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Farm level implementation of soil conservation measures: farmers’ beliefs and intentions
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Field applications of pure biochar in the North Sea region and across Europe
Get PDFAs demonstrated by several scientific studies there is no doubt that biochar in general is very recalcitrant compared to other organic matter additions and soil organic matter fractions and also that it is possible to sequester carbon at a climate change relevant time scale (~100 years or more) by soil application of biochar. However, the carbon stability of biochar in soil is strongly correlated with the degree of thermal alteration of the original feedstock (the lower the temperature, the larger the labile fraction) and in depth understanding of the technology used and its effect on the biochar quality is necessary in order to produce the most beneficial biochars for soil application. Beside carbon sequestration in soil biochar may improve the GHG balance by reducing N2O and CH4 soil emissions, although contrasting results are found in the literature. The mechanisms behind these reductions remain unclear and more research is required in order to investigate the various hypotheses in more detail, and to unravel the complex interaction between biochar, crop and soil, especially under field conditions. In conclusion, our current knowledge is largely based on short-term lab studies and pot experiments, which have provided detailed insight in certain processes and aspects of biochar application to soils, but suffer from large uncertainties when scaled-up to the farmers field level. In order to produce more realistic scenarios of the potential impact of biochar on C sequestration and soil GHG emissions there is a need to bring biochar research up to the field-scale, and to perform longer-term studies
Effects of biochar on soil processes, soil functions and crop growth
Get PDFBiochar is the carbon-rich product obtained when organic material is pyrolyzed, during which bioenergy is produced. When applied to soil, biochar is claimed to have positive effects on soil properties and processes and carbon could be sequestered. For these reasons, biochar production and application to soil is often associated with raising agricultural productivity while mitigating climate change. Especially in (tropical) highly weathered soils, biochar has shown positive effects on soil properties and crop yields, but it is uncertain whether the same positive effects can be obtained in (temperate) more fertile soils. Therefore the overarching aim of this PhD research was to get a better understanding of biochar effects on soil chemical, physical and biological properties, plant growth, and soil greenhouse gas emissions in agricultural northwestern European soils. Lab, pot and field experiments have been conducted to gain insight into biochar effects on plant and soil.
15N tracing lab experiments suggested that in the short term, biochar addition to soil stimulated mineralization of more complex SOC, thereby increasing mineral N availability. However, in the absence of plants this available N was rapidly, biotically immobilized. Furthermore, nitrification rates were increased with biochar addition. In contrast, in the longer term, these effects faded, probably due to the transient effects of biochar labile C fraction and pH. Moreover, lab experiments have shown that biochar can reduce mineral N availability in the short term, likely due to biotic or abiotic N immobilization. It is unknown when and to which extent the immobilized N could become available again. These experiments also show that biochar can increase soil pH, through which several soil processes can be affected, e.g. NH3 volatilization, nitrification and denitrification However, bulk soil pH was not always significantly increased by biochar addition. There was a trend for a higher increase in soil pH after biochar application in low pH soils while at more neutral soil pH, this was not the case as observed in the biochar field trial. It cannot be excluded that elevated pH micro-sites close to biochar particles affect soil processes, despite biochar having no effect on bulk soil pH.
In the short term, likely microbial activity and abundance should be altered through biochar, as the 15N tracing experiments showed that biochar affected soil N cycling in the short term. This effect seems to be transient, probably due to a change in biochar properties, as biochar seems to act as an inert substance regarding N cycling in the longer term as biochar seems to act as an inert substance regarding N cycling in the longer term. This was shown by a 15N tracing experiment conducted with soil sampled one year after biochar application.
Furthermore, biochar addition to soil did not influence soil microbiological community structure to a large extent in six European North Sea region countries during the first year after biochar application, as only certain bacterial biomarker PLFAs were significantly affected by biochar addition. It was remarkable that fungal biomarker PLFAs were not significantly influenced by biochar addition.
Biochar addition to soil reduced N2O and NO emissions compared to the control soil after urea and NO3- fertilizer application, and NO emissions after NH4+ fertilizer application. N2O emissions were more decreased at high compared to low pyrolysis temperatures. Also reduced NO3- availability after biochar addition was observed. We hypothesize that decreased N2O and NO emissions were mediated by multiple interacting phenomena: stimulated NH3 emissions, microbial N immobilization, non-electrostatic sorption of NH4+ and NO3-, and pH effects.
Pot trial results showed that biochar can cause short-term reductions in biomass production due to reduced NO3- availability. This effect was biochar feedstock and pyrolysis temperature dependent. Hence biochar addition might in some cases require increased fertilizer N application to avoid crop growth retardation.
In the field trial, a complex interaction between soil physical parameters, time after biochar application and time of tillage operations was observed. Effects on bulk density, porosity and soil water retention curves were non-consistent over time, possibly due to interaction with tillage operations. Biochar increased soil water content in 2012, although mostly not significantly. However, in 2013, when soil water content was overall lower compared to during 2012, it was not affected by biochar addition.
Under field circumstances, biochar addition to soil did not affect spring barley grain or straw yield, nor N or P uptake during the first two years after biochar application. In the field trial, biochar was applied to soil in autumn, as it was our hypothesis that there could be a negative crop response due to reduced N availability when the biochar would be applied in spring and a crop would be immediately sown. However, biochar did not affect soil mineral N availability, neither immediately after biochar application, nor afterwards.
Overall, our results indicate that biochar has mixed effects on soil quality properties in the short term, as effects can be positive, negative, and neutral. The field trial results showed that in medium term, biochar does hardly affect soil properties. Our study shows relatively short-term results, and long-term data are needed to confirm these first results
Ruimtelijke en temporele variabiliteit van bodemverliezen als gevolg gewasoogst
Get PDFRuimtelijke en temporele variabiliteit van bodemverliezen als gevolg van gewasoogst Decennialang werden water- en winderosie beschouwd als de belangrijkste bodemerosieprocessen op akkerland. In het begin van de jaren 90 heeft m en vastgesteld dat ook bodembewerkingen, zoals ploegen, aanzienlijke bod emherverdelingen teweeg kunnen brengen met gevolgen voor de bodemkwalite it. Dat ook het oogsten van gewassen zoals suikerbieten, aardappelen, ci choreiwortelen, penen, cassave en zoete aardappel tot een verlaging van het bodemprofiel kan leiden, werd door aardwetenschappers tot hiertoe ui terst zelden in rekening gebracht. Nochtans kunnen aanzienlijke massas grondkluiten en grond die aan dergelijke gewassen blijft kleven samen me t de oogst van de akker geëxporteerd worden. Dit bodemverlies wordt afge kort als SLCH of Soil Loss due to Crop Harvesting. In dit proefschrift werd het belang en de controlerende factoren van SLC H onderzocht op verschillende ruimtelijke en temporele schaalniveaus. Hi ertoe werd een uitgebreide literatuur studie uitgevoerd, werden veldmeti ngen verricht en grondtarragegevens van gewasverwerkende fabrieken geana lyseerd. De aandacht ging hierbij vooral uit naar machinaal gerooide sui kerbieten en aardappelen aangezien zij qua areaal veruit de belangrijkst e SLCH-gewassen in België en Europa zijn.SLCH-waarden variëren van enkel e Mg tot enkele tientallen Mg per hectare en per oogst. Dit is van dezel fde grootteorde als bodemverliezen door water- en bewerkingserosie. De c ontrolerende factoren kunnen worden onderverdeeld in vier categorieën, m et name bodem, gewaskenmerken, landbouwpraktijken en oogsttechniek. Bij de oogst van suikerbieten bleek bodemvocht tijdens het rooien de belangr ijkste controlerende variabele te zijn. Dit is in tegenstelling tot de o ogst van aardappelen. Anders dan bij suikerbieten, is het niet de grond die aan het gewas kleeft, maar de grondkluiten die voor de grootste vari atie aan bodemverliezen zorgen. Deze grondkluiten zijn voornamelijk afha nkelijk van de bodemtextuur. Verschillen in oogsttechniek kunnen vergeli jkingen binnen Europa bemoeilijken en zorgen ervoor dat resultaten van g emechaniseerde landbouw in Europa niet zomaar geëxtrapoleerd kunnen word en naar niet-gemechaniseerde landbouw elders in de wereld. Ook op lange termijn spelen, naast veranderingen in gewasopbrengsten, evoluties in oo gsttechniek een belangrijke rol. Voor de mechanisatie waren bodemverliez en door gewasoogst slechts een derde tot een vijfde van de huidige bodem verliezen. Bij het begin van de mechanisatie stegen deze bodemverliezen sterk, waarna ze, vooral vanaf het eind van de jaren 80, terug begonnen af te nemen omwille van een betere reinigingscapaciteit van de rooimach ines. Op langere termijn moeten ook gewasrotaties in rekening worden geb racht. In het midden van de 19de eeuw bedroeg SLCH in België gemiddeld 0 .4 Mg per hectare en per jaar. Dit gemiddeld bodemverlies steeg naar 2.4 Mg ha-1 jaar-1 in de jaren 70 terwijl de huidige bodemverliezen ca. 1. 8 Mg ha-1 jaar-1 bedragen. Dit zorgde sedert 1846 voor een bodemprofielv erlaging van 1.2 cm of een totale bodemexport van de Belgische akkers va n meer dan 163 miljoen Mg (109 hm³). De hoeveelheid grond die in Vlaande ren omwille van gewasoogst over de weg wordt getransporteerd, i.e. jaarl ijks meer dan 600 000 Mg of 0.4 hm³ (ca. 20 000 vrachtwagens van 30 Mg), is aanzienlijk groter dan de massa grond die jaarlijks omwille van wate rerosie, i.e. ca. 360 000 Mg, in de rivieren terechtkomt.status: Publishe
Biochar carbon stability and effect on greenhouse gas emissions
No full textAs demonstrated by several scientific studies there is no doubt that biochar in general is very recalcitrant compared to other organic matter additions and soil organic matter fractions and also that it is possible to sequester carbon at a climate change relevant time scale (~100 years or more) by soil application of biochar. However, the carbon stability of biochar in soil is strongly correlated with the degree of thermal alteration of the original feedstock (the lower the temperature, the larger the labile fraction) and in depth understanding of the technology used and its effect on the biochar quality is necessary in order to produce the most beneficial biochars for soil application. Beside carbon sequestration in soil biochar may improve the GHG balance by reducing N2O and CH4 soil emissions, although contrasting results are found in the literature. The mechanisms behind these reductions remain unclear and more research is required in order to investigate the various hypotheses in more detail, and to unravel the complex interaction between biochar, crop and soil, especially under field conditions. In conclusion, our current knowledge is largely based on short-term lab studies and pot experiments, which have provided detailed insight in certain processes and aspects of biochar application to soils, but suffer from large uncertainties when scaled-up to the farmers field level. In order to produce more realistic scenarios of the potential impact of biochar on C sequestration and soil GHG emissions there is a need to bring biochar research up to the field-scale, and to perform longer-term studies.As demonstrated by several scientific studies there is no doubt that biochar in general is very recalcitrant compared to other organic matter additions and soil organic matter fractions and also that it is possible to sequester carbon at a climate change relevant time scale (~100 years or more) by soil application of biochar. However, the carbon stability of biochar in soil is strongly correlated with the degree of thermal alteration of the original feedstock (the lower the temperature, the larger the labile fraction) and in depth understanding of the technology used and its effect on the biochar quality is necessary in order to produce the most beneficial biochars for soil application. Beside carbon sequestration in soil biochar may improve the GHG balance by reducing N2O and CH4 soil emissions, although contrasting results are found in the literature. The mechanisms behind these reductions remain unclear and more research is required in order to investigate the various hypotheses in more detail, and to unravel the complex interaction between biochar, crop and soil, especially under field conditions. In conclusion, our current knowledge is largely based on short-term lab studies and pot experiments, which have provided detailed insight in certain processes and aspects of biochar application to soils, but suffer from large uncertainties when scaled-up to the farmers field level. In order to produce more realistic scenarios of the potential impact of biochar on C sequestration and soil GHG emissions there is a need to bring biochar research up to the field-scale, and to perform longer-term studies
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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