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Language: English

In: Journal of agricultural and food chemistry, 10 March 2010, Vol.58(5), pp.3101-6

Description: Sorption of atrazine on soils subjected to three different organic amendments was measured using a batch equilibrium technique. A higher K(F) value (2.20 kg(-1)(mg L(-1))(-N)) was obtained for soil fertilized with compost, which had a higher organic matter (OM) content. A correlation between the K(FOC) values and the percentage of aromatic carbon in OM was observed. The highest K(FOC) value was obtained for the soil with the highest aromatic content. Higher aromatic content results in higher hydrophobicity of OM, and hydrophobic interactions play a key role in binding of atrazine. On the other hand, the soil amended with farmyard manure had a higher content of carboxylic units, which could be responsible for hydrogen bonding between atrazine and OM. Dominance of hydrogen bonds compared to hydrophobic interactions can be responsible for the lower desorption capacity observed with the farmyard manure soil. The stronger hydrogen bonding can reduce the leaching of atrazine into drinking water resources and runoff to rivers and other surface waters.

Keywords: Soil ; Atrazine -- Chemistry ; Environmental Restoration and Remediation -- Methods ; Herbicides -- Chemistry

ISSN: 00218561

E-ISSN: 1520-5118

DOI: 10.1021/jf903937d

URL: View this record in MEDLINE/PubMed

Language: English

In: Plant and Soil, 2015, Vol.387(1), pp.37-47

Description: Aims and background Release of 'non-exchangeable' N[H.sup.4+]-N from interlayers of 2:1 clay minerals is postulated to depend not only on soil solution N[H.sup.4+]-N concentration but also on the concentration of [K.sup.+] and [Ca.sup.2+]. Concentrations of all three cations are altered in rhizosphere compared to soil solution at larger distance from the root surface. Methods Non-exchangeable N[H.sup.4+]-N pool was labelled with [sup.15]N. Treatments including application of [K.sup.+], [Ca.sup.2+] and [K.sup.+] + [Ca.sup.2+] were established. In a compartment system approach we analysed changes in soil solution concentrations of [sup.15]N[H.sup.4+]-N, [sup.15]N[O.sup.-.sub.3]-N, [K.sup.+] and [Ca.sup.2+] in situ at different distances from the root surface over time and related them to the release of non-exchangeable [sup.15]N[H.sup.4+]-N and uptake of [sup.15]N by plants. Results and conclusions The [sup.15]N enrichment in plant tissue was significantly lower in treatments with [K.sup.+] application compared to those without. This was in line with smaller depletion of non-exchangeable [sup.15]N[H.sup.4+]-N in the rhizosphere for these treatments and also with lower [sup.15]N abundance in soil solution N[O.sub.-.sup.3]-N fraction. Hence, [K.sup.+] application hampered the release of N[H.sup.4+] from the interlayers. A promoting effect of increasing [Ca.sup.2+] concentrations on release of non-exchangeable N[H.sup.4+]-N could not be evaluated since the [Ca.sup.2+] concentration in soil solution was largely controlled by small amounts of carbonate contained in the substrate and thus the addition of [Ca.sup.2+] did not result in a relevant increase of soil solution [Ca.sup.2+] concentration as originally intended. The use of [sup.15]N to follow the fate of non-exchangeable N[H.sup.4+]-N proved very useful as it provides a higher sensitivity for all measured fractions compared to total N. However, as soil N fractions equilibrate with each other labelling one fraction exclusively is not possible. Keywords Clay minerals * Non-exchangeable N[H.sup.4+]-N Rhizosphere * Soil solution * Stable isotopes

Keywords: Clay minerals ; Non-exchangeable NH -N ; Rhizosphere ; Soil solution ; Stable isotopes

ISSN: 0032-079X

E-ISSN: 1573-5036

DOI: 10.1007/s11104-014-2275-6

URL: View full text in Springer (Subscribers only)

Language: English

In: Biology and Fertility of Soils, 2011, Vol.47(1), pp.1-14

Description: Fixed NH 4 + (NH 4 + f ) and fixation and defixation of NH 4 + in soils have been the subject of a number of investigations with conflicting results. The results vary because of differences in methodology, soil type, mineralogical composition, and agro-climatic conditions. Most investigators have determined NH 4 + f using strong oxidizing agents (KOBr or KOH) to remove organic N and the remaining NH 4 + f does not necessarily reflect the fraction that is truly available to plants. The content of native NH 4 + f in different soils is related to parent material, texture, clay content, clay mineral composition, potassium status of the soil and K saturation of the interlayers of 2:1 clay minerals, and moisture conditions. Evaluation of the literature shows that the NH 4 + f -N content amounts to 10–90 mg kg −1 in coarse-textured soils (e.g., diluvial sand, red sandstone, granite), 60–270 mg kg −1 in medium-textured soils (loess, marsh, alluvial sediment, basalt) and 90–460 mg kg −1 in fine-textured soils (limestone, clay stone). Variable results on plant availability of NH 4 + f are mainly due to the fact that some investigators distinguished between native and recently fixed NH 4 + while others did not. Recently fixed NH 4 + is available to plants to a greater degree than the native NH 4 + f , and soil microflora play an important role in the defixation process. The temporal changes in the content of recently fixed NH 4 + suggest that it is actively involved in N dynamics during a crop growth season. The amounts of NH 4 + defixed during a growing season varied greatly within the groups of silty (20–200 kg NH 4 + -N ha −1  30 cm −1 ) as well as clayey (40–188 kg NH 4 + -N ha −1  30 cm −1 ) soils. The pool of recently fixed NH 4 + may therefore be considered in fertilizer management programs for increasing N use efficiency and reducing N losses from soils.

Keywords: Fixed NH ; (NH ) ; Native NH ; Recently fixed NH ; N dynamics ; NH ; availability to plants and microflora

ISSN: 0178-2762

E-ISSN: 1432-0789

DOI: 10.1007/s00374-010-0506-4

URL: View full text in Springer

Language: English

In: Agricultural Water Management, October 2017, Vol.192, pp.180-188

Description: Irrigated agriculture is the dominant user of global freshwater resources and improvements in water management are considered key to simultaneously enhance food production and to secure regional water resources. Irrigation management requires reliable estimates of crop evapotranspiration (ET ) which can be derived from tabulated crop coefficients and estimates of phenological stage lengths or alternatively from remotely sensed canopy data. In order to compare both approaches under sufficient nitrogen and water supply, field trials with winter wheat ( L.) were performed in 2013/14 and 2014/15 at Duelmen, Germany. Crop growth dynamics were measured by a handspectrometer and leaf canopy analyzer, and phenological stages were recorded. ET was calculated in two different ways: Firstly based on tabulated crop coefficients (K ) and stage durations (FA-approach) and secondly based on remotely sensed K -values (NDVI-approach). Both approaches were used to calculate a daily field water balance (FWB) and compared with measured (FDR-techniques) dynamics of soil water content. Both ET estimates predicted seasonal dynamics of the FWB reasonably good RMSE: 0.7, 0.6 (FA-approach); 0.6, 0.8 (NDVI-approach) in 2014 and 2015, respectively. ET estimates of the FA approach for 2014 and 2015 were 403 mm and 430 mm and exhibited larger between-year variation when the NDVI approach was used (377 mm and 463 mm). Agronomic water-use efficiencies varied between 1.93–2.76 g/l. The relevance of reliable in-field estimates of Kc-values and stage lengths was quantified with a sensitivity analysis. The results indicate that NDVI-based estimates of ET can be used instead of ET estimates which are based on tabulated Kc values and estimates of growth stage length. The use of NDVI-based estimates of ET enables to apply irrigation water more site-specific.

Keywords: Crop Coefficient ; Stage Duration ; Sensitivity Analysis ; Agriculture

ISSN: 0378-3774

E-ISSN: 1873-2283

DOI: 10.1016/j.agwat.2017.07.010

URL: View record in ScienceDirect (Access to full text may be restricted)

Language: English

In: Chemosphere, 2010, Vol.78, pp.389-396

Description: Includes references ; p. 389-396.

Keywords: Zinc ; Soil Amendments ; Sewage ; Copper ; Soil Pollution ; Lead ; Composts ; Risk Assessment ; Extraction ; Leaching ; Animal Manures ; Luvisols

ISSN: 0045-6535

Source: AGRIS (Food and Agriculture Organization of the United Nations)

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Language: English

In: Chemosphere, 2010, Vol.78(4), pp.389-396

Description: The effects of long-term application of different organic amendments, as compared to mineral fertilizer, on Zn, Cu and Pb content and leachability in a luvisol derived from loess were assessed. The organic fertilizers, applied since 1962, were compost (COM) – from green organic household waste, sewage sludge (SLU) – from municipal water treatment facilities, farmyard manure (FYM) and the doses applied since 1997 were 90 t ha , 10 t ha and 9 t ha , once in 3 years, respectively. The kinetics of metals extraction with 0.05 mol dm EDTA at pH 6.0 has been studied. The was fitted to the kinetic data and allowed to distinguish two pools for each metal: a “labile” fraction ( ), quickly extracted with a rate constant , and a “moderately labile” fraction ( ), more slowly extracted, with a rate constant . Simultaneously, the pseudo-total metal contents in the soil samples were determined after digestion with (3:1 HCl + HNO ). The obtained parameters , , , , for the kinetics of extraction of each metal in the three replicates of each fertilization mode, as well as the pseudo-total metal contents, were statistically analysed. COM and SLU application resulted in an increase of the total contents of Pb, Zn and Cu in soil. Further, the percentage of labile Zn and Pb also increased in consequence of the application of those amendments, particularly COM. The increase was more noticeable for Zn. FYM, despite not increasing the total content of Pb, Zn or Cu, did also have an effect on the leachability of Zn and Pb, increasing their labile fraction in soil. These results point to a potential risk of increasing metals mobility in soil, mainly Zn, associated to the use of organic amendments, particularly COM or SLU.

Keywords: Compost ; Sewage Sludge ; Soils ; Metal Mobility ; Edta ; Kinetics ; Chemistry ; Ecology

ISSN: 0045-6535

E-ISSN: 1879-1298

DOI: 10.1016/j.chemosphere.2009.11.008

URL: View record in ScienceDirect (Access to full text may be restricted)

Language: English

In: Soil Biology and Biochemistry, February 2013, Vol.57, pp.1003-1022

Description: In arable farming systems, the term ‘subsoil’ refers to the soil beneath the tilled or formerly tilled soil horizon whereas the latter one is denoted as ‘topsoil’. To date, most agronomic and plant nutrition studies have widely neglected subsoil processes involved in nutrient acquisition by crop roots. Based on our current knowledge it can be assumed that subsoil properties such as comparatively high bulk density, low air permeability, and poverty of organic matter, nutrients and microbial biomass are obviously adverse for nutrient acquisition, and sometimes subsoils provide as little as less than 10% of annual nutrient uptake in fertilised arable fields. Nevertheless, there is also strong evidence indicating that subsoil can contribute to more than two-thirds of the plant nutrition of N, P and K, especially when the topsoil is dry or nutrient-depleted. Based on the existing literature, nutrient acquisition from arable subsoils may be conceptualised into three major process components: (I) mobilisation from the subsoil, (II) translocation to the shoot and long-term accumulation in the Ap horizon and (III) re-allocation to the subsoil. The quantitative estimation of nutrient acquisition from the subsoil requires the linking of field experiments with mathematical modelling approaches on different spatial scales including Process Based Models for the field scale and Functional–Structural Plant Models for the plant scale. Possibilities to modify subsoil properties by means of agronomic management are limited, but ‘subsoiling’ – i.e. deep mechanical loosening – as well as the promotion of biopore formation are two potential strategies for increasing access to subsoil resources for crop roots in arable soils. The quantitative role of biopores in the nutrient acquisition from the subsoil is still unclear, and more research is needed to determine the bioaccessibility of nutrients in subsoil horizons. ► Subsoil is relevant for nutrient acquisition by plants especially in the long term. ► Biopores in the subsoil can be hot spots for nutrient acquisition. ► A conceptual model of nutrient acquisition from the subsoil is presented.

Keywords: Structure Dynamics ; Biopore Formation ; Root Growth ; Drilosphere ; Rhizodeposition ; Microbial Activity ; Agriculture ; Chemistry

ISSN: 0038-0717

E-ISSN: 1879-3428

DOI: 10.1016/j.soilbio.2012.09.014

URL: View record in ScienceDirect (Access to full text may be restricted)

Language: English

In: Soil biology & biochemistry, 2013, Vol.57, pp.1003-1022

Description: In arable farming systems, the term ‘subsoil’ refers to the soil beneath the tilled or formerly tilled soil horizon whereas the latter one is denoted as ‘topsoil’. To date, most agronomic and plant nutrition studies have widely neglected subsoil processes involved in nutrient acquisition by crop roots. Based on our current knowledge it can be assumed that subsoil properties such as comparatively high bulk density, low air permeability, and poverty of organic matter, nutrients and microbial biomass are obviously adverse for nutrient acquisition, and sometimes subsoils provide as little as less than 10% of annual nutrient uptake in fertilised arable fields. Nevertheless, there is also strong evidence indicating that subsoil can contribute to more than two-thirds of the plant nutrition of N, P and K, especially when the topsoil is dry or nutrient-depleted. Based on the existing literature, nutrient acquisition from arable subsoils may be conceptualised into three major process components: (I) mobilisation from the subsoil, (II) translocation to the shoot and long-term accumulation in the Ap horizon and (III) re-allocation to the subsoil. The quantitative estimation of nutrient acquisition from the subsoil requires the linking of field experiments with mathematical modelling approaches on different spatial scales including Process Based Models for the field scale and Functional–Structural Plant Models for the plant scale. Possibilities to modify subsoil properties by means of agronomic management are limited, but ‘subsoiling’ – i.e. deep mechanical loosening – as well as the promotion of biopore formation are two potential strategies for increasing access to subsoil resources for crop roots in arable soils. The quantitative role of biopores in the nutrient acquisition from the subsoil is still unclear, and more research is needed to determine the bioaccessibility of nutrients in subsoil horizons. ; p. 1003-1022.

Keywords: Topsoil ; Bulk Density ; Roots ; Bioavailability ; Mathematical Models ; Field Experimentation ; Microbial Biomass ; Organic Matter ; Farming Systems ; Subsoiling ; Nutrients ; Poverty ; Nutrient Uptake ; Shoots ; Air ; Arable Soils ; Permeability ; Plant Nutrition

ISSN: 0038-0717

Source: AGRIS (Food and Agriculture Organization of the United Nations)

URL: View full text (authentication may be required)

Language: English

In: Journal of Plant Nutrition and Soil Science, December 2004, Vol.167(6), pp.713-719

Description: Mobilization of non‐exchangeable ammonium (NH) by hyphae of the vesicular‐arbuscular mycorrhizal (VAM) fungus was studied under controlled experimental conditions. Maize () and parsley () were grown either alone or in symbiosis with in containers with separated compartments for roots and hyphal growth. In one experiment, NH was added to the soil to differentiate between the native non‐exchangeable NH and the non‐exchangeable NH derived from N fertilization. Non‐exchangeable NH was mobilized by plant growth. Plant dry weight and N uptake, however, were not significantly influenced by mycorrhizal colonization of the roots. The influence of root infection with mycorrhizal fungus on the mobilization of non‐exchangeable NH was negligible. In the hyphal compartment, hyphal uptake of N resulted in a decrease of NH in the soil solution and of exchangeable NH. However, the NH concentration was still too high to permit the release of non‐exchangeable NH. The results demonstrate that, in contrast to roots, hyphae of VAM fungi are not able to form a non‐exchangeable‐NH depletion zone in the adjacent soil. However, under conditions of a more substantial depletion of the exchangeable NH in the mycorrhizal sphere (, with longer growth), an effect of mycorrhiza on the non‐exchangeable NH might be found. Mobilisierung des nicht‐austauschbaren NH$ _4^+ $‐N im Kontaktraum Wurzel–Boden und Hyphen–Boden bei durch VA‐Mykorrhiza infiziertem Mais (Zea mays) und Petersilie (Petroselinum sativum) Es wurde der Einfluss der Hyphen vesiculär‐arbusculärer Mykorrhiza (VAM) auf die Mobilisierung von nicht austauschbarem NH unter kontrollierten Bedingungen untersucht. Hierzu wurden Mais () und Petersilie () alleine oder in Symbiose mit in speziellen Versuchsgefäßen mit Kompartimenten für ein getrenntes Wurzel‐ und Hyphenwachstum angezogen. In einem Versuch wurde der Versuchsboden mit NH markiert, um eine Differenzierung zwischen bodenbürtigem und nach der Düngung nicht austauschbar gebundenem NH vornehmen zu können. Der Trockenmasseertrag der Pflanzen und der N‐Entzug wurden durch die Mykorrhiza‐Infektion nicht signifikant beeinflusst. Unter Bewuchs wurde zwar nicht austauschbares NH mobilisiert, der Einfluss der Mykorrhiza‐Infektion auf die Mobilisierung dieser N‐Fraktion war allerdings vernachlässigbar, obwohl der N‐Gehalt in den Hyphenkompartimenten abgesenkt wurde. Die NH‐Konzentration war aber wahrscheinlich für eine Mobilisierung des nicht austauschbaren NH noch zu hoch. Insgesamt bringen die Ergebnisse zum Ausdruck, dass im Gegensatz zu den Wurzeln um die Hyphen keine Verarmungszone an nicht austauschbarem NH gebildet wurde. Im Falle einer stärkeren Absenkung des Gehalts an austauschbarem NH in der Mycosphäre (z. B. durch einen längeren Versuchszeitraum) könnte ein Einfluss der Mykorrhiza auf das nicht austauschbare NH jedoch erwartet werden.

Keywords: Nitrogen ; Mobilization ; Vesicular‐Arbuscular Mycorrhiza ; Hyphal Uptake ; Depletion Zone

ISSN: 1436-8730

E-ISSN: 1522-2624

DOI: 10.1002/jpln.200420449

Language: English

In: Journal of Plant Nutrition and Soil Science, April 2002, Vol.165(2), pp.185-189

Description: An experiment with two typical paddy soils from China and two clay minerals was conducted to study the effect of reduction of octahedral Fe on fixation of NH ions. Reduction of octahedral Fe was achieved by treating soils and clay minerals with dithionite‐citrate‐bicarbonate (DCB) followed by dialyzing the samples under oxygen free conditions. Reduction of Fe increased the negative charge of interlayers and resulted in a significantly higher ammonium fixation. Close positive correlations were found between the Fe concentration or the ratio of Fe/Fe and non‐exchangeable NH‐N. Therefore, it is concluded that the reduction of octahedral Fe induced by flooding is one of the important prerequisites for the pronounced ammonium fixation in flooded soils. However, the relation between ΔFe and Δfix‐N was not stoichiometric. Untersuchungen über den Mechanismus der Fixierung und der Freisetzung von Ammonium in Sumpfreisböden nach der Überstauung. 3: Einfluss des Oxidationszustandes des oktaedrischen Fe auf die Ammoniumfixierung Es wurde der Einfluss der Reduktion des oktaedrisch gebundenen Fe auf die Fixierung von NH‐Ionen in zwei typischen chinesischen Sumpfreisböden und zwei Tonmineralen untersucht. Die Reduktion des oktaedrischen Fe erfolgte durch Behandlung der Bodenproben und der Tonminerale mit Dithionit‐Citrat‐Bicarbonat‐Lösung und anschließender Dialyse unter sauerstofffreien Bedingungen. Reduktion des Fe führte zu einer Erhöhung der negativen Ladung der Zwischenschichten, was die Ammoniumfixierung signifikant erhöhte. Zwischen der Fe‐Konzentration oder dem Verhältnis von Fe/Fe und dem Gehalt an nicht austauschbaren NH‐N bestand eine enge positive Beziehung. Dies weist daraufhin, dass die Fixierung von Ammonium von der Reduktion des oktaedrischen Fe und der Ladung der Tonmineralzwischenschichten beeinflusst wird. Hieraus wird abgeleitet, dass die durch die Überflutung des Bodens hervorgerufene Reduktion des oktaedrischen Fe einer der Hauptgründe für die verstärkte Ammoniumfixierung in überfluteten Böden ist. Die Beziehung zwischen Δ Fe und Δfix‐N war allerding nicht stöchiometrisch.

Keywords: Ammonium Fixation ; Clay Minerals ; Paddy Soils ; Octahedral Fe ; Reducing Conditions

ISSN: 1436-8730

E-ISSN: 1522-2624

DOI: 10.1002/1522-2624(200204)165:2〈185::AID-JPLN185〉3.0.CO;2-1