Chemically versus thermally processed brown shrimp shells or Chinese mitten crab as a source of chitin, nutrients or salts and as microbial stimulant in soilless strawberry cultivation

Brown shrimp (Crangon crangon) shells and Chinese mitten crab (Efiocheir sinensis) were chemically demineralized and deproteinized (denoted as M1 to M4 for the shrimp shells and MS to M7 for the Chinese mitten crab), and shrimp shells were torrefied at 200 to 300 degrees C (denoted as R200, R255, R300), and were compared with a commercially available chitin source (denoted as reference chitin). Based on their chemical characteristics, a selection of chitin sources was tested for their N mineralization capacity. The N release was high for the chemically treated shrimp shells and Chinese mitten crab, but not for the Dandled shrimp shells with or without acid treatment, indicating that treatment at 200 et or higher resulted in low N availability. Interaction with nutrients was tested in a leaching experiment with limed peat for three thermally and two chemically processed shrimp shells and the reference chitin source. The K concentrations in the leachate for the chemically treated shrimp shells and the reference chitin were lower than for limed peat during fertigation. Irreversible K retention was observed for one source of chemically treated shrimp shells, and the reference chitin. The thermally treated shrimp shells had a significantly higher net release of P. Na and CI than the treatment without chitin source. Three shrimp shell based materials (M4, R200 and 8300) and the reference chitin were tested in a greenhouse trial with strawberry at a dose of 2 g/L limed peat. A very positive and significant effect on Borryris cinerea disease suppression in the leaves was found for the reference chitin, M4 and R200 compared to the unamended control. The disease suppression of the 3 chitin sources was linked with an increase of the microbial biomass in the limed peat with 24% to 28% due to chitin decomposition and a 9-44% higher N uptake in the plants

Tapping into the maize root microbiome to identify bacteria that promote growth under chilling conditions

Background When maize (Zea mays L.) is grown in the Northern hemisphere, its development is heavily arrested by chilling temperatures, especially at the juvenile phase. As some endophytes are beneficial for plants under stress conditions, we analyzed the impact of chilling temperatures on the root microbiome and examined whether microbiome-based analysis might help to identify bacterial strains that could promote growth under these temperatures. Results We investigated how the maize root microbiome composition changed by means of 16S rRNA gene amplicon sequencing when maize was grown at chilling temperatures in comparison to ambient temperatures by repeatedly cultivating maize in field soil. We identified 12 abundant and enriched bacterial families that colonize maize roots, consisting of bacteria recruited from the soil, whereas seed-derived endophytes were lowly represented. Chilling temperatures modified the root microbiome composition only slightly, but significantly. An enrichment of several chilling-responsive families was detected, of which the Comamonadaceae and the Pseudomonadaceae were the most abundant in the root endosphere of maize grown under chilling conditions, whereas only three were strongly depleted, among which the Streptomycetaceae. Additionally, a collection of bacterial strains isolated from maize roots was established and a selection was screened for growth-promoting effects on juvenile maize grown under chilling temperatures. Two promising strains that promoted maize growth under chilling conditions were identified that belonged to the root endophytic bacterial families, from which the relative abundance remained unchanged by variations in the growth temperature. Conclusions Our analyses indicate that chilling temperatures affect the bacterial community composition within the maize root endosphere. We further identified two bacterial strains that boost maize growth under chilling conditions. Their identity revealed that analyzing the chilling-responsive families did not help for their identification. As both strains belong to root endosphere enriched families, visualizing and comparing the bacterial diversity in these communities might still help to identify new PGPR strains. Additionally, a strain does not necessarely need to belong to a high abundant family in the root endosphere to provoke a growth-promoting effect in chilling conditions

Grow - store - steam - re-peat : reuse of spent growing media for circular cultivation of Chrysanthemum

Substantially extending the life span of peat- and perlite-based growing media is a measure to increase the sustainability of soilless cultivation. The extraction of peat from pristine peatlands threatens these sensitive ecosystems and carbon sinks, meanwhile resulting in increased emissions of greenhouse gasses. Each batch of peat that is reused, results in a clear reduction in CO2 emissions and a lower impact on the climate. After using growing media for one cultivation, we aim at reusing the spent material as growing medium for another crop. Spent peat and perlite-based growing media from strawberry and cucumber cultivation were upcycled after steam treatment. We tested the effectiveness of steaming to reduce phytosanitary risks. The hygienisation efficiency of the steam treatment was confirmed: plant pathogenic fungi, larvae of vine weevils and weed seeds added or already present before the process were killed by the steam treatment. As the upcycled spent growing medium already contained high nutrient levels, the fertilizer application in the reused growing medium should be reduced, especially for P and K. Five indicators for assessing stability of the materials were used: CO2 flux measurements, oxygen uptake rate (OUR), biodegradation potential, mineral N content and risk for N immobilization. The spent growing media had a low decomposition rate and the release of nutrients in a leaching experiment was lower than for a fertilized peat-based growing medium, being a reference blend for open field cultivated Chrysanthemum. N mineralisation and P uptake were tested in an incubation and pot trial, respectively, and the upcycled spent growing medium was found to be an important source of plant-available K and P. Steam treatment did not severely affect the microbial biomass and diversity of the spent growing media. Blending the steam-treated spent media with other materials or inoculating by a commercially available biocontrol fungus also had a limited effect, indicating that newly introduced microorganisms do not easily establish in steamed-treated spent growing media (SSGM). Acidification of the SSGM was achieved by a low dose of elemental S. The steam-treated growing medium was tested for growing Chrysanthemum cuttings and plantlets. Spent growing media were not able to supply sufficient mineral N, but the stored amounts of P and K in the media were sufficiently plant available for optimal crop growth

Complexation of copper with dissolved organic matter in soil solution: relationship with organic matter characteristics and effects on mobility of copper in the soil profile

Langdurig gebruik van dierlijke mest, fungiciden en slib in de landbouw heeft het gehalte aan koper (Cu) in de bodem verhoogd. Door een verstren gd milieubeleid zijn de huidige koperemissies naar landbouwbodems lager dan vroeger. Toch blijft de koperconcentratie in de bodem stijgen in geb ieden met intensieve landbouw. Op lange termijn kan dit tot negatieve ef fecten op de bodemkwaliteit leiden. Bovendien kan verhoogde uitloging va n Cu vanuit bodem naar grondwater een effect hebben op de kwaliteit van het aquatisch systeem. Deze studie onderzoekt de processen die koperuitl oging in de bodem beïnvloeden. Kopermobiliteit in de bodem is sterk gere lateerd aan de concentratie van de opgeloste organische stof (DOM, Disso lved Organic Matter), aanwezig in de bodemoplossing, die sterke complexe n vormt met Cu2+. De samenstelling van DOM is bijzonder variabel en het is niet duidelijk in welke mate de kopermobilisatie beïnvloed wordt door deze structurele variabiliteit van DOM (hierna de DOM-kwaliteit genoemd ). Het doel van deze studie is de variabiliteit in koperaffiniteit van D OM te kwantificeren en te relateren aan de variabiliteit in DOM-oorspron g en eigenschappen. Daarnaast wordt het belang van de dissociatiek inetiek van Cu-DOM-complexen voor koperuitloging in bodems nagegaan. In deze studie werd een methode ontwikkeld om het kopermobilisatiepotent ieel (CuMP) van DOM te bepalen. In deze methode wordt de koperconcentrat ie gemeten die door DOM gecomplexeerd is bij een constante en voor de bo dem relevante samenstelling (pCu 11,3; pH 7,0; [Ca] = 1,5 mM). Het CuMP, uitgedrukt per eenheid opgeloste organische koolstof (DOC, Dissolved Or ganic Carbon), varieerde tienvoudig voor DOM die geïsoleerd werd uit een reeks landbouwbodems. De specifieke UV-absorbantie van DOM bij 254 nm ( SUVA, een maat voor de aromaticiteit) was significant positief gecorrele erd met het CuMP (r = 0,76). Bodemextracties (met water of zoutoplossing en) isoleerden meer én structureel verschillende DOM dan de DOM aanwezig in bodemoplossingen (poriewater) die bemonsterd werden via bodemcentrif ugatie. Het courant gebruik van bodemextracties, eerder dan poriewateris olatie-methodes, om DOM te isoleren en te karakteriseren moet bijgevolg ontmoedigd worden. Droog/nat-cycli of het lang droog bewaren van bodems verhogen DOM-concentraties. Deze extra DOM vertoont lage SUVA- en CuMP-w aarden en is gemakkelijk afbreekbaar omdat het minder gehumificeerd is. In een akkerveld werden uitloogoplossingen gedurende 5 opeenvolgende maa nden bemonsterd op 45 cm diepte. Opgeloste Cu- en DOC-concentraties vari eerden zevenvoudig en waren slechts zwak gecorreleerd (r = 0,56). De [Cu ]/[DOC]-verhouding varieerde vijfvoudig en vertoonde een significant pos itieve correlatie (r = 0,77) met de SUVA van DOM. Dit bevestigde de toen emende koperaffiniteit van DOM bij hogere aromaticiteit. De hoogste [Cu] /[DOC]-verhoudingen werden waargenomen bij de laagste DOC-concentraties. Voorspellingen van de koperconcentraties in oplossing met het WHAM6-mod el verbeterden systematisch wanneer de DOM-eigenschappen, meer bepaald d e SUVA-waarden, in rekening gebracht werden. De resultaten van dit labo- en veldexperiment tonen het belang aan van de DOM-kwaliteit om de koper mobiliteit in bodems in te schatten. Om de koperaffiniteit te relateren aan de DOM-structuur zijn aangepaste methodes nodig voor de karakterisering van bodem-DOM. Er werd een geauto matiseerde kolomfractionatiemethode ontwikkeld die 10 mL DOM-stalen opsp litst in hydrofiele (HPI), hydrofobe zure (HPOA) en hydrofobe neutrale ( HPON) fracties. De verdeling van DOM uit 8 bodems varieerde tussen 31 72 % HPI, 25 46% HPOA en 2 28% HPON DOM-componenten. Binnen elk DOM-staal w as de SUVA van HPI DOM steeds lager dan van HPOA DOM. Fractionatie resul teerde echter niet in een verminderde variabiliteit van de SUVA-waarden binnen de fracties ten opzichte van de niet-gefractioneerde stalen. Bijg evolg kan er getwijfeld worden aan de aanname dat fractionaties resulter en in meer homogene fracties. Het onderzoek naar de variatie van DOM-kwaliteit werd uitgebreid met een aantal bodembehandelingen, bodemoplossingsbemonsteringsmethodes en enke le niet-landbouw-bodems, waaronder venen en bosbodems. De DOC-concentrat ies varieerden tussen 4 en 175 mg L 1 waarbij de laagste waarden werden waargenomen voor akkerbodems. De SUVA varieerde tussen 18 en 54 L g 1 cm 1, het percentage humuszuren (%HA) tussen 17 en 76%, het %HPI tussen 4 en 34%, het %HPOA tussen 11 en 64% en het %HPON tussen 7 en 33%. Er werd en geen duidelijke effecten van het landgebruik of de bodemeigenschappen op de DOM-concentratie en -kwaliteit waargenomen. Iets lagere DOC-conce ntraties, SUVA- en %HPI-waarden werden gemeten in kolom- en lysimeterper colaten in vergelijking met de bodemoplossingen die via centrifugatie be monsterd werden. Toevoeging van plantenresidu s (stro) aan de bodem deed het %HPI toenemen en de SUVA en %HA afnemen. De SUVA was significant ge correleerd met %HA (positief, r = 0,81) en %HPI (negatief, r = 0,88). De variatie in DOM-kwaliteit was kleiner dan de variatie in DOC-concentrat ie, zo varieerde de SUVA slechts drievoudig terwijl de DOC-concentratie een bijna veertigvoudige variatie vertoonde. Dit suggereert dat de DOM-k wantiteit op grotere schaal belangrijker voor de kopermobilisatie is dan de DOM-kwaliteit. Cu-DOM-complexen die zeer traag dissociëren kunnen koperuitloging door d iepere bodemlagen bewerkstelligen wanneer transportsnelheden groter zijn dan dissociatie- en adsorptiesnelheden. De dissociatiekinetiek van vers chillende Cu-DOM-complexen afkomstig van bodem, afvalwater, varkensdrijf mest en afvalslib werd gemeten met CLEM (Competitive Ligand Exchange Met hod) en DGT (Diffusive Gradient in Thin films). De gemiddelde dissociati esnelheidsconstante kd van de complexen, gemeten met CLEM, was ongeveer 10 3 s 1 en de koperfracties in oplossing die niet gedissocieerd waren n a 8 uur varieerden tussen <1 en 25%. Deze fracties waren significant gec orreleerd met de niet-labiele fracties gemeten met de DGT-methode (0 83% ), en er werd aangetoond dat de DGT-data voorspeld konden worden met beh ulp van de CLEM-data. De dissociatiesnelheden daalden wanneer Cu-DOM-com plexen in evenwicht waren bij een lagere Cu2+ activiteit en bij langere Cu-DOM-contacttijd (7 297 dagen). De positieve correlatie tussen de niet -labiele fracties en de SUVA van DOM suggereert dat aromatische groepen in DOM de niet-labiele koper binden. De niet-labiele Cu-fracties waren e chter te klein om hun aandeel in koperuitloging in bodemkolomexperimente n te bevestigen. Er werd aangetoond dat structurele en functionele eigenschappen van bode m-DOM tot een factor tien kunnen variëren over verschillende bodems, bod emcondities en zelfs binnen één seizoen op veldschaal. De verschillende resultaten suggereren dat de koperaffiniteit van DOM toeneemt bij toenem ende humificatie van DOM. Dit kan afgeleid worden uit de positieve corre laties tussen de CuMP-waarden of de [Cu]/[DOC]-verhouding en de SUVA, di e op zijn beurt toeneemt met de fractie humuszuur in de oplossing en afn eemt met de hydrofiele DOM-fractie. Op grotere bodem- en landgebruikscha al blijkt de DOM-kwantiteit belangrijker dan de DOM-kwaliteit voor de ko permobilisatie. Kinetisch niet-labiele koperfracties maakten minder dan 25% uit van Cu-DOM. De eerder geformuleerde hypothese dat niet-labiele k opercomplexen preferentiële uitspoeling van Cu veroorzaken in bodem, wer d niet bevestigd in de experimenten van deze studie.Dankwoord i Samenvatting iii Summary vii List of abbreviations xi List of symbols xiii Chapter 1: Complexation of copper with dissolved organic matter in soil solution: relationship with organic matter characteristics and effects on mobility of copper in the soil profile: background, rationale and research objectives 1 Chapter 2: The copper mobilizing potential of dissolved organic matter in soils varies tenfold depending on soil incubation and extraction procedures 17 Chapter 3: The UV-absorbance of dissolved organic matter predicts the fivefold variation in its affinity for mobilizing Cu in an agricultural soil horizon 35 Chapter 4: Adapted DAX-8 fractionation method for dissolved organic matter (DOM) from soils: development, calibration with test components and application to contrasting soil solutions 53 Chapter 5: Structural properties of soil dissolved organic matter as affected by soil type, residue application and solution sampling method 73 Chapter 6: The dissociation kinetics of Cu-dissolved organic matter complexes from soil and soil amendments 93 Chapter 7: General conclusions 125 Annex 1: The copper mobilizing potential: method development and verification 133 Annex 2: Derivation of the correction factor for [Cu]DGT calculations in case of bulk depletion 139 References 143 List of publications 155nrpages: 170status: publishe

A soil P-test to predict the threshold for yield decrease in a depletion scenario

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DAX-8 fractionation of dissolved organic matter (DOM) from soils: calibration with test components and application to contrasting soil solutions

Most methods to fractionate natural dissolved organic matter (DOM) rely on sorption of acidified DOM samples onto XAD-8 or DAX-8 resin. Procedural differences among methods are large and their interpretation is limited because there is a lack of calibration with DOM model molecules. An automated column-based DOM fractionation method was set up for 10-ml DOM samples, dividing DOM into hydrophilic (HPI), hydrophobic acid (HPOA) and hydrophobic neutral (HPON) fractions. Fifteen DOM model components were tested in isolation and in combination. Three reference DOM samples of the International Humic Substances Society were included to facilitate comparison with other methods. Aliphatic low-molecular-weight acids (LMWAs) and carbohydrates were classified as HPI DOM, but some LMWAs showed also a partial HPO character. Aromatic LMWAs and polyphenols partitioned in the HPOA fraction, menadione (quinone) and geraniol (terpenoid) in HPON DOM. Molecules with log K-ow > 0.5 had negligible HPI fractions. The HPO molecules except geraniol had specific UV absorbance (SUVA, measure for aromaticity) > 3 litres g-1 cm-1 while HPI molecules had SUVA values < 3 litres g-1 cm-1. Distributions of DOM from eight soils ranged from 31 to 72% HPI, 25 to 46% HPOA and 2 to 28% HPON of total dissolved organic carbon. The SUVA of the HPI DOM was consistently smaller compared with the HPOA DOM. The SUVA of the natural DOM samples was not explained statistically by fractionation and the variation coefficient of SUVA among samples was not reduced by fractionation. Hence, fractionation did not reduce the variability in this DOM property, which casts some doubts on the practical role of DOM fractionation in predicting DOM properties.status: publishe

The dissociation kinetics of Cu-dissolved organic matter complexes from soil and soil amendments

Complexes between dissolved organic matter (DOM) and copper (Cu) that dissociate very slowly can theoretically facilitate Cu leaching to the groundwater. Data on dissociation kinetics of Cu-DOM complexes present in soil and in soil amendments are limited. The dissociation kinetics of different Cu-DOM complexes from soil, wastewater, pig manure and sewage sludge was measured with the Competitive Ligand Exchange Method (CLEM) and Diffusive Gradient in Thin films (DGT) technique. The solutions were set at constant pH, Ca concentration and free Cu2+ activity to allow comparison between the different samples. The average dissociation rate constant kd of the complexes, as measured by CLEM, was about 10-3 s-1 and the fractions of dissolved Cu that were undissociated after 8 hours ranged from <1 to 25%. These fractions determined by CLEM were significantly correlated with the non-labile fractions (0–82%) determined in the DGT tests and data analysis show that DGT data can be predicted from CLEM data. The dissociation rates decreased when Cu-DOM complexes had been equilibrated at lower Cu2+ activities. Increasing the Cu-DOM contact time (7–297 days) decreased the dissociation rate. The non-labile fractions were positively correlated with the specific UV absorbance suggesting that aromatic moieties in DOM hold non-labile Cu. All natural Cu-DOM complexes contained a detectable fraction with a dissociation rate constant kd lower than 10-5 s-1 which can theoretically lead to non-equilibrium conditions and leaching risks in soil.status: publishe

Influence of compost characteristics and compost : soil ratio on soil properties and growth of Vicia faba

Quality of compost is divers, and measurement of compost characteristics can help to estimate the fitness of a compost for the intended use. Especially compost maturity is important in case of high compost:soil ratios. In this study, it was verified how compost:soil ratios affect growth of garden bean Vicia faba, and what compost characteristics determine the fitness of compost for plant development. Four agricultural waste composts with varying characteristics were mixed with soil at 0, 10, 30, 50 and 100 volume percentage. Characteristics of the mixtures could be well estimated from the weighted mean of the pure soil and compost characteristics. Garden bean growth in these mixtures was monitored during 5 weeks. Final plant biomass was larger when 10% compost was added, compared to pure soil. Also plant K content increased by compost addition. At 50% and 100% compost, plant biomass decreased or even became zero depending upon the compost. Compost EC and nutrient content showed positive correlations with plant biomass at 10% compost additions, but negative correlations at 30% compost addition. Relatively small compost doses have positive effects on plant growth, whereas larger additions can have negative effects, possibly related to salt stress. Compost C/N ratio, often used as maturity characteristic, turned out not to be a good indicator of the fitness of compost for plant growth

Renewable P sources: P use efficiency of digestate, processed animal manure, compost, biochar and struvite

International audienc

Investigation on the control of phosphate leaching by sorption and colloidal transport: Column studies and multi-surface complexation modelling

© 2018 Elsevier Ltd Surface complexation modelling (SCM) is a powerful tool to estimate speciation and fate of solutes in soil, provided sufficient model validation. This study aims to describe phosphate (PO4) leaching with SCM. The leachate phosphorus concentrations ([P]) of 120 unsaturated columns of contrasting agricultural soils were measured and modelled. Leachate [P] ranged 0.7–240 μM. Leachate [P] increased as the ratio of P to iron and aluminium ([Formula presented]) in acid oxalate soil extracts increased and as leachate Fe and Al concentrations ([Al + Fe]) increased. SCM was used to describe PO4 sorption to ferrihydrite (CD-MUSIC model). This yielded adequate description of leachate [P] (RMSElog10 = 0.39), but only when reactive PO4 was described from isotopically exchangeable PO4, when organic matter was included as the main competing adsorbate and when mobile colloidal ferrihydrite was included. The model reveals that colloidal PO4 transport enhanced leachate PO4 concentrations up to a factor 50 at small soil P content and small calcium (Ca2+) concentration in solution, as a large Ca2+ concentration enhances colloidal stability. This modelling approach explained that long-term application of organic fertilisers with higher Ca content reduced P leaching, likely due to the effect of Ca2+ on colloidal stability. A two-parameter empirical Langmuir model, based on soil Fe and Al oxyhydroxides, fitted data better than any SCM, suggesting that the empirical model might be advocated for application at large scale. This study revealed the power of SCM to better understand colloidal transport of P in soil.status: publishe