Seroprevalence of and Risk Factors for Toxoplasma gondii in the US Swine Herd Using Sera Collected During the National Animal Health Monitoring Survey (Swine 2006)

The United States Department of Agriculture (USDA) initiated the National Animal Health Monitoring System (NAHMS) in 1983 to collect, analyse and disseminate data on animal health, management and productivity in US domestic livestock populations, including swine. The programme includes an on‐farm serological sampling component which can be used to monitor seroprevalence of various pathogens, including Toxoplasma gondii. The purpose of this study was to determine the seroprevalence of T. gondii in grower/finisher pigs using sera collected during NAHMS Swine 2006 and to determine farm level factors associated with differences in seroprevalence on farms where sera was collected during the Swine 2006 survey. Sera and data on management practices for this study were collected from 185 grower/finisher swine production sites located in 16 states accounting for >90% of US swine production (Arkansas, Colorado, Iowa, Illinois, Indiana, Kansas, Michigan, Minnesota, Missouri, Nebraska, North Carolina, Ohio, Pennsylvania, South Dakota, Texas and Wisconsin). A total of 6238 sera were tested for T. gondii antibodies using a commercial ELISA assay (Vet. Parasitol. 128 , 2005, 177). Seroprevalence in this study, as determined by ELISA, was 2.6%, with a herd prevalence of 21.6% and a mean within‐herd prevalence of 2.7%. Analysis of swine management practices indicated that rodent control methods and carcass disposal methods were associated with differences in the number of T. gondii positive samples on farm. These results are consistent with current epidemiological knowledge of the transmission of Toxoplasma on the farm (ingestion of organic matter containing oocysts, or ingestion of infected animal tissues). Production practices which eliminate these sources of exposure can reduce the risk of Toxoplasma infection in pigs, and reduce the likelihood of human infection from consumption of infected pork.     

烤烟GAP种植中植保产品的使用与管理

随着良好农业管理规范在烟草种植的引入,植保产品的使用和管理已经成为亟待研究和探索的重要课题。提出了烤烟GAP种植模式下,植保产品的选择、使用、储存、处理、残留检测和危害处理措施,对深入探讨烤烟GAP有重要意义。     

剔除林下灌草及添加固氮植物对华南地区4种人工林土壤甲烷(CH4)通量的影响

CH4是重要的温室气体之一,其主要排放源是森林土壤。本研究采用静态箱法对华南地区尾叶桉林（Eucalyptusurophylla）（B1）,厚荚相思林（Acacia crassicarpa）（B2）,10个树种的混交林（B3）和30个树种的混交林（B4）4种林型土壤CH4通量进行了原位测定,研究剔除林下灌草和添加翅荚决明（Cassia alata）对土壤CH4通量的影响。4个处理包括：（1）剔除林下灌草并添加翅荚决明（UR＋CA）;（2）仅剔除林下灌草（UR）;（3）仅添加翅荚决明（CA）;（4）对照（CK）。研究结果表明：林型变化对土壤CH4通量有重要影响,B1和B2表现为CH4的汇,而B3和B4为CH4的源,剔除林下灌草能改善土壤微生物活性,加快土壤矿化速度,促进CH4的吸收;而林下添加翅荚决明,由于翅荚决明根系的固氮作用,能加快土壤CH4的排放,表层土壤温度和湿度与土壤CH4通量具有强相关性;土壤有机碳（SOC）和可溶性N也是影响CH4通量的重要因子。本研究对探寻人工林管理措施对土壤CH4捧放影响机制具有重要的意义。     

农户的农药残留认知及其对施药行为的影响

农药残留是困扰农产品安全的重大问题。农户是农药施用的主体,研究农户对农药残留的认知及其施用行为,对于在源头上保障农产品安全供给,最大程度地减少对环境、人类健康的影响方面具有重要意义。以农户的农药残留认知及农户的认知对其施药行为的影响为主题进行了综述。     

不同耕作措施对旱地玉米生长环境及产量的影响

采用田间定位试验,研究了羊粪4 m3+深耕30~35 cm(MP3)、羊粪4 m3+深耕20~25 cm(MP2)、羊粪4 m3+旋耕10~15 cm(MP1)、深耕30~35 cm(P3)、深耕20~25 cm(P2)、旋耕10~15 cm(P1)6种耕作措施下旱地玉米土壤温度、土壤水分、土壤呼吸速率及产量的变化。结果表明:采用不同耕作措施均能有效促进旱地玉米生长,与传统耕作方式(P1)相比,MP3、P3处理的土壤体积含水量分别提高了39.00%、32.44%;MP3处理下土壤温度显著高于传统耕作0.94℃;随着旱地玉米生育期的推进,土壤呼吸速率峰值出现在6月底,不同耕作方式下土壤呼吸速率较传统耕作提高了0.68~1.26倍;深耕处理、深耕+羊粪处理的旱地玉米产量均显著高于传统耕作,其增幅在11.94%~36.51%。通过3年试验比较,羊粪4 m3+深耕30~35 cm、羊粪4 m3+深耕20~25 cm、深耕30~35 cm效果较好。     

从“学”的角度谈广西大学园林专业教学实践

广西大学园林专业具有近20年的办学经验;在简述广西大学园林专业沿革、培养目标、教学设置的基础上,从“学”的角度,探讨学生对园林专业教学实践中“学”的愿望和园林专业“教”与“学”实践的结合问题,以期为广西大学园林专业教学提供一些建设性意见。     

Long-Term Effects of Tillage and Manure Applications on Soil Phosphorus Fractions

Application of manure on the basis of crop nitrogen (N) need increases the level of soil phosphorus (P), which is concern for deterioration of surface water quality. Soil samples were collected from a long-term field study to investigate the impact of crop N need–based manure application on soil P fractions and P adsorption and release kinetics. The field experiment was initiated in 1990. The soil was moderately well-drained Kennebec (fine silty, mixed, mesic Cumulic Hapludolls). No-tillage (NT) and conventional-tillage (CT) treatments were established in main plots, and subplots had five N treatments, including a control, and annual application of 84 or 168 kg N ha^?1 applied as ammonium nitrate (NH₄NO₃) or beef (Bos taurus) manure. Manure at the high N application rate had significantly greater Bray 1 P under NT than under CT at 0- to 5-cm soil depth. Nitrogen fertilizer treatments were not significantly different than the control for Bray 1 P. Continuous application of manure at the high N rate significantly increased all Hedley P fractions; however, the major increase was observed in high bioavailable P pools [iron oxide (FeO) P and sodium bicarbonate (NaHCO₃) P_i] and hydrochloric acid (HCl) P fractions. Soil organic P (P_o) pools, including both labile (NaHCO₃-P_o) and resistant [sodium hydroxide (NaOH) P_o], were increased by application of N from any source, suggesting biomass production and return of residue to soil surface was the responsible factor. Continuous application of manure based on N need also significantly increased FeO-P, NaHCO₃-P_i, and HCl-P fractions at lower soil depths (5–15 and 15–30 cm). Results from the P-adsorption study suggest that ability of soil to adsorb additional P was decreased by manure application and that EPC₀ was increased. Maximum desorbable P was observed for manure treatments under NT, although the release constant k (h^?1) was significantly less than with fertilizer N treatments.     

轮耕对宁南旱区土壤理化性状和旱地小麦产量的影响

为了探索免耕/深松隔年轮耕对土壤理化性状及冬小麦产量的影响,2007年至2010年在宁南旱区采用免耕/深松/免耕、深松/免耕/深松与连年翻耕3种耕作模式,对土壤容重、团聚体、养分及小麦产量等进行了研究。结果表明:与传统耕作相比,免耕/深松/免耕和深松/免耕/深松模式显著(p<0.05)降低土壤容重,改善了土壤的孔隙状况;两种轮耕模式可显著(p<0.05)增加0～40 cm各土层2～0.25 mm水稳性团聚体的含量。3种耕作方式比较,深松/免耕/深松模式最能有效增加0～40 cm土壤有机质和0～20 cm土层全氮含量;免耕/深松/免耕和深松/免耕/深松处理较传统耕作显著增加0～40 cm土层碱解氮和有效磷含量、20～40 cm土壤速效钾含量,改善了土壤的养分状况。试验期间,免耕/深松/免耕、深松/免耕/深松模式3年平均小麦籽粒产量较传统耕作显著增加,分别增产9.59%和10.69%(p<0.05),以深松/免耕/深松处理增产效果最佳。     

Evaluation of efficacy of several disinfectants against Campylobacter jejuni strains by a suspension test

The objective of this study was to determine the efficacy of 16 active compounds and 11 commercial disinfectants against Campylobacter jejuni. Two reference strains (one of avian origin and the other isolated from bovine) and two avian field strains were tested in suspension test in the presence and absence of serum. Chloramine-T, povidone–iodine (1% available iodine), cetylpiridinium chloride, ethanol, isopropanol, chlorhexidine digluconate, formaldehyde, phenol, and 10 of the 11 commercial formulations (eight of them based on quaternary ammonium compounds) showed an excellent disinfectant capability, resulting in the highest level of reduction (>6-log₁₀) in colony-forming units of the four C. jejuni strains compared regardless of the presence or absence of organic material. These compounds might be helpful in the adoption of environmental control measures against C. jejuni.