Estimates of Potentially Mineralizable Soil Nitrogen Based on Short-term Incubations

Nitrogen mineralization potentials were determined for a large number of soils by a method involving determination of N mineralized after several consecutive incubations at 35C under optimum soil water conditions. The determination of N mineralization potential, No, based on the first-order equation, log (No — Nt) = log No — kt/2.303, is laborious and usually requires incubation periods of 8 weeks or more. From the present study, involving soils from major agricultural areas throughout the United States, it was demonstrated that No could be estimated reliably from the amounts of N mineralized during 2-week incubations following preliminary incubations of 1 to 2 weeks. From the above first-order equation, No = Nt / (1-10–kt/2.303). Hence, for a 2-week incubation (t = 2), No = 9.77Nt (Nt = N mineralized in 2 weeks and k is the rate constant, weeks-1). Estimates of No from short-term incubations were similar to those derived after extensive periods of incubation. Preincubation of soils is required in order to decompose plant residues and for other possible reasons noted. Estimates of No from preliminary incubations are meaningless. The implications of No as a basis for predicting amounts of soil N mineralized under fluctuating temperature and soil water conditions are discussed

Residual Nitrate and Mineralizable Soil Nitrogen in Relation to Nitrogen Uptake by Irrigated Sugarbeets

Previously reported studies on N fertilization of sugarbeets (Beta vulgaris L.) in southern Idaho revealed considerable variation among sites in amounts of residual soil NO? and N mineralized during short-term laboratory incubations. Consequently, the amount of N fertilizer needed to achieve near-maximum yields of sucrose differed markedly. The purpose of this study was to determine the feasibility of estimating amounts of N mineralized in the root zone during the season, taking into account site variations in temperature and soil water regimes. Residual soil NO?--N and mineralizable N to approximate rooting depth were estimated for 21 field sites in 1971 and six sites in 1972. The relative contributions of these two N sources to total N uptake by the crop, in the absence of applied fertilizer N, were then assessed. Estimates of N mineralized in the upper 45- cm soil layer for each successive month, ?N, over a 6- month period were derived using the expression, ?N/ ?t kWN (k = fraction of N mineralized during each month, ?t, adjusted for average air temperature; and W the estimated soil water content expressed as a fraction of the available water storage capacity). Resulting estimates of the fraction of potentially mineralizable N converted to (NO?- + NH?+)-N between 1 April and 30 September ranged from 0.15 to 0.22 (mean ± S.D. = 0.18 ± 0.02) in 1971 and 1972. On the average, mature sugarbeets recovered about 73% of the estimated N mineralized (6 months) plus residual NO?--N. The relative contributions of these two sources of soil derived N, respectively, were approximately 66 and 75%, as estimated from multiple regression analyses

Residual Nitrate and Mineralizable Soil Nitrogen in Relation to Nitrogen Uptake by Irrigated Sugarbeets

Previously reported studies on N fertilization of sugarbeets (Beta vulgaris L.) in southern Idaho revealed considerable variation among sites in amounts of residual soil NO? and N mineralized during short-term laboratory incubations. Consequently, the amount of N fertilizer needed to achieve near-maximum yields of sucrose differed markedly. The purpose of this study was to determine the feasibility of estimating amounts of N mineralized in the root zone during the season, taking into account site variations in temperature and soil water regimes. Residual soil NO?--N and mineralizable N to approximate rooting depth were estimated for 21 field sites in 1971 and six sites in 1972. The relative contributions of these two N sources to total N uptake by the crop, in the absence of applied fertilizer N, were then assessed. Estimates of N mineralized in the upper 45- cm soil layer for each successive month, ?N, over a 6- month period were derived using the expression, ?N/ ?t kWN (k = fraction of N mineralized during each month, ?t, adjusted for average air temperature; and W the estimated soil water content expressed as a fraction of the available water storage capacity). Resulting estimates of the fraction of potentially mineralizable N converted to (NO?- + NH?+)-N between 1 April and 30 September ranged from 0.15 to 0.22 (mean ± S.D. = 0.18 ± 0.02) in 1971 and 1972. On the average, mature sugarbeets recovered about 73% of the estimated N mineralized (6 months) plus residual NO?--N. The relative contributions of these two sources of soil derived N, respectively, were approximately 66 and 75%, as estimated from multiple regression analyses

Rapid assembly and rejuvenation of a large silicic magmatic system : insights from mineral diffusive profiles in the Kidnappers and Rocky Hill deposits, New Zealand.

The timescales over which magmas in large silicic systems are reactivated, assembled and stored remains a fundamental question in volcanology. To address this question, we study timescales from Fe–Mg interdiffusion in orthopyroxenes and Ti diffusion in quartz from the caldera-forming 1200 km3 Kidnappers and 200 km3 Rocky Hill eruptions from the Mangakino volcanic centre (Taupo Volcanic Zone, New Zealand). The two eruptions came from the same source area, have indistinguishable 40Ar/39Ar ages (∼1.0 Ma) and zircon U–Pb age spectra, but their respective deposits are separated by a short period of erosion. Compositions of pumice, glass and mineral species in the collective eruption deposits define multiple melt dominant bodies but indicate that these shared a common magmatic mush zone. Diffusion timescales from both eruptions are used to build on chemical and textural crystal signatures and interpret both the crystal growth histories and the timing of magma accumulation. Fe–Mg interdiffusion profiles in orthopyroxenes imply that the three melt-dominant bodies, established through extraction of melt and crystals from the common source, were generated within 600 years and with peak accumulation rates within 100 years of each eruption. In addition, a less-evolved melt interacted with the Kidnappers magma, beginning ∼30 years prior to and peaking within 3 years of the eruption. This interaction did not directly trigger the eruption, but may have primed the magmatic system. Orthopyroxene crystals with the same zoning patterns from the Kidnappers and Rocky Hill pumices yield consistently different diffusion timescales, suggesting a time break between the eruptions of ∼20 years (from core–rim zones) to ∼10 years (outer rim zones). Diffusion of Ti in quartz reveals similarly short timescales and magmatic residence times of <30 years, suggesting quartz is only recording the last period of crystallization within the final eruptible melt. Accumulation of the eruptible magma for these two, closely successive eruptions was accomplished over centuries to decades, in contrast to the gestation time of the magmatic system of ∼200 kyr, as indicated by zircon age patterns. The magmatic system was able to recover after the Kidnappers eruption in only ∼10–20 years to accumulate enough eruptible melt and crystals for a second ∼200 km3 eruption. Our data support concepts of large silicic systems being stored as long-lived crystal mushes, with eruptible melts generated over extraordinarily short timescales prior to eruption

Nitrate Determination by a Modified Conway Microdiffusion Method

The proposed modified Conway microdiffusion method provides for consecutive determinations of NH?- and NO?-N in a given aliquot of soil extract. Analyses of primary nitrate standards showed essentially complete recovery in the range of 1 to 20 ppm NO?-N (4 to 80 µg N/aliquot). Results for (NH? + NO?)-N and NO?-N in soil extracts are comparable to those obtained, respectively, by macrodistillation with Devarda's alloy and by the phenoldisulfonic acid colorimetric method. The method is rapid and suitable for routine analyses of soil extracts, the equipment is inexpensive, and no interferences are apparent

Measuring Atmospheric Neutrino Oscillations with Neutrino Telescopes

Neutrino telescopes with large detection volumes can demonstrate that the current indications of neutrino oscillation are correct or if a better description can be achieved with non-standard alternatives. Observations of contained muons produced by atmospheric neutrinos can better constrain the allowed region for oscillations or determine the relevant parameters of non-standard models. We analyze the possibility of neutrino telescopes measuring atmospheric neutrino oscillations. We suggest adjustments to improve this potential. An addition of four densely-instrumented strings to the AMANDA II detector makes observations feasible. Such a configuration is competitive with current and proposed experiments.Comment: 36 pages, 21 figures, revte

A CRISPR/Cas9-based genome-editing system for yam (Dioscorea spp.)

Open Access Journal; Published online: 22 Nov 202

Untangling the complexities of processing and analysis for untargeted LC-MS data using open-source tools

Untargeted metabolomics is a powerful tool for measuring and understanding complex biological chemistries. However, employment, bioinformatics and downstream analysis of mass spectrometry (MS) data can be daunting for inexperienced users. Numerous open-source and free-to-use data processing and analysis tools exist for various untargeted MS approaches, including liquid chromatography (LC), but choosing the ‘correct’ pipeline isn’t straight-forward. This tutorial, in conjunction with a user-friendly online guide presents a workflow for connecting these tools to process, analyse and annotate various untargeted MS datasets. The workflow is intended to guide exploratory analysis in order to inform decision-making regarding costly and time-consuming downstream targeted MS approaches. We provide practical advice concerning experimental design, organisation of data and downstream analysis, and offer details on sharing and storing valuable MS data for posterity. The workflow is editable and modular, allowing flexibility for updated/changing methodologies and increased clarity and detail as user participation becomes more common. Hence, the authors welcome contributions and improvements to the workflow via the online repository. We believe that this workflow will streamline and condense complex mass-spectrometry approaches into easier, more manageable, analyses thereby generating opportunities for researchers previously discouraged by inaccessible and overly complicated software

Observation of hard scattering in photoproduction events with a large rapidity gap at HERA

Events with a large rapidity gap and total transverse energy greater than 5 GeV have been observed in quasi-real photoproduction at HERA with the ZEUS detector. The distribution of these events as a function of the $\gamma p$ centre of mass energy is consistent with diffractive scattering. For total transverse energies above 12 GeV, the hadronic final states show predominantly a two-jet structure with each jet having a transverse energy greater than 4 GeV. For the two-jet events, little energy flow is found outside the jets. This observation is consistent with the hard scattering of a quasi-real photon with a colourless object in the proton.Comment: 19 pages, latex, 4 figures appended as uuencoded fil