Modelisation du bilan hydrique d'un sol cultivé : approches deterministes et stochastique

A capacity-based simulation model has been developed to predict components of the field water balance. The model requires daily information such as the atmospheric evaporative demand and rain events, maximum-available soil water storage (MAWS) and root growth characteristics as weil as crop and soil factors. Actual evapotranspiration is modelled using Eagleman's parameterization. The model was tested for upland rice grown on a 3500 m2 field plot and on an undisturbed Iysimeter, both located at Bouaké, Ivory Coast. Good agreement between calculations and observations of actual evapotranspiration (AET) and drainage (D) measured at 15 sites equipped with neutron access tubes and tensiometers demonstrates the reliability of the mode!. This is also independently confirmed against the Iysimeter data. The model was used to study the influence of the soil spatial variability on AET and D at the bottom of the soil profile. This was achieved by considering MAWS as a stochastic process defined by its probability density and covariance functions. Therefore, the model response for the entire field is expressed in terms of probability. It is shown that a deterministic simulation obtained with the mean value of MAWS may lead to unacceptable predictions of the field average AET and D values, the difference with the stochastic mean strongly depending on the degree of variability and on the water supply conditions. (Résumé d'auteur

Résultats du programme REBECCA phase 1 de septembre 2011 à mars 2012. Volet agro-variétal modèle d'estimation de la qualité de la biomasse par des mesures SPIR chlordécone dans le système sol-plante : Note pour le COPIL n° 4 du 17 avril 2012

Cette note est préparée en vue du COPIL du 17 avril. Elle fait état des principaux résultats obtenus depuis celui de septembre 2011, concernant les volets agro-variétal, qualité de la biomasse et chlordécone (CLD) dans la plante. Elle constituera, avec le rapport intermédiaire portant sur la première année, le matériau de base du rapport scientifique final de la phase 1 (2 ans, 2010-2012). (Résumé d'auteur

REBECCA-DB.A: an opensource flexible database for managing data from energy cane

REBECCA is a research project on energy cane in Guadeloupe aiming at producing electricity from the burning of the whole sugarcane. This project has emphasised the importance to store, share and manipulate numerous field data and NIRS analyses collected. A relational database named REBECCA-DB.A has been created to manage agronomic and genotypic data from the project including biomass, fibre content, and low heating value of several above-ground biomass components (millable stalks, top of the stalks, green and dead leaves). The results of the analysis of fibre content and low heating value can be automatically imported into the database from the NIRS system. Data can be exported in an appropriate format to be used in other statistical and modelling tools; for example as input data in the tool REBECCA-LCA to carry out environmental studies on energy cane. From the results of biomass and biomass quality of 35 cultivars, it has been possible to easily select the best three cultivars for use as energy canes taking into account the main functional characteristics. REBECCA-DB.A, originally designed for a specific project, could be adapted for other applications on energy or fibre cane studies. This is a free tool within the scientific community. (Résumé d'auteur

Root architecture of two sorghum varieties differ than drought stress tolerance : [Abstract, P 7.17]

Root architecture of two sorghum varieties, fitted in #Durra race# and with different response in drought conditions, has been studied on hydroponic system, pot and in situ on field. These varieties have similar aerial agro-morphological characteristics in optimal growth conditions. In pre-flowering drought stress condition, tolerant variety (SSM1611), has a stable and higher yield than the non-tolerant one (IS16101). On hydroponics conditions and pot growth, varieties are studied at young stage. On field, observations concerned the whole plant cycle. Frequent observations of the aerial system have been made in all the trials, with counting of emerged leaves number and measuring stem height. Adventitious roots number and adventitious roots ranks number have been daily observed on hydroponic system and observations was not destructive. Spatial root disposition on stem was observed on hydroponic condition. On pot and field, these observations were destructive and realised once a week. Adventitious root and their different regions growth (basal none branched region, branched region, apical none branched region) were studied in hydroponic system and in pot. The distribution of the root length density according depth in situ condition was studied using passage model from root impacts to length density. Results show that, the development and the growth of aerial system are practically similar for both of varieties whatever trials conditions. However, for the root system there are some differences in favour of the drought stress tolerant varieties (SSM1611). All the trials showed that, SSM1611 presents a higher adventitious roots number and adventitious roots ranks number than IS16101. Adventitious roots number per rank varies according to the rank and the variety. The distribution of the adventitious roots around the stem seems to be leaded by the same low. Adventitious root of the same rank are balanced distribution around the stem. Until three roots per adventitious root rank, adventitious roots of two successive ranks are distributed in a complementary way around the stem. The growth of adventitious roots and their different regions ((basal none branched region, branched region, apical none branched region)e) present similarity for both of varieties. On hydroponic system, adventitious root length increase first time and then stop their growth to maximal level. However in pot, adventitious root growth seems to bee unlimited. SSM1611 variety reveals a root length density according to depth more important than IS16101 variety one in field. Adventitious roots number, adventitious roots ranks number, and root length density could constitute pertinent and easily accessible drought stress tolerance criterions. (Texte intégral