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131.
Crop residues and tillage are being advocated for their potential effectiveness to modify the soil hydrothermal regime. This study was carried out to quantify the effect of straw mulching and rotary hoeing on the soil water and thermal regimes of a loess soil. The field experiment consisted of four treatments: (1) no mulching and no rotary hoeing as control, (2) rotary hoeing, (3) wheat straw mulching, and (4) wheat straw mulching with rotary hoeing. During the study period from 5 August to 20 September 2002, soil water content and pressure head were measured daily at five soil depths (0.05, 0.15, 0.30, 0.45 and 0.60 m). Soil temperatures were measured at hourly resolution at three depths (0.05, 0.15 and 0.30 m). Mulching decreased soil water loss on an average by 0.39 mm d−1 and rotary hoeing increased water loss on an average by 0.12 mm d−1 as compared to control. Volumetric soil water contents at pF 1, 1.8 and 2.5 up to 30 cm depth were highest (0.418, 0.390, and 0.360 m3 m−3, respectively) with the application of wheat straw mulch and lowest (0.393, 0.363, and 0.333 m3 m−3, respectively) with the rotary hoeing. Soil thermal conductivity measured at pF 1, 1.8, 2.5, 3, and 3.7 decreased with increasing suctions in all the treatments. However, the tillage and mulching did not affect the soil thermal conductivity. Further, compared with the control, mulching reduced average soil temperatures by 0.74, 0.66, 0.58 °C at 0.05, 0.15, and 0.30 m, respectively, during the study period. The rotary hoeing tillage slightly increased the average soil temperature by 0.21 °C at 0.05 m depth compared to control. The tillage effect did not transmit to deeper depths. The numerical model Hydrus-1D was used to simulate the water and temperature regimes of the treatments. Simulations with hydraulic parameters derived from laboratory measurements did not yield satisfactory results. Only when the hydraulic parameters were optimized by the inverse method, simulations performed well. The largest deviations were observed in the wheat straw mulching treatment. Simulations were further improved by adjusting the potential evaporation rate from the measured data which was achieved by linking the inversion code UCODE to the Hydrus-1D. Soil temperatures at 0.05 and 0.15 m in all the treatments were modeled well, yielding root mean square errors between 0.3 and 1.7 °C. As for soil water, the largest temperature deviations were found for the mulching treatment. All simulations underestimated soil temperatures at 0.30 m. In conclusion, crop residue can be utilized as mulching to improve the soil hydrothermal regime and the Hydrus-1D model can be used as a tool for analyzing water and heat transport processes and for estimating hydraulic transport parameters under field conditions. 相似文献
132.
Prediction of the first occurrence of potato late blight (Phytophthora infestans) given by the SIMPHYT1 model, which has been used for about 20 years, has not been found satisfactory in years with high soil moisture. Consequently, a new model, SIMBLIGHT1, has been developed. As input parameters SIMBLIGHT1 requires temperature, relative humidity and information on soil moisture, crop prevalence and cultivar susceptibility. SIMBLIGHT1 calculates a cumulative risk index for several groups of emergence dates and signals the start of the epidemic once a given threshold is overridden. Model validation and comparison of SIMBLIGHT1 with SIMPHYT1 were performed with field data from 11 years. Results were promising and SIMBLIGHT1 gave better results than SIMPHYT1 when soils of potato fields were waterlogged. Efforts are currently being made to improve SIMBLIGHT1 and in the long term this model will replace SIMPHYT1. 相似文献
133.
Dorette?Müller-St?verEmail author Holger?Buschmann Joachim?Sauerborn 《European journal of plant pathology / European Foundation for Plant Pathology》2005,111(3):193-202
Fusarium oxysporum Schlecht. f.sp. orthoceras (Appel & Wollenw.) Bilai is a potential biocontrol agent against the root-parasitic weed Orobanche cumana. In pot experiments with different sunflower cultivars, the application of F. oxysporum was combined with a treatment of BTH (Benzo(1,2,3)thiadiazole-7-carbothioic acid S-methyl ester), a product known to induce resistance against O. cumana in sunflower. The combined treatments resulted in highly reliable control and sometimes in increased control level compared to the Fusarium treatment alone. In laboratory experiments, no enhancing effect of BTH on virulence and growth of the fungus was observed. Future experiments should further investigate the basic mechanisms of the effect achieved by combining the two control strategies as well as the transfer of this innovative control approach into field experiments. 相似文献
134.
In our study we elaborated an overview on the contamination grade of fish from Turkish waters by selected organochlorine pesticides, nitromusks and chlorobiphenyl congenres. We could demonstrate, that the tested fish species, being prior processed to canned products and brought to the market, contained particularly unmistakable amounts of the above mentioned analytes. Sardines, sardelles and trout gave results generally far below the German regulatory limits. However total DDT in pelamides reached an order of magnitude near the German limit of 0.5 mg/kg (based on wet weight). The necessity of enhanced systematic measurements for monitoring pollutants in fish from Turkish waters thus becomes evident. 相似文献
135.
The subtractive suppressive hybridization (SSH), a method that allows the identification of sequences that are present in one genome (tester) but not in the other (driver), is a promising technique for the comparison of Mycoplasma agalactiae pathogenic strains. The optimal conditions for SSH were established by subtracting the M. agalactiae type strain PG2 DNA from the M. agalactiae strain 5632 DNA. Because these two strains possess different vpma gene repertoires, 5632-specific vpma sequences (and possibly other 5632-specific sequences) were predicted to be retrieved by SSH. The subtracted tester DNA was PCR-amplified and cloned into the pGEM-T easy E. coli vector. Two independent libraries were generated and used to prepare individual probes that were tested by Southern blot with genomic DNA from various field isolates and mycoplasma reference strains. Sequence analysis of two overlapping clones showed that they potentially code for a large carboxyterminal portion of a new vpma ORF. Several DNA fragments homologous to insertion sequences were also found in 5632 and related strains. These preliminary data suggest that SSH is a powerful method to investigate differences between mycoplasma strains, and may be applied to molecular epidemiology, diagnostic, and host specificity or pathogenicity determinant discovery. 相似文献
136.
Joachim Peter 《Asia Pacific viewpoint》2000,41(3):253-267
Travelling, as movement, has always been a tradition of atoll islanders. Their travels continue to identify the ways in which atoll peoples understand, appropriate, and manipulate space and boundaries. This paper argues that travelling is as relevant to islanders today as in the past and examines meanings in Chuuk islanders' travel. ‘Horizon’, the space ‘out there’, is a metaphorical model of space for atoll peoples with many traditions of travel. ‘Horizon’ is also a dual concept. The horizon is the space within which the islander traveller is located that is ‘strange’ and ‘foreign’. It is also the horizon, as a defined space, that locates and brings those strange and foreign forces into the places of atoll residents and across familiar boundaries. The narrative traditions of Chuuk islanders will be used to explore these dual formulations of horizon and the different terms for travelling among an atoll people. Discussion will focus on how islanders define the boundaries of their horizon in their travels and the meanings that these boundaries give travelling or movements. 相似文献
137.
Josef Knott Melanie Mueller Joachim Pander Juergen Geist 《Ecology of Freshwater Fish》2020,29(1):74-88
Hydropower structures hinder the movement and migration of fishes, impairing their life cycles. Additionally, downstream moving fish are often at risk of being injured during turbine passage. To improve hydropower production towards more fish-friendly techniques and management, knowledge on timing and extent of natural patterns of fish downstream movement is necessary. So far, migration behaviour of long-distance migrators such as eel or salmon has been well studied, but little is known about seasonal and diurnal movement patterns of nonmigratory species or medium-distance migrators. In this study, movement patterns of 39 fish species captured by stownets while transiting hydropower facilities in four impounded rivers were assessed and compared with the fish community composition directly upstream of the hydropower plants assessed by electrofishing. Strong differences between the fish community composition inhabiting the upstream sides of the dams and the fish detected in downstream passage were evident. In each study river, the downstream moving fish community composition differed significantly between spring and autumn. On average, significantly more fish were caught during the night (2.9 fish/hr) than during the day (1.3 fish/hr). Topmouth gudgeon, European grayling and pike-perch mostly moved downstream during the night, whereas roach, spirlin and bleak were the most frequent downstream moving fish during daytime. Downstream fish movement was positively related with turbidity, water temperature and discharge. The strong differences in seasonal and diurnal fish movement patterns suggest that fish damage can be strongly reduced by adaptive turbine and corridor management, for example by shutting down turbines at peak movements. 相似文献
138.
139.
A new insect order, Mantophasmatodea, is described on the basis of museum specimens of a new genus with two species: Mantophasma zephyra gen. et sp. nov. (one female from Namibia) and M. subsolana sp. nov. (one male from Tanzania). This is the first time since 1914 that a newly described extant insect taxon has proved unplaceable within a recognized order. Mantophasmatodeans are apterous carnivores. Their closest phylogenetic relationships may be to Grylloblattodea (ice-crawlers) and/or Phasmatodea (stick insects), but the morphological evidence is ambiguous. Raptophasma Zompro from Baltic amber is assigned to the Mantophasmatodea, revealing a wider previous range for the lineage. 相似文献
140.
MA Shi-ming Joachim Sauerborn 《中国农业科学(英文版)》2006,5(3):169-178
The history of the organic farming worldwide was reviewed in this paper. The development of the organic farming worldwide had gone through three stages, emergence, expansion, and growth. The contributors and their thoughts during the different development stages of the organic farming were briefly introduced. And the development status of the organic farming worldwide was reviewed from the aspects of land area under organic management, land area under organic management in percentage of total agricultural area, and world markets for organic products. Besides, the main existing problems for the further development of the world's organic farming, as well as the development status, problems and strategies of the Chinese organic farming were discussed. 相似文献