Solute dynamics and the Ontario nitrogen index: I. Chloride leaching

2016 ◽  
Vol 96 (2) ◽  
pp. 105-121 ◽  
Author(s):  
W. Daniel Reynolds ◽  
Craig F. Drury ◽  
Gary W. Parkin ◽  
John D. Lauzon ◽  
Joseph K. Saso ◽  
...  
Keyword(s):  
Transport Theory ◽  
Root Zone ◽  
Sandy Loam ◽  
Drainage Water ◽  
Low Risk ◽  
Soil Core ◽  
Southern Ontario ◽  
Risk Levels ◽  
Crop Root ◽  
Solute Dynamics

The nitrogen (N) index for humid temperate southern Ontario, Canada (Ontario N index) incorporates previous and current crop type, fertilizer and (or) manure management, and hydrologic soil group (HSG) to estimate risk for contamination of tile drainage water and groundwater by nitrate leached below the primary crop root zone (top 60 cm of soil). The Ontario N index has received limited ground-truthing, and the leaching component was assessed using chloride tracer (ClTR) on five soils (one sandy loam, two loams, and two clay loams) representing four HSG-based risk levels (HSG-A, high risk; HSG-B, medium risk; HSG-C, low risk; HSG-D, very low risk). A square-wave pulse of ClTR was applied to the soil surfaces in fall 2007 as KCl, and movement and loss of ClTR was tracked over 1–1.2 years using monthly soil core samples collected from the top 60–80 cm. For all five soils, 60–96% of ClTR was leached out of the primary crop root zone (below 60 cm depth) during the noncropping period (October 2007 to March 2008 inclusive), and >80% was leached out of the root zone within 1 year. The percentage of ClTR that leached did not correlate with precipitation or HSG designation, but produced significant (P < 0.05) power function regressions with minimum and harmonic mean saturated soil hydraulic conductivity (Ksat) measured in the top 50–60 cm. ClTR leaching rate appeared to be controlled primarily by Ksat in a manner consistent with infiltration and solute transport theory. It was consequently proposed that solute leaching loss versus Ksat relationships may improve N index risk estimates for both southern Ontario and other humid temperate regions.

Evaluation of the Root Zone Water Quality Model (RZWQM) for Southern Ontario: Part I. Sensitivity Analysis, Calibration, and Validation

2007 ◽  
Vol 42 (3) ◽  
pp. 202-218 ◽  
Author(s):  
Imran Ahmed ◽  
Ramesh Rudra ◽  
Kevin McKague ◽  
Bahram Gharabaghi ◽  
John Ogilvie
Keyword(s):  
Crop Yield ◽  
Root Zone ◽  
Drainage Water ◽  
Tile Drainage ◽  
Quality Model ◽  
N Loss ◽  
Southern Ontario ◽  
Drain Flow ◽  
Fitting Parameters ◽  
Zone Water

Abstract This study focuses on the performance of the Root Zone Water Quality Model (RZWQM) for corn production in southern Ontario. The model was used to simulate the amount of subsurface tile drainage, residual soil nitrate-nitrogen (NO3-N), NO3-N in subsurface drainage water, and crop yield. A precalibration sensitivity analysis of the model was conducted for several key parameters using field data collected at the study site. The RZWQM's hydrology component was most sensitive to the Brooks and Corey fitting parameters and saturated hydraulic conductivity (Ks), while the tile drain flow and the water table depth were sensitive to the Brooks and Corey fitting parameters of bubbling pressure (ψbp) and pore-size-distribution index (λ). The fraction of dead-end pores had relatively little effect on tile drain N loss. The crop yield is most affected by N uptake, age, and evapotranspiration rate. RZWQM simulated evapotranspiration was within the range (568 ± 55 mm) of the observed evapotranspiration. The model simulated corn yield very well (-0.1% difference) at the calibration site; however, it underestimated yield (-14.1%) at the validation site. Overall, the RZWQM simulated tile drain flow, NO3-N loss to tile drainage water, and crop yield with reasonable accuracy, but tended to underestimate the amount of soil NO3-N (mean deviation, -0.971). The inability of the model to handle the spatial and temporal variability of the soil may have affected its prediction accuracy. The model also needs improvement in simulating early spring snowmelt hydrology.

Evaluation of the Root Zone Water Quality Model (RZWQM) for Southern Ontario: Part II. Simulating Long-Term Effects of Nitrogen Management Practices on Crop Yield and Subsurface Drainage Water Quality

2007 ◽  
Vol 42 (3) ◽  
pp. 219-230 ◽  
Author(s):  
Imran Ahmed ◽  
Ramesh Rudra ◽  
Kevin McKague ◽  
Bahram Gharabaghi ◽  
John Ogilvie
Keyword(s):  
Water Quality ◽  
Crop Yield ◽  
Management Practices ◽  
Root Zone ◽  
Sandy Loam ◽  
Drainage Water ◽  
Long Term Effects ◽  
Quality Model ◽  
Loam Soil

Abstract Loss of nitrogen from the agricultural production system is of concern in Ontario. The challenge for researchers and farmers is to fulfill crop water requirements while limiting chemical movement with surface and subsurface runoff. The main objective of this study was to evaluate the long-term effects of current N management practices for corn production for two different soil types using the Root Zone Water Quality Model (RZWQM) for southern Ontario conditions. The model simulated the amount of subsurface tile drainage, residual soil nitrate-nitrogen (NO3-N), NO3-N in subsurface drainage water, and crop yield. The validated RZWQM for silt loam and sandy loam soils showed that the relative long-term effectiveness of the most economic rate of nitrogen (MERN) for corn production fluctuates significantly from year-to-year in response to weather patterns. In addition, soil type had a small but significant effect on the MERN. Side-dress application of N on sandy loam resulted in significant reduction in corn yield and NO3-N loss to shallow groundwater. Also, crop rotation from corn-soybean to corn-soybean-soybean resulted in a greater reduction of NO3-N loads in the tile outflow on silt loam soil than on sandy loam soil. Overall, the RZWQM simulated tile drain flow, NO3-N loss, and crop yield with reasonable accuracy. However, more field work is needed to assist with identifying suitable values for a number of coefficients used in the RZWQM's nutrient component for Ontario conditions.

A New Automated Passive Capillary Lysimeter for Logging Real-Time Drainage Water Fluxes

2017 ◽  
Vol 33 (6) ◽  
pp. 849-857
Author(s):  
J. D. Jabro ◽  
W. M. Iversen ◽  
W. B. Stevens ◽  
B. L. Allen ◽  
U. M. Sainju
Keyword(s):  
Real Time ◽  
Vadose Zone ◽  
Spread Spectrum ◽  
Root Zone ◽  
Sandy Loam ◽  
Irrigation System ◽  
Cropping Systems ◽  
Soil Surface ◽  
Drainage Water ◽  
Water Fluxes

Abstract.Effective monitoring of chemical transport through the soil profile requires accurate and appropriate instrumentation to measure drainage water fluxes below the root zone of cropping systems. The objectives of this study were to methodically describe in detail the construction and installation of a novel automated PCAP (passive capillary) lysimeter design, and to evaluate the efficacy of this design for logging and monitoring real-time drainage water fluxes occurring below the root zone of corn ( L.) and soybean ( L.) under an overhead sprinkler irrigation system. Sixteen cylindrical PCAP lysimeters with outside dimensions of 32.39 cm in diameter ×74.8 cm height (1000 cm2 surface area) were designed, constructed, and placed 90 cm below the soil surface in a Lihen sandy loam. Two watermark soil moisture and temperature sensors were positioned at 30 and 76 cm depths above each PCAP to monitor soil temperature and water potential continuously. This new design incorporated wireless spread spectrum technology to enable an automated datalogger to transmit drainage water amounts simultaneously every 15 min to a remote host. Logged drainage amounts were compared with those manually collected using several statistical methods. The root mean square error (RMSE), the logging efficacy (EF), and the mean difference (MD) were 0.0375, 0.964 and 0.0335 cm, respectively, for 4-yr combined data. The MD between logged and collected drainage amounts was very small and not significantly different from zero for 4-yr combined results. Statistical results indicated that the new lysimeter performed exceptionally well and was capable of monitoring drainage water fluxes in the vadose zone. Real-time seamless monitoring and logging drainage water fluxes was thus possible without the need for costly time-consuming supportive procedures. Keywords: Drainage, Lysimeter, Root zone, Vadose zone.

Solute dynamics and the Ontario nitrogen index: II. Nitrate leaching

2016 ◽  
Vol 96 (2) ◽  
pp. 122-135 ◽  
Author(s):  
C.F. Drury ◽  
W.D. Reynolds ◽  
G.W. Parkin ◽  
J.D. Lauzon ◽  
J.K. Saso ◽  
...  
Keyword(s):  
Root Zone ◽  
Agricultural Soils ◽  
Sandy Loam ◽  
N Leaching ◽  
N Recovery ◽  
N Loss ◽  
Solute Dynamics ◽  
N Management ◽  
N Rates ◽  
Leaching Risk

Nitrogen (N) leaching from soil into surface and ground waters is a concern in humid areas of Canada. As a result, N management protocols, including the Ontario N Index, are widely used to identify N leaching risk, although field assessment remains limited. Nitrogen fertilizer and chloride (Cl) tracer were fall-applied to five agricultural soils in Ontario with different textures and hydrologic soil groups (HSG) to assess the Ontario N Index and characterize inorganic N movement over 1 yr. The treatments included three N rates (0, 100, and 200 kg N ha−1) plus Cl tracer and 200 kg N ha−1 rate without Cl. After spring thaw, N loss from the crop root zone (top 60 cm) ranged from 68% for Brookston clay loam to 99% for Harrow sandy loam. A strong linear relationship between apparent N recovery and apparent Cl recovery indicated that N loss from the root zone occurred primarily by downward leaching. Leaching was controlled by the minimum measured saturated hydraulic conductivity (Ksat), and good estimates of N leaching were obtained using a quasi-theoretical relationship between N loss and Ksat. We concluded that Ontario N Index estimates of N leaching risk might be improved by including site-specific measurements of Ksat.

scholarly journals Infiltration and sealing for managing non-cavitated proximal lesions: a systematic review and meta-analysis

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Yuanyuan Chen ◽  
Dongru Chen ◽  
Huancai Lin
Keyword(s):  
Systematic Review ◽  
High Risk ◽  
Meta Analysis ◽  
Low Risk ◽  
Caries Risk ◽  
Moderate Risk ◽  
Risk Levels ◽  
Non Invasive ◽  
Randomised Controlled ◽  
Caries Lesions

Abstract Background Infiltration and sealing are micro-invasive treatments for arresting proximal non-cavitated caries lesions; however, their efficacies under different conditions remain unknown. This systematic review and meta-analysis aimed to evaluate the caries-arresting effectiveness of infiltration and sealing and to further analyse their efficacies across different dentition types and caries risk levels. Methods Six electronic databases were searched for published literature, and references were manually searched. Split-mouth randomised controlled trials (RCTs) to compare the effectiveness between infiltration/sealing and non-invasive treatments in proximal lesions were included. The primary outcome was obtained from radiographical readings. Results In total, 1033 citations were identified, and 17 RCTs (22 articles) were included. Infiltration and sealing reduced the odds of lesion progression (infiltration vs. non-invasive: OR = 0.21, 95% CI 0.15–0.30; sealing vs. placebo: OR = 0.27, 95% CI 0.18–0.42). For both the primary and permanent dentitions, infiltration and sealing were more effective than non-invasive treatments (primary dentition: OR = 0.30, 95% CI 0.20–0.45; permanent dentition: OR = 0.20, 95% CI 0.14–0.28). The overall effects of infiltration and sealing were significantly different from the control effects based on different caries risk levels (OR = 0.20, 95% CI 0.14–0.28). Except for caries risk at moderate levels (moderate risk: OR = 0.32, 95% CI 0.01–8.27), there were significant differences between micro-invasive and non-invasive treatments (low risk: OR = 0.24, 95% CI 0.08–0.72; low to moderate risk: OR = 0.38, 95% CI 0.18–0.81; moderate to high risk: OR = 0.17, 95% CI 0.10–0.29; and high risk: OR = 0.14, 95% CI 0.07–0.28). Except for caries risk at moderate levels (moderate risk: OR = 0.32, 95% CI 0.01–8.27), infiltration was superior (low risk: OR = 0.24, 95% CI 0.08–0.72; low to moderate risk: OR = 0.38, 95% CI 0.18–0.81; moderate to high risk: OR = 0.20, 95% CI 0.10–0.39; and high risk: OR = 0.14, 95% CI 0.05–0.37). Conclusion Infiltration and sealing were more efficacious than non-invasive treatments for halting non-cavitated proximal lesions.

Nondestructive Sampling to Monitor Macrophomina phaseolina Root Colonization in Overwintering Stevia

2021 ◽  
Author(s):  
Layne W. Rogers ◽  
Alyssa M. Koehler
Keyword(s):  
Root Colonization ◽  
Root Zone ◽  
Macrophomina Phaseolina ◽  
Field Trials ◽  
Soil Core ◽  
Climate Data ◽  
Sample Weight ◽  
The Family ◽  
Soil Temperatures

Macrophomina phaseolina is a soilborne fungal pathogen in the family Botryosphaeriaceae. Microsclerotia of M. phaseolina were first observed at the base of overwintering stevia stems in North Carolina in spring 2016. Previous studies utilized destructive sampling methods to monitor M. phaseolina in stevia fields; however, these methods are not feasible for long-term monitoring of disease in a perennial system. In the current study, nondestructive root soil-core sampling was conducted during overwintering months, from October 2018 to January 2020, to monitor M. phaseolina root colonization in stevia in Rocky Mount, NC. Two-inch-diameter soil cores were collected through the root zone, and fresh weight of roots was recorded for each soil core. M. phaseolina recovery was evaluated by examining mycelial growth from roots plated onto potato dextrose agar. There was no significant effect of sample weight on M. phaseolina across all dates, but there was one date for which sample weight had a significant effect on recovery (P = 0.01; α = 0.05). For both recovery and sample weight, sampling date was a significant predictor (P = 1.68e-5 and P = 0.0389, respectively; α = 0.05). Weather and climate data revealed that dates with no M. phaseolina recovery had lowest mean air and soil temperatures and the greatest number of days below freezing in the month prior to sampling. In separate sampling years, October sampling dates had the highest recovery of M. phaseolina. Future field trials should determine if October samplings can predict survival and vigor of reemerging stevia plants.

LONG-TERM TILLAGE AND CROP ROTATION EFFECTS ON RESIDUAL NITRATE IN THE CROP ROOT ZONE AND NITRATE ACCUMULATION IN THE INTERMEDIATE VADOSE ZONE

1997 ◽  
Vol 40 (5) ◽  
pp. 1321-1327 ◽  
Author(s):  
A. Katupitiya ◽  
D. E. Eisenhauer ◽  
R. B. Ferguson ◽  
R. F. Spalding ◽  
F. W. Roeth ◽  
...  
Keyword(s):  
Crop Rotation ◽  
Vadose Zone ◽  
Root Zone ◽  
Nitrate Accumulation ◽  
Crop Root ◽  
Residual Nitrate

scholarly journals Comparison of three measurement methods of saturated hydraulic condutivity

2006 ◽  
Vol 3 (3) ◽  
pp. 987-1019 ◽  
Author(s):  
C. Fallico ◽  
E. Migliari ◽  
S. Troisi
Keyword(s):  
Hydraulic Conductivity ◽  
Measurement Method ◽  
Sandy Loam ◽  
Measurement Methods ◽  
Soil Core ◽  
Statistical Parameters ◽  
Factors Affecting ◽  
Average Value ◽  
Constant Head ◽  
Log Normal

Abstract. After pointing out the importance of the saturated hydraulic conductivity (ks) measurements and the difficulties and uncertainties that are present, and after recalling salient aspects of three well-known measurement methods of this parameter (i.e. constant-head tension infiltrometer (TI) method, constant-head pressure infiltrometer (PI) method and soil core (SC) estimates method), the results of an investigation on data which were obtained during a measurement campaign on an area of 800 m2, on a sandy loam hillslope, located in Southern Italy, were carried out again here. Three sets of values of ks, obtained with these measurement methods, were analyzed statistically, verifying that the log-normal distribution describes these better than the normal one; moreover, the more significant statistical parameters of each set were compared (average value , amplitude A, coefficient of variation CV and standard deviation SD), individualizing the more significant differences. The greatest value of hydraulic conductivity was found with method (PI), while the smallest with (SC) and the intermediate with (TI); these differences were translated into macroporosity and into the influence of the single measurement method. Moreover, referring to the possible factors affecting the results, the importance can be noted of the structure, the texture and the soil events, in terms of utilization, which can affect the measure of ks leading often to very different values even for similar soils, but with a different history, independently of the coincidence of the measurement points and they can be determining to explain the differences affecting the results obtained in analogous investigations by other researchers. Having confirmed that generalization is not possible, the need was emphasized to adopt the necessary devices relating to the specific measurement method, case by case, and to carefully explain the obtained results, in the light of the peculiarities and the limits of each situation. Finally, the results of similar statistical analysis carried out on a greater number of ks values, measured through the (TI) and (PI) methods are shown in this paper, with some statistical considerations on the increasing of the measurements number.

scholarly journals Use and Misuse of Aspirin in Primary Cardiovascular Prevention

2017 ◽  
Vol 11 ◽  
pp. 117954681770214 ◽  
Author(s):  
Sergio Coccheri
Keyword(s):  
Primary Prevention ◽  
Clinical Benefit ◽  
Cardiovascular Prevention ◽  
Bleeding Risk ◽  
Threshold Value ◽  
Low Risk ◽  
Risk Levels ◽  
Net Clinical Benefit ◽  
European Society Of Cardiology ◽  
Meta Analyses

The use of low-dose aspirin in primary prevention of cardiovascular (CV) events in healthy or apparently healthy people is a widely debated topic. Many arguments indicate that “primary prevention” is only a conventional definition and that the transition from primary to secondary prevention represents a continuum of increasing levels of CV risk. Although there are no direct proofs of a different efficacy of aspirin at different CV risk levels, in low-risk populations aspirin will appear to be less efficient. In fact, the lower number of events occurring in patients at low risk yields lower absolute numbers of events prevented. As many as 6 meta-analyses of trials of primary CV prevention with aspirin versus placebo, performed between 2009 and 2016, confirmed the above concepts and showed a concordant, significant reduction in nonfatal myocardial infarction, with no significant effects on stroke, as well as on CV and all-cause mortality. The recent demonstration of a moderate protective effect of aspirin on cancer (especially colorectal) confers, however, additional value to the use of aspirin, although unusually long durations of treatment and optimal daily compliance seem to be necessary. Because aspirin increases the bleeding risk, the evaluation of its net clinical benefit is an important point of debate. Thus, it is justified to search for a cutoff level of global CV risk above which the net clinical benefit of aspirin becomes evident. Such a threshold value has been calculated considering the data of 9 primary prevention trials, by the Thrombosis Group of the European Society of Cardiology, and has been indicated as a risk value of 2 or more major CV events per 100 persons per year. Also, in the recent 2016 US Guidelines, the main criterion adopted for the indication of aspirin is the level of global CV risk (suggested cutoff is 1 or more major CV events per 100 persons per year). Beyond the different values selected, it is seems very important to introduce to clinical practice and future trials a new criterion based on the level of global CV risk.

Basic Concepts of Modeling Pesticide Fate in the Crop Root Zone

Weed Science ◽  
1985 ◽  
Vol 33 (S2) ◽  
pp. 25-32 ◽  
Author(s):  
R. J. Wagenet ◽  
P.S.C. Rao
Keyword(s):  
Environmental Fate ◽  
Root Zone ◽  
Effective Means ◽  
Simulation Models ◽  
Cost Effective ◽  
Natural Processes ◽  
Modeling Approach ◽  
Efficacy Trials ◽  
Sorption Leaching ◽  
Crop Root

Modeling is increasingly being used as a tool for the evaluation of the environmental fate of pesticides. Sorption, leaching, degradation, and volatilization are some of the processes being integrated through the use of simulation modeling techniques. Several research programs are focusing their attention on such issues (16, 17, 18, 32, 35), with regulatory agencies involved in management of pesticides also taking a modeling approach (3, 7). Because of the extreme complexity of agroecosystems, it is obvious that the use of simulation models will continue to be the most expeditious, reliable, and cost-effective means of integrating the various processes acting upon a pesticide to determine its fate. For example, modeling will help to summarize and interpret efficacy trials and will provide the vehicle for transferring experimental results to unstudied situations, such as the potential environmental fate of an applied herbicide. However, proper development, testing, and responsible use of a modeling approach must be based upon a thorough, comprehensive understanding of interdependent and dynamic natural processes.

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