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Effect of nitrogen fertilization on the response of pearl millet (Pennisetum glaucum (L.) R. Br.) to drought

Diouf O., Diouf M., Sarr B., Ogbonnaya C.I., Diop N.N., Braconnier S., Roy-Macauley H., Delhaye J.P.. 2000. In : ESA. Third International Crop science Congress, 17-22 August 2000, Hamburg, Germany. s.l. : s.n., 2 p.. International Crop Science Congress. 3, 2000-08-17/2000-08-22, Hambourg (Allemagne).

Pearl millet is an important crop in the sub-Saharan West Africa. In Senegal, the instability in millet production is caused mainly by soil water deficit and nitrogen deficiency. For this reason, this study was conducted in a sandy soil in Senegal for three years during the dry and rainy seasons, to assess the effect of interaction between drought and N deficiency on the agrophysiological responses of millet. The experimental design incorporated two watering regimes (water stressed and well irrigated control) and three level of N fertilization (0.00, 17.13, and 68.5 kg N ha-1). When water stress was applied at early vegetative stage and during flowering - grain filling phases, high fertilizer application reduced grain yield and grain N yield more than zero fertilizer input. Yield components analysis showed that higher grain and grain N yields in zero fertilizer input were due to dry matter partitioning in favour of the grains resulting from the attainment of higher water status. The lower leave area index (LAI) combined with zero fertilizer input induced lower water losses (evapotranspiration) which became beneficial in terms of soil water stock when water stress was applied. Associated with deep rooting, these responses were responsible for the higher water potential, stomatal conductance, rates of transpiration and photosynthesis under zero N fertilization. The implications of these drought responses on the performance of millet under N deficiency are discussed on the basis of cropping systems and climatic risks.

Mots-clés : pennisetum glaucum; stress dû à la sécheresse; réponse de la plante; fertilisation; engrais azoté; stade de développement végétal; composante de rendement; bilan hydrique; relation source puits; photosynthèse; transpiration; sénégal

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