräparate stimulierten die Entwicklung der Krankheiten. The effect of various fertilization methods on the diseases of sugar beet was estimated on the basis of nine-year studies (1994-2002) conducted in the Experimental Production Farm in Ba?cyny on loess-based, sedimentary-gley, light-clay soil. The following fertilization methods were applied: A - mineral fertilization, B - mineral and manure fertilization, C - straw, green manure and mineral fertilization, D - ecological compost and biodynamic preparations fertilization. In the objects A, B and C fertilized with phosphorus and potassium, various doses of nitrogen ranging from 0 to 180 kg/ha^?1 were used. In the ecological object D, where mineral fertilization was not used, biodynamic preparations P₅₀₀ and P₅₀₁ were applied instead of nitrogen. The lowest ratio of the diseases of sugar beet was observed in the object fertilized with the compost and biodynamic preparations. In view of the conventional fertilization methods, generally the highest incidence of diseases was noted in the sugar beet fertilized with straw, green manure and mineral fertilizers. The exception was the occurrence of powdery mildew and the black leg. In objects A, B and C the incidence of the diseases increased with the increase in nitrogen doses. The applied biodynamical preparations in the object D stimulated the development of diseases too.     

Prospects for control of Pythium damping-off of lettuce with Trichoderma,Gliocladium and Enterobacter spp.

Summary Damping-off of lettuce (Lactuca sativa) caused by Pythium ultimum was studied in pots containing a non-sterile potting mix in the glasshouse. Fifty P. ultimum sporangia g^-1 compost reduced the plant stand to 15% and shoot dry weight to 18%, but this reduction was totally prevented by applying Trichoderma harzianum at 2×10⁵ viable propagules g^-1 potting mix. Gliocladium virens and Enterobacter cloacae also alleviated the damping-off. E. cloacae did not adversely affect the action of the fungal antagonists. The co-existence of the bacterial and fungal antagonists was revealed on the root surface and inner surface of the testa by scanning electron microscopy, indicating the compatibility of the biocontrol agents.     

细菌、真菌及植物氮营养信号研究进展

氮素吸收代谢是所有生物生命活动的核心部分,因此,各种生物对氮的吸收与同化过程都有精细的调节。这种调节依赖于生物对体内氮素状况信号及体外（生长介质中）氮素信号的感受。过去几十年中,在细菌、真菌中已经对氮素营养信号有了较好的研究,而植物中则相对缓慢,但也有了一定的认识。本文重点比较细菌、真菌及植物中氮信号系统的组成,以期为进一步认识植物中的氮信号接受与转导系统提供启示。     

Aircraft operations near concentrations of birds in Antarctica: The development of practical guidelines

Aircraft operations have the potential to disturb and to impact negatively on bird life. A gradient of increasing behavioural response is evident in birds when exposed to increasing aircraft stimulus. The most major disturbance is likely to lead to impacts on the health, breeding performance and survival of individual birds, and perhaps bird colonies. A process of revision to policies on aircraft operations contained in management plans for a number of specially protected areas in Antarctica by the United Kingdom, accompanied by consultations made within the scientific community through the Scientific Committee on Antarctic Research (SCAR) and with operational interests through the Council of Managers of National Antarctic Programmes (COMNAP) resulted in new guidelines being adopted by the Antarctic Treaty Consultative Parties in June 2004. The principal recommendations of the guidelines are that bird colonies should not be overflown below 2000 ft (∼610 m) above ground level and landings within 1/2 nautical mile (∼930 m) of bird colonies should be avoided wherever possible. These guidelines are less stringent and less specific than those that were recommended by the SCAR specialist group on birds, and represent a compromise to accommodate operational needs. While the adoption of clear and consistent guidelines for the operation of aircraft in Antarctica is welcome in that this provides practical advice that is likely to reduce incidences of close aircraft/bird encounters, there remains insufficient knowledge of the interactions between aircraft and birds in Antarctica, and the consequent impacts on individual birds and on bird populations. It is important, therefore, that the guidelines adopted are considered interim, and should be kept under scrutiny with revisions made as new and improved research results appear.     

Potential of wild species for genetic enhancement of some semi-arid food crops

Discovery and incorporation of genes from wild species provide means to sustain crop improvement, particularly when levels of resistance in the cultigens are low and virulent strains of pests and pathogens overcome the host plant resistance. The extent of utilization and the potential of the wild genepool for genetic enhancement were reviewed in five important food crops viz. sorghum, pearl millet, chickpea, pigeonpea and groundnut grown in the semi-arid tropics. Introgression from compatible wild germplasm in the primary gene pool resulted in transfer of new cytoplasmic male sterility systems in pearl millet and pigeonpea, development of high protein, cleistogamous flower and dwarf pigeonpea lines and foliar disease resistant groundnut cultivars. Utilization of wild species in secondary and tertiary gene pools has been generally limited due to sterility, restricted recombination or cross incompatibility. Nevertheless, these species are extremely important as they contain high levels of resistance to several important biotic and abiotic stresses. Several of them, like those belonging to the Parasorghum section and the rhizomatous Arachis species are sources of multiple resistances and hold great promise to sustain crop productivity.