Toward sustainable nitrogen management in vegetable production: balancing yield and nitrogen use efficiency

Non-Peer ReviewedCover crops (CC) have the potential to immobilize nutrients, especially nitrogen (N), that would otherwise be lost during post- or pre-harvest periods, leading to improved N management. However, information on how CCs influence N management for vegetable production are scarce. This study aims to determine agronomic responses (yield and N use efficiency, NUE) of three common prairie vegetable crops when produced with and without an overwintering rye CC. In 2017 and repeated in 2018, trials were initiated on a Sutherland clay soil (Dark Brown Chernozem) in Saskatoon for a fully phased broccoli-sweet corn-carrot sequence, with each crop type receiving five N fertilizer treatments (ranging from 0 to 300 kg N ha-1) arranged in a randomized complete block design with three replicates. After harvest, sub-plots were established with vs without a shoulder-season rye CC, and the effect followed into the subsequent growing season. Compared with zero N control, N fertilizer rate did not affect vegetable crop yields in either year, demonstrating the N-rich nature of the soil at this site. Depending on the crop, moderate to high application rates of N significantly reduced crop NUE; N rates above zero N control reduced NUE for sweet corn, rates above 75 kg N ha-1 reduced NUE for broccoli, all rates above 55 kg N ha-1 reduced NUE for the root crop in 2018. Subsequent to the CC in 2018, we found no N fertilizer by CC interaction for crop yields or NUE. The rye CC had no effect on crop yield or NUE for sweet corn or carrot, but significantly reduced broccoli yield and NUE. Regression analysis showed a decreasing trend in NUE with increasing N rates for all three vegetables, regardless of the CC. Our results suggest that the repetition of this experiment for a number of years is necessary to avoid excessive N application and improvement of productivity with cover crops

Developing a soil health assessment protocol for Saskatchewan producers

Non-Peer ReviewedMaintaining and building soil health is an essential component of long-term sustainable agriculture. Soil health can be defined as the capacity of a soil to function, which reflects sustained biological productivity, environmental quality, and plant health. Farmers need appropriate tools or methods for assessing and interpreting the soil health status of their soils, however, there is no standardized and prairie-based soil health test available. Thus, research is needed to address this gap. We currently have a project underway to assess soil health across Saskatchewan, which will contribute to developing a Saskatchewan Soil Health Assessment Protocol (SSHAP). Soil samples from the 0-15, 15-30, and 30-60 cm depth were collected from 56 fields across 26 sites in Sept and Oct 2018. The selected sites represented various Agri-Arm sites, producer fields, and AAFC long-term sites. The selected sites were representative of Saskatchewan agriculture as most sites were previously cropped with wheat or canola; other sites had barley, chickpea, lentil, field pea, soybean, potato, and green manure. Native prairie samples were also collected. Soil samples were air dried and sieved (2mm) prior to analyses. Lab-work in currently underway to characterize soil health attributes, such as wet aggregate stability, active carbon, texture, pH, EC, organic matter, nutrient composition, mineralizable nitrogen, etc. The dataset will enable descriptive statistics for each soil health attribute, form which soil health scoring functions will be explored (similar to the Cornell Soil Health Assessment, but based on Saskatchewan soils). Maintaining soil health is an essential constituent of sustainable agriculture and having an appropriate and standardized method for quantifying and interpreting soil health status a logical first-step

Vacuum polarization in the spacetime of charged nonlinear black hole

Building on general formulas obtained from the approximate renormalized effective action, the approximate stress-energy tensor of the quantized massive scalar field with arbitrary curvature coupling in the spacetime of charged black hole being a solution of coupled equations of nonlinear electrodynamics and general relativity is constructed and analysed. It is shown that in a few limiting cases, the analytical expressions relating obtained tensor to the general renormalized stress-energy tensor evaluated in the geometry of the Reissner-Nordstr\"{o}m black hole could be derived. A detailed numerical analysis with special emphasis put on the minimal coupling is presented and the results are compared with those obtained earlier for the conformally coupled field. Some novel features of the renormalized stress-energy tensor are discussed

Inter-study reproducibility of arterial spin labelling magnetic resonance imaging for measurement of renal perfusion in healthy volunteers at 3 Tesla

Background: Measurement of renal perfusion is a crucial part of measuring kidney function. Arterial spin labelling magnetic resonance imaging (ASL MRI) is a non-invasive method of measuring renal perfusion using magnetised blood as endogenous contrast. We studied the reproducibility of ASL MRI in normal volunteers.<p></p> Methods: ASL MRI was performed in healthy volunteers on 2 occasions using a 3.0 Tesla MRI scanner with flow-sensitive alternating inversion recovery (FAIR) perfusion preparation with a steady state free precession (True-FISP) pulse sequence. Kidney volume was measured from the scanned images. Routine serum and urine biochemistry were measured prior to MRI scanning.<p></p> Results: 12 volunteers were recruited yielding 24 kidneys, with a mean participant age of 44.1 ± 14.6 years, blood pressure of 136/82 mmHg and chronic kidney disease epidemiology formula estimated glomerular filtration rate (CKD EPI eGFR) of 98.3 ± 15.1 ml/min/1.73 m2. Mean kidney volumes measured using the ellipsoid formula and voxel count method were 123.5 ± 25.5 cm3, and 156.7 ± 28.9 cm3 respectively. Mean kidney perfusion was 229 ± 41 ml/min/100 g and mean cortical perfusion was 327 ± 63 ml/min/100 g, with no significant differences between ASL MRIs. Mean absolute kidney perfusion calculated from kidney volume measured during the scan was 373 ± 71 ml/min. Bland Altman plots were constructed of the cortical and whole kidney perfusion measurements made at ASL MRIs 1 and 2. These showed good agreement between measurements, with a random distribution of means plotted against differences observed. The intra class correlation for cortical perfusion was 0.85, whilst the within subject coefficient of variance was 9.2%. The intra class correlation for whole kidney perfusion was 0.86, whilst the within subject coefficient of variance was 7.1%.<p></p> Conclusions: ASL MRI at 3.0 Tesla provides a repeatable method of measuring renal perfusion in healthy subjects without the need for administration of exogenous compounds. We have established normal values for renal perfusion using ASL MRI in a cohort of healthy volunteers.<p></p&gt

Possible wormholes in a brane world

The condition R=0, where R is the four-dimensional scalar curvature, is used for obtaining a large class (with an arbitrary function of r) of static, spherically symmetric Lorentzian wormhole metrics. The wormholes are globally regular and traversable, can have throats of arbitrary size and can be both symmetric and asymmetric. These metrics may be treated as possible wormhole solutions in a brane world since they satisfy the vacuum Einstein equations on the brane where effective stress-energy is induced by interaction with the bulk gravitational field. Some particular examples are discussed.Comment: 7 pages, revtex4. Submitted to Phys. Rev.

Investigating linkage rates among probabilistically linked birth and hospitalization records

BACKGROUND: With the increasing use of probabilistically linked administrative data in health research, it is important to understand whether systematic differences occur between the populations with linked and unlinked records. While probabilistic linkage involves combining records for individuals, population perinatal health research requires a combination of information from both the mother and her infant(s). The aims of this study were to (i) describe probabilistic linkage for perinatal records in New South Wales (NSW) Australia, (ii) determine linkage proportions for these perinatal records, and (iii) assess records with linked mother and infant hospital-birth record, and unlinked records for systematic differences. METHODS: This is a population-based study of probabilistically linked statutory birth and hospital records from New South Wales, Australia, 2001-2008. Linkage groups were created where the birth record had complete linkage with hospital admission records for both the mother and infant(s), partial linkage (the mother only or the infant(s) only) or neither. Unlinked hospital records for mothers and infants were also examined. Rates of linkage as a percentage of birth records and descriptive statistics for maternal and infant characteristics by linkage groups were determined. RESULTS: Complete linkage (mother hospital record – birth record – infant hospital record) was available for 95.9% of birth records, partial linkage for 3.6%, and 0.5% with no linked hospital records (unlinked). Among live born singletons (complete linkage = 96.5%) the mothers without linked infant records (1.6%) had slightly higher proportions of young, non-Australian born, socially disadvantaged women with adverse pregnancy outcomes. The unlinked birth records (0.4%) had slightly higher proportions of nulliparous, older, Australian born women giving birth in private hospitals by caesarean section. Stillbirths had the highest rate of unlinked records (3-4%). CONCLUSIONS: This study shows that probabilistic linkage of perinatal records can achieve high, representative levels of complete linkage. Records for mother’s that did not link to infant records and unlinked records had slightly different characteristics to fully linked records. However, these groups were small and unlikely to bias results and conclusions in a substantive way. Stillbirths present additional challenges to the linkage process due to lower rates of linkage for lower gestational ages, where most stillbirths occur

Twin Paradox and the logical foundation of relativity theory

We study the foundation of space-time theory in the framework of first-order logic (FOL). Since the foundation of mathematics has been successfully carried through (via set theory) in FOL, it is not entirely impossible to do the same for space-time theory (or relativity). First we recall a simple and streamlined FOL-axiomatization SpecRel of special relativity from the literature. SpecRel is complete with respect to questions about inertial motion. Then we ask ourselves whether we can prove usual relativistic properties of accelerated motion (e.g., clocks in acceleration) in SpecRel. As it turns out, this is practically equivalent to asking whether SpecRel is strong enough to "handle" (or treat) accelerated observers. We show that there is a mathematical principle called induction (IND) coming from real analysis which needs to be added to SpecRel in order to handle situations involving relativistic acceleration. We present an extended version AccRel of SpecRel which is strong enough to handle accelerated motion, in particular, accelerated observers. Among others, we show that the Twin Paradox becomes provable in AccRel, but it is not provable without IND.Comment: 24 pages, 6 figure

Denominators of Eisenstein cohomology classes for GL_2 over imaginary quadratic fields

We study the arithmetic of Eisenstein cohomology classes (in the sense of G. Harder) for symmetric spaces associated to GL_2 over imaginary quadratic fields. We prove in many cases a lower bound on their denominator in terms of a special L-value of a Hecke character providing evidence for a conjecture of Harder that the denominator is given by this L-value. We also prove under some additional assumptions that the restriction of the classes to the boundary of the Borel-Serre compactification of the spaces is integral. Such classes are interesting for their use in congruences with cuspidal classes to prove connections between the special L-value and the size of the Selmer group of the Hecke character.Comment: 37 pages; strengthened integrality result (Proposition 16), corrected statement of Theorem 3, and revised introductio