Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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Chemisch-fysische schematisering van de bodem voor NHI-waterkwaliteit : naar een nieuwe fysisch-chemische schematisering van de Nederlandse bodem
Bolt, Frank van der; Walvoort, Dennis ; Vries, Folkert de; Hoogland, Tom ; Vroon, Henk ; Groenendijk, Piet ; Renaud, Leo ; Massop, Harry ; Veldhuizen, Ab ; Walsum, Paul van - \ 2016
Wageningen : Wageningen Environmental Research (Wageningen Environmental Research rapport 2753) - 34
bodem - bodemkwaliteit - hydrologie - bodemeigenschappen - bodemkarteringen - soil - soil quality - hydrology - soil properties - soil surveys
Voor de ontwikkeling van het Nationaal Hydrologisch Instrumentarium-waterkwaliteit is een aanpak opgesteld om de fysisch-chemische schematisering van de bodem in Nederland verder te ontwikkelen. Op korte termijn (2017-2018) is een pragmatische werkwijze nodig om de bodemchemische parameters met bijbehorende schematisering in representatieve eenheden voor de operationele toepassing voor landelijke beleidsstudies te actualiseren. Het gebruik van de huidige fysischchemische karakterisering voor de bodemkaart 1:50.000 vormt de geëigende methode. Op de langere termijn is het de wens om het Nationaal Hydrologisch Instrumentarium-waterkwaliteit ook te kunnen inzetten voor regionale toepassingen. Dit kan alleen als er een gedetailleerde geostatistisch gesimuleerde 3D-bodemkaart aan ten grondslag ligt die recht doen aan regionale variabiliteit van de bodem.
Perspectives for the use of biochar in horticulture
Blok, C. ; Regelink, I.C. ; Hofland-Zijlstra, J.D. ; Streminska, M.A. ; Eveleens-Clark, B.A. ; Bolhuis, P.R. - \ 2016
Bleiswijk : Wageningen UR Glastuinbouw (Rapport GTB 1388) - 42 p.
biochar - growing media - greenhouse horticulture - pot experimentation - soil chemistry - soil properties - residual streams - biobased economy - groeimedia - glastuinbouw - potproeven - bodemchemie - bodemeigenschappen - reststromen
Biochars were produced using different production parameters and consequently measured in a rooting media laboratory and used as a constituent in potting soil mixes for 8 and 12 week growth experiments. The biochar feedstock influences the biochar’s eventual nutrient and salt content, the pH, the buffer capacity and the cation exchange capacity all of which can potentially hamper normal growth. It is indicated which materials may result in effective biochars regarding nutrient and salt content. A method to measure and compensate unwanted pHs is described and validated. The production parameters are shown to influence growth defining properties such as phytotoxicity, water behaviour and degradability. Finally growth experiments with mixes of biochar and other rooting media constituents were performed and used for further advice on compensating unwanted properties. In the experiments up to 20%-v/v biochar was used without adverse effects on production. De lab results indicate the maximum amounts could at least be 25%-v/v when mixing with rooting media constituents with sufficiently complementary properties. Porous biochars are shown to be able to host microbial life but to fully utilize this promising trait more rigorous pretreatment of the biochar particles are suggested.
Handboek melkveehouderij 2015/16
Remmelink, G.J. ; Middelkoop, J.C. van; Ouweltjes, W. ; Wemmenhove, H. - \ 2015
Wageningen : Wageningen UR Livestock Research (Handboek / Wageningen UR Livestock Research 30) - 386
melkvee - melkveehouderij - bodemeigenschappen - bemesting - graslandbeheer - voedergrassen - voedergewassen - rundveevoeding - dierveredeling - diergezondheid - melkproductie - landbouwbedrijfsgebouwen - nederland - handboeken - dairy cattle - dairy farming - soil properties - fertilizer application - grassland management - fodder grasses - fodder crops - cattle feeding - animal breeding - animal health - milk production - farm buildings - netherlands - handbooks
Evaluating coffee yield gaps and important biotic, abiotic, and management factors limiting coffee production in Uganda
Wang, N. ; Jassonge, L. ; Asten, P.J.A. van; Mukasa, D. ; Wanyama, I. ; Kagezi, G.H. ; Giller, K.E. - \ 2015
European Journal of Agronomy 63 (2015). - ISSN 1161-0301 - p. 1 - 11.
boundary-line analysis - soil properties
Coffee is Uganda's biggest export commodity, produced mainly by an estimated one million smallholder farmers (1400. m) such as Eastern, Southwest, and Northwest Uganda. Actual yields are far below (
Bodem en weerbaarheid tegen Pythium en Meloidogyne
Wurff, Andre van der - \ 2015
greenhouse horticulture - plant protection - plant health - field tests - pythium - plant pathogenic fungi - fungus control - biological control - soil properties - soil ecology - cut flowers - chrysanthemum
GIS-Based Multi-Criteria Analysis for Arabica Coffee Expansion in Rwanda
Nzeyimana, I. ; Hartemink, A.E. ; Geissen, V. - \ 2014
PLoS One 9 (2014)10. - ISSN 1932-6203
suitability evaluation - soil properties - land evaluation - prediction - framework - quality - yield - model - corn
The Government of Rwanda is implementing policies to increase the area of Arabica coffee production. Information on the suitable areas for sustainably growing Arabica coffee is still scarce. This study aimed to analyze suitable areas for Arabica coffee production. We analyzed the spatial distribution of actual and potential production zones for Arabica coffee, their productivity levels and predicted potential yields. We used a geographic information system (GIS) for a weighted overlay analysis to assess the major production zones of Arabica coffee and their qualitative productivity indices. Actual coffee yields were measured in the field and were used to assess potential productivity zones and yields using ordinary kriging with ArcGIS software. The production of coffee covers about 32 000 ha, or 2.3% of all cultivated land in the country. The major zones of production are the Kivu Lake Borders, Central Plateau, Eastern Plateau, and Mayaga agro-ecological zones, where coffee is mainly cultivated on moderate slopes. In the highlands, coffee is grown on steep slopes that can exceed 55%. About 21% percent of the country has a moderate yield potential, ranging between 1.0 and 1.6 t coffee ha(-1), and 70% has a low yield potential (<1.0 t coffee ha(-1)). Only 9% of the country has a high yield potential of 1.6-2.4 t coffee ha(-1). Those areas are found near Lake Kivu where the dominant soil Orders are Inceptisols and Ultisols. Moderate yield potential is found in the Birunga (volcano), Congo-Nile watershed Divide, Impala and Imbo zones. Low-yield regions (<1 t ha(-1)) occur in the eastern semi-dry lowlands, Central Plateau, Eastern Plateau, Buberuka Highlands, and Mayaga zones. The weighted overlay analysis and ordinary kriging indicated a large spatial variability of potential productivity indices. Increasing the area and productivity of coffee in Rwanda thus has considerable potential.
A Multi-Criteria Index for Ecological Evaluation of Tropical Agriculture in Southeastern Mexico
Huerta, E. ; Kampichler, C. ; Ochoa-Gaona, S. ; Jong, B. de; Hernandez-Daumas, S. ; Geissen, V. - \ 2014
PLoS One 9 (2014)11. - ISSN 1932-6203
land-use change - farming systems - sustainability indicators - cropping systems - soil properties - food security - fuzzy-logic - management - agroecosystems - biodiversity
The aim of this study was to generate an easy to use index to evaluate the ecological state of agricultural land from a sustainability perspective. We selected environmental indicators, such as the use of organic soil amendments (green manure) versus chemical fertilizers, plant biodiversity (including crop associations), variables which characterize soil conservation of conventional agricultural systems, pesticide use, method and frequency of tillage. We monitored the ecological state of 52 agricultural plots to test the performance of the index. The variables were hierarchically aggregated with simple mathematical algorithms, if-then rules, and rule-based fuzzy models, yielding the final multi-criteria index with values from 0 (worst) to 1 (best conditions). We validated the model through independent evaluation by experts, and we obtained a linear regression with an r(2) = 0.61 (p = 2.4e-06, d.f. = 49) between index output and the experts' evaluation.
Werken aan bodemweerbaarheid
Broek, R.C.F.M. van den; Berg, W. van den; Lamers, J.G. ; Cuijpers, W.J.M. ; Hospers-Brands, A.J.T.M. ; Smits, S. - \ 2014
Praktijkonderzoek Plant & Omgeving B.V. - 63
teeltsystemen - bodemweerbaarheid - bestrijdingsmethoden - agrarische bedrijfsvoering - phytophthora cactorum - bodemeigenschappen - gewasbescherming - proeven - biotesten - fragaria - biologische technieken - vollegrondsteelt - cropping systems - soil suppressiveness - control methods - farm management - soil properties - plant protection - trials - bioassays - biological techniques - outdoor cropping
De land- en tuinbouw ontwikkelt zich in de richting van steeds intensievere en complexere bedrijfssystemen. Vanuit de sector groeit het besef dat de chemische benadering van ziekten en plagen haar grenzen begint te bereiken. Ook de consument verlangt van de producent dat de inzet van chemische middelen gereduceerd wordt en gezocht wordt naar andere, meer duurzame oplossingen. Een van de oplossingsrichtingen is het creëren van een gezonde, veerkrachtige en weerbare bodem. Op zulke bodems groeit een gezond gewas met een goede opbrengst die minder gevoelig is voor ziekten en plagen en efficiënter omgaat met nutriënten waardoor er minder verliezen optreden. Hierdoor hoeven telers minder gewasbeschermingsmiddelen en nutriënten te gebruiken en kunnen ze, met een beter inkomen, milieuvriendelijker telen. Aardbei is een voorbeeld van een zeer intensieve teelt, die erg gevoelig is voor ziekten en plagen. In de teelt worden relatief veel gewasbeschermingsmiddelen gebruikt, en er is een sterke behoefte aan kennis die de inzet van deze middelen kan beperken. Aardbei is ook een heel geschikt toetsgewas, omdat het sterk reageert op de bodemgezondheid van een perceel. Is deze goed dan ligt de aardbeienproductie veel hoger dan op percelen waarop de bodemgezondheid matig of slecht is. Opbrengstverschillen kunnen oplopen tot meer dan 50%. De verkregen resultaten bij aardbei kunnen ook vertaald worden naar andere vollegronds gewassen.
Evaluation and Selection of Indicators for Land Degradation and Desertification Monitoring: Methodological Approach
Kosmas, C. ; Karis, O. ; Karavitis, C. ; Ritsema, C.J. ; Salvati, L. ; Acikalin, S. ; Alcala, S. ; Alfama, P. ; Atlhopheng, J. ; Barrera, J. ; Belgacem, A. ; Sole-Benet, A. ; Brito, J. ; Chaker, M. ; Chanda, R. ; Coelho, C. ; Darkoh, M. ; Diamantis, I. ; Ermolaeva, O. ; Fassouli, V. ; Fei, W. ; Fernandez, F. ; Ferreira, A. ; Gokceoglu, C. ; Gonzalez, D. ; Gungor, H. ; Hessel, R. ; Juying, J. ; Khatteli, H. ; Kounalaki, A. ; Laouina, A. ; Lollino, P. ; Lopes, M. ; Magole, L. ; Medina, L. ; Mendoza, M. ; Morais, P. ; Mulale, K. ; Ocakoglu, F. ; Ouessar, M. ; Ovalle, C. ; Perez, C. ; Perkins, J. ; Pliakas, F. ; Polemio, M. ; Pozo, A. ; Prat, C. ; Qinke, Y. ; Ramos, A. ; Riquelme, J. ; Romanenkov, V. ; Rui, L. ; Santaloia, F. ; Sebego, R. ; Sghaier, M. ; Silva, N. ; Sizemskaya, M. ; Soares, J. ; Sonmez, H. ; Taamallah, H. ; Tezcan, L. ; Torri, D. ; Ungaro, F. ; Valente, S. ; Vente, J. de; Zagal, E. ; Zeiliguer, A. ; Zhonging, W. ; Ziogas, A. - \ 2014
Environmental Management 54 (2014)5. - ISSN 0364-152X - p. 951 - 970.
mediterranean conditions - aggregate stability - soil properties - rock fragments - organic-matter - vegetation - tillage - biomass - erosion - greece
An approach to derive relationships for defining land degradation and desertification risk and developing appropriate tools for assessing the effectiveness of the various land management practices using indicators is presented in the present paper. In order to investigate which indicators are most effective in assessing the level of desertification risk, a total of 70 candidate indicators was selected providing information for the biophysical environment, socio-economic conditions, and land management characteristics. The indicators were defined in 1,672 field sites located in 17 study areas in the Mediterranean region, Eastern Europe, Latin America, Africa, and Asia. Based on an existing geo-referenced database, classes were designated for each indicator and a sensitivity score to desertification was assigned to each class based on existing research. The obtained data were analyzed for the various processes of land degradation at farm level. The derived methodology was assessed using independent indicators, such as the measured soil erosion rate, and the organic matter content of the soil. Based on regression analyses, the collected indicator set can be reduced to a number of effective indicators ranging from 8 to 17 in the various processes of land degradation. Among the most important indicators identified as affecting land degradation and desertification risk were rain seasonality, slope gradient, plant cover, rate of land abandonment, land-use intensity, and the level of policy implementation.
Transport and degradation of contaminants in the vadose zone
Schotanus, D. - \ 2013
University. Promotor(en): Sjoerd van der Zee, co-promotor(en): Martine van der Ploeg. - S.l. : s.n. - ISBN 9789461735850 - 125
uitspoelen - transportprocessen - besmetters - verontreinigende stoffen - grondwater - bodemeigenschappen - degradatie - leaching - transport processes - contaminants - pollutants - groundwater - soil properties - degradation

Leaching of contaminants from the vadose zone to the groundwater depends on the soil properties and the infiltration rate. In this thesis, organic degradable contaminants were studied, such as de-icing chemicals (consisting of propylene glycol, PG) and pesticides. Heterogeneous soil properties lead to spatial variability in leaching, which is particularly important for degradable contaminants. The infiltration rate determines the travel time in the vadose zone, and thus the time available for degradation.

Two field experiments were performed with a multi-compartment sampler (consisting of 10 x 10 cells of 3.15 x 3.15 cm2each) to examine the dependence of spatial variability in contaminant leaching on the infiltration rate. The first experiment was carried out during the snowmelt period, characterized by high infiltration rates from snowmelt. The second experiment was carried out with irrigation to mimic homogeneous rainfall. The preferential flow paths were similar for both experiments. With a high infiltration rate during the snowmelt experiment, the leaching was distributed more homogeneous than during the irrigation experiment. Therefore, it is concluded that the soil heterogeneity is mainly caused by spatial differences in the soil hydraulic properties, and not by macropores. The leached masses of the degradable PG and a nondegradable tracer were highly correlated. At the scale of the experiment, heterogeneous infiltration resulting from spatial differences in snowmelt did not have much influence on the flow and solute paths.

The results from the field experiment were used to parameterize a random field for the scaling factor of the retention curve. As a criterion to compare the results from simulations and observations, the sorted and cumulative total drainage in a cell was used. The effect of the ratio of the infiltration rate over the degradation rate on leaching of degradable solutes was investigated. Furthermore, the spatial distribution of the leaching of degradable and non-degradable solutes was compared. The infiltration rate influences contaminant leaching in two ways. Firstly, the travel time of the contaminant in the vadose zone depends on the infiltration rate. Secondly, the fraction of the soil which is active in transport is influenced by the infiltration rate. As a result, the spatial distribution of contaminant leaching, and therefore the leached fraction, depends on the infiltration rate.

The leached fraction of a degradable contaminant is often estimated from average soil properties and stationary weather series. For contaminants that degrade in both the adsorbed and aqueous phase, it is known how these averaged properties should be derived from heterogeneous properties. However, for contaminants that only degrade in the aqueous phase, this is not well known. In soils that are layered with respect to the adsorption constant, the propagation of the contaminant plume, and thus the travel time in the vadose zone, depends on the adsorption constant, degradation rate, and dispersivity. Regarding variable weather series, seasonal fluctuations in precipitation lead to large differences in travel times in a dry climate, and thus large differences in the leached fraction, especially for contaminants with little adsorption. In a wet climate, the effect of such seasonal fluctuations is diminished.

In the vadose zone, PG can be degraded by micro-organisms, for which electron-acceptors are needed. A field experiment showed that aerobic as well as anaerobic degradation occurs in the vadose zone. For anaerobic degradation, manganese-oxides (which are present in the soil) or nitrate (applied to enhance biodegradation) can be used as electron-acceptors. Reduced forms of manganese can be transported to the groundwater, and thus the soil could be depleted from manganese-oxides. A model was developed in which both types of degradation were included. The application of nitrate did not lead to a lower PG leaching, or in a slower depletion of manganese-oxides. The leached fraction is higher with a thick snowcover and high meltrate, as then PG is transported rapidly in the soil. Snowmelt did not result in anaerobic soil, despite the high soil moisture content, and thus low oxygen diffusion.

Proximal soil sensors and data fusion for precision agriculture
Mahmood, H.S. - \ 2013
University. Promotor(en): Eldert van Henten, co-promotor(en): Willem Hoogmoed. - S.l. : s.n. - ISBN 9789461735799 - 205
meettechnieken - sensors - bodemeigenschappen - meetsystemen - precisielandbouw - vollegrondsteelt - akkerbouw - measurement techniques - soil properties - measurement systems - precision agriculture - outdoor cropping - arable farming
different remote and proximal soil sensors are available today that can scan entire fields and give detailed information on various physical, chemical, mechanical and biological soil properties. The first objective of this thesis was to evaluate different proximal soil sensors available today and to identify their capacity of quantifying soil properties. The second objective of this thesis was to enhance the usefulness of a single sensor system by multiple sensor data fusion that can improve the performance of currently available soil sensors when a single sensor does not function optimally due to certain set of soil and environmental constraints.
Assessment of crop growth and water productivity for five C3 species in semi-arid Inner Mongolia
Yuan, M. ; Zhang, L. ; Gou, F. ; Su, Z. ; Spiertz, J.H.J. ; Werf, W. van der - \ 2013
Agricultural Water Management 122 (2013). - ISSN 0378-3774 - p. 28 - 38.
simulate yield response - use efficiency - soil properties - cotton - irrigation - management - deficit - china - model - wheat
Water availability is a key biophysical factor determining agricultural production potential. The FAO crop water response model AquaCrop was developed to estimate crop production under water limiting conditions. This model uses the normalized water productivity, WP* (g m-2 d-1), to estimate the attainable rate of crop growth under water limitation. In this study we assessed the value and the consistency of WP* under the semi-arid growing conditions of Inner Mongolia. Field experiments on productivity and water use of oats (Avena sativa), sunflower (Helianthus annuus), vetch (Vicia sativa), faba bean (Vicia faba) and potato (Solanum tuberosum) were conducted in 2009, 2010 and 2011. Yield, biomass, evaporation and transpiration varied substantially and significantly between crop species and years. Likewise, water use efficiency (WUE) was affected by these factors, including a significant interaction. WUE (units of yield/unit water) varied between years: from 1.1 to 1.3 kg m-3 in oats, from 1.5 to 2.6 kg m-3 in sunflower, from 0.5 to 1.1 kg m-3 in the two legumes and from 3.1 to 4.4 kg m-3 in potato (DM yields). Normalized water productivity did not vary significantly between crop species and years or their interaction, showing an overall value of 14.0 ± 0.32 g m-2 d-1 in an overarching regression pooling all the data. We conclude that WP* differs from the conventional parameter for water productivity, but is a useful parameter for assessing attainable rate of crop growth and yield in the agro-pastoral ecotone of Inner Mongolia
Web-based tool for expert elicitation of the variogram
Truong, N.P. ; Heuvelink, G.B.M. ; Gosling, J.P. - \ 2013
Computers and Geosciences 51 (2013). - ISSN 0098-3004 - p. 390 - 399.
spatial covariance parameters - residual maximum-likelihood - probability-distributions - robust estimation - soil properties - models - knowledge - inference - opinion - scale
The variogram is the keystone of geostatistics. Estimation of the variogram is deficient and difficult when there are no or too few observations available due to budget constraints or physical and temporal obstacles. In such cases, expert knowledge can be an important source of information. Expert knowledge can also fulfil the increasing demand for an a priori variogram in Bayesian geostatistics and spatial sampling optimization. Formal expert elicitation provides a sound scientific basis to reliably and consistently extract knowledge from experts. In this study, we aimed at applying existing statistical expert elicitation techniques to extract the variogram of a regionalized variable that is assumed to have either a multivariate normal or lognormal spatial probability distribution from expert knowledge. To achieve this, we developed an elicitation protocol and implemented it as a web-based tool to facilitate the elicitation of beliefs from multiple experts. Our protocol has two main rounds: elicitation of the marginal probability distribution and elicitation of the variogram. The web-based tool has three main components: a web interface for expert elicitation and feedback; a component for statistical computation and mathematical pooling of multiple experts’ knowledge; and a database management component. Results from a test case study show that the protocol is adequate and that the online elicitation tool functions satisfactorily. The web-based tool is free to use and supports scientists to conveniently elicit the variogram of spatial random variables from experts. The source code is available from the journal FTP site under the GNU General Public License.
Influence of landscape composition and diversity on contaminant flux in terrestrial food webs: A case study of trace metal transfer to European blackbirds Turdus merula
Fritsch, C. ; Coeurdassier, M. ; Faivre, B. ; Baurand, P.E. ; Giraudoux, P. ; Brink, N.W. van den; Scheifler, R. - \ 2012
Science of the Total Environment 432 (2012). - ISSN 0048-9697 - p. 275 - 287.
ecological risk-assessment - small mammals - soil properties - heavy-metals - host factors - birds - lead - bioavailability - exposure - cadmium
Although understanding the influence of the spatial arrangement of habitats and interacting communities on the processes of pollutant flux and impacts is critical for exposure and risk assessment, to date few studies have been devoted to this emergent topic. We tested the hypothesis that landscape composition and diversity affect the transfer of trace metals to vertebrates. Bioaccumulation of Cd and Pb in blood and feathers of European blackbirds Turdus merula (n=138) was studied over a smelter-impacted area (Northern France). Landscape composition (type and occurrence of the different habitats) and diversity (number of different habitat types and the proportional area distribution among habitat types) were computed around bird capture locations. Diet composition and contamination were assessed. No sex-related differences were detected, while age-related patterns were found: yearlings showed a sharper increase of tissue residues along the pollution gradient than older birds. Factors determining bird exposure acted at nested spatial scale. On a broad scale, environmental contamination mainly influenced metal levels in blackbirds, tissue residues increasing with soil contamination. At a finer grain, landscape composition and soil properties (pH, organic matter, clay) influenced metal transfer, while no influence of landscape diversity was detected. landscape composition better explained metal transfer than soil properties did. Diet composition varied according to landscape composition, but diet diversity was not influenced by landscape diversity. Surprisingly, metal accumulation in some insect taxa was as high as in earthworms (known as hyper-accumulators). Results strongly suggested that variations in diet composition were the drivers through which landscape composition influenced metal transfer to blackbirds. This study shows that landscape features can affect pollutant transfer in food webs, partly through ecological processes related to spatial and foraging behavior of birds, and brings evidences underpinning the need to better consider landscape in environmental risk assessment and management of contaminated lands.
Bodem als buffer
Snellen, W.B. ; Hattum, T. van - \ 2012
Amersfoort : Stowa
buffercapaciteit - bodemeigenschappen - waterbeheer - wateropslag - neerslag - buffering capacity - soil properties - water management - water storage - precipitation
Het belang van de bufferende werking van de bodem wordt in deze Deltafact onderstreept. De natuurlijke buffercapaciteit van de bodem is door bewerking van de bodem, afname van organisch stofgehalte en versnelde afvoer van water op veel plaatsen in Nederland de afgelopen decennia aantoonbaar afgenomen. Door het veranderende klimaat komen steeds vaker perioden van droogte en perioden met extreme neerslag voor. Het optimaal gebruik maken van de buffercapaciteit van de bodem wordt daarom steeds belangrijker, met name op de hoge zandgronden. Voor de waterbeheerder is de bodem vooral van belang als buffer van neerslagoverschotten en -tekorten.
A hybrid design-based and model-based sampling approach to estimate the temporal trend of spatial means
Brus, D.J. ; Gruijter, J.J. de - \ 2012
Geoderma 173-174 (2012). - ISSN 0016-7061 - p. 241 - 248.
soil properties - optimization - variograms - patterns
This paper launches a hybrid sampling approach, entailing a design-based approach in space followed by a model-based approach in time, for estimating temporal trends of spatial means or totals. The underlying space–time process that generated the soil data is only partly described, viz. by a linear mixed model for the temporal variation of the spatial means. The model contains error terms for model inadequacy (model or process error) and for the sampling error in the estimated spatial means. The linear trend is estimated by Generalized Least Squares. The covariance matrix is obtained by adding the matrix with design-based estimates of the sampling variances and covariances and the covariance matrix of the model errors. The model parameters needed for the latter matrix are estimated by REML. The error variance of the estimated regression coefficients can be decomposed into the model variance of the errorless regression coefficients and the model expectation of the conditional sampling variance. In a case study on forest soil eutrophication, inclusion of the model error led to a considerable increase of the error variance for most variables. In the topsoil the contribution of the process error to the standard error of the estimated trend was much larger than that of the sampling error. For pH there was no contribution of the model error. Important advantages of the presented approach over the fully model-based approach are its simplicity and robustness to model assumptions.
Bodemweerbaarheid complex begrip voor onderzoek en praktijk (interview met G. van Os, J. Postma en A. van der Wurff)
Dwarswaard, A. ; Os, G.J. van; Postma, J. ; Wurff, A.W.G. van der - \ 2012
BloembollenVisie 2012 (2012)256. - ISSN 1571-5558 - p. 16 - 17.
bloembollen - bodemfactoren - bodemonderzoek - bodemeigenschappen - weerstand - ziekteresistentie - landbouwkundig onderzoek - kennisoverdracht - ornamental bulbs - edaphic factors - soil testing - soil properties - resistance - disease resistance - agricultural research - knowledge transfer
Wie pakweg tien jaar geleden in de bloembollensector begon over bodemweerbaarheid werd een beetje meewarig aangekeken. Nu is dat anders. Belangrijk, meer aan doen, dat zijn de opvattingen die een groeiende groep telers heeft. Om die reden wijdt BloembollenVisie een serie aan bodemweerbaarheid, bodemvruchtbaarheid en bodemleven. In de vierde aflevering is het woord aan drie onderzoekers van PRI en PPO van Wageningen UR die zich met deze drie onderwerpen bezighouden.
Improving water use efficiency in drylands
Stroosnijder, L. ; Moore, D. ; Alharbi, A. ; Argaman, E. ; Elsen, H.G.M. van den - \ 2012
Current Opinion in Environmental Sustainability 4 (2012)5. - ISSN 1877-3435 - p. 497 - 506.
nutrient management - soil properties - rainwater use - mulch - irrigation - reuse - conservation - environment - repellency - ethiopia
Drylands cover 41% of the global terrestrial area and 2 billion people use it for grazing and cropping. Food security is low owing to institutional and technical constraints. Absolute water scarcity and also the inability of crops to use available water are major technical issues. Significant progress has been made in identifying land management practices that improve water use efficiency in terms of more crop per drop. Examples are presented that improve infiltration and storage of rainwater, reduce evaporation losses, harvest and conserve water in the Mediterranean region and Africa and use treated waste water for irrigation. Drylands show a wide diversity and therefore, require appropriately adapted best mitigation practices and strategies.
Soil organic carbon stocks and changes upon forest regeneration in East Kalimantan- Indonesia
Yassir, I. - \ 2012
University. Promotor(en): Pavel Kabat, co-promotor(en): Peter Buurman; Bram van Putten. - S.l. : s.n. - ISBN 9789064645761 - 175
natuurlijke verjonging - tropische bossen - imperata cylindrica - secundaire bossen - koolstofvastlegging in de bodem - organisch bodemmateriaal - bodemeigenschappen - vegetatie - plantensuccessie - kalimantan - indonesië - natural regeneration - tropical forests - secondary forests - soil carbon sequestration - soil organic matter - soil properties - vegetation - ecological succession - indonesia

Imperata grassland is a common vegetation type in Kalimantan (Indonesia), and other parts of South-East Asia. It indicates a high degree of degradation of the vegetation, and mostly occurs after slashing and burning of primary forest. Through secondary succession Imperata grassland is converted into new secondary forest and much of the original biodiversity is restored. The overall objective of the thesis was to study the regeneration of Imperata grasslands in East Kalimantan, and to measure the effects of regeneration on soil properties, with emphasis on the organic fraction. The research strategy was to compare plots of different regeneration stages, characterized by the period elapsed since the vegetation was last burned.
Results show that during regeneration of Imperata grasslands, both vegetation composition and soil properties change, including chemistry of soil organic matter. Soil carbon stocks are higher under Imperata grasslands than under primary forest, and increase further upon natural regeneration of grassland to secondary forest. Highest carbon stocks are found in the later regeneration phases. Lower carbon stocks under primary forests are due to extremely low fertility, combined with shallow soils and low root mass in the topsoil. Root density as observed in the field is much higher under the grass vegetation. Results show as well that soil organic matter decomposition is most advanced under forest, as indicated by lower amounts of plant derived compounds and higher contribution of microbial matter. The results indicate that decomposition efficiency is related to soil organic matter chemistry, but more to abundance of N-compounds than to that of potentially recalcitrant compounds.
In our case study, soil texture appears an important factor in the vegetation succession. On sandy soils, there is a strong increase with time of Pteridium aquilinum L., while the number of other species is lower. This slows down the development towards secondary forest. Canonical correspondence analysis (CCA) of environmental factors and vegetation show that pH, bulk density, sand and clay are the factors related to the distribution of species. The rapid secondary succession indicates that Imperata grasslands are not a final and stable stage of land degradation, but that frequent fires are necessary to maintain Imperata grasslands. If protected from fire and other intrusions such as shifting cultivation, Imperata grassland will readily develop into secondary forest. Imperata grasslands seem to be permanent because of human interference, especially through burning, and because so far few attempts have been made to sustainable rehabilitation.

Bol zeil geen garantie goed stoomresultaat (interview met Daniel Ludeking)
Lier, A. van; Ludeking, D.J.W. - \ 2012
Vakblad voor de Bloemisterij 67 (2012)13. - ISSN 0042-2223 - p. 28 - 29.
sierplanten - grondbehandeling - stoomsterilisatie - bereikt resultaat - meting - temperatuur - besluitvorming - bodemeigenschappen - ornamental plants - soil treatment - steam sterilization - achievement - measurement - temperature - decision making - soil properties
Telers gebruiken de tijd dat het stoomzeil bol staat vaak als indicator voor de kwaliteit van het stoomproces. Maar dit is onterecht. De bolling van het zeil geeft geen garantie dat de grond goed ontsmet is, menen 'stoomexperts'. Een gedegen voorbereiding en geregeld meten zijn de sleutels tot succes.
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