Simulating nitrogen balance in Canadian agricultural soils from 1981 to 2016

Agriculture produces food, fiber and biofuels for the world's growing population, however, agriculture can be a major contributor of nitrogen (N) losses including emissions of ammonia (NH₃), nitrous oxide (N₂O) and nitrate (NO₃^-) leaching and runoff. A Canadian Agricultural Nitrogen Budget for Reactive N (CANBNr) model was developed to estimate the soil N balance in 3487 soil landscape of Canada polygons from 1981 to 2016. The CANBNr model integrates NH₃ emission from fertilizers, manure from housing, storage and field, as well as direct/indirect N₂O emissions from fertilizers, manures, crop residues and soil organic matter. The NO₃^- leaching is estimated based on the residual soil N (RSN) at harvest and drainage derived with the DeNitrification-DeComposition (DNDC) model. From 1981 to 2016, the N input from fertilizer and N fixation increased at a greater rate than N removal in harvested crops in all provinces of Canada, resulting in an increase in the RSN and N losses. In 2016, the Prairie provinces had lower N losses (11.7 kg N ha^-1) from N₂O, NH₃ and NO₃^- compared with 43.2 kg N ha^-1 in central Canada, and 76.5 kg N ha^-1 in Atlantic Canada. However, the Prairie provinces had 84.3% of the total Canadian farmland (74.3% of the total Canadian N input), while central Canada had 12.9% of Canadian farmland (21.7% of the total Canadian N input). In the Prairie provinces, the total N₂O loss from fertilizer N ranged 4.4-8.6 Gg N whereas NH₃ loss ranged from 17.1 to 44.6 Gg N and these values were influenced by both emission intensity and total land area. Total N₂O losses from manure were highest in Alberta, Ontario and Quebec resulting in 4.8, 4.4, and 3.4 Gg N and NH₃ losses from manure were also highest in these 3 provinces at 61.1, 45.2 and 40.4 Gg N, respectively. Nitrate leaching was impacted by drainage volumes, soil type and N inputs. In the non-growing season, NO₃^- leaching losses (36-yr average) were 63.3 Gg in Ontario and 57.5 Gg N in Quebec compared with 20.8 Gg N for Ontario and 35.5 Gg N for Quebec in the growing season. In contrast, the Prairie provinces showed higher NO₃^- leaching in the growing season (23.1-37.4 Gg N) than in the non-growing season (10.4-13.7 Gg N). In summary, total fertilizer N increased the most over the 36 years in the Prairies which resulted in increased RSN and N leaching losses that will require further intervention.

Assessing the impacts of diversified crop rotation systems on yields and nitrous oxide emissions in Canada using the DNDC model

Process-based models are effective tools for assessing the sustainability of agricultural productivity and environmental health under various management practices and rotation systems. The objectives of this study were to (1) calibrate and evaluate the DeNitrification-DeComposition (DNDC) model using measurements of yields, nitrogen (N) uptake, soil inorganic N, soil temperature, soil moisture and nitrous oxide (N₂O) emissions under long-term fertilized continuous corn (CC) and corn-oats-alfalfa-alfalfa (COAA) rotation systems in southwest Ontario from 1959 to 2015, Canada, and (2) explore the impacts of four diverse rotation systems (CC, COAA, corn-soybean-corn-soybean (CSCS) and corn-soybean-winter wheat (CSW)) on corn yields and annual N₂O emissions under long-term climate variability. DNDC demonstrated "good" performance in simulating corn, oats and alfalfa yield (normalized root mean square error (nRMSE) < 20%, Nash-Sutcliffe efficiency (NSE) > 0.5 and index of agreement (d) > 0.8). The model provided "fair" to "good" simulations for corn N uptake and soil inorganic N (NSE > 0.2 and d > 0.8), and also daily soil temperature and soil moisture (nRMSE <30% and d > 0.7) for both calibration and validation periods. The model demonstrated "good" performance in estimating daily and cumulative N₂O emissions from both the continuous and rotational corn, whereas it produced "poor" to "good" predictions for N₂O emissions from the rotational oats and alfalfa crops, however, the emissions from these crops were very low and the relative magnitude of these emissions between all crops investigated were well predicted. The lowest N₂O emissions were from COAA followed by CSCS, CSW then CC. The highest corn yields were from COAA, followed by CSW, CSCS, then CC. This study highlights how modelling approaches can help improve the understanding of the impacts of diversified rotations on crop production and greenhouse gas emissions and contribute towards developing policies aimed at improving the sustainability and resiliency of cropping systems.

Identifying N fertilizer management strategies to reduce ammonia volatilization: Towards a site-specific approach

Concerns about ammonia (NH₃) losses from nitrogen (N) mineral fertilizers have forced policymakers to set emission reduction commitments across Europe. Although best available techniques (BATs) have been recommended, large uncertainties still exist due to poorly targeted site-specific approaches that might compromise their effectiveness. Here we proposed and tested a conceptual framework designed to identify most effective BATs that reduce NH₃ at the site-specific level. The study was conducted in the Veneto region, northeast Italy. After the mapping of NH₃ emission potential areas, BATs and business-as-usual N fertilization scenarios were assessed using a modified version of the DNDC agroecosystem model and compared with urea broadcast distribution under different pedo-climatic conditions. The most promising practices were further tested in a field experiment using a wind tunnel combined with a FTIR gas analyzer. Results showed that closed-slot injection reduced NH₃ emissions with any type of mineral or organic fertilizers. Injected application, with ammonium nitrate or organic fertilizers, reduced NH₃ loss in maize by 75% and 96%, respectively, and in winter wheat by 87% and 98%, compared to surface broadcast. Injection was the most promising technology to support, being already available to farmers. However, some increase in nitrate leaching was observed, mostly in case of winter wheat (+24% for AN injection; +89% for organic fertilizers). By contrast, urea incorporation with hoeing, the most common technique used by farmers in spring crops, did not show satisfactory results, because the partial burial of urea caused strong NH₃ emissions that were even higher compared to surface broadcast. Recommended NH₃ reduction techniques should be tailored to local pedo-climatic and management conditions, and evaluated, in a holistic approach, considering all N fluxes in the environment.

Assessing the effects of manure application rate and timing on nitrous oxide emissions from managed grasslands under contrasting climate in Canada

It is uncertain whether process-based models are currently capable of simulating the complex soil, plant, climate, manure management interactions that influence soil nitrous oxide (N₂O) emissions from perennial cropping systems. The objectives of this study were (1) to calibrate and evaluate the DeNitrification DeComposition (DNDC) model using multi-year datasets of measured nitrous oxide (N₂O) fluxes, soil moisture, soil inorganic nitrogen, biomass and soil temperature from managed grasslands applied with manure slurry in contrasting climates of Canada, and (2) to simulate the impact of different manure management practices on N₂O emissions including slurry application i) rates (for both single vs. split); and ii) timing (e.g., early vs. late spring). DNDC showed "fair" to "excellent" performance in simulating biomass (4.7% ≤ normalized root mean square error (NRMSE) ≤ 29.8%; -9.5% ≤ normalized average relative error (NARE) ≤ 16.1%) and "good" performance in simulating soil temperature (13.2% ≤ NRMSE ≤ 18.1%; -0.7% ≤ NARE ≤ 10.8%) across all treatments and sites. However, the model only showed "acceptable" performances in estimating soil water and inorganic N contents which was partially attributed to the limitation of a cascade water sub-model and inaccuracies in simulating root development/uptake. Although, the DNDC model only demonstrated "fair" performance in simulating daily N₂O fluxes, it generally captured the impact of the timing and rate of slurry application and soil texture (loam vs. sandy loam) on total N₂O emissions. The DNDC model simulated N₂O emissions from spring better than split manure application (fall and spring) at the Manitoba site partially due to the overestimation of available substrates for microbial denitrification from fall application during the wet spring periods. Although DNDC performed adequately for simulating most of the manure management impacts considered in this study we recommend improvements in the simulation of soil freeze-thaw cycles, manure decomposition dynamics, soil water storage, rainfall canopy interception, and microbial denitrification and nitrification activities in grasslands.

Understanding the Fertilizer Management Impacts on Water and Nitrogen Dynamics for a Corn Silage Tile-Drained System in Canada

Effective management of dairy manure is important to minimize N losses from cropping systems, maximize profitability, and enhance environmental sustainability. The objectives of this study were (i) to calibrate and validate the DeNitrification-DeComposition (DNDC) model using measurements of silage corn ( L.) biomass, N uptake, soil temperature, tile drain flow, NO leaching, NO emissions, and soil mineral N in eastern Canada, and (ii) to investigate the long-term impacts of manure management under climate variability. The treatments investigated included a zero-fertilizer control, inorganic fertilizer, and dairy manure amendments (raw and digested). The DNDC model overall demonstrated statistically "good" performance when simulating silage corn yield and N uptake based on normalized RMSE (nRMSE) < 10%, index of agreement () > 0.9, and Nash-Sutcliffe efficiency (NSE) > 0.5. In addition, DNDC, with its inclusion of a tile drainage mechanism, demonstrated "good" predictions for cumulative drainage (nRMSE < 20%, > 0.8, and NSE > 0.5). The model did, however, underestimate daily drainage flux during spring thaw for both organic and inorganic amendments. This was attributed to an underestimation of soil temperature and soil water under frequent soil freezing and thawing during the 2013-2014 overwinter period. Long-term simulations under climate variability indicated that spring applied manure resulted in less NO leaching and NO emissions than fall application when manure rates were managed based on crop N requirements. Overall, this study helped highlight the challenges in discerning the short-term climate interactions on fertilizer-induced N losses compared with the long-term dynamics under climate variability.

Simple equations to predict concentric lower-body muscle power in older adults using the 30-second chair-rise test: a pilot study

Although muscle power is an important factor affecting independence in older adults, there is no inexpensive or convenient test to quantify power in this population. Therefore, this pilot study examined whether regression equations for evaluating muscle power in older adults could be derived from a simple chair-rise test. We collected data from a 30-second chair-rise test performed by fourteen older adults (76 +/- 7.19 years). Average (AP) and peak (PP) power values were computed using data from force-platform and high-speed motion analyses. Using each participant's body mass and the number of chair rises performed during the first 20 seconds of the 30-second trial, we developed multivariate linear regression equations to predict AP and PP. The values computed using these equations showed a significant linear correlation with the values derived from our force-platform and high-speed motion analyses (AP: R = 0.89; PP: R = 0.90; P < 0.01). Our results indicate that lower-body muscle power in fit older adults can be accurately evaluated using the data from the initial 20 seconds of a simple 30-second chair-rise test, which requires no special equipment, preparation, or setting.

Correlation analyses and regression modeling between isokinetic testing and on-court performance in competitive adolescent tennis players

Tennis requires skill, physical attributes, and strategy. Ball velocity and placement are two of the most important components in winning the faster-paced modern game. Although isokinetic testing has been used to evaluate physical characteristics and injury potential in tennis players, few studies have compared isokinetics and on-court performance. Such a comparison would help establish links between speed-specific properties of functioning muscles and stroke production and could affect overall training strategy. This study compared isokinetic peak torque (PT), average power (AP), and total work (TW) during specific testing patterns correlated with ball velocity or stroke accuracy during the service, forehand, and backhand and developed predictive equations for each stroke using these variables. Thirty-five players, aged 13-18 years with at least 4 years playing experience, were evaluated using internal and external shoulder rotation, leg extension, and diagonal throwing motions. Ball velocity was measured using a radar gun. Accuracy was evaluated on the basis of shot position and depth. Significant correlations were found between ball velocity and a number of isokinetic variables, while no significant correlations were observed with shot accuracy. Significant isokinetic variables for each stroke were entered into regression models. One isokinetic speed sufficiently predicted ball velocity for each stroke, since no increase in predictive capacity was observed with the addition of other isokinetic parameters. We conclude that isokinetics at testing speeds between 1.57 and 4.71 rad.s(-1) can effectively predict ball velocity, but not accuracy, and that our results may be helpful in planning strategies for training and rehabilitation.

Alteration of contractile force and mass in the senescent diaphragm with beta(2)-agonist treatment

Aging is associated with a decrease in diaphragmatic maximal tetanic force production (P(o)) in senescent rats. Treatment with the beta(2)-agonist clenbuterol (CB) has been shown to increase skeletal muscle mass and P(o) in weak locomotor skeletal muscles from dystrophic rodents. It is unknown whether CB can increase diaphragmatic mass and P(o) in senescent rats. Therefore, we tested the hypothesis that CB treatment will increase specific P(o) (i.e., force per cross-sectional area) and mass in the diaphragm of old rats. Young (5 mo) and old (23 mo) male Fischer 344 rats were randomly assigned to one of the following groups (n = 10/group): 1) young CB treated; 2) young control; 3) old CB treated; and 4) old control. Animals were injected daily with either CB (2 mg/kg) or saline for 28 days. CB increased (P < 0.05) the mass of the costal diaphragm in both young and old animals. CB treatment increased diaphragmatic-specific P(o) in old animals (approximately 15%; P < 0.05) but did not alter (P > 0.05) diaphragmatic-specific P(o) in young animals. Biochemical analysis indicated that the improved maximal specific P(o) in the diaphragm of CB-treated old animals was not due to increased myofibrillar protein concentration. Analysis of the myosin heavy chain (MHC) content of the costal diaphragm revealed a CB-induced increase (P < 0.05) in type IIb MHC and a decrease in type I, IIa, and IIx MHC in both young and old animals. These data support the hypothesis that CB treatment can restore the age-associated decline in both diaphragmatic-specific P(o) and muscle mass.

Use of a flotation tank to sling horses and cattle undergoing surgery to the limbs

A system using a suitably sized flotation tank has been developed to reduce the weight that horses and cattle place upon their legs after undergoing surgery to their limbs. The system overcomes the need for the patient to lie down for long periods, thus preventing decubitus. The system is well tolerated with few side effects; after prolonged flotation alopecia may occur on those parts of the patient which remain continuously immersed in water. The method is now commonly referred to as the 'Queensland Sling'.

Calcification of membranes isolated from Bacterionema matruchotii

Lytic cultures of Bacterionema matruchotii were found to release vesicular membranes into the medium which could be obtained virtually free of other cell structures by differential centrifugation. Suspension of the membrane fraction in a metastable calcium phosphate solution resulted in the formation of both amorphous mineral and hydroxyapatite. Examination by electron microscopy showed that mineralization was associated with the membrane bilayers. The results provide further evidence that calcification of B matruchotii is related to intracytoplasmic membranes.

Calcification of selected strains of Streptococcus mutans and Streptococcus sanguis

Nine strains of cariogenic Streptococcus mutans and two strains of Streptococcus sanguis were tested for their ability to form hydroxyapatite. The cells were examined by X-ray diffraction and electron microscopy for apatite crystals after growth in a synthetic calcification medium. Each of the test isolates, except for one strain of S. sanguis, produced intracellular mineral. Two strains of S. mutans formed both intra- and extracellular crystals. There was no apparent relationship between calcifiability and serotype.

Characteristics of an induced variant of Bacterionema matruchotii

Bacterionema matruchotii, a calcifiable filamentous organism, was treatetl ultrasonically. The disrupted cells produced typical colonies that developed macroscopic globular structures. A nonfilamentous, pleomorphic variant was derived from the globules. The variant retained the calcification potential of the filament, as well as fermentation and ultrastructural similarities.

Distribution of mucosubstances in the developing rat heart

Mucosubstances (MS) were examined in 10½-14½-day embryonic rat hearts utilizing nonaqueous fixatives or formaldehyde vapor-fixed frozen sections hydrated in concentrated solutions of cetylpyridinium chloride. Ribonuclease-resistant, polyanionic sites were limited to the extracellular cardiac jelly, endocardium and fibroblastic cells (cushion tissue) associated with the endocardium. The cardiac jelly and endocardium of day 10½ embryos principally contained a hyaluronic acid-like carboxylated mucosubstance whose alcianophilia at pH 2.5 was abolished by hyaluronidase but was resistant to NaOH extraction and neuraminidase and trypsin digestion. A critical electrolyte concentration of 0.2 M MgCl2 abolished alcianophilia. On days 13½-14½ carboxylated MS were restricted to cushion tissue and partially resisted mild methylation. Sulfated MS were limited to primitive endocardial cells which gave origin to cushion tissue. Dye deposits of aldehyde fuchsin, high iron diamine or Alcian Blue (pH 1.0) were localized on cell surfaces and such staining was prevented by strong (60°C) methylation. Hyaluronidase sensitivity of sulfated MS decreased with gestation. The critical electrolyte concentration varied from 0.5-0.7 M MgCl2 on days 11½-12½ to 0.8-0.9 M MgCl2 after day 12½. The sulfated MS of endocardial cells were preceded by a transitory accumulation of diastase-resistant, periodic acid-Schiff-positive material. Possible roles of MS in normal and abnormal cardiac septation processes are discussed.

Isolation of Bacillary and Streptococcal Variants from Bacterionema matruchotii

Bacterionema matruchotii , an oral filamentous organism, dissociated to form unusual flat colonies. Subculture of the flat colonies, composed of diphtheroids, yielded pure cultures of bacillary and streptococcal variants.

Influence of testosterone upon sexual maturation in the rat

1. Testosterone injected into the neonatal female rat induces permanent sterility. This study was carried out in an endeavour to determine where this change is induced.2. Hypophysectomized, but otherwise normal, female rats bearing anterior pituitary transplants from androgen-sterilized female rats under the median eminence of the hypothalamus and vascularized from it, show oestrous cycles in the vaginal smear, have corpora lutea in the ovaries and are fertile.3. Hypophysectomized androgen-sterilized female rats bearing anterior pituitary transplants from normal female rats under the median eminence and vascularized from it show persistent oestrus in the vaginal smear, have small ovaries containing large follicles but no corpora lutea and are sterile.4. Testosterone injected into the female rat, and leading to sterility and ovarian malfunction, does not act at the level of the anterior pituitary, which retains the ability to function normally. It is considered that it may act upon the central nervous system to cause a disturbance of the gonadotrophin-releasing mechanism.