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Accueil du site → Doctorat → Royaume-Uni → 1995 → Fertilizer use efficiency and nitrogen dynamics in rainfed and irrigated wheat under a Mediterranean-type climate

University of Reading (1995)

Fertilizer use efficiency and nitrogen dynamics in rainfed and irrigated wheat under a Mediterranean-type climate

Garabet, S

Titre : Fertilizer use efficiency and nitrogen dynamics in rainfed and irrigated wheat under a Mediterranean-type climate

Auteur : Garabet, S

Université de soutenance : University of Reading

Grade : Doctor of Philosophy (PhD) 1995

Résumé
After drought, nitrogen is the most limiting factor for crop production in the dryland west-Asia-north Africa region. Efforts to improve the use efficiency of this expensive input hinge upon a thorough understanding of the dynamics of N in the field. While much is already known about N, there are gaps in our knowledge which need to be elucidated. Therefore, a study was conducted for two growing seasons in northern Syria to evaluate the effect of N and water on yield, water consumption and N fertilizer-use efficiency (at successive times after planting) of rainfed and irrigated wheat in a semi-arid, Mediterranean-type climate. Concomitant incubation experiments were done under controlled moisture and temperature conditions to verify their effect on the mineralization rates of the soil under study. Isotope enriched fertilizer (15N) was used in field and laboratory experiments to distinguish between soil N and fertilizer N.Rainfall and irrigation were important factors in determining N uptake by plants as well as dry matter and grain yield. Nitrification of fertilizer NH4+-N was lower under low moisture or low temperature conditions. Fertilizer N did not move below the 40 cm soil depth in either of the two years. Nitrogen fertilizer use efficiency reached a maximum around anthesis and decreased during the grain-filling period. Thus, the nitrogen fertilizer use efficiency appeared highly dependent upon date of measurement. Nitrogen fertilizer-use efficiency values were higher by the Difference method than by the Direct method. These values ranged between 28 and 95% by the Difference method and between 21 and 63% by the Direct method in the two years. As no priming effect was apparent in either year, the discrepancy between the two methods was attributed to the mineralization/immobilization process occurring in this soil.

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