Impact of Climate Change on the Technical Efficiency of Striped Catfish,Pangasianodon hypophthalmus,Farming in the Mekong Delta,Vietnam

The technical efficiency of randomly sampled pangasius farms in the Mekong Delta of Vietnam was estimated using data envelopment analysis, and factors affecting technical and scale efficiency were examined with bootstrap truncated regression. The mean technical efficiency score assuming variable returns to scale was 0.84. The technical efficiency of downstream farmers was higher due to lower energy costs and stocking once a year. Most of the up‐ and midstream farms needed to pump water and stocked at least three times in 2 yr. Regression analysis showed a positive effect on technical efficiency of the farmers' education level and having experienced climate change impact through flooding or salinity intrusion in the past. Farms affected by salinity intrusion had a lower scale efficiency as they reduce stocking frequency and rate. In general, reducing fish mortality and the cost of inputs, increasing scale of operation, and being trained, using appropriate methods, in management strategies may improve technical efficiency.     

生物炭耦合水分管理对稻田土壤As-Cd生物有效性及稻米累积的影响

选取湖南某矿区重金属Cd、As复合污染稻田土,以泰优390号为材料,通过盆栽试验研究湿润灌溉(CK)、农艺措施淹水(WF)、竹炭(ZC)、竹炭结合淹水措施(ZF)、稻壳炭(GC)、稻壳炭结合淹水措施(GF),对土壤中As、Cd生物有效性及水稻糙米中As、Cd累积效应的影响。结果表明,6种处理土壤pH值上升幅度为0.12~0.72个单位,均呈现先升高再下降,最后趋于中性的规律。相比对照,水稻全生育期5种处理Eh值均呈现下降趋势,而单一添加生物炭ZC、GC 2种处理乳熟期Eh显著高于同一生育期配施生物炭的WF、ZF、GF 3种淹水处理,并始终处于弱还原状态。各处理均能显著降低成熟期土壤Cd的有效态、酸可提取态和TCLP提取态含量,而As的有效态和TCLP提取态含量显著升高。WF、ZF、GF淹水配施生物炭处理糙米中Cd含量降低51.46%~57.28%,其中GF抑制效果最佳,与ZF呈现显著性差异;而籽粒中As的含量分别达到0.29、0.32、0.30 mg·kg-1,较CK组升高了39.74%~53.58%,三者并无显著性差异。2种仅添加生物炭的ZC、GC处理与对照相比,糙米中Cd含量降低16.50%、39.81%,糙米中As含量增加了27.24%、12.23%,但GC与CK处理并无显著性差异。因此,WF、ZF、GF及ZC处理可减少土壤中Cd的生物有效性,对重金属Cd污染稻田土壤修复具有重要意义,但会增加土壤中As溶出的风险及其生物有效性。而单一添加生物炭的GC处理可用于Cd-As复合污染农田,为稻田土壤Cd-As复合污染粮食安全生产提供理论依据。     

Improvement of seedling establishment under flood condition by seed coating with molybdenum compounds for wheat and barley

Wheat and barley are often cultivated also in paddy fields in winter in Japan. The drainage of paddy fields is often poor. The seedling establishment of wheat and barley is more prone to become poor if it rains heavily after sowing. The flooding damage on seedling establishment is thought to be caused by many factors. The generation of sulfide ions in flooded and reduced soil is thought to be one factor of the flooding damage. In this study, the effect of seed coating with molybdenum compounds, which suppress the generation of sulfide ions, on the flooding damage of wheat and barley seedling establishment. Two poorly soluble molybdenum compounds were coated on wheat or barley seeds at different amounts. Coated seeds were sown in soil and soon flooded for 2 d at 20 °C. When seeds were not coated with molybdenum compounds, rates of seedling establishment were no more than 32%. However, when any molybdenum compounds of .05–.5 mol-Mo kg^?1 were coated, seedling establishment was significantly improved and rates of seedling establishment were no less than 54%. However, when sown seed were not flooded, the establishment rates of the seeds, which were coated with a molybdenum compound of no less than .1 or .2 mol-Mo kg-1, were significantly decreased. Accordingly, coating of molybdenum compounds could improve the seedling establishment of coated seeds under flooded condition, but might impair the seedling establishment of coated seeds under unflooded condition.     

覆膜滴灌条件下稻田CH_4排放研究

为了揭示覆膜滴灌对稻田CH_4综合排放的影响,采用比较分析法分析了覆膜滴管条件下稻田甲烷的排放变化。试验采用覆膜滴灌Ⅰ、覆膜滴灌Ⅱ和漫灌3个处理,分别对当地高产主栽品种吉旱1号进行CH_4排放通量的测定。结果表明,覆膜滴灌稻田CH_4排放通量显著高于漫灌稻田;覆膜滴灌处理条件下,土壤含水率高的覆膜滴灌Ⅰ稻田CH_4排放通量高于覆膜滴灌Ⅱ,说明土壤水分是稻田CH_4排放的主要影响因素之一;3个处理下CH_4的排放趋势大体一致,排放高峰均出现在水稻分蘖的前中期和拔节孕穗期,说明覆膜滴灌未改变稻田CH_4排放的进程。     

膜下滴灌和淹灌两种栽培模式下水稻光合生理特性的研究

以粳稻品系T-04和T-43为试材,通过盆栽控水试验,比较了在膜下滴灌和淹灌两种栽培模式下乳熟期叶片的光合色素含量、光合特性、叶绿素荧光参数和渗透调节物质含量的差异,分析了两种栽培模式下的水分利用效率和产量构成因素。结果表明,在膜下滴灌栽培模式下,2个水稻品系的水分利用效率显著高于淹灌,叶绿素a、叶绿素b、类胡萝卜素含量均降低;最大净光合速率、胞间CO2浓度、气孔导度、蒸腾速率显著降低,表明光合速率下降受叶绿素含量和气孔的双重影响;表观量子效率、羧化效率、ΦPSII、电子传递速率、Fv/Fm均显著降低,说明光合色素含量降低导致PSⅡ反应中心捕光能力减弱和光化学转化效率降低,从而使叶片光合速率降低;可溶性糖、可溶性蛋白均显著低于淹灌栽培;丙二醛、脯氨酸含量高于淹灌栽培,说明滴灌栽培水稻植株的膜脂过氧化加剧,细胞膜系统受到一定程度的破坏,通过主动积累渗透调节物质,适应干旱胁迫。膜下滴灌栽培水稻单位面积有效穗数和结实率显著降低,导致最终减产。     

水涝胁迫对常绿欧洲荚蒾生理指标的影响

以盆栽常绿欧洲荚蒾幼苗为试验材料,研究了幼苗在浸水处理条件下的相关生理指标。结果表明:在水涝胁迫下,常绿欧洲荚蒾叶片中脯氨酸含量、可溶性蛋白含量和可溶性糖含量显著高于对照,表明常绿欧洲荚蒾通过积累这些物质来适应水涝逆境。到水涝胁迫处理12 d,尽管叶片的叶绿素含量有所下降,相对电导率增至24.8%,但与对照相比,植株外表的生长状况并无多大变化,说明常绿欧洲荚蒾较耐水涝。     

冀东平原设施辣椒水肥一体化技术应用效果研究

水肥一体化滴灌技术是提高设施蔬菜水分利用率的有效途径之一。通过设置2个不同施肥量处理,对滴灌施肥与畦灌冲肥作了比较。试验结果表明:设施辣椒采用水肥一体化滴灌技术具有较好的节水节肥效果,能够提高辣椒产量,改善辣椒品质,同时提高水分利用率。水肥一体化滴灌技术可节肥2 265 kg/hm2,节肥率40.3%;节水5 670 m3/hm2,节水率60.0%;增产6 435 kg/hm2,增产率达7.2%,为今后水肥一体化滴灌技术在设施辣椒上的推广应用提供一定的理论基础和技术支持。     

淹水程度对长江滩地枫杨导管及微纤丝角的影响

运用体视学方法,对枫杨导管、微纤丝角变异规律进行研究.结果表明,枫杨导管长宽比约为3.2,水淹程度不同的两组间的导管平均直径在径、轴向上变化有一定差异.枫杨微纤维角由髓心向外逐渐变小,与年轮显著相关,但水淹程度不同的两组间微纤丝角在轴向上的变化趋势不一致.在0.05水平上,经T-检验水淹程度不同的两组间的导管平均直径、形状因子、单位体积中导管所占面积及微纤丝角差异不显著.     

稻麦轮作下秸秆还田对稻麦产量和稻田可溶性有机碳含量的影响

为阐明稻麦轮作体系下秸秆还田对作物产量与稻田可溶性有机碳（DOC）的影响,通过连续2年盆栽试验研究了两种典型土壤（壤土和黏土）在无秸秆还田、半量秸秆还田、全量秸秆还田3种处理下稻麦产量和稻季土壤溶液DOC浓度的动态变化。结果表明,秸秆还田显著增加了两种土壤大多数处理的水稻产量,增幅1.6%~11.9%,其中全量秸秆还田的增产效果大于半量秸秆还田（第1年不显著,第2年显著）。秸秆还田对小麦产量的影响因土壤类型而异,壤土中小麦产量显著增加7.2%~10.6%（第1年）或增产不显著（第2年）,但全量秸秆还田和半量秸秆还田处理之间没有显著差异;黏土中小麦显著减产（5.0%~9.3%）,其中第2年的全量秸秆还田减产效应显著大于半量秸秆还田。秸秆还田及土壤类型显著影响水稻前期（烤田之前）的土壤溶液DOC浓度,全量秸秆还田、半量秸秆还田分别比无秸秆还田处理平均增加141.7%、61.9%,壤土比黏土平均增加89.6%;间歇淹水之后,所有秸秆还田处理及土壤类型的DOC浓度均迅速降低。总体上,秸秆还田对两种土壤的水稻增产都有利,但对黏土小麦增产不利,秸秆还田显著增加了稻田前期的DOC浓度,间歇淹水可以迅速降低稻田DOC浓度。     

淹水和风干过程对水稻土磷吸附、解吸及有效磷的影响（英文）

 在室内研究了淹水和风干过程对两种水稻土磷吸附、解吸及有效磷的影响。结果表明,淹水过程明显增加土壤对磷的吸附,降低磷解吸和有效磷,而淹水后的风干过程则可显著减少土壤磷吸附,提高磷解吸量和有效磷含量。微生物对磷的矿化或活化作用是淹水土壤风干过程提高土壤有效磷的主要原因之一。建议在评价磷对水稻的有效性时应采用新鲜样品。