Pulp Fiber Residue and Supplemental Irrigation on Yield and Nutrient Uptake of Potato

ABSTRACT

Organic matter levels combined with drought periods during the growing season have adverse impacts on rain-fed potato production in coarse textured soils of eastern Canada. Using pulp fiber residues (PFR) may build up soil organic matter, improve crops yield and nutrient uptake, and reduce the need for supplemental irrigation in this region. A box experiment with 3 rates of PFR [0, 45, and 90 Mg ha^{? 1} dry mater carbon (C) basis] with or without supplementary drip irrigation was established in a sandy loam soil in New Brunswick, Canada. Red clover, barley, and potato were cultivated as three crops of the rotation in 1999, 2000, and 2001, respectively. The PFR only applied before red clover in fall 1998. Selected soil chemical and physical properties were measured before planting and after harvest. Crops yield and nitrogen (N), phosphorus (P), and potassium (K) accumulation were determined at harvest. Soil organic-C content, bulk density and water holding capacity were improved by PFR application. Red clover and barley biomass production were significantly increased by PFR application. This effect was promoted by supplemental irrigation. Potato tuber yield was not affected by PFR and it was higher in rain-fed compared to supplementary irrigated system. Although, there was some initial evidence of N immobilization but generally PFR application increased N, P, and K bioavailability. This research has demonstrated that PFR can successfully be used as soil amendment in coarse textured soils without any adverse effect.     

Characterization of intracellular and extracellular saxitoxin levels in both field and cultured Alexandrium spp. samples from Sequim Bay, Washington

Traditionally, harmful algal bloom studies have primarily focused on quantifying toxin levels contained within the phytoplankton cells of interest. In the case of paralytic shellfish poisoning toxins (PSTs), intracellular toxin levels and the effects of dietary consumption of toxic cells by planktivores have been well documented. However, little information is available regarding the levels of extracellular PSTs that may leak or be released into seawater from toxic cells during blooms. In order to fully evaluate the risks of harmful algal bloom toxins in the marine food web, it is necessary to understand all potential routes of exposure. In the present study, extracellular and intracellular PST levels were measured in field seawater samples (collected weekly from June to October 2004–2007) and in Alexandrium spp. culture samples isolated from Sequim Bay, Washington. Measurable levels of intra- and extra-cellular toxins were detected in both field and culture samples via receptor binding assay (RBA) and an enzyme-linked immunosorbent assay (ELISA). Characterization of the PST toxin profile in the Sequim Bay isolates by pre-column oxidation and HPLC-fluorescence detection revealed that gonyautoxin 1 and 4 made up 65 ± 9.7 % of the total PSTs present. Collectively, these data confirm that extracellular PSTs are present during blooms of Alexandrium spp. in the Sequim Bay region.     

科学理解农药最大残留限量的概念

农药在作物及食品生产中的有益作用已为世界所公认,但是食品中残留微量农药是否对人体健康有危害仍是目前人们关注的焦点。允许的农药残留不应该对人体健康产生影响,因为任何农药在可以使用前必须经过一个包括科学的风险评估在内的农药登记管理程序的评审。最大残留限量（MRLs）是指在优良农业措施（GAP）下使用某农药可能产生的在食物中的最高残留浓度（单位为mg/kg, 指每公斤商品中残留农药的毫克数）,其数值必须是毒理学上可以接受的。MRLs的主要作用是来检验食品生产过程是否严格执行GAP,以及帮助经农药处理的农产品在国际贸易中正常进行进出口活动。MRLs不是一个绝对的安全限量,即接触残留超标的食品并不一定肯定意味着对健康有危害。但是MRLs也经常作为食品安全管理的第一道防线,成为保障人类健康最初级的预警机制。MRLs是各国政府和联合国食品法典委员会设定的,这些设定的标准被应用于国际贸易中。     

Cumulative racing-speed exercise distance cluster as a risk factor for fatal musculoskeletal injury in Thoroughbred racehorses in California

Thoroughbred racehorses which suffered a fatal musculoskeletal injury (FMI) while racing or race training at a California racetrack during 9 months of 1991 were studied to determine the importance of intensive, high-speed exercise schedules prior to injury. Seventy-seven horses which sustained an FMI while racing and 45 horses which sustained an FMI while race training were successfully matched by race or timed workout session with one control horse and included in the analyses. Race and timed workout (racing-speed exercise) histories were obtained for the case and control horses. Two-month cumulative, racing-speed cutoff distances were calculated from the control horse sample by two methods. Median racing-speed exercise frequencies and distances of the control horses were used to estimate age-specific (2, 3, 4 and ≥ 5 years), 2-month cumulative, racing-speed distances (Method 1). For the second method, the last race or timed workout for each control horse occurring just prior to, or on the date of injury for the matched case horse was identified. Cumulative racing-speed distances 2 months prior to these exercise events were determined for each control horse and used to estimate median age-specific (2, 3, 4 and ≥ 5 years), 2-month cumulative racing-speed distances (Method 2). The cumulative cutoff distances estimated from both methods were used to classify each matched pair according to the presence or absence of a 2-month cumulative, racing-speed distance which exceeded the age-appropriate cutoff distance (exercise distance cluster) within 6 months prior to injury. Manlel-Haenszel matched-pair odds ratios and 95% confidence limits were calculated separately for the racing and race-training fatal injuries. The relative risk for racing FMI was significantly greater for those horses which ran 2-month, cumulative racing and timed workout distances in excess of the cutoff values determined with Method 1 (relative risk (RR) = 3.0, 95% confidence interval (CI) = 1.2, 7.6) and Method 2 (RR = 7.2, 95% CI = 2.6, 20.6). The relative risk for race-training FMI was significantly greater for those horses which ran 2-month, cumulative racing and timed workout distances in excess of the cutoff values determined with Method 2 (RR = 3.4, 95% CI =1.0, 13.2).