scholarly journals Strong hydroclimatic controls on vulnerability to subsurface nitrate contamination across Europe

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
R. Kumar ◽  
F. Heße ◽  
P. S. C. Rao ◽  
A. Musolff ◽  
J. W. Jawitz ◽  
...  
Keyword(s):  
Root Zone ◽  
Aridity Index ◽  
Nitrate Contamination ◽  
Transient Behaviour ◽  
Time Dynamics ◽  
Transport Dynamics ◽  
Transient Nature ◽  
Reactive Solutes ◽  
Biogeochemical Transformations ◽  
Hydrologic Transport

AbstractSubsurface contamination due to excessive nutrient surpluses is a persistent and widespread problem in agricultural areas across Europe. The vulnerability of a particular location to pollution from reactive solutes, such as nitrate, is determined by the interplay between hydrologic transport and biogeochemical transformations. Current studies on the controls of subsurface vulnerability do not consider the transient behaviour of transport dynamics in the root zone. Here, using state-of-the-art hydrologic simulations driven by observed hydroclimatic forcing, we demonstrate the strong spatiotemporal heterogeneity of hydrologic transport dynamics and reveal that these dynamics are primarily controlled by the hydroclimatic gradient of the aridity index across Europe. Contrasting the space-time dynamics of transport times with reactive timescales of denitrification in soil indicate that ~75% of the cultivated areas across Europe are potentially vulnerable to nitrate leaching for at least one-third of the year. We find that neglecting the transient nature of transport and reaction timescale results in a great underestimation of the extent of vulnerable regions by almost 50%. Therefore, future vulnerability and risk assessment studies must account for the transient behaviour of transport and biogeochemical transformation processes.

The potential impact of soil carbon content on ground water nitrate contamination

1996 ◽  
Vol 33 (4-5) ◽  
pp. 227-232 ◽  
Author(s):  
D. D. Adelman ◽  
M. A. Tabidian
Keyword(s):  
Ground Water ◽  
Soil Carbon ◽  
Nitrate Leaching ◽  
Management Practices ◽  
Root Zone ◽  
Denitrifying Bacteria ◽  
Farm Management ◽  
Nitrate Contamination ◽  
Risk Calculation ◽  
Carbon Level

A potential buildup of nitrate in the ground water resources of the eastern Sandhills of Nebraska has been projected to occur due to the intensive use of nitrogen fertilizer on irrigated cropland. A root-zone nitrate leaching study in this area revealed that soils with a high carbon concentration had minimal leaching compared to soils with lower concentrations. Soils high in carbon have an active population of denitrifying bacteria possibly causing denitrification and in turn reduction of nitrate leaching. Denitrifying bacteria are principally heterotrophic using soil organic carbon for both an energy and carbon source. The objective of this research was to interpret how root-zone denitrification affected nitrate leaching and ground water contamination by nitrate. A modified version of a solute transport model developed for the Eastern Sandhills was used to assess the risk of nitrate contamination for combinations of fertilizer and irrigation rates and for various soil carbon levels. The first attempt was to make risk assessment with eight farm management practices for cells with increasingly greater carbon levels until only those cells with the greatest carbon level were kept in production. Results of this assessment showed that even with excessive fertilizer and irrigation rates, risk of nitrate leaching was reduced as the minimum carbon level was increased. However, since less cropland was leaching nitrate with each successive risk calculation, the impact that root-zone denitrification had in nitrate leaching reduction could not be definitively determined. This prompted a model modification of the risk calculation procedure which kept all cropland in production and computed nitrate leachate risk for increasingly higher artificial carbon levels during successive risk calculations. Changing carbon levels was still more detrimental on nitrate leaching rates than changing farm management practices.

Towards large-scale characterization of subsurface vulnerability due to agrochemical pollutants across Europe

2020 ◽  
Author(s):  
Rohini Kumar ◽  
Falk Hesse ◽  
Suresh Rao ◽  
Andreas Musolff ◽  
James Jawitz ◽  
...  
Keyword(s):  
Large Scale ◽  
Root Zone ◽  
Soil Layer ◽  
Aridity Index ◽  
Climatic Forcing ◽  
Transport Reaction ◽  
Near Surface ◽  
Subsurface Contamination ◽  
Continental Scale ◽  
Spatio Temporal

<p>Subsurface contamination due to diffuse agrochemical pollutants such as pesticides, herbicides, excess nutrients (N, P, K) is a widespread problem in a cultivated areas across Europe. Large-scale spatio-temporal patterns emerge from interplay of heterogeneous and dynamic hydrologic and biogeochemical processes in the near-surface critical zone (top one-meter of root-zone soil layer) which contribute to landscape filtering of stochastic hydro-climatic forcing. Such outcomes are of interest in characterizing the transient behavior of transport-reaction dynamics operating in the root-zone soil compartment which drive recharge and solute loads to sub-surface compartments (shallow groundwater and eventually to river networks).  Here, using novel state-of-the art daily-scale hydrologic simulations (mHM; around 5x5 km grid) driven by observed hydro-climatic forcing, we demonstrate the strong spatio-temporal heterogeneity of hydrologic transport at the continental scale – reflected in time-varying travel time distributions (TTDs) – primarily controlled by the prevailing hydro-climatic gradient of aridity index across Europe. We link the space-time dynamics of TTDs – representing the intrinsic vulnerability of hydrologic system - to spatial heterogeneity and temporal fluctuations of biogeochemical turnover time-scales to provide a parsimonious  biogeochemical model for identifying the extent of subsurface contamination due to diffuse (agrochemical) pollutants. Our assessment results show a large increase in the extent of vulnerable areas that are prone to subsurface nitrate leaching across Europe, compared to current (static) indices based approaches. We highlight the implications of improved vulnerability maps to better support agricultural subsidies and nitrate management across Europe. </p>

scholarly journals Estimating spatial mean root-zone soil moisture from point-scale observations

2006 ◽  
Vol 3 (4) ◽  
pp. 1447-1485 ◽  
Author(s):  
A. J. Teuling ◽  
R. Uijlenhoet ◽  
F. Hupet ◽  
E. E. van Loon ◽  
P. A. Troch
Keyword(s):  
Soil Moisture ◽  
Root Zone ◽  
Spatial Scales ◽  
Space Time ◽  
Time Variability ◽  
Point Scale ◽  
Area Index ◽  
Time Dynamics ◽  
Landscape Characteristics ◽  
Moisture Field

Abstract. Root zone soil moisture is a key variable in many land surface hydrology models. Often, however, there is a mismatch in the spatial scales at which models simulate soil moisture and at which soil moisture is observed. The limited spatial support of observations combined with the large spatial variability of the soil moisture field complicates model validation. The increased availability of detailed datasets on space-time variability of root-zone soil moisture allows for a posteriori analysis of the uncertainties in the relation between point-scale observations and the spatial mean. In this paper we analyze three comprehensive datasets from three different regions. We identify different strategies to select observation sites, and we present methods for quantifying the uncertainty that is associated with each strategy. In general there is a large correspondence between the different datasets with respect to the relative uncertainties for the different strategies. For all datasets, the uncertainty can be strongly reduced if some information is available that relates soil moisture at that site to the spatial mean. However this works best if the space-time dynamics of the soil moisture field are known. Selection of the site closest to the spatial mean on a single random date only leads to minor reduction of the uncertainty with respect to the spatial mean over seasonal timescales. Since soil moisture variability is the result of a complex interaction between soil, vegetation, and landscape characteristics, the soil moisture field will be correlated with some of these characteristics. Using available information, we show that the correlation with leaf area index or a wetness coefficient alone is insufficient to predict if a site is representative for the spatial mean soil moisture.

scholarly journals Soil electrical conductivity estimated by time domain reflectometry and electromagnetic induction sensors: Accounting for the different sensor observation volumes

2017 ◽  
Vol 48 (4) ◽  
pp. 223-234 ◽  
Author(s):  
Ali Saeed ◽  
Alessandro Comegna ◽  
Giovanna Dragonetti ◽  
Nicola Lamaddalena ◽  
Angelo Sommella ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Spatial Scale ◽  
Time Domain ◽  
Electromagnetic Induction ◽  
Root Zone ◽  
Saline Water ◽  
Time Domain Reflectometry ◽  
Regression Equations ◽  
Time Dynamics ◽  
Observation Volume

This paper dealt with the calibration of an EMI sensor for monitoring the time dynamics of root zone salinity under irrigation with saline water. Calibration was based on an empirical multiple regression approach largely adopted in the past and still applied in practice for its relative simplicity. Compared to the more complex inversion approaches, it requires an independent dataset of local σb measured within discrete depth intervals, to be compared to horizontal and vertical electrical conductivity (ECaH and ECaV) readings for estimating the parameters of the empirical regression equations. In this paper, we used time domain reflectometry (TDR) readings to replace direct sampling for these local σb measurements. When using this approach, there is the important issue of taking into account the effect of the different sensor observation volumes, making the readings not immediately comparable for empirical calibration. Accordingly, a classical Fourier’s filtering technique was applied to remove the high frequency part (at small spatial scale) of the original data variability, which, due to the different observation volume, was the main source of dissimilarity between the two datasets. Thus, calibration focused only on the lower frequency information, that is, the information at a spatial scale larger than the observation volume of the sensors. By this analysis, we showed and quantified the degree to which the information of the set of TDR readings came from a combination of local and larger scale heterogeneities and how they have to be manipulated for use in EMI electromagnetic induction sensor calibration.

Ferrihydrite dissolution at the root zone of crops under semi-arid condition controls the plant uptake of uranium and arsenic

2020 ◽  
Author(s):  
Arindam Malakar ◽  
Michael Kaiser ◽  
Daniel D. Snow ◽  
Harkamal Walia ◽  
Chittaranjan Ray
Keyword(s):  
Plant Uptake ◽  
Root Zone ◽  
Arid Condition ◽  
Semi Arid

Managing Landscape Irrigation to Avoid Soil and Nutrient Losses

EDIS ◽  
2013 ◽  
Vol 2013 (11) ◽  
Author(s):  
George Hochmuth ◽  
Laurie Trenholm ◽  
Don Rainey ◽  
Esen Momol ◽  
Claire Lewis ◽  
...  
Keyword(s):  
Natural Environment ◽  
Management Practices ◽  
Root Zone ◽  
Irrigation Management ◽  
Critical Factor ◽  
Nutrient Losses ◽  
County Agents ◽  
The Right ◽  
Soil And Water

Proper irrigation management is critical to conserve and protect water resources and to properly manage nutrients in the home landscape. How lawns and landscapes are irrigated directly impacts the natural environment, so landscape maintenance professionals and homeowners must adopt environmentally-friendly approaches to irrigation management. After selecting the right plant for the right place, water is the next critical factor to establish and maintain a healthy lawn and landscape. Fertilization is another important component of lawn and landscape maintenance, and irrigation must be applied correctly, especially following fertilization, to minimize potential nutrient losses. This publication supplements other UF/IFAS Extension publications that also include information on the role of soil and the root zone in irrigation management. This publication is designed to help UF/IFAS Extension county agents prepare materials to directly address nutrient losses from lawns and landscapes caused by inadequate irrigation management practices. This 6-page fact sheet was written by George Hochmuth, Laurie Trenholm, Don Rainey, Esen Momol, Claire Lewis, and Brian Niemann, and published by the UF Department of Soil and Water Science, October 2013. http://edis.ifas.ufl.edu/ss586

Orientation of processes of biological nitrogen transformation in winter rye agroecosystems under different levels of fertilization background

2016 ◽  
Vol 3 (3) ◽  
pp. 28-34
Author(s):  
V. Volkogon ◽  
I. Korotka
Keyword(s):  
Root Zone ◽  
Field Studies ◽  
Nitrogen Transformation ◽  
Mineral Nitrogen ◽  
Nitrogen Fertilizers ◽  
Winter Rye ◽  
Podzolic Soils ◽  
Microbial Preparation ◽  
Biological Nitrogen

Aim. To determine physiologically expedient rates of mineral nitrogen in winter rye production on sod-podzol- ic soils based on the orientation of the processes of biological nitrogen transformation in the plants rhizosphere. Methods. Field studies, gas chromatography determination of potential nitrogen fi xation activity and potential emissions of N 2 O. Results. The results obtained have demonstrated that the rates of mineral nitrogen, not ex- ceeding 60 kg/ha, can be considered physiologically expedient for winter rye production on sod-podzolic soils. Under the application of microbial preparation Diazobakteryn, there is a higher physiological need of plants for nitrogen, which allows increasing the rates of nitrogen fertilizers up to 90 kg/ha. Conclusions. The orienta- tion of the processes of biological nitrogen transformation in the root zone of plants is a reliable indicator of determining the appropriateness of nitrogen fertilization of crops.

Effectiveness of complex inoculation of spring wheat with N[2] -fi xing bacteria Azospirillum brasilense and mold-antagonist Chaetomium cochliodes

2014 ◽  
Vol 1 (3) ◽  
pp. 57-61
Author(s):  
E. Kopylov
Keyword(s):  
Spring Wheat ◽  
Root Zone ◽  
Wheat Root ◽  
Root Surface ◽  
Atmospheric Nitrogen ◽  
Rhizospheric Soil ◽  
Chain Reaction ◽  
Wheat Roots ◽  
Chlorophyll A And B ◽  
Polymerase Chain

Aim. To study the specifi cities of complex inoculation of spring wheat roots with the bacteria of Azospirillum genus and Chaetomium cochliodes Palliser 3250, and the isolation of bacteria of Azospirillum genus, capable of fi xing atmospheric nitrogen, from the rhizospheric soil, washed-off roots and histoshere. Materials and meth- ods. The phenotypic features of the selected bacteria were identifi ed according to Bergi key. The molecular the polymerase chain reaction and genetic analysis was used for the identifi cation the bacteria. Results. It has been demonstrated that during the introduction into the root system of spring wheat the strain of A. brasilensе 102 actively colonizes rhizospheric soil, root surface and is capable of penetrating into the inner plant tissues. Conclusions. The soil ascomucete of C. cochliodes 3250 promotes better settling down of Azospirillum cells in spring wheat root zone, especially in plant histosphere which induces the increase in the content of chlorophyll a and b in the leaves and yield of the crop.

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