Leuven, Belgium
Leuven, Belgium

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Janssens P.,Soil Service of Belgium | Diels J.,Catholic University of Leuven | Vanderborght J.,Catholic University of Leuven | Vanderborght J.,Jülich Research Center | And 4 more authors.
Agricultural Water Management | Year: 2015

Irrigation in Belgian 'Conference' pear orchards is often managed by soil water potential (Ψsoil) sensors. The most widespread sensor among fruit growers in Belgium is the Watermark sensor (Irrometer Co., USA). To gain better insight into the use of the Watermark soil sensor for irrigation scheduling in pear orchards the water extraction pattern of the 'Conference' pear trees was acquired by a numerical calculation of Ψsoil in three experimental plots. A reasonable accordance between calculated and measured Ψsoil was observed with R2=0.56 and RMSE=13.4kPa over 1320 observations. Furthermore the sensitivity of the numerical calculation to the selected root distribution was shown. The Ψsoil calculation with the root distribution parameterized by site specific fine root length observations gave satisfactory results for all plots, in contrast to Ψsoil calculation based on other root distributions. © 2014 Elsevier B.V.


Landschoot S.,University College Ghent | Landschoot S.,Ghent University | Waegeman W.,Ghent University | Audenaert K.,University College Ghent | And 6 more authors.
Computers and Electronics in Agriculture | Year: 2013

Fusarium head blight is a worldwide problem in wheat growing areas. In addition to yield loss, Fusarium species can also synthesise mycotoxins and thus threaten animal and human health. Models for predicting Fusarium head blight and deoxynivalenol content in wheat provide farmers with a tool for preventing yield loss and mycotoxin contamination. Growers may use the predictions to underpin decision making on cultivation techniques and the application of fungicides. At the end of the growing season, the food and feed industry may use the predictions to make marketing decisions. Furthermore, the predictions are helpful to identify regions with a higher disease pressure and thus improve sampling efficiency. Based on the data of 3100 wheat samples from 18 locations throughout Belgium between 2002 and 2011, various predictive models were evaluated. The most accurate models were implemented in a web tool to provide growers with field-specific predictions of Fusarium head blight incidence and deoxynivalenol content. The predictions are based on the agronomic variables of a specific wheat field and weather data from the nearest weather station. During the growing season several predictions can be asked. The web tool provides a graphical representation of the predicted results together with an advice on management strategies and recommendations for fungicide application. © 2013 Elsevier B.V.


Holscher D.,Nuclear Magnetic Resonance Research Group | Holscher D.,University of Kassel | Dhakshinamoorthy S.,Laboratory of Tropical Crop Improvement | Alexandrov T.,University of Bremen | And 27 more authors.
Proceedings of the National Academy of Sciences of the United States of America | Year: 2014

The global yield of bananas - one of the most important food crops - is severely hampered by parasites, such as nematodes, which cause yield losses up to 75%. Plant-nematode interactions of two banana cultivars differing in susceptibility to Radopholus similis were investigated by combining the conventional and spatially resolved analytical techniques 1H NMR spectroscopy, matrixfree UV-laser desorption/ionization mass spectrometric imaging, and Raman microspectroscopy. This innovative combination of analytical techniques was applied to isolate, identify, and locate the bananaspecific type of phytoalexins, phenylphenalenones, in the R. similiscaused lesions of the plants. The striking antinematode activity of the phenylphenalenone anigorufone, its ingestion by the nematode, and its subsequent localization in lipid droplets within the nematode is reported. The importance of varying local concentrations of these specialized metabolites in infected plant tissues, their involvement in the plant's defense system, and derived strategies for improving banana resistance are highlighted.


Van Beek J.,Catholic University of Leuven | Tits L.,Catholic University of Leuven | Somers B.,Catholic University of Leuven | Deckers T.,Pcfruit Research Station | And 2 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2014

High spatial resolution satellite imagery provides an alternative for time consuming and labor intensive in situ measurements of biophysical variables, such as chlorophyll and water content. However, despite the high spatial resolution of current satellite sensors, mixtures of canopies and backgrounds will be present, hampering the estimation of biophysical variables. Traditional correction methodologies use spectral differences between canopies and backgrounds, but fail with spectrally similar canopies and backgrounds. In this study, the lack of a generic solution to reduce background effects is tackled. Through synthetic imagery, the mixture problem was demonstrated with regards to the estimation of biophysical variables. A correction method was proposed, rescaling vegetation indices based on the canopy cover fraction. Furthermore, the proposed method was compared to traditional background correction methodologies (i.e. soil-adjusted vegetation indices and signal unmixing) for different background scenarios. The results of a soil background scenario showed the inability of soil-adjusted vegetation indices to reduce background admixture effects, while signal unmixing and the proposed method removed background influences for chlorophyll (ΔR2 = ∼0.3; ΔRMSE = ∼1.6 μg/cm2) and water (ΔR2 = ∼0.3; ΔRMSE = ∼0.5 mg/cm2) related vegetation indices. For the weed background scenario, signal unmixing was unable to remove the background influences for chlorophyll content (ΔR2 = -0.1; ΔRMSE = -0.6 μg/cm 2), while the proposed correction method reduced background effects (ΔR2= 0.1; ΔRMSE = 0.4 μg/cm2). Overall, the proposed vegetation index correction method reduced the background influence irrespective of background type, making useful comparison between management blocks possible. © 2014 SPIE.


Janssens P.,Soil Service of Belgium | Deckers T.,PCFruit Research Station | Elsen F.,Soil Service of Belgium | Elsen A.,Soil Service of Belgium | And 3 more authors.
Agricultural Water Management | Year: 2011

The present study examines the need for irrigation in pear trees (Pyrus Communis, cv. 'Conference') under low evaporative demand conditions, like in Belgium, in order to maintain a consistent fruit yield and high fruit size. To determine the sensitivity of the pear yield under low evaporative demand conditions three different orchards were monitored. The study shows that a Ψsoil of -60kPa during shoot growth has no effect on fruit yield but lower Ψsoil values induced a decline in both fruit size and total yield. Just as for arid environments a Ψstem of -1.5MPa is related to negative yield responses. In dry conditions lower Ψsoil and Ψstem values were observed in root pruned trees compared to not root pruned trees in the same irrigation treatment, however without yield decline. In one orchard a biannual bearing tendency was observed after root pruning. Furthermore intensive Ψsoil measurements show a high variation in Ψsoil between orchards, and within an orchard. This underlines the need for irrigation management on a parcel level and the need for new irrigation scheduling techniques which take the spatial variation in the orchard into account. © 2011 Elsevier B.V.


Janssens P.,Soil Service of Belgium | Elsen F.,Soil Service of Belgium | Vandendriessche H.,Soil Service of Belgium | Deckers T.,PCFruit Research Station | And 2 more authors.
Acta Horticulturae | Year: 2011

To prevent drought stress, pear trees (Pyrus communis 'Conference') in Belgium and the Netherlands, under temperate conditions are equipped with a drip irrigation system. To determine the optimal soil water potential (Ψsoil) threshold during shoot growth a field experiment was accomplished in a commercial orchard during three successive years (2007-2008-2009). The objective is to see the effect of a different soil moisture content during the shoot growth period. The orchard was situated on a silt loam soil, and was composed of 11 year old root pruned pear trees cultivar 'Conference' on Quince Adams rootstock. Each year two different irrigation regimes where accomplished and monitored by granular matrix sensors (Watermark) and gravimetric soil moisture determination. Tree water status was examined by stem water potential (Ψ stem). At harvest yield, fruit quality and fruit size where evaluated. Fruit size was negatively influenced when Ψsoil declined to -90 kPa. However a moderate depressed Ψsoil up to -60 kPa had no negative influence on production.


Janssens P.,Soil Service of Belgium | Elsen F.,Soil Service of Belgium | Elsen A.,Soil Service of Belgium | Deckers T.,PCFruit Research Station | Vandendriessche H.,Catholic University of Leuven
Acta Horticulturae | Year: 2011

Pear growing (Pyrus Communis 'Conference') is an important part of horticulture in Belgium and The Netherlands. Drip irrigation techniques are implemented to achieve maximum production with a high fruit size distribution. The financial return of fruits having a diameter of ≥60 mm is twice the return of smaller sized fruits (≤55 mm). Maximum fruit size distribution and high productivity on 'Conference' pear trees can be achieved by applying regulated deficit irrigation (RDI). However, unpredictable summer rains and drought periods make it difficult to establish the optimal irrigation thresholds. To overcome these difficulties, an adapted Soil Water Balance model is presented to monitor the evolution of soil water content in the root zone on a daily basis. The input parameters for the model are soil water retention characteristics, rain, irrigation events and evapotranspiration. A specific algorithm has been developed for drip irrigation and tree transpiration in an orchard with weed free strips under the trees and grass strips between tree rows. Gravimetric moisture determination is used to calibrate the model during the growing season. The performance of the model was studied in three commercial orchards in the period 2008-2009. A significant correlation (R>0.80) was observed between predicted and observed soil water content. It illustrates the possibilities of the approach to use the soil water balance model as a base to schedule the irrigation for pear trees under orchard conditions with sufficient accuracy.


van Beek J.,Catholic University of Leuven | Tits L.,Catholic University of Leuven | Somers B.,Catholic University of Leuven | Deckers T.,Pcfruit Research Station | And 2 more authors.
International Journal of Applied Earth Observation and Geoinformation | Year: 2015

Satellite remote sensing provides an alternative to time-consuming and labor intensive in situ measurements of biophysical variables in agricultural crops required for precision agriculture applications. In orchards, however, the spatial resolution causes mixtures of canopies and background (i.e. soil, grass and shadow), hampering the estimation of these biophysical variables. Furthermore, variable background mixtures obstruct meaningful comparisons between different orchard blocks, rows or within each row. Current correction methodologies use spectral differences between canopies and background, but struggle with a vegetated orchard floor. This background influence and the lack of a generic solution areaddressed in this study. Firstly, the problem was demonstrated in a controlled environment for vegetation indices sensitive to chlorophyll content, water content and leaf area index. Afterwards, traditional background correction methods (i.e. soil-adjusted vegetation indices and signal unmixing) were compared to the proposed vegetation index correction. This correction was based on the mixing degree of each pixel (i.e. tree cover fraction) to rescale the vegetation indices accordingly and was applied to synthetic and WorldView-2 satellite imagery. Through the correction, the effect of background admixture for vegetation indices was reduced, and the estimation of biophysical variables was improved (δR2= 0.2-0.31). © 2014 Elsevier B.V.


Tits M.,Soil Service of Belgium | Elsen A.,Soil Service of Belgium | Bries J.,Soil Service of Belgium | Vandendriessche H.,Soil Service of Belgium | Vandendriessche H.,Catholic University of Leuven
Plant and Soil | Year: 2012

Aims: Substantial amounts of VFG-compost are produced annually in Flanders. Our objective was to analyse the effects of VFG-compost applications in a common crop rotation. Methods: Data from a long-term (1997 - present) field trial were analysed. Simulations with the RothC-model were performed to get a better insight into the dynamics of the underlying soil organic matter. Results: VFG-compost applications (15 t.ha -1 3-yearly up to 45 t.ha -1 yearly) can replace a substantial part of the mineral nitrogen fertilisation. Nitrogen recovery rates ranged from 6 to 22 %. Plots fertilised according to the nitrogen advice had comparable yields, whether this advice had been provided (partially) through VFG-compost or not. Long-term VFG applications resulted in carbon accumulation in the top soil. The RothC-model gave a good prediction of the carbon change with low to moderate VFG applications, but tended to overestimate the carbon change with high applications. The simulation results indicated that the carbon accumulation was mainly due to an increase of the more resistant carbon fractions. In the long term, compost applications increased the nitrogen supplying capacity of the soil, as illustrated by the gradual increase of the mineral nitrogen stocks in spring over the years. Conclusions: VFG-compost applications had a positive effect both on crop yields and soil organic matter. The RothC-model was used to simulate long-term effects, but its calibration should be improved for long-term compost applications. © 2012 Springer Science+Business Media B.V.


Dewaelheyns V.,Catholic University of Leuven | Elsen A.,Soil Service of Belgium | Vandendriessche H.,Soil Service of Belgium | Gulinck H.,Catholic University of Leuven
Landscape and Urban Planning | Year: 2013

Collectively domestic gardens form an important landscape component, but environmental and land use policies tend to ignore domestic gardens. This paper investigates nutrient cycling in domestic gardens: fertilizer and soil conditioner use, composting, removal of grass clippings and the soil fertility states in the case of Flanders (the northern part of Belgium). Data was assembled from an internet survey about garden management and a database on soil fertility of domestic gardens. The combined analysis of these data reveals new insight in the link between garden management and the chemical condition in gardens (in terms of soil carbon content, pH and phosphate). Flemish gardeners used 0.07kg fertilizer and removed 2.3l grass clippings per m2 garden in 2007. Meanwhile, garden soils appear to have a higher pH and phosphorus content and lawns a lower carbon content than optimal agronomic standards. These insights show that gardens are a dynamic socio-ecological system with considerable nutrient flows from and to the household and the environment, indicating the need for more detailed and systematic environmental monitoring. This way, domestic gardens can be compared to agriculture, horticulture and other land use types. This and complementary research helps to complete insights in the dynamics across complex rural and urban landscapes. Future research should take into account, among other things, prevailing practices and habits of garden owners. © 2013 Elsevier B.V.

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