Hilde Vandendriessche

Advisory systems for nitrogen fertilizer recommendations

During the last decades several methods have been proposed to optimize N fertilization, some of them being implemented in advisory systems.

Assessment of the parameters of a mechanistic soil-crop-nitrogen simulation model using historic data of experimental field sites in Belgium

Abstract Intensification of the agricultural sector and the increase in quantity and decrease in quality of municipal and industrial wastewater, in particular during the past decades, resulted in many industrial countries, such as Belgium, in a sharp degradation of surface water and groundwater. To control the current degree of contamination and reduce the environmental impact of the agricultural sector, the Flemish government recently introduced a number of regulations aiming at controlling the use of nitrogen fertilisers. To facilitate the implementation and the control of the new regulations, threshold values of allowable doses of organic and inorganic nitrogen fertilisers, and their spreading in time were made soil independent. As the soil physical, chemical and biological response depends on the geohydrology of the site and the past fertilisation practice, fertiliser standards applied on different soil–crop systems result in different leaching patterns. To assess the effect of the soil on the nitrogen leaching, a number of past experimental field trials were analysed using the WAVE model as modelling tool for the reconstruction of the nitrogen dynamics. As a first step in the study, the historic data of the field experiments were used to calibrate and validate the WAVE model. The deterministic calibration and validation of the WAVE model yielded a set of model parameters for the examined soil–crop–fertiliser practice conditions. The bottlenecks in the calibration were the nitrogen mineralisation parameters and the initialisation and subdivision of the soil organic matter over the different organic pools. The model validation, being the second step in the study, revealed the power of the WAVE model to predict the evolution and transformations of nitrogen in the soil profile and the leaching of nitrate at the bottom of the root zone. In a third step, the WAVE model was used in a scenario-analysis exercise to examine the factors effecting the amount of nitrate leached at the bottom of the root zone. This analysis revealed that the nitrate leached out of the soil profile is controlled by the fertiliser practice, the rainfall depth and its distribution, the soil texture, the soil mineralisation capacity and the past fertilisation practice.

A model of growth and sugar accumulation of sugar beet for potential production conditions: SUBEMOpo I. Theory and model structure

SUBEMOpo (SUgar BEet MOdel potential production) is a mechanistic simulation model to simulate sugar beet growth and sugar accumulation for potential production conditions. Under those conditions sugar beet growth and sugar accumulation are entirely controlled by the prevailing weather (radiation, temperature) and by the crop characteristics (plant density). The only site characteristic required for modelling the potential production is the latitude. Dry matter and sugar accumulation are calculated from the CO2 assimilation of the crop, taking into account the respiration losses and a teleonomic mechanism for the allocation of the carbohydrates to the diAerent plant organs and to sugar storage. A functional balance, consisting of source and sink terms, is thereby used. The computer code of SUBEMOpo is written in the Fortran 77 standard. The model structure consists of a main program and 11 subprograms which describe processes occurring in sugar beet plants, such as, assimilation, respiration, transpiration, growth, development and ageing or deal with the initialization of state variables and fluxes and with the translation of daily weather data into hourly data. # 2000 Elsevier Science Ltd. All rights reserved.

Experience with fertilizer expert systems for balanced fertilizer recommendations

Abstract To evaluate soil fertility and to calculate fertilizer recommendations for different soil types and crop rotations, two expert systems were developed and are being used in Belgium and the Northern part of France. The BEMEX expert system (BEMEX, coming from BEMEstingsEXpertsysteem, Dutch for fertilization expert system) calculates field specific fertilizer recommendations for macronutrients and liming recommendations for crop rotations with arable crops and vegetable crops and for grasslands. The N‐INDEX method is a field specific advice‐system for N‐fertilizer recommendation for most arable and vegetable crops. The knowledge base of BEMEX as well as of N‐INDEX contains empirical and theoretical knowledge. The required information to run the expert systems consists of measurements of the chemical soil fertility on soil samples on the one hand and of information concerning the parcel and the crop on the other hand. The final output of the expert system is a two‐to‐five page bulletin, with the resul...

Crop Models and Decision Support Systems for Yield Forecasting and Management of the Sugar Beet Crop

Abstract Models for the sugar beet crop have been developed for various purposes : (i) sugar yield forecasting with regard to campaign planning and marketing strategies ; (ii) integration of scientific knowledge and hypothesis testing ; (iii) decision support, in particular tactical and operational decisions at the farm level. It is difficult to satisfy these three objectives with one model ; each aim requires its own model. Available sugar beet models can be divided into descriptive models and explanatory models integrating various processes. The first are mainly used for prediction, the latter for research. For decision support and the management of the sugar beet crop at the farm level a combination of descriptive or explanatory crop models, databases and expert systems may be used. This paper gives a comprehensive review of models used to forecast yield and of mechanistic models and decision support systems. Analysis of the literature revealed that so far no models are available to simulate sugar beet quality.

Experience with a nitrogen-index expert-system - a powerful tool in nitrogen recommendation

Abstract The expert system nitrogen (N)‐index calculates N fertilizer recommendations for arable crops in temperate regions. The knowledge base of N‐index leans on different fundamentals, such as the measurement of the mineral N stock in soil in spring, the calculation of the evolution of the mineral N content in time and depth in the soil profile as well as the crop response to N fertilizer rates. The calculations with the empirical and theoretical founded knowledge base results in a N‐index value, which is subdivided into different values each representing a major point of vue to know the N availability for the growing crop. Since the introduction of the N‐index expert system in Belgium and the northern part of France in 1979, many crops were added to the knowledge base. The number of samples and correlated analysis data increased, making it possible to review accurately the mineral N stock in the soil after the winter period as a function of many factors, e.g. previous crop and organic fertilizer appli...

A model of growth and sugar accumulation of sugar beet for potential production conditions: SUBEMOpoII. Model performance

Abstract A model SUBEMOpo, to simulate sugar beet growth and sugar accumulation for potential production conditions has been evaluated. Given initial conditions, the growth, development and sugar accumulation of the model are driven by observed weather (i.e. maximum and minimum temperatures, rainfall, wind speed, relative humidity and solar radiation). Soil water and nutrients are considered as non limiting in the model. To evaluate the model, results of historical field trials as well as of field trials especially conducted for this evaluation study were used. These data concern growth, yield and sugar content of sugar beets grown on sandy, loess and clay profiles in Belgium and the Netherlands during several growing seasons. The agreement between measurements and simulation results is so far acceptable. The weakest section of SUBEMOpo is the partitioning of dry matter between structural and non structural dry matter of the tap root.

Residual Soil Nitrate: A Comparison between Air-Dried and Field-Moist Soil Samples

In the framework of the European nitrate directive (91/676/EEG), losses of nitrate (NO3)– nitrogen (N) to both surface and groundwater are limited to 50 mg/l. Because the residual NO3-N in the soil profile after harvest is considered the main determinant of nitrate leaching during wintertime, the Flemish government imposed a limit value of 90 kg NO3-N ha−1 up to a soil depth of 90 cm between 1 October and 15 November. This study compared two different soil sample preparation methodologies. When samples were analyzed immediately upon arrival, no differences in NO3-N concentration were observed. However, although field-moist samples are maintained at 4 °C, nitrification is not completely stopped, as indicated by the increased NO3-N concentration in field-moist samples 10 days after storage at 4 °C . In contrast, nitrification in air-dried samples is stopped during the oven drying when 40 °C is reached. Moreover, the reproducibility was significantly greater in air-dried samples as compared to field-moist samples.

Monitoring of N-uptake by green manures and of the influence of N-release on N-availability, production and quality of sugar beet

To study N-cycling in a crop system with green manures, on two field trials, a monitoring programme was set up to evaluate the N-uptake and the N-release capacity of several types of green manure. The studied green manures vary not only with the efficiency with which they take up nitrate but also with which they release it again when ploughed- in. The N-release depends on the time of dying of the green manure (frost, chemical damage or mechanical cut), the time of ploughing-in, and, the type of green manure (easily decomposable or not). Important is whether this N is made available quickly enough to the following commercial sugar beet crop and if there is no reduction in yield and quality of the sugar beet. Monitoring of nitrate content in soil during the experiments, allows to classify green manures into several classes. One class are the winter-hardy green manures, like ryegrass and reply of winter barley. Notwithstanding their N-uptake capacity, there is seldom N available for the following sugar beet crop. Yield and sugar beet quality are not significantly influenced. A second class are green manures with a good developed aerial plant part like phacelia and mustard. A clear net mineralization of these green manures is determined but crop technical and climatic factors determine whether this mineralization results in a higher N-availability for the following crop. A third class are the legumes like vetch. In the two field trials the N-uptake by vetch is the highest and N is made available during a longer period in comparison with phacelia and mustard. The root and sugar yield were higher, but not significantly. No significant difference in technological quality of the beets is measured.

Correction: Van Beek, J. et al. Stem Water Potential Monitoring in Pear Orchards through WorldView-2 Multispectral Imagery. Remote Sens. 2013, 5, 6647-6666

The suitability of high resolution satellite imagery to provide the water status in orchard crops, i.e. stem water potential (Ψstem) was evaluated in [1]. However, the contribution of a number of collaborators was not properly acknowledged. Pieter Janssens, Wendy Odeurs, Hilde Vandendriessche and Tom Deckers all provided a substantial contribution to the conception and the design of the work. They furthermore had a leading role in the acquisition, processing, analysis, and interpretation of the reference evapotranspiration (ETo) and Ψstem data. The article [1] would not have been possible without their valuable input, and the authors would like to correct the authors list as follows. [...]