Résumés
Abstract
In Morocco, water availability is becoming a national priority for the agricultural sector. In this context, the stakeholders try continuously to improve strategies of water irrigation management, on one hand, and to assess vegetation water content status, on the other hand, in order to improve irrigation scheduling and prevent water stress that affects yield adversely. The aim of this study was to evaluate the potential of two spectral indices, calculated from SPOT-5 high resolution visible (HRV) data, to retrieve the vegetation water content values of wheat in an irrigated area. These indices were the normalized difference water index (NDWI) and the moisture stress index (MSI). The values of these indices were compared with corresponding values of in situ-measured vegetation water content in 16 fields of wheat during the 2012-2013 cropping season. Good correlations were found between observed vegetation water content values and NDWI and MSI values during the crop growth period from anthesis to grain filling. These results were validated using the k-fold cross validation method and showed a good stability of the proposed regression models with a slight advantage for the NDWI. Based on these results, the NDWI was chosen to map the spatial variability of vegetation water content of wheat at the east of the Beni-Moussa irrigated perimeter. These results proved that the indices based on near and shortwave infrared band (NIR and SWIR) are able to monitor vegetation water content changes in wheat from anthesis to the grain filling stage. These indices could be used to improve irrigation and crop management of wheat at both the field and regional levels.
Keywords:
- Normalized difference water index,
- moisture stress index,
- vegetation water content,
- wheat,
- semi-arid,
- irrigated area
Résumé
Au Maroc, la disponibilité de l'eau est devenue une priorité nationale pour le secteur agricole. Dans ce contexte, les acteurs et les décideurs essaient en permanence d'améliorer les stratégies de gestion de l'irrigation, d'une part, pour évaluer l’état de l’humidité du couvert végétal et d'autre part, afin d'améliorer la planification de l'irrigation et éviter le stress hydrique qui affecte le rendement. Le but de cet article était d'évaluer le potentiel de deux indices spectraux, calculés à partir des données du proche infrarouge et du moyen infrarouge du capteur à haute résolution visible (HRV) de SPOT-5, pour estimer la teneur en eau du blé dans une zone irriguée. Les valeurs de l'indice normalisé d'eau (NDWI) et de l'indice de stress hydrique (MSI) ont été comparées avec les valeurs correspondantes à la teneur en eau de la végétation mesurée in situ dans 16 parcelles de blé au cours de la campagne agricole 2012-2013. Les indices NDWI et MSI ont montré une bonne concordance en comparaison aux mesures de terrain collectées entre la floraison et le remplissage des grains du blé. Ces résultats ont été validés à l'aide de la méthode de validation croisée k-fold et ils montrent une bonne stabilité des deux modèles proposés avec un léger avantage du NDWI. Sur la base de ces résultats, le NDWI a été choisi pour cartographier la variabilité spatiale de la teneur en eau du blé à l'est du périmètre irrigué de Beni-Moussa. Ces résultats ont prouvé que les indices utilisant la bande spectrale du moyen infrarouge et du proche infrarouge sont capables d’assurer le suivi de la teneur en eau du blé de la floraison au remplissage des grains. Ces indices pourraient être utilisés pour améliorer la gestion de l'irrigation du blé à l’échelle de la parcelle et/ou de la région.
Mots-clés :
- Indice de l’eau,
- indice du stress hydrique,
- teneur en eau de la végétation,
- blé,
- semi-aride,
- zone irriguée
Parties annexes
References
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