硝态氮源及碳源有效性对土壤N_2O和CO_2排放的影响

以华北平原农田土壤为对象,通过室内静态培养系统研究NO_3~--N与不同碳源组合对土壤N_2O和CO_2排放的影响。结果表明,NO_3~--N作为氮源和不同碳源施入土壤,除NO_3~-+纤维素,其余土壤N_2O排放通量均高于对照组和只添加氮源土壤;NO_3~--N和不同碳源组合的CO_2累积排放量均高于对照和只添加氮源土壤。NO_3~-+果胶的N_2O排放量在第1 d达到最大值1 383.42μg N·kg~(-1)·d~(-1);NO_3~-+葡萄糖的CO_2排放量在第1 d达到最大值370.13 mg C·kg~(-1)·d~(-1),CO_2累积排放量顺序为:葡萄糖果胶秸秆纤维素淀粉木质素。土壤NO_3~--N含量与N_2O排放呈极显著正相关。总之,添加纤维素可以抑制N_2O的排放,促进CO_2排放,并增加土壤中NO_3~--N含量,添加其余碳源均会促进土壤N_2O和CO_2排放。     

添加生物炭对华南早稻田CH4和N2O排放的影响

通过田间试验,采用静态箱-气象色谱法研究生物炭添加对华南早稻田甲烷(CH4)和氧化亚氮(N2O)排放的影响.试验设对照(CK),BC1、BC2、BC3(土壤中分别混入5、10、20t·hm-2生物炭)、RS(稻草直接还田)和RI(稻草加腐熟剂还田)6个处理.结果表明,与CK、RS和RI相比,生物炭处理能降低稻田CH4和N2O排放量及排放强度,综合排放强度最低的为BC3处理,值为0.98 kgCO2-eq· kg-1.在本实验的处理范围内,生物炭添加量越高,CH4平均排放通量及其季节排放总量越低,最低值分别为22.11mg·m-2·h-1和93.21kg·hm-2;N2O排放通量和季节排放总量则随生物炭添加量的增加呈上升趋势,最高值分别为285.65 μg·m-2·h-1和1.07kg·hm-2,但依然小于对照处理(368.13μg·m-2 ·h-1和1.13kg·hm-2).此外,试验发现高用量的生物炭(即BC3)处理水稻产量最高,值为7152.58kg·hm-2.综合分析各处理,BC3对减缓温室效应和稳定水稻生产贡献最大.     

炭输入及生化调控对设施菜田土壤N_2O排放的影响

本研究以河北永清蔬菜基地设施菜田土壤为研究对象,控制温度(25±1)℃和土壤含水量(70%WFPS),采用静态培养方法,通过监测培养期间土壤N_2O排放通量、无机氮含量及土壤中酶活性的变化情况,研究炭输入及生化调控对设施菜田N_2O排放及氮素转化的影响。结果表明,土壤添加尿素后,N_2O排放峰值达到644.11μg N·kg~(-1)·d~(-1),添加双氰胺(DCD)和石灰氮(CaCN_2)的土壤N_2O排放峰值分别为101.47μg N·kg~(-1)·d~(-1)和36.74μg N·kg~(-1)·d~(-1),对于N_2O减排效果好,且能有效抑制亚硝态氮的产生;施用控释尿素、添加黑炭或有机肥能减少N_2O排放,而添加石灰氮闷棚显著增加了N_2O排放。控释尿素、秸秆、黑炭、DCD和CaCN_2均对铵态氮向硝态氮的转化有一定抑制作用,施加石灰氮或有机肥有助于减少硝态氮向亚硝态氮的转化。相关分析表明,土壤中硝态氮和亚硝态氮含量增加,有助于反硝化过程的进行,增加了N_2O排放的风险。     

不同氮肥管理方式对华北粮田N_2O排放和作物产量的影响分析

通过华北小麦和玉米田已发表文献分析,明确不同施氮量、氮肥基追比及氮素调控措施对土壤N_2O排放和作物产量的影响。结果表明:高氮水平下减少氮肥用量并调整基追比有助于减少土壤N_2O排放;添加硝化抑制剂双氰胺(DCD)对小麦和玉米产量的提高和土壤N_2O的减排效果均较好。兼顾华北粮田N2O减排和作物产量,小麦季推荐合理施氮量167~174 kg·hm~(-2),基追比1∶1,添加DCD,土壤N_2O总排放量为0.31 kg·hm~(-2),籽粒产量6 200 kg·hm~(-2)以上;玉米季推荐合理施氮量177~181 kg·hm~(-2),基追比2∶3~1∶2,添加DCD,土壤N_2O总排放量1.70 kg·hm~(-2),籽粒产量9 000 kg·hm-2以上。     

不同氮肥管理方式对华北粮田2排放和作物产量的影响分析

通过华北小麦和玉米田已发表文献分析,明确不同施氮量、氮肥基追比及氮素调控措施对土壤N2O排放和作物产量的影响。结果表明：高氮水平下减少氮肥用量并调整基追比有助于减少土壤N2O排放;添加硝化抑制剂双氰胺（DCD）对小麦和玉米产量的提高和土壤N2O的减排效果均较好。兼顾华北粮田N2O减排和作物产量,小麦季推荐合理施氮量167~174 kg·hm-2,基追比1：1,添加DCD,土壤N2O总排放量为0.31 kg·hm-2,籽粒产量6200 kg·hm-2以上;玉米季推荐合理施氮量177~181 kg·hm-2,基追比2：3~1：2,添加DCD,土壤N2O总排放量1.70 kg·hm-2,籽粒产量9000 kg·hm-2以上。     

西北干旱区两种不同栽培管理措施下棉田CH4和N2O排放通量研究

采用静态箱-气相色谱法对西北干旱区当前普遍采用的膜下滴灌和传统的无膜漫灌两种栽培管理下土壤CH4和N2O通量日变化和季节变化特征进行了研究。结果表明,随时间的推移,无膜漫灌栽培管理措施下棉田土壤CH4日变化通量呈先降后升趋势,而膜下滴灌栽培处理CH4排放通量日变化则呈现先升后降趋势;在整个生长季节,无膜漫灌和膜下滴灌土壤CH4季节变化规律不太明显,前者吸收大气CH4 45.2～52.5 mg m-2 a-1,后者释放CH4通量为0.7～23.1 mg m-2 a-1。两种栽培管理措施下棉田土壤N2O通量的日变化和季节变化均随时间的推移均呈现先升后降趋势,但是,无膜漫灌日均排放N2O通量显著高于膜下滴灌。在整个生长季节,无膜漫灌土壤N2O释放量(N2O 99.3～320.0 mg m-2 a-1)显著高于膜下滴灌(N2O60.0～259.0 mg m-2 a-1)。以上结果说明,膜下滴灌栽培管理措施可以改变旱田传统无膜漫灌栽培土壤与大气CH4的交换方向,促进土壤CH4向大气的排放,但对N2O通量日变化和季节变化规律不产生影响,显著降低土壤N2O的排放量。     

浮萍对福州平原稻田CH4和N2O排放的影响分析

浮萍是稻田中常见的漂浮在水面的水生植物,具有固氮作用,但是,浮萍对稻田温室气体排放的影响尚不明确.以位于湿润亚热带的福州平原稻田为研究对象,探讨浮萍对该区域稻田CH4和N2O排放的影响,为科学评价、准确编制我国水稻田温室气体排放清单提供基础数据.研究结果表明,观测期内,有萍小区和无萍小区CH4排放范围分别为0.19～26.50 mg·m-2·h-1和1.02～28.02 mg·m-2·h-1,平均值分别为9.28 mg·m-2·h-1和11.66 mg·m-2·h-1,有萍小区CH4排放低于无萍小区(P＜0.01),有萍小区CH4排放高峰比无萍小区约提前1周,高峰期后排放迅速降低;有萍小区和无萍小区N2O排放范围分别为-50.11～201.82 μg·m-2·h-1和-28.93～54.42μg·m-2·h-1,平均值分别为40.29 μg·m-2·h-1和11.93 μg·m-2·h-1,有萍小区N2O排放高于无萍小区(P＜0.05).稻田排干后,N2O排放迅速上升,2个小区N2O排放呈现出相似的规律.有萍小区和无萍小区的CH4与N2O排放的影响因子有所不同.综合考虑CH4和N2O两种温室气体,CH4仍是稻田温室效应产生的主要贡献者,浮萍可降低位于沿海区域的福州平原稻田综合温室效应的17.3％.     

氮肥配施纳米碳对植烟土壤氮素转化及N2O排放的影响

采用实验室静态培养方法,通过氮肥配施不同量纳米碳来探究纳米碳对植烟土壤氮素转化以及N_2O排放的影响。试验在等氮条件下共设置5个处理:CK,硝酸铵(N 200 mg/kg,下同);NC1,硝酸铵+纳米碳(2.5 g/kg);NC2,硝酸铵+纳米碳(5 g/kg);NC3,硝酸铵+纳米碳(10 g/kg);NC4,硝酸铵+纳米碳(15 g/kg)。结果表明:NC3和NC4处理较CK处理显著降低了土壤pH(P0.05);与CK处理相比,NC1、NC2、NC3和NC4处理在培养前期增加了土壤NH_4~+-N含量,相应降低了NO_3~–-N含量;在培养结束时,与CK处理相比,添加纳米碳处理显著降低了无机氮含量,而显著增加了CO_2累积排放量(P0.05);另外,添加纳米碳处理较CK处理增加了N_2O累积排放量,但仅NC4处理与CK处理间差异显著(P0.05),N_2O累积排放量与CO_2累积排放量呈显著正相关关系(R~2=0.50,P0.001)。可见,添加纳米碳能够降低土壤pH和无机氮含量,抑制土壤硝化作用,同时还可以提高微生物活性和增加N_2O排放量。     

施氮及添加硝化抑制剂对苜蓿草地N2O排放的影响

为探究旱作紫花苜蓿(MedicagosativaL.)栽培草地氧化亚氮(N_2O)排放对施氮水平及添加硝化抑制剂的响应特征,采用传统静态箱法研究了不同施氮水平[0kg(N)·hm~(-2)(N0)、 50kg(N)·hm~(-2)(N50)、 100kg(N)·hm~(-2)(N100)和150kg(N)·hm~(-2)(N150)]以及添加硝化抑制剂双氰胺(DCD)150kg(N)·hm~(-2)(N150+DCD)对陇东苜蓿草地N_2O排放特征的影响。结果显示,监测期内N0、N50、N100和N150处理N_2O平均排放速率分别为3.5μg·m~(-2)·h~(-1)、4.1μg·m~(-2)·h~(-1)、5.0μg·m~(-2)·h~(-1)和6.1μg·m~(-2)·h~(-1),随着施氮梯度的增加, N_2O排放速率呈增加趋势。添加硝化抑制剂DCD对N_2O排放产生明显的抑制作用。与N150处理相比, N150+DCD处理下苜蓿草地N_2O平均排放速率下降50.7%, N_2O累计排放量显著降低61.6%(P0.05)。施氮对苜蓿产量没有显著影响,而N0、N50、N100和N150处理下单位苜蓿产量N_2O排放量随氮肥梯度的增加而增加,各处理分别为6.5 mg·kg~(-1)、7.8 mg·kg~(-1)、11.3 mg·kg~(-1)和12.5 mg·kg~(-1)。N_2O排放受土壤含水量影响深刻,生长季N_2O排放通量与土壤水分呈显著正相关关系(P0.05),而与土壤温度无显著相关性(P0.05)。综上,旱作紫花苜蓿栽培草地N_2O排放通量随施氮水平的增加明显增加,在相同施氮水平下添加硝化抑制剂DCD能显著抑制N_2O排放。相关研究结果对于该区域苜蓿草地合理施肥以及N_2O减排具有一定的实践指导意义。     

基于DNDC模型模拟江汉平原稻田不同种植模式条件下温室气体排放

稻田被认为是温室气体CH_4和N_2O的主要排放源之一。湖北省江汉平原地区水稻常年种植面积约8×105 hm2,占湖北省水稻种植面积的40%左右。研究江汉平原地区稻田温室气体排放特征,对于评估区域稻田温室气体排放以及稻田温室气体减排具有重要意义。目前,DNDC模型已被广泛应用于模拟和估算田间尺度的温室气体排放,DNDC模型与地理信息系统(Arc GIS)结合,可进行区域尺度的温室气体排放模拟与估算。本研究以湖北省典型稻作区江汉平原为研究区域,运用DNDC模型模拟和估算江汉平原稻田区域尺度的温室气体排放。设置大田定点观测试验,监测中稻-小麦(RW)、中稻-油菜(RR)、中稻-冬闲(RF)3种种植模式下稻田温室气体CH_4和N_2O的周年排放特征。通过田间观测值与DNDC模拟值的比较进行模型验证,并利用获取DNDC模型所需的气象、土壤、作物及田间管理等区域数据,模拟江汉平原稻田不同种植模式下温室气体CH_4和N_2O的排放量。田间试验表明,江汉平原稻田RW、RR和RF模型的CH_4排放通量为-2.80~39.78 mg·m-2·h-1、-1.74~42.51 mg·m-2·h-1和-1.57~55.64 mg·m-2·h-1,N_2O周年排放通量范围分别为0~1.90 mg·m-2·h-1、0~1.76mg·m-2·h-1和0~1.49 mg·m-2·h-1;CH_4排放量RW和RR模式显著高于RF模式,N_2O排放量为RF显著低于RW和RR模式。模型验证结果表明,不同种植模式温室气体排放实测值与模拟值比较的决定系数(R2)为0.85~0.98,相对误差绝对值(RAE)为8.29%~16.42%。根据DNDC模型模拟和估算的结果,江汉平原区域稻田CH_4周年的排放量为0.292 9 Tg C,N_2O周年的排放量为0.009 2 Tg N,不同种植模式稻田CH_4排放量表现为RWRRRF,N_2O排放量表现为RWRFRR,增温潜势(GWP)表现为RWRRRF。不同地区稻田CH_4排放量表现为监利县荆门市公安县天门市仙桃市洪湖市松滋市汉川市潜江市石首市荆州市江陵县赤壁市嘉鱼县,N_2O排放量表现为监利县荆门市公安县洪湖市仙桃市天门市汉川市潜江市松滋市荆州市江陵县赤壁市石首市嘉鱼县。本研究结果表明DNDC模型能较好地应用于模拟江汉平原稻田温室气体排放,RR和RF模式相比RW模式可有效减少温室气体CH_4和N_2O的排放。     

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.     

“绿色革命”以来大气CO2浓度升高对C3作物营养品质的影响

自20世纪60年代"绿色革命"以来,育种技术和农耕技术的发展促进了农作物产量的大幅提升,然而作物的营养品质出现下降趋势。在相似的遗传背景下,大气CO_2浓度升高会使单位体积农作物产品的营养元素含量下降,因此"绿色革命"至今,农作物产品的营养元素下降可能受大气CO_2浓度升高影响。通过植物生长箱模拟"绿色革命"初期和目前的大气CO_2浓度水平(310μmol/mol和400μmol/mol),针对主要C_3作物水稻、小麦和大豆,研究"绿色革命"以来大气CO_2浓度升高对其籽粒的C、N、Fe、Zn元素含量的影响,结果表明:CO_2浓度升高对3种作物籽粒的C元素含量几乎没有影响,变化幅度在±1.5%之间;籽粒的N、Fe、Zn元素含量普遍呈现下降趋势,但均未达到显著水平。     

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.     

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.     

Faculty positions:Center for Agricultural Resources Research,Chinese Academy of Sciences

正The Center for Agricultural Resources Research(CARR),the Institute of Genetics and Developmental Biology(IGDB),Chinese Academy of Sciences,invites applicants for several research group leader positions.CARR is one of the research organizations in Chinese Academy of Sciences(CAS).We seek nominations and applications     

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.