保护性耕作对麦-豆轮作土壤有机碳全氮及微生物量碳氮的影响

通过设置在甘肃省定西市李家堡镇的保护性耕作措施长期定位试验,共设4个处理（T：传统耕作;NT：免耕无覆盖;TS：传统耕作＋秸秆还田;NTS：免耕＋秸秆覆盖）,采用春小麦豌豆双序列轮作（即小麦→豌豆→小麦和豌豆→小麦→豌豆,本文中所指春小麦地、豌豆地分别指2008年种植春小麦、豌豆的轮作次序）,于2008年3月中旬对春小麦、豌豆双序列轮作下的土壤有机碳、全氮、土壤微生物量碳及土壤微生物量氮含量进行了采样测定。结果表明,经过7a的轮作后,两种轮作次序下,0-30cm土层中土壤有机碳、全氮、土壤微生物量碳、土壤微生物量氮含量均有在免耕＋秸秆覆盖、传统耕作＋秸秆还田处理较免耕不覆盖、传统耕作处理高的趋势,且其含量均随着土壤深度的增加而降低。其中,土壤微生物量碳含量在两种轮作次序下的排序均为：免耕＋秸秆覆盖（NTS）〉传统耕作＋秸秆还田（TS）〉免耕不覆盖（NT）〉传统耕作（T）;而土壤微生物量氮含量在春小麦地和豌豆地的排序则分别表现为：免耕＋秸秆覆盖（NTS）〉传统耕作＋秸秆还田（TS）〉传统耕作（T）〉免耕不覆盖（NT）和免耕＋秸秆覆盖（NTS）〉传统耕作＋秸秆还田（TS）〉免耕不覆盖（NT）〉传统耕作（T）。同时,微生物量碳、微生物量氮与有机碳和全氮均呈显著正相关,说明提高土壤有机质、全氮含量的保护性耕作模式有利于土壤微生物量碳与氮的积累。     

不同耕作措施下豆麦双序列轮作农田温室气体的排放特征及其增温潜势

基于甘肃农业大学在定西市李家堡镇开展的保护性耕作长期定位试验,采用CO2分析仪、静态箱-气相色谱法对2011年度不同耕作措施下豆麦双序列轮作农田土壤CO2和N2O的排放通量进行全年连续观测。结果表明:测定期内不同耕作措施下豆麦双序列轮作农田土壤均表现为CO2源和N2O源;免耕不覆盖有利于降低两个序列土壤的CO2排放通量,免耕秸秆覆盖、免耕不覆盖和传统耕作+秸秆还田三种保护性耕作处理不同程度的减少了两个序列土壤的N2O排放通量;两个序列下CO2的相对增温潜势最大,W→P→W序列传统耕作+秸秆还田处理对温室效应贡献最多,相反免耕不覆盖处理能相对减少温室气体排放量,从而降低温室效应;P→W→P序列传统耕作不覆盖处理对温室效应的贡献最大,传统耕作+秸秆还田处理对温室效应贡献最小,对温室气体有减排效应。     

不同耕作措施对旱地作物生育期农田耗水结构和水分利用效率的影响

陇中黄土高原旱农区降水有限、水分利用效率低下是导致该区作物生产力水平低而不稳的主要原因。发展保护性耕作是保护水土资源、提高水分利用效率的重要途径。为揭示耕作措施影响水分利用效率的机制,2015—2016年在陇中黄土高原旱农区研究了不同耕作措施对土壤棵间蒸发、农田耗水量、作物蒸腾量、棵间蒸发与蒸散的比例、产量及水分利用效率的影响。试验设置传统耕作(T)、免耕秸秆覆盖(NTS)、免耕(NT)、传统耕作+秸秆翻入(TS)、传统耕作+覆膜(TP)、免耕覆膜(NTP)6个处理,春小麦和豌豆年间轮作。结果表明:(1)春小麦和豌豆全生育期棵间蒸发量NTS、TP、NTP比T显著减少6.52%~50.81%,NTS降低棵间蒸发量的作用主要在小麦开花后和豌豆结荚后,地膜覆盖在各个生育时期基本上都显著减少了棵间蒸发。(2)NTS对全生育期耗水量无显著影响,NTP的耗水量只在小麦地显著高于T。相比T,NTS显著提高了小麦开花-收获和豌豆结荚-收获期间的阶段耗水量及其占总耗水的比例。(3)NTS、TP、NTP均显著提高了春小麦和豌豆的蒸腾量,降低了田间的蒸发占蒸散的比例,降低了水分的无效损耗。(4)各年份春小麦和豌豆的产量NTS、TP、NTP比T提高了7.64%~62.79%,水分利用效率比T提高了0.43%~50.88%。因此,在陇中黄土高原旱农区,免耕秸秆覆盖、地膜覆盖等保护性耕作措施均能提高水分利用效率及小麦和豌豆的产量。免耕秸秆覆盖通过降低作物生长后期棵间蒸发量,提高作物生长后期耗水量,降低蒸发与蒸散的比例,从而提高春小麦和豌豆的水分利用效率及产量。而地膜覆盖处理主要是通过减少全生育期棵间蒸发量,增加作物全生育期蒸腾量,降低蒸发与蒸散的比例,从而实现作物水分高效利用,提高作物产量。     

保护性耕作对黄土旱塬箭筈豌豆地土壤呼吸的影响

[目的]揭示保护性耕作对土壤呼吸的影响,为旱区保护性农业的发展提供理论依据。[方法]采用多通道土壤碳通量系统监测传统耕作(T)、传统耕作+秸秆覆盖(TS)、免耕(NT)和免耕+秸秆覆盖(NTS)下箭筈豌豆(Vicia sativa)地的土壤呼吸速率。[结果]各措施下花期呼吸速率比收获期高10.45%~45.09%,NTS处理下土壤呼吸速率最低别比TS,NT和T处理显著减少39.17%,21.37%和30.25%(p0.01)。耕作处理(T,TS)下日均土壤呼吸速率高于免耕处理(NT,NTS)(p0.05)。晴天土壤呼吸变化呈单峰曲线,最大值出现在14:00。耕作下土壤呼吸速率与气温显著线性相关,免耕下(NT,NTS)与气温呈指数关系(p0.01)。不同耕作措施间气温敏感性Q10值大小依次为:T(1.97)NT(1.62)TS(1.58)NTS(1.52)。[结论]免耕加秸秆还田处理对减少温室气体排放有一定的贡献。     

黄土高原半干旱区保护性耕作适应性评价

在黄土高原半干旱区连续4年保护性耕作试验的基础上,利用层次分析法,对5种保护性耕作法与传统耕作法适应性(生态与经济)进行综合评价,探究适合黄土高原半干旱区的保护性农业技术体系.结果表明:在两种轮作次序(小麦/豌豆、豌豆//小麦)、两种投入方式(计秸秆和不计秸秆)下,保护性耕作法免耕秸秆覆盖(NTS)综合适应性指数(PI)均显著高于其他几种耕作方式,且PI在0.76～0.86之间,是传统耕作法(T)的2～2.5倍,NTS在该地区的适应性最强;NTS、免耕不覆盖(NT)、免耕结合地膜覆盖(NTP)3种耕作方式的PI高于传统耕作结合秸秆还田(TS)、T、传统耕作结合地膜覆盖(TP),说明NTS、NT、NTP在该区的适应性优于TS、T、TP.因此,在黄土高原半干旱区实施保护性耕作措施NTS,更能促进该区农业的持续发展.     

河西绿洲灌区保护性耕作防风蚀效应的风洞试验研究

通过对河西地区民勤县绿洲春小麦生产田实施保护性耕作,采用风洞试验,以传统耕作为对照,从风蚀量、风速廓线、风蚀速率和地表粗糙度等方面比较分析了不同保护性耕作措施(免耕不覆盖、免耕秸秆覆盖、残茬压倒处理)的防风蚀效应。结果表明:与传统耕作相比,保护性耕作土壤风蚀量减少,地表风速减小,土壤风蚀速率降低,地表粗糙度增大,土壤风蚀速率与地表粗糙度呈负相关关系。不同保护性耕作措施抑制风蚀的程度不同,4种耕作方式的风蚀速率从大到小依次为传统耕作、残茬压倒、免耕不覆盖、免耕秸秆覆盖,其中免耕秸秆覆盖处理的防风蚀效应最佳。     

黄土塬区长期不同耕作、覆盖措施对表层土壤理化性状和玉米产量的影响

【目的】研究不同耕作、覆盖措施对土壤理化性质及对作物农艺性状的影响,为选择适合黄土高原沟壑区最佳耕作、覆盖措施提供参考。【方法】田间定位试验设置12个处理,分别为传统耕作、传统耕作+膜上种植、传统耕作+秸秆覆盖、传统耕作+膜侧种植、传统耕作+全膜覆盖、传统耕作+秸秆覆盖+地膜覆盖、隔年耕作、免耕、免耕+地膜覆盖、免耕+秸秆覆盖、免耕+生草覆盖、免耕+秸秆覆盖+地膜覆盖,每个处理3个重复。于2014年对已持续12年的不同耕作、覆盖措施土壤理化性质与农艺指标进行测定与分析。【结果】免耕处理降低了土壤容重,提高了土壤饱和导水率和4月下旬至10月上旬表层土壤含水量,降低了作物出苗期温度,降低了成熟期土壤全磷与速效磷含量,降低了株高、叶面积指数和产量。相反,地膜覆盖极显著增加了土壤容重(P < 0.01),显著降低了土壤饱和导水率(P < 0.05),降低了成熟期土壤有机质、全氮含量,有较为明显的保持和调节温度的作用,不同类型的地膜覆盖均能极显著提高玉米株高和叶面积指数进而提高产量(P < 0.01)。秸秆覆盖对土壤容重和含水量的影响与耕作方式有关,翻耕条件下,秸秆覆盖增加了土壤容重;免耕条件下,降低了土壤容重且均不显著。翻耕+秸秆覆盖土壤表层含水量最高;免耕+秸秆覆盖处理的土壤含水量最低。但秸秆覆盖下土壤有机质含量、全氮含量、作物株高、叶面积指数和产量与未覆盖时相比均有增加,影响皆达到显著水平(P < 0.05),且均有降低地表温度的作用。【结论】免耕虽有利于改良土壤物理性状,却较传统耕作降低了作物产量。免耕条件下秸秆+地膜处理显著提高作物产量和土壤全氮、有机质含量(P < 0.05),是免耕处理组中最优选择。不同类型的地膜覆盖均可显著提高作物产量(P < 0.05),而且秸秆+地膜双覆盖增产效果最显著,并显著提高土壤全氮、有机质含量,是黄土塬区最适宜的覆盖措施。     

陇中黄土高原不同耕作措施下土壤磷动态研究

依托陇中黄土高原旱作农田已实施13 a的保护性耕作试验,研究传统耕作、免耕、传统耕作秸秆还田、免耕秸秆覆盖、传统耕作地膜覆盖和免耕地膜覆盖6种耕作措施下土壤全磷及磷组分动态变化特征。结果表明:试验期各处理土壤全磷和总无机磷均逐年增长;两个秸秆还田处理总有机磷逐年增长,免耕地膜覆盖和免耕处理总体增长,传统耕作和传统耕作地膜覆盖处理相对稳定;各无机磷组分均总体增长,其中氢氧化钠提取态无机磷、水溶态无机磷和碳酸氢钠提取态无机磷涨幅较大,平均涨幅分别为253.6%、128.6%和66.9%;保护性耕作可不同程度地提高水溶态无机磷、碳酸氢钠提取态无机磷和氢氧化钠提取态无机磷含量,相同覆盖条件下免耕较传统耕作效果明显,尤其免耕秸秆覆盖处理最明显;耕作方式对浓盐酸提取态无机磷和残留磷的影响不明显;保护性耕作可提高碳酸氢钠提取态有机磷和氢氧化钠提取态有机磷含量,两个秸秆还田处理最明显,两处理也可提高浓盐酸提取态有机磷含量,但免耕、传统耕作地膜覆盖和免耕地膜覆盖处理下该组分含量降低。综上,采取保护性耕作可适当减少磷肥用量,保护性耕作尤其是免耕秸秆覆盖方式值得在该区推广。     

保护性耕作对土壤物理特性及玉米产量的影响

保护性耕作措施是干旱区农田提高作物产量的新型耕作技术。为了探讨其区域适应性,在2004～2007年期间,以毛乌素沙地南缘的靖边县北部风沙区农田为研究对象,选用了免耕、秸秆覆盖、覆膜和传统翻耕(CK)4种措施,采用完全随机试验设计进行了田间定位试验研究。结果表明,秸秆覆盖和免耕地的地温在春播初期略比传统翻耕低0.1℃,但随后迅速回升,覆膜在玉米生长期都高于其他措施。耕作措施对播种前土壤容重没有显著影响,而对收获后土壤容重影响显著,与传统翻耕相比,免耕降低了表层土壤容重1.65%,但次层20～40 cm容重增加了1.8%。3种保护性耕作措施均增加了土壤含水量,顺序依次为秸秆覆盖>覆膜>免耕>翻耕,且在作物需水关键期免耕和秸秆覆盖下的土壤含水量相对稳定,保证作物需水,提高水分利用率,分别为8%、22.0%和13.3%。使作物分别增产4.44%、13.14%和19.26%。因此,保护性耕作在风沙区有利于改善农田土壤物理条件,提高作物产量,适于在风沙区推广。     

保护性耕作对陇中黄土高原雨养农田土壤物理性状的影响

依托设置于陇中黄土高原雨养农田豆麦双序列轮作系统的保护性耕作长期定位试验,探讨不同耕作措施对土壤物理性状的影响。共设6种耕作措施:T(传统耕作)、NT(免耕不覆盖)、TS(传统耕作+秸秆还田)、NTS(免耕+秸秆覆盖)、TP(传统耕作+地膜覆盖)及NTP(免耕+地膜覆盖)。结果表明:保护性耕作可降低土壤容重,提升土壤总孔隙度,NTS处理可显著降低0-30cm各土层土壤容重,并显著提升0-30cm各土层总孔隙度和表层土壤饱和导水率;保护性耕作可增大0-30cm各土层机械稳定性和水稳性团聚体含量(≥0.25mm)、平均重量直径(MWD)和平均几何直径(GMD),NTS效果最好;容重和总孔隙度分别与产量呈极显著负相关、极显著正相关,机械稳定性团聚体的含量、MWD和GMD分别与产量呈极显著正相关、显著正相关、显著正相关;水稳性团聚体的含量、MWD和GMD均与产量呈极显著正相关。说明保护性耕作可以改善土壤结构,进而促进作物增产。     

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.