Soil Factors and their Influence on Within-field Crop Variability, Part I: Field Observation of Soil Variation

A fundamental component of adopting the concept of precision farming in practice is the ability to measure spatial variation in soil factors and assess the influence of this on crop variability in order to apply appropriate management strategies. The aim of this study was to appraise potential methods for measuring spatial variability in soil type, nutrient status and physical properties in practical farming situations. Five fields that are representative of more than 30% of soils used for arable production in England and Wales were selected for use as case studies. Maps of soil type were generated from a conventional hand-auger survey on a 100 m grid and the excavation of targeted soil profile pits. These were compared with those refined using a mechanised soil coring device and scans of electromagnetic inductance (EMI) carried out while the soil could reasonably be considered to be at, or near, field-capacity moisture content. In addition, soil sampling for nutrient analyses was conducted on a 50 m grid to examine the spatial variation in nutrient status. Conventional methods for sampling soil were found to be appropriate for identifying soil types at specific locations within the field sites, however, they were time-consuming to perform which placed an economic and therefore a practical limitation on the sampling density possible. The resulting data were considered to be too sparse for demarcating soil-type boundaries for use in the context of precision farming. The location of soil boundaries were refined by using the mechanised soil corer, however, the limitation of this was found to be the time required to analyse the soil cores produced. Maps of soil variation generated from EMI scans conducted at field capacity appear to reflect the underlying variation in soil type observed in maps generated using the mechanised soil corer and, therefore, this approach has potential as a cost-effective, data-rich, surrogate for measures of soil variability. Results from analyses of soil samples for measurement of nutrient status indicated that whilst there was considerable variation in macro- and micro-nutrient levels in each field, with the exception of pH, these levels were above commonly accepted agronomic limits. Results, however, did demonstrate the potential for addressing variation in critical factors such as pH at specific locations, however, there is a need to develop protocols for targeting sampling in order to reduce costs.     

Endangered species managing endangered species: Polyculture of piscivorous Colorado Pikeminnow (Ptychocheilus lucius) with production Bonytail (Gila elegans) to control recruitment and increase growth rates

The decline and endangerment of native fish has led to an increase in hatcheries that sustain and augment threatened and endangered species. In an effort to restore self‐sustaining populations, hatchery‐reared Bonytail (Gila elegans) are released into the lower Colorado River annually. Current augmentation protocols for Bonytail require a minimum stocking size of 300 mm total length due to greater apparent survival of larger individuals. The fish culture process of reaching this desired target size requires multiple years of growth, during which precocious individuals regularly spawn. Recruitment in production ponds increases densities, potentially reducing growth rates and adversely affecting culture conditions. Polyculture techniques have been shown to have synergistic effects and under proper conditions effectively control unwanted biota. In an effort to address the management implications of Bonytail recruitment on adult growth and survival, we tested the use of a historically co‐occurring piscivore, Colorado Pikeminnow (Ptychocheilus lucius), as a biological control agent. Colorado Pikeminnow effectively controlled Bonytail recruitment and had a positive effect on adult growth rates. Our results suggest polyculture of these two species can aid management actions by increasing augmentation efforts.     

Predatory dinosaur remains from madagascar: implications for the cretaceous biogeography of gondwana

Recent discoveries of fossil vertebrates from the Late Cretaceous of Madagascar include several specimens of a large theropod dinosaur. One specimen includes a nearly complete and exquisitely preserved skull with thickened pneumatic nasals, a median frontal horn, and a dorsal projection on the parietals. The new materials are assigned to the enigmatic theropod group Abelisauridae on the basis of a number of unique features. Fossil remains attributable to abelisaurids are restricted to three Gondwanan landmasses: South America, Madagascar, and the Indian subcontinent. This distribution is consistent with a revised paleogeographic reconstruction that posits prolonged links between these landmasses (via Antarctica), perhaps until late in the Late Cretaceous.     

Granular convection observed by magnetic resonance imaging

Vibrations in a granular material can spontaneously produce convection rolls reminiscent of those seen in fluids. Magnetic resonance imaging provides a sensitive and noninvasive probe for the detection of these convection currents, which have otherwise been difficult to observe. A magnetic resonance imaging study of convection in a column of poppy seeds yielded data about the detailed shape of the convection rolls and the depth dependence of the convection velocity. The velocity was found to decrease exponentially with depth; a simple model for this behavior is presented here.     

Sampling fish assemblages in forested floodplain wetlands

Abstract– Four quantitative (area-standardized electrofishing, trap nets, small-mesh [1.3 and 2-cm bar mesh] gill nets, large-mesh [2.5 and 5-cm bar mesh] gill nets) and two qualitative (non-standardized electrofishing, dip netting) sampling techniques were concurrently used to capture larval to adult fish in forested wetland habitats on seasonally inundated floodplains of two Alabama (USA) streams. Standardized area electrofishing appeared to be the best sampling technique for collecting and quantifying species because of high catch rate, broad species and size coverage, and rapid sampling. Electrofishing accounted for most fish (47 and 57% of pooled catch), almost all taxa, and a broad range of fish sizes. Large-mesh gill nets captured few fish (2% and 8%), a distinct subset of the species present, and the largest fish. Light traps were the most efficient and taxa-comprehensive sampling technique for larval fish. Light traps captured the vast majority of the pooled larval fish catch, including 6 of 7 families recorded at the sites. Larval fish dip netting captured larval fish of most families known to be present but in low numbers. For surveys of species composition and rapid bioassessments, nonstandardized electrofishing and larval fish dip netting appear adequate. For intensive research studies, the combination of area electrofishing, large-mesh (and in some cases small-mesh) gill nets, and light traps provide thorough and comprehensive data on wetland fish assemblages.     

Effects of pregnenolone, cyclic adenosine monophosphate, and human chorionic gonadotropin on in vitro progesterone and estrone synthesis by the porcine placenta and endometrium.

Two experiments were conducted to determine the effects of pregnenolone (P5), cyclic adenosine monophosphate (cAMP), and human chorionic gonadotropin (hCG) on porcine placental and endometrial production of progesterone (P4) and estrone (E1) in vitro at days 30, 60 and 90 of gestation. Placental P4 production increased between days 30 and 90 and was enhanced by the addition of P5. A further increase in placental P4 production occurred at days 30 and 90 due to cAMP supplementation. Addition of hCG failed to increase placental P4 production at any day. Placental E1 production in vitro was biphasic and mimicked the pattern seen in maternal plasma and fetal fluids. Placental E1 production in P5-supplemented medium was enhanced by the addition of cAMP at day 90. However, hCG supplementation reduced placental E1 production at day 90. Endometrial P4 and E1 production were similar to those of the placenta at day 30 of gestation. However, unlike placental steroidogenesis, endometrial hormone production remained relatively constant over the 3 days of gestation examined. Supplemental P5 enhanced endometrial P4 and E1 production. The overall magnitude of response to supplementation was considerably less in endometrial vs placental tissue. We conclude that both porcine placental and endometrial tissues are steroidogenically competent but that placenta is the far more active and responsive tissue. The mechanism controlling placental steroidogenesis apparently does not involve LH/hCG tropic stimulation, but cAMP is an effective intracellular second messenger.     

In vitro release of progesterone and estrone by the porcine placenta throughout gestation

In vitro release of progesterone (P₄) and estrone (E₁) by the porcine placenta was characterized at 12 days of gestation between d 20 and 110. Placental P₄ rose linearly from d 25 to 40, plateaued between d 40 and 50, continued to increase to a peak concentration at d 100, then decreased sharply to d 110. Placental E₁ decreased abruptly from d 30 to a nadir at d 40, then increased continuously from d 70 to peak values at d 110. This biphasic pattern for E₁ mimicked the pattern observed in allantoic fluid and maternal plasma pools. Only trace amounts of testosterone (T) were measured at d 20, 50, 60, and 100, suggesting rapid aromatization of C₁₉ steroids to estrogens. The results of this in vitro study indicate that the porcine placenta collected throughout gestation can release large quantities of P₄, although the lack of an increase in systemic P₄ suggests that under in vivo conditions P₄ is utilized and/or metabolized within the uterus.     

Colostral and serum IgG, IgA, and IgM concentrations in Standardbred mares and their foals at parturition

Immunoglobulin G, IgM, and IgA concentrations were measured in serum collected from 36 Standardbred mares within 12 hours of foaling, in colostrum collected within 6 hours of foaling, and in serum collected from foals 24 to 48 hours after birth. In serum collected from mares after parturition, mean concentrations of IgG, IgM, and IgA were 2,463.9 +/- 1,337.3 mg/dl, 136.4 +/- 218 mg/dl, and 305.2 +/- 237.5 mg/dl, respectively. In serum from foals, mean concentrations of IgG, IgM, and IgA were 1,953.3 +/- 1,635 mg/dl, 33.8 +/- 30.4 mg/dl, and 58.4 +/- 42.2 mg/dl, respectively. In colostrum, mean concentrations of IgG, IgM, and IgA were 8,911.9 +/- 6,282.2 mg/dl, 957 +/- 1088.1 mg/dl, and 122.9 +/- 77.3 mg/dl, respectively. The IgG concentrations in foal serum were poorly correlated with IgG concentrations in colostrum (r = 0.462, P less than 0.01). Correlations of IgM or IgA concentrations in serum from foals with IgM or IgA concentrations in colostrum and correlations of IgG concentrations in serum from mares with those in colostrum were not significant (P less than 0.01). Of 36 foals, 1 (2.8%) had a serum IgG concentration less than 400 mg/dl. Of 36 foals monitored for 4 months, 6 developed infectious respiratory tract disease requiring antimicrobial therapy at ages varying from 55 to 113 days; these infections were probably not related to failure or partial failure of passive transfer of antibody.     

Efficacy of albendazole for prevention of fascioliasis in sheep

Daily doses of albendazole administered as a premix in the feed for 35 days were effective in preventing Fasciola hepatica infections in 17 sheep in three groups: 5 mg/kg/day (6 sheep) was 100% effective; 3 mg/kg/day (5 sheep) was 98% effective; and 1 mg/kg/day (6 sheep) was 42% effective. Infective cysts were given daily for 5 days during the first week of treatment, treatment was continued an additional 28 days, and sheep were necropsied 14 weeks after final cyst inoculation. There were no visible lesions in any livers of sheep given albendazole at the rate of 5 mg/kg/day or in three of five livers of sheep dosed at the rate of 3 mg/kg/day. Sheep treated with albendazole had a mean weight gain of 2.7 kg, 4.0 kg, and 4.0 kg greater than the controls for the dosages of 1, 3, and 5 mg/kg/day, respectively. Determination of bile duct damage by measurement of serum gamma-glutamyl transpeptidase activity at 9 weeks after final cyst inoculation revealed increases of 3.0X, 1.0X, and 1.1X for the dosages of 1, 3, and 5 mg/kg/day, respectively, and 2.3X for the control, as compared with 7 weeks after final cyst inoculation.