Morphological analysis of viral communities in the floodwater of a Japanese paddy field

Capsid size distributions of viral communities in the floodwater of a Japanese paddy field under a long-term fertilizer trial were surveyed during the rice cultivation period by using transmission electron microscopy. The capsid size distributions were monophasic, and the median values fell within the range of 50-70 nm. The quartile intervals were narrow from either 40-50 nm or 50-60 nm to either 60-70 nm or 70-80 nm for most samples. There was no clear seasonal variation in the capsid size distribution of viral communities. The difference in size distributions among different fertilizer plots was also not found. Viral communities in the floodwater were predominated by isometric icosahedral forms. Viruses with octahedral capsids and elongated ones were rare and sporadic in the floodwater.     

Effect of methods of application on the efficiency of urea broadcast onto lowland rice (Oryza sativa L.)

Summary We evaluated the effect of different methods of application on the efficiency of urea broadcast at a rate of 100 kg N ha^-1 onto lowland rice (Oryza sativa L. var. SPR 60) in a field experiment conducted on a Phimai soil (Fluvic Tropaquepts) during the dry season of 1989. Analysis of the floodwater on the first day after the fertilizer application showed a high initial concentration of urea-N. Addition of the urease inhibitor N-(n-butyl) thiophosphoric triamide (nBTPT), broadcast with the urea into the floodwater, caused an apparent reduction in the rate of urea disappearance and a subsequent accumulation of NH₃–N in the floodwater; this ureas inhibitor also suppressed the rise in floodwater pH, with a resultant reduction in the partial pressure of ammonia (pNH₃) compared with the unamended urea application. The use of nBTPT did not decrease the N loss from broadcast urea not did it increase the grain yield. Among the different methods of applying broadcast urea that we tested, the broadcast application of granular urea onto drained soil shortly after removing floodwater followed by flooding 2 days later appeared to be a good N management practice, offering considerable potential for improving the efficiency of urea applied to lowland rice crops.     

蓄滞洪区洪水灾害信息传播机制研究

介绍了蓄滞洪区和灾害信息传播的相关概念,在此基础上进一步界定了蓄滞洪区洪水灾害信息传播的涵义,并说明其传播的一般过程。从洪水灾害信息传播的构成要素、洪水灾害信息传输与扩散以及洪水灾害信息反馈和信息共享4个方面对蓄滞洪区洪水灾害信息传播的机制加以分析,并提出了相应的机制运行与优化的建议。     

施用尿素和控释氮肥的双季稻田表层水氮素动态及其径流损失规律

【目的】通过比较研究洞庭湖区双季稻田施用尿素（CF）和控释氮肥（CRNF）的表层水pH、电导率（EC）、总氮（TN）、NH4+-N和NO3--N浓度变化动态及TN径流损失规律，寻找有效控制氮素流失的最佳施肥管理措施。【方法】在渗漏池中按河沙泥（ASP）和紫潮泥（PCP）土壤的剖面层次填装土壤，对天然降雨引起的稻田氮素径流损失进行模拟试验。【结果】稻田土壤施用尿素后，表层水TN、NH4+浓度分别在第1、3天达到高峰，然后随着时间的延长而迅速下降；早稻表层水pH在施用尿素后15 d内（晚稻3 d）逐渐升高，EC表现与NH4+的变化同步。与施用尿素相比，施用CRNF能显著降低稻田表层水TN、NH4+浓度峰值，pH、EC峰值也有明显下降。氮素径流损失监测结果显示，洞庭湖区双季稻田施用尿素TN径流损失量为7.47 kg•ha-1，占施氮量的2.49%；施用CRNF、70%CRNF的TN损失量比施用CF的分别减少了24.5%和27.2%。早稻施肥后20 d内发生的2次降雨径流事件，施用尿素、CRNF和70%CRNF处理的2次TN径流损失量分别占全生育期径流损失总量的72%、70%和58%。其中，早稻施肥后第10天发生的第1次径流的2个控释肥处理的TN损失比施用尿素分别降低了42.9%和44.2%。【结论】双季稻田施用尿素后15 d内表层水氮素浓度高，是氮素流失的关键时期；控释氮肥能显著降低这个时期的表层水和所发生的径流液中的氮素浓度，从而显著削减水稻全生育期内的TN径流损失量。     

Phylogenetic study on a bacterial community in the floodwater of a Japanese paddy field estimated by sequencing 16S rDNA fragments after denaturing gradient gel electrophoresis

Phylogenetic positions of characteristic bands of 16S rDNA that were obtained from the floodwater of a Japanese paddy field by denaturing gradient gel electrophoresis (DGGE) analysis in a previous work (Biol Fertil Soils 36:306–312, 2002) were determined to identify dominant bacterial members in the floodwater. Sequences of DGGE bands were affiliated with the Cytophaga–Flavobacterium–Bacteroides group, β-Proteobacteria, and Actinobacteria and showed phylogenetically close relationships with species inhabiting other aquatic environments, although most of their closest relatives were uncultured bacterial clones.     

Ring dike system to harness floodwater from the Mekong River for paddy rice cultivation in the Tonle Sap Lake floodplain in Cambodia

Located in the floodplain of the Mekong River and the Tonle Sap River, Batheay irrigation system and its reservoir directly receive floodwater from the Mekong. The Batheay reservoir formed by a ring dike functions as both a reservoir and a paddy field. In the wet season, the ring dike prevents floodwater from entering the reservoir and rainy season rice is grown inside the dike. After harvesting, the gates on the ring dike are opened to receive floodwater. The water is stored inside the dike for cultivating dry season rice outside the dike. In this paper, the irrigation system is studied as a model site for future development of the floodplain of the Tonle Sap Lake of Cambodia. Specifically, this paper is concerned with the study of water balance and analysis of the hydrologic components of the Batheay irrigation system, and the effectiveness of the ring dike system. The study found that floodwater of the Mekong River contributed about 74% to the total inflow to the Batheay reservoir. Contributions to the total water supply of reservoir water, floodwater remaining in the fields, and precipitation were 73, 12, and 15%, respectively. The efficiency of the system was found to be 92%. The dike system is expected to be a paradigm for the floodplain of the Tonle Sap Lake.     

城市化对洪水的影响研究--以深圳市对深圳河设计洪水的影响为例

城市化作为影响洪水形成的下垫面条件的因素之一对洪水形成影响较大,通过对城市化影响洪水作用机理的分析得出,城市化使城市集水区天然调蓄能力减弱,汇流速度明显加快,径流系数也明显增大,城市化所及地区的产汇流过程发生显著变化。另外还以深圳城市化对深圳河设计洪水的影响为例计算得出“城市化”将加大深圳河流域坡面汇流及河槽汇流的速度,缩短汇流时间,加大洪峰流量。对于百年一遇洪水,干流各控制点汇流历时缩减15.4%~21.7%,相应洪峰流量增加11.8%~19.0%     

城市化对洪水的影响研究--以深圳市对深圳河设计洪水的影响为例

城市化作为影响洪水形成的下垫面条件的因素之一对洪水形成影响较大,通过对城市化影响洪水作用机理的分析得出,城市化使城市集水区天然调蓄能力减弱,汇流速度明显加快,径流系数也明显增大,城市化所及地区的产汇流过程发生显著变化。另外还以深圳城市化对深圳河设计洪水的影响为例计算得出“城市化”将加大深圳河流域坡面汇流及河槽汇流的速度,缩短汇流时间,加大洪峰流量。对于百年一遇洪水,干流各控制点汇流历时缩减15.4%~21.7%,相应洪峰流量增加11.8%~19.0%     

洪涝灾害对猪繁殖性能的影响

我们研究了洪水灾害对太湖猪繁殖性能的影响，研究表明，１９９１年夏季洪水，高温，高湿，阳光短等恶劣生态因子导致母猪情期受胎率明显下降（Ｐ〈０．０１），产仔数及活产仔数均明显减少。     

Comparison of g23 gene sequence diversity between Novosphingobium and Sphingomonas phages and phage communities in the floodwater of a Japanese paddy field

Our previous study indicated that the diversity of the major capsid gene (g23) of T4-type bacteriophages (phages) of Novosphingobium and Sphingomonas strains isolated from the floodwater of a Japanese paddy field is comparable to those of the clones obtained from other Japanese paddy fields. For more strict comparison of the diversity, this study examined g23 sequences between Novosphingobium and Sphingomonas phages and phage communities in the identical floodwater of a Japanese paddy field. The clones were obtained by applying g23-specific primers to DNA extracted from the floodwaters. Many 23 clones in the floodwater were grouped into the same clusters of Paddy Groups I-VI with g23 genes of Novosphingobium/Sphingomonas phages with some clones belonging to an additional cluster. In addition, the remaining clones belonged to the clusters of marine clones and T4-type enterophages. These findings indicate that the g23 genes in the floodwater are more diversified than those of Novosphingobium/Sphingomonas phages including g23 genes closely related to the genes of enterophages and marine origins.