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Impacts of soil and water management, and of genotype characteristic on crop productivity and sustainability in irrigated rice

Bueno Crisanta Sunio. 2010. Impacts of soil and water management, and of genotype characteristic on crop productivity and sustainability in irrigated rice s.l. : Chiba University, 118 p. Thesis Ph. D. : Chiba University

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Encadrement : Lafarge, Tanguy ; Inubushi, Kazuyuki

Résumé : The irrigated rice system faces great challenges in terms of productivity and sustainability with respect to food shortage and environmental issues. This study was done to address concerns with regards to the soil resources availability, methane emissions, water scarcity and slow gain in grain yield. Comparison of soil properties between cultivated and uncultivated soils in farmer's field is a promising approach to evaluate soil fertility and to adjust existing practices to ensure that nutrient outflow will be in balanced with the nutrient inflow. In this study, cultivated soils had significantly lower fertility when compared with the uncultivated soils as indicated by the soil properties measured. The amount of fertilizer being added by the farmers was not sufficient. Moreover, soil management practices should be well monitored as methane emissions increased dramatically upon straw incorporation and methane was emitted mostly during the early growth phase of the rice crop. But, drainage during mid-tillering abruptly reduced methane emissions by 15-80% as compared with continuous flooding and without a significant effect on grain yield. The choice of inorganic fertilizer and cultivar also influenced the amount of methane emission rates. Ammonium sulfate plus urea significantly reduced emission by 50- 66% than urea alone. Drying the field during midtillering mitigated methane emission and also saved water. Alternate wetting and drying (AWD) practice in irrigated rice fields starting from mid-tillering with a threshold of -30 kPa appeared as a more effective water-saving technology than field drying at mid-tillering: water productivity was significantly increased for all the contrasted genotypes evaluated and the amount of water input (WI) was significantly reduced by 33?41% in -30 kPa depending on the genotypes. However, the delay in tiller cessation reported under AWD, where higher and prolonged duration of tiller emergence was observed compared with continuous flooding, was probably not favorable for maximizing grain yield (GY). The higher GY of rice hybrids compared with inbreds (by 14-18% average) was due to the higher biomass accumulation and efficient biomass partitioning among plant organs, related with earlier cessation of tiller emergence. This earlier cessation is associated with better partitioning of biomass within the plant and ultimately to the panicle. This then indicates that breeding programs targeted for high yield potential will be different with those for genotypes under water saving conditions. (Résumé d'auteur)

Mots-clés Agrovoc : Oryza sativa, Riz irrigué, Système de culture, Propriété physicochimique du sol, Rendement des cultures, Fertilité du sol, Génotype, Conservation de l'eau, Gestion des eaux, Durabilité, émission de méthane, séquestration du carbone, Type de sol

Classification Agris : F01 - Culture des plantes
P35 - Fertilité du sol
P33 - Chimie et physique du sol
F30 - Génétique et amélioration des plantes
P10 - Ressources en eau et leur gestion
F08 - Systèmes et modes de culture
P01 - Conservation de la nature et ressources foncières

Axe stratégique Cirad : Axe 1 (2005-2013) - Intensification écologique

Auteurs et affiliations

  • Bueno Crisanta Sunio, IRRI (PHL)

Source : Cirad - Agritrop

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