Microbial Activity in Paddy Soil and Water-Use Efficiency of Rice as Affected by Irrigation Method and Nitrogen Level

The thin-shallow-wet-dry irrigation (TIR) method is one of water-saving irrigation methods of rice cultivation. The effects of TIR method on water-use efficiency (WUE) of rice and soil microbial activities were investigated under three rates of nitrogen (N) compared to conventional flood irrigation. The TIR method decreased total water consumption (21.7–23.5%) and increased rice WUE (17.8–27.2%). At high N level, the TIR method significantly increased the number of nitrifying bacteria; the activities of catalase, invertase, and urease in soil at the jointing, booting, and milky stages; and the number of denitrifying bacteria at the milky stage. Increased N rate increased grain yield and water consumption simultaneously, and middle N level increased microbial biomass carbon (MBC) and N, the number of nitrifying and denitrifying bacteria, and the activities of catalase, urease, and invertase. Thus the TIR method at the middle N level can effectively improve rice WUE and soil MBC and enzyme activity.     

顶果木抗旱生理特性研究

为了评价顶果木(Acrocarpus fraxinifolius)的耐旱性,采取模拟自然极度干旱条件方法,利用盆栽方式,研究顶果木在干旱胁迫期间的生理特性。结果表明,在水分胁迫期间,顶果木叶片的叶绿素a、b含量出现先升高后降低的趋势,而类胡萝卜素含量出现增加趋势,叶绿素a的含量明显高于叶绿素b和类胡萝卜素的含量;顶果木叶片的可溶性糖、可溶性蛋白质、游离脯氨酸含量出现先增加后降低的趋势;受水分胁迫的影响,顶果木叶片质膜透性越来越大。干旱胁迫开始在停止供水后的第11~16天的某一天,干旱胁迫的临界土壤含水量在20%左右;第21天顶果木各种生理机能开始丧失,已经达到顶果木的萎蔫系数(12.99%)。     

首创直接利用野生稻杂交选育恢复系与应用

袁隆平先生利用野生稻的败育型细胞质基因育成不育系,而笔者则首创了直接利用野生稻细胞核基因选育恢复系的新途径。笔者介绍了直接利用野生稻杂交选育恢复系的技术路线及方法,该法利用野生稻作为主体亲本,与多个各具有显著特点的恢复材料杂交,充分利用野生稻抗性强、适应性广、米质优等特点。采用“大群体多世代”的育种方法成功育成强优广谱性恢复系测253,并育成一系列高产、优质、多抗的新组合。笔者还介绍了测253及其配组组合的应用和产生的社会效益。     

CZDM膜制氮机组降氧工艺与氧气浓度变化规律研究

对CZDM膜制氮机组降氧工艺与氧气浓度变化规律进行了研究,利用CZDM膜制氮机纽产生的低氧浓度气体,采用一系列降氧工艺使试验仓粮堆内的氧气浓度从20.9%降低到2.0%共用去408 h.各工艺阶段粮堆平均氮气(氧气)浓度变化与该工艺前粮堆平均氮气(氧气)浓度和该工艺充入粮堆氮气浓度差成正比.本研究结果为开展低氧防治储粮害虫技术的应用提供了参考依据.     

Variations in clinical presentation and anatomical distribution of gross lesions of African swine fever in domestic pigs in the southern highlands of Tanzania: a field experience

African swine fever is a contagious viral disease responsible for up to 100% mortality among domestic pigs. A longitudinal study was carried out to determine the clinical presentation and anatomical distribution of gross lesions in affected pigs in Mbeya region, Tanzania during the 2010 to 2014 outbreaks. Data were collected during clinical and postmortem examination by field veterinarians and using a structured questionnaire. A total of 118 respondents (100%) showed awareness about African swine fever. During previous outbreaks, the mortality rate was almost 100%, while in 2014 it was estimated to be less than 50%.The clinical picture of the 2010–2012 outbreaks was characterized by high fever, depression, inappetance, mucosal congestion, hemorrhages, erythematous lesions in different body parts, and abortion. Several internal organs including the kidneys, spleen, and liver were congested and edematous. During the 2014 outbreak, a number of pigs (49.7%) were asymptomatic when brought to slaughter slabs but were found to have African swine fever gross lesions at postmortem examination as compared to 12.3% in 2010–2012. Bluish discoloration, which is normally distributed on the non-hairy parts of the body, was not apparent in some pigs except at postmortem examination. Some pigs (36.1%) presented nasal and/or oral bloody discharges which were uncommon (9.1%) during previous outbreaks. Moreover, other gross features included enlarged dark red renal lymph nodes and spleen. Clinical signs such as anorexia, diarrhea, and pyrexia were mainly observed when affected pigs reached moribund stage. The majority of pregnant sows died without presenting abortions. In some litters, suckling piglets (3–6 weeks) survived from the disease. These findings indicated that in 2014, African swine fever outbreak in Mbeya region was characterized by a different clinical picture.     

加速碳酸化法稳固化工业危险废物焚烧飞灰重金属的研究

该文对某危险废物处置中心工业危险废物焚烧产生飞灰的加速碳酸化过程进行了研究。测定飞灰中Cr、Ni、Cu、Zn、Cd、Hg、Pb等重金属浸出浓度,其中Pb浸出浓度超过危险废物鉴别标准及填埋场入场控制标准限值,高达288.40mg/L。对飞灰进行碳酸化处理,探讨碳酸化反应时间、反应温度、液固比和CO_2浓度等因素对飞灰中重金属Pb浸出特性的影响。结果表明,在反应时间2~4h,反应温度10~50℃、液固比3∶1~5∶1,CO_2浓度60%~100%范围内碳酸化效果显著。并通过正交实验得到最优反应条件为CO_2浓度100%,反应时间3h,液固比4∶1,反应温度30℃。通过利用X射线衍射(XRD),扫描电镜(SEM)对飞灰碳酸化前后进行表征。结果表明,碳酸化后飞灰中Ca(OH)2、CaClOH消失,CaCO_3增加明显,晶体吸附使得重金属浸出明显下降,飞灰颗粒表面生成了以CaCO_3为主的片状和圆柱状的晶体物质。重金属浸出实验表明,飞灰经碳酸化处理后,重金属Pb浸出浓度由288.40mg/L降至0.02mg/L。碳酸化法处理工业危险焚烧产生飞灰可以有效控制重金属Pb的浸出以及降低体系的pH(由13~14降至7左右),同时实现对温室气体CO_2的固定,具有潜在的应用价值。     

不同下限基点温度对积温模型模拟效果的影响

为探究不同下限基点温度对作物发育阶段积温稳定性和对发育期模拟效果的影响,本研究基于一个下限温度的线性生长假设,以1990—2015年北京密云冬小麦抽穗至成熟期为例,统计设定下限温度5.0~15.0℃不同基点温度的阶段活动积温和有效积温,分析活动积温和有效积温这2种积温模型的阶段积温及其标准偏差和变异系数随下限温度的变化情况,并以模拟均方根误差和模拟准确率为指标对比分析下限温度指标对积温模型模拟效果的影响。结果表明:阶段积温随下限温度而变化,有效积温随下限温度升高而降低的趋势和程度比活动积温更快;阶段活动积温大于有效积温,且两者差值随着下限温度的升高而增大;在一定的下限温度范围内,以标准偏差为指标时有效积温绝对稳定度优于活动积温,而以变异系数为指标时则活动积温相对较有效积温相对稳定;以均方根误差检验模拟效果,则阶段活动积温模拟效果优于有效积温;以发育期模拟误差在2d以内表征模拟准确率时,2种积温模型的模拟效果随下限温度而变化,下限温度在5.0~12.5℃时,有效积温的模拟准确率高于活动积温的,而当下限温度≥12.5℃时,活动积温的模拟准确率大于有效积温的。     

Marker-Assisted Selection of Xa21 Conferring Resistance to Bacterial Leaf Blight in indica Rice Cultivar LT2

Bacterial leaf blight of rice (BLB), caused by Xanthomonas oryzae pv. oryzae, is one of the most destructive diseases in Asian rice fields. A high-quality rice variety, LT2, was used as the recipient parent. IRBB21, which carries the Xa21 gene, was used as the donor parent. The resistance gene Xa21 was introduced into LT2 by marker-assisted backcrossing. Three Xoo races were used to inoculate the improved lines following the clipping method. Eleven BC₃F₃ lines carrying Xa21 were obtained based on molecular markers and agronomic performance. The 11 lines were then inoculated with the three Xoo races. All the 11 improved lines showed better resistance to BLB than the recipient parent LT2. Based on the level of resistance to BLB and their agronomic performance, five lines (BC₃F₃ 5.1.5.1, BC₃F₃ 5.1.5.12, BC₃F₃ 8.5.6.44, BC₃F₃ 9.5.4.1 and BC₃F₃ 9.5.4.23) were selected as the most promising for commercial release. These improved lines could contribute to rice production in terms of food security.     

基于系统动力学的稻田塘堰系统水转化模拟及验证

为了描述稻田塘堰系统水转化过程,以水量平衡原理为基础,建立稻田塘堰系统水转化系统动力学模型。利用漳河灌区三干渠中游区域尺度塘堰日水位观测资料对模型进行检验,模拟结果的复相关系数、Nash-Sutcliffe系数和均方根误差分别为0.90、0.79和0.155 m/d。在浅水灌溉模式下,对研究区域内塘堰调蓄方式进行动态模拟,结果表明,塘堰在完全调蓄时可以保障作物充分灌溉,在部分调蓄与不调蓄时作物分别在第72天和45天发生水分胁迫,塘堰灌溉对保证作物正常生长天数具有显著效果。当塘堰完全调蓄时,在浅水灌溉、湿润灌溉及间歇灌溉模式下,塘堰最低蓄水量占最大蓄水量的比例分别为2.0%、18.9%和41.3%,塘堰的有效水利用率分别为84.7%、80.9%和67.7%。研究可为稻田塘堰系统合理利用雨水资源、灌溉管理提供理论依据。     

Congener-specific evaluation of biota-sediment accumulation factor model for HCHs and DDTs under small-scale in situ riverine condition

Purpose

The congener-specific biota-sediment accumulation factors (BSAFs) model for hexachlorocyclohexanes (HCHs) and dichlorodiphenyltrichloroethanes (DDTs) was evaluated for four different freshwater fish species (Orienus plagiostomus, Tor putitora, Glyptothorax punjabensis, and Cyprinus carpio) in in situ riverine conditions of Kabul River, Pakistan.

Materials and methods

The congeners of HCH and DDT were quantified using gas chromatograph (GC-ECD). The BSAF for each congener (HCHs and DDTs) was calculated from paired observation of congener’s measured concentrations in fish and sediment taken at the same site. Pearson’s correlation and linear regression analyses were performed to determine the influence of sediment organic carbon fraction (f _soc ) and organism lipid fraction (f _lipid ) on BSAF, and the relationship between BSAFs and logarithm of octanol-water partition coefficients (log K _ows) of HCH and DDT congeners, respectively.

Results and discussion

The BSAFs for total HCH (t-HCH) and total DDT (t-DDT) ranged from 0.6 to 1.5 and from 0.2 to 1.6, respectively. The model was significantly influenced by both fish (p = 0.004) and chemical types (p = 0.002) at 95 % confidence level. The sediment organic carbon fraction (f _soc ) and fish lipid fraction (f _lipid ) had not-too-weak effects on BSAF values for all fish species. The BSAF values were linearly fitted with logarithmic octanol-water partition coefficients (log K _ows) of HCH and DDT congeners, despite the different chemical structures, and different compound class significant negative correlations between log K _ows and BSAF values were found, indicating that hydrophobicity is one of the key factors influencing the bioaccumulation potential of the investigated compounds.

Conclusions

The present study confirmed the applicability of the BSAF model as a screening tool for predicting bioaccumulation of sediment-associated HCH and DDT congeners in investigated fish species under small-scale in situ riverine conditions of Kabul River and suite the model for benthic fish (G. punjabensis) on the basis of the 25th and 75th percentiles of congener-specific BSAF values.