Mars north polar deposits: stratigraphy, age, and geodynamical response

The Shallow Radar (SHARAD) on the Mars Reconnaissance Orbiter has imaged the internal stratigraphy of the north polar layered deposits of Mars. Radar reflections within the deposits reveal a laterally continuous deposition of layers, which typically consist of four packets of finely spaced reflectors separated by homogeneous interpacket regions of nearly pure ice. The packet/interpacket structure can be explained by approximately million-year periodicities in Mars' obliquity or orbital eccentricity. The observed approximately 100-meter maximum deflection of the underlying substrate in response to the ice load implies that the present-day thickness of an equilibrium elastic lithosphere is greater than 300 kilometers. Alternatively, the response to the load may be in a transient state controlled by mantle viscosity. Both scenarios probably require that Mars has a subchondritic abundance of heat-producing elements.     

Pesticides to control ostracods grazing on blue-green algae

Means to control ostracods grazing on blue-green algae (cyanobacteria) important in fixing nitrogen in flooded rice soils were studied. The relative acute lethal toxicity (LC₅₀⁴⁸) to the ostracods Cyprinotus carolinensis and Heterocypris luzonensis grazing on Tolypothrix tenuis was 0.4 and 2.4 μg ml^?1 for carbofuran and 4.5 and more than 56.0 μ g ml^?1 for lindane. Complete inhibition of grazing was achieved with 1.0 and 25 μ g carbofuran ml^?1 and 0.1 and 5.6μ g lindane ml^?1 for C. carolinensis and H. luzonensis, respectively. Lindane at concentrations below 0.02 μ g ml^?1 stimulated feeding by C. carolinensis on the alga. Breakdown of carbofuran markedly reduced its effectiveness as a measure to control grazing, but lindane did not rapidly lose its effectiveness. The toxicity of carbofuran to C. carolinensis feeding on T. tenuis was not affected by pH. The difference in ostracod responses to the pesticides, which may be associated with resistance acquired through previous exposure, is an important consideration in designing practical means to reduce grazing in paddy fields.     

The effect of organic and chemical fertilizers on oilseed rape productivity and weed competition in short rotation

Abstract

A two-year field experiment was conducted to investigate the impact of short crop rotation and organic amendments on rapeseed yield under weed competition conditions. The primary experimental plots consisted of either triticale or pea as a prior crop, consisting of four subplots with either 25 tons of composted cattle manure (CCM), 150?kg urea N ha^?1 (N), 25 tons composted cattle manure + 75?kg urea N ha^?1 (CCM?+?N), or no urea N or manure added as the control (C0). Rapeseed seed yield was not significantly affected by previous crops, except for rapeseed grown after pea which had slightly higher seed yield (2058?kg ha^?1) than those grown after triticale (1942?kg ha^?1). Plants that received CCM?+?N produced the highest amount of seed yield (2447?kg ha^?1), but were not significantly different from plants that received just urea N (2218?kg ha^?1). Weeds gained more biomass when the previous crop was pea compared to those whose previous crop was triticale. Weeds in plots that received CCM?+?N produced the greatest biomass, followed by N, and CCM plots, respectively.     

Detection and quantification ofSpongospora subterranea f. sp.subterranea by PCR in host tissue and naturally infested soils

A polymerase chain reaction (PCR) assay using primers SsF and SsR designed from the internal transcribed spacer (ITS) regions ofSpongospora subterranea f. sp.subterranea was developed for the specific identification and quantification ofS. subterranea. These primers amplified a 434 bp product from DNA ofS. subterranea spore balls, but not from DNA of healthy potato, common scab tuber, and taxonomically related plasmodiophorids. This PCR assay was successfully used for the detection ofS. subterranea in naturally infected symptomatic and asymptomatic potato tubers.Spongospora subterranea in other infected symptomless host plants was detected by PCR. The PCR assay was modified with improved soil DNA extraction methods to detectS. subterranea in soil. The assay was sensitive, and one spore ball per gram of soil could be detected. Following the design of a heterologous competitor DNA template from the sequence of λDNA, a competitive PCR assay for the quantification ofS. subterranea in soil was developed and provided accurate quantification in the range of 1 to 10⁴ spore balls per 0.25 g of soil. In a preliminary survey of naturally infested field soil samples, spore ball concentrations were estimated to vary from ca 0 to 3600 spore balls per 0.25-g soil sample by this competitive PCR assay. The spore ball levels were compared with the powdery scab disease incidence of potatoes in these fields, and a correlationship between spore ball levels and subsequent disease incidence was found. The PCR assays developed in this investigation can be routinely used to detect and quantifyS. subterranea in diseased plant tissue, asymptomatic plant tissue, and infested soil.     

Blood,plasma, and serum inorganic and organic reference values for two-year old Irish Thoroughbreds during the racing season

The concentration of 13 inorganic and organic components in the blood, plasma, and serum of 51 two-year old Irish Thoroughbreds were measured on seven occasions over a ten-month period including the racing season. Reference values were established for calcium, magnesium, inorganic phosphorus, potassium, copper, iron, zinc, total protein, albumin, globulin, urea, glucose, and alkaline phosphatase. The components measured were those usually considered to be useful aids in clinical diagnosis. No significant differences were established between the best and worst eight track performers with the exception of inorganic phosphorus which in the best eight was significantly lower (P<0.01).     

Comparison of the microtitration agglutination test and the enzyme-linked immunosorbent assay for the detection of herds affected with swine dysentery

A method was designed to evaluate and compare the microtitration agglutination test (MAT) and the enzyme-linked immunosorbent assay (ELISA) to detect antibodies in swine sera to Treponema hyodysenteriae and thereby establish a method for determining the prevalence of swine dysentery (SD) in herds. According to sampling criteria based on the hypergeometric distribution, sera were collected from 3 age groups of swine from farms having a history of SD on the premises (SD+) recently or being free of the disease (SD-). The highest degree of test sensitivity was obtained when sera from market age swine were evaluated with the ELISA. Of 14 SD+ herds from which sera were obtained from market-age swine, 13 were positive with the ELISA (93%); none of the 8 SD- herds was positive. The detection rates of individual swine in the SD+ herds for the 2 tests by age group were as follows: MAT--adult swine 1.4%, market-age swine 6%, and weaned pigs 0.8%; ELISA--adult swine 16%, market swine 31%, and weaned pigs 0.5%.     

An investigation into human pandemic influenza virus (H1N1) 2009 on an Alberta swine farm

On May 2, 2009 the Canadian Food Inspection Agency notified the World Organization for Animal Health that an emerging novel influenza A virus (pandemic H1N1 2009) had been confirmed on a swine farm in Alberta. Over a 4-week period pigs in this farrow-to-finish operation were clinically affected by respiratory disease consistent with an influenza A virus infection and the presence of active viral infection was confirmed in all production areas by real-time polymerase chain reaction (RT-PCR). Despite clinical recovery of animals, there was reluctance by purchasers to receive animals from this operation due to concerns about the effect on both domestic and international markets. The owner decided to depopulate the entire herd due to impending welfare issues associated with overcrowding and economic concerns resulting from the inability to market these animals. Carcasses were rendered or composted and did not enter the human food or animal feed chain. The source of virus in this herd was determined to be an infected human. Zoonotic transmission to 2 individuals responding to the outbreak was suspected and recommendations to prevent occupational exposure are discussed.     

Effect of different salts of sodium and potassium on the growth of Atriplex prostrata (Chenopodiaceae)

Although there are a variety of ions occurring in the soil throughout most of North America, the majority of halophyte literature focuses on the effects of NaCl on plants. In this study, a comparison is made of the effects of NaCl, KC1, Na₂SO₄, and K₂SO₄, on growth of the halophyte Atriplex prostrata Boucher ex DC (SYN: A. triangularis Willd.) at 0, ‐0.75, ‐1.00, and ‐1.50 MPa. Plant survival, height, number of leaves, nodes, and branches were recorded weekly. Photosynthesis was measured once before plants were harvested and dry mass was determined after one month. Content of Na⁺, K⁺,‐Mg²⁺, and Cl^‐ in plant tissue was also measured. A general trend observed was that all plant growth parameters decreased with a lowering of the medium osmotic potential, and that K⁺ salts were more inhibitory than Na⁺ salts. Ion content of plant tissue generally increased with a lowering of osmotic potential. Our data indicated that K⁺, a plant macronutrient, was more inhibitory to plant growth than Na⁺. It is possible that halophytes such as Atriplex prostrata could use Na⁺ as an osmoticum to adjust the vacuolar water potential, but were unable to use K⁺ for this function because of a specific ion toxicity. The inhibitory effect of salt on plant growth parameters and survival follow the pattern; K₂SO₄ >KCl>Na₂SO₄=NaCl.     

Corn nitrogen management using NDVI and SPAD sensor-based data under conventional vs. reduced tillage systems

Present analyses to calculate nitrogen fertilizer recommendations are time consuming and costly. Therefore, a field study determining the efficiency of SPAD and NDVI meters to calculate soil N deficiency and guide fertilizer application timing and rate was completed. Reduced vs. conventional tillage at various N application rates was studied. Regardless of tillage system, both NDVI and SPAD were able to detect N deficiency at early growth stages, however, SPAD measurements better reflected plant N status regarding N application rates. A modified Michaelis-Menten model was used to illustrate the relationship between N rates and grain yield, as well as grain N content and leaf N content, and both showed acceptable goodness of fit. Grain yield under reduced tillage was significantly higher than that of conventional tillage. The combination of leaf nitrogen, SPAD, and NDVI data may become a tool to manage corn field nitrogen status and predict grain yield.