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See detailClimatic risk assessment to improve nitrogen fertilisation recommendations : A strategic crop model-based approach
Dumont, Benjamin ULg; Basso, Bruno; Bodson, Bernard ULg et al

in European Journal of Agronomy (2015), 65(10-17),

Within the context of nitrogen (N) management, since 1950, with the rapid intensification of agriculture, farmers have often applied much larger fertiliser quantities than what was required to reach the ... [more ▼]

Within the context of nitrogen (N) management, since 1950, with the rapid intensification of agriculture, farmers have often applied much larger fertiliser quantities than what was required to reach the yield potential. However, to prevent pollution of surface and groundwater induced by nitrates, The European Community launched The European Nitrates Directive 91/6/76/EEC. In 2002, in Wallonia (Belgium), the Nitrates Directive has been transposed under the Sustainable Nitrogen Management in Agriculture Program (PGDA), with the aim of maintaining productivity and revenue for the country’s farmers, while reducing the environmental impact of excessive N application. A feasible approach for addressing climatic uncertainty lies in the use of crop models such as the one commonly known as STICS (simulateur multidisciplinaire pour les cultures standard). These models allow the impact on crops of the interaction between cropping systems and climatic records to be assessed. Comprehensive historical climatic records are rare, however, and therefore the yield distribution values obtained using such an approach can be discontinuous. In order to obtain better and more detailed yield distribution information, the use of a high number of stochastically generated climate time series was proposed, relying on the LARS-Weather Generator. The study focused on the interactions between varying N practices and climatic conditions. Historically and currently, Belgian farmers apply 180 kg N ha−1, split into three equal fractions applied at the tillering, stem elongation and flag-leaf stages. This study analysed the effectiveness of this treatment in detail, comparing it to similar practices where only the N rates applied at the flag-leaf stage were modified. Three types of farmer decision-making were analysed. The first related to the choice of N strategy for maximising yield, the second to obtaining the highest net revenue, and the third to reduce the environmental impact of potential N leaching, which carries the likelihood of taxation if inappropriate N rates are applied. The results showed reduced discontinuity in the yield distribution values thus obtained. In general, the modulation of N levels to accord with current farmer practices showed considerable asymmetry. In other words, these practices maximised the probability of achieving yields that were at least superior to the mean of the distribution values, thus reducing risk for the farmers. The practice based on applying the highest amounts (60–60–100 kg N ha−1) produced the best yield distribution results. When simple economical criteria were computed, the 60–60–80 kg N ha−1 protocol was found to be optimal for 80–90% of the time. There were no statistical differences, however, between this practice and Belgian farmers’ current practice. When the taxation linked to a high level of potentially leachable N remaining in the soil after harvest was considered, this methodology clearly showed that, in 3 years out of 4, 30 kg N ha−1 could systematically be saved in comparison with the usual practice. [less ▲]

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See detailIntegrating the impact of wheat fungal diseases in the Belgian crop yield forecasting system (B-CYFS)
El Jarroudi, Moussa ULg

in European Journal of Agronomy (2012), 40

Field experiments were conducted over four growing seasons to assess the relationship between fungal disease attacks and wheat grain yield in the agrometeorological part of the Belgian crop yield ... [more ▼]

Field experiments were conducted over four growing seasons to assess the relationship between fungal disease attacks and wheat grain yield in the agrometeorological part of the Belgian crop yield forecasting system (i.e., Belgian crop growth monitoring system, B-CGMS) by recalibrating the lifespan of wheat leaves (SPAN parameter). The results from 133 experimental fields in Belgium (the Wallonia region) and the Grand-Duchy of Luxembourg were analyzed in terms of site factors such as cultivar, previous crop, sowing date and geographical area. A significant relationship was found between green leaf area (GLA) duration expressing the infection pressure (parameter m; using a modified Gompertz model and calculated from observed GLA) and final grain yield (R2 = 0.79; P < 0.001). Based on this relationship and by recalibrating the B-CGMS in terms of its SPAN parameter, there was a significant improvement in estimating final grain yield. From a R2 of 0.11 when the B-CGMS was run with the default SPAN value, the relationship between observed and simulated yields was strengthened, with a R2 of 0.47 and 0.57, respectively, when a linear or quadratic relationship was considered between m and SPAN. Although, from a practical point of view, the m value has to be estimated annually for each spatial grid or group of grids on the basis of field or possibly remotely sensed data, and although estimating this parameter is possible only late in the season, these encouraging results illustrate the potential of integrating pest and disease impact in the B-CGMS. [less ▲]

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