Tillage erosion within potato production systems in Atlantic Canada: I. Measurement of tillage translocation by implements used in seedbed preparation

In Canada, there is growing acceptance that tillage erosion is a serious form of soil degradation and a threat to the sustainability of agriculture across the country. To date, the potential risk for tillage erosion within potato production systems has not been investigated. The objective of this study was to generate tillage translocation values for primary and secondary tillage implements common to seedbed preparation within conventionally and conservation tilled potato production systems in Atlantic Canada. Tillage translocation was measured for each implement by labelling a plot of soil with a tracer. The tracer redistribution along the path of tillage was used to generate a summation curve to calculate mean soil movement in the direction of tillage. The results show that each primary and secondary tillage operation moved vast quantities of soil and is potentially erosive. Maximum displacement distances were considerably larger in this project than those reported in previous studies looking at tillage erosion by primary and/or secondary tillage implements. All four tillage implements tested moved soil at least 3 m, with the greatest translocated distances (5.6 m) observed for the chisel plough (CP) and vibrashank (VS). The mass of translocated soil (T_M) was greatest for the CP, followed by the mouldboard plough (MP), VS and offset disc (OD). In addition, compared to travelling downslope, the upslope speed of tillage was reduced by 38%, 21%, 32% and 12% for the MP, CP, OD and VS, respectively, while the depth of tillage was reduced by 6%, 5%, 35% and 2%, respectively. It is apparent that conservation tillage implements (the CP is generally promoted to reduce water erosion in Atlantic Canada) and secondary tillage implements (OD and VS) can move as much soil as conventional tillage implements such as the mouldboard plough, and must be considered when developing plans to reduce soil erosion within potato fields in Atlantic Canada.     

加拿大林火天气指标系统在吉林省的应用1）

针对吉林省林火发生特点,引入加拿大林火天气指标系统,利用1996—2010年气象资料和吉林省1996—2010年森林火灾数据,采用薄板样条插值方法,研究林火天气指标与林火的相关性,并划分森林火险等级。结果表明：加拿大林火天气指标系统适用于吉林省,分级方法也比较适用。但还需要进一步检验和对比研究,以使系统能够更好地适用于吉林省的林火预报工作。     

Differences in Ichthyophonus prevalence and infection severity between upper Yukon River and Tanana River chinook salmon, Oncorhynchus tshawytscha (Walbaum), stocks

Two genetically distinct populations of chinook salmon, Oncorhynchus tshawytscha (Walbaum), were simultaneously sampled at the confluence of the Yukon and Tanana rivers in 2003. Upper Yukon-Canadian fish had significantly higher infection prevalence as well as more severe infections (higher parasite density in heart tissue) than the lower Yukon-Tanana River fish. Both populations had migrated the same distance from the mouth of the Yukon River at the time of sampling but had significantly different distances remaining to swim before reaching their respective spawning grounds. Multiple working hypotheses are proposed to explain the differences between the two stocks: (1) the two genetically distinct populations have different inherent resistance to infection, (2) genetically influenced differences in feeding behaviour resulted in temporal and/or spatial differences in exposure, (3) physiological differences resulting from different degrees of sexual maturity influenced the course of disease, and (4) the most severely infected Tanana River fish either died en route or fatigued and were unable to complete their migration to the Tanana River, thus leaving a population of apparently healthier fish.     

中国与欧洲、加拿大的定向刨花板产品标准比较

对中国和欧洲、加拿大的定向刨花板标准进行比较,分析国内标准与国外标准在质量要求等方面的差异,为中国定向刨花板的生产、贸易和标准制修订提供参考。     

Foliar applied harpin effects on fruit quality of peppers

Abstract

During the past century, changes in cropping systems have led to selective pressure on weed flora. The number of competitive species with decreased susceptibility to herbicides has increased, at the cost of more susceptible species. For a long period, the economically important perennial weed species Cirsium arvense (L.) Scop. and Sonchus arvensis L. have mainly been controlled by the herbicide MCPA (phenoxy-acetic acid), which stimulates the weed plant to abnormal growth. However, it has been reported from Sweden, Great Britain, Hungary and North America that C. arvense has become less susceptible to MCPA since the 1950s. Therefore, two greenhouse experiments were performed at Uppsala, Sweden with clones of C. arvense and S. arvensis. The purpose was to study whether ecotypes (clones) from high input farmland, where herbicides had been used intensively and regularly for a long time, were less susceptible to herbicide (MCPA) treatment than ecotypes from low input farmland. Sixty clones of C. arvense and 36 clones of S. arvensis were treated with nine different doses of MCPA. The results supported the suggestion that a shift towards less MCPA-susceptible ecotypes of C. arvense had occurred on high input farmland. Clone material from such farmland had, on average, significantly higher dry matter content after herbicide treatment than ecotypes from low input farmland. Similar decrease in susceptibility was not detected for S. arvensis. This was probably due to S. arvensis generally being less susceptible to MCPA than C. arvense. Sonchus arvensis has therefore being exposed to a lower selection pressure than C. arvense.     

葡萄糖氧化酶在改良面包粉中的应用

介绍了葡萄糖氧化酶对面粉增筋的原理,研究了酶的不同添加量对面包粉的理化指标、烘焙特性的影响。结果表明：添加合理比例的葡萄糖氧化酶,能够提高面筋强度,增强弹性;改善面团对机械冲击的承受力;提高面团入炉急涨特性,增大面包体积;降低了加麦使用的比例,获得了较好的经济效益。     

Contribution of Health Attributes,Research Investment,and Innovation to Developments in the Blueberry Industry

Abstract

This paper examines how the United States and Canadian highbush and lowbush blueberry industries have changed over the last two decades. Production increases have been driven by a combination of changing consumer preferences for healthy foods and the development of new cultivars that have opened new production regions, expanded fresh market opportunities, and created new food products. Canada has found it advantageous and economical to invest its research effort in the development of the lowbush blueberry, exploiting its health protective properties. The Unites States has concentrated its research effort on highbush cultivars to lengthen the harvest window and promote diversification opportunities in the Southern United States. Highbush production expansion in the Pacific Northwest has relied very little on new cultivar development and improvements in yield but more on increases in cultivated area.     

Contribution of crop residue carbon to soil respiration at a northern Prairie site using stable isotope flux measurements

Heterotrophic respiration from agricultural soils can be differentiated as originating from microbial decomposition of recent litter inputs or crop residue carbon (CRC) and resident soil organic carbon (SOC) pools of varying age and stages of decomposition. Our objective was to determine the relative contributions of these pools to respiration in a northern agroecosystem where the non-growing season is long. A tunable diode laser trace gas analyzer was used to determine atmospheric stable C isotope ratio (δ¹³C) values and ¹²CO₂ and ¹³CO₂ fluxes over an agricultural field in the Red River Valley of southern Manitoba, Canada. Measurement campaigns were conducted in the fall of 2006 and spring of 2007 following harvest of a maize (C₄) crop from soil having SOC derived from previous C₃ crops. Stable CO₂ isotopologue gradients were measured from the center of four 200 × 200 m experimental plots, and fluxes were calculated using the aerodynamic flux gradient method. The soil in two of the experimental plots underwent intensive tillage, while the other two plots were managed using a form of reduced tillage. Approximately 70% and 20-30% of the total respiration flux originated from the maize C₄-CRC during the fall of 2006 and spring of 2007, respectively. At least 25% of the maize residue was lost to respiration during this non-growing period. No difference in the partitioning of heterotrophic respiration into that derived from CRC and SOC was detected between the intensive tillage and recently established reduced tillage treatments at the site.     

国内外绿豆农药最大残留限量标准对比研究

为了研究农药最大残留限量标准对中国绿豆对外贸易的影响,以中国、国际食品法典委员会(CAC)、欧盟、日本、美国、韩国和加拿大等国家绿豆农药最大残留限量标准为基础,从限量标准数量、限量大小和占比、限量宽松度等方面对比分析中国与贸易国之间的差异.结果发现,中国绿豆农药最大残留限量标准少,共83项,与日本的388项、欧盟的56...