Suivi du devenir de l'eau et des nitrates sous culture de pommes de terre (Solanum tuberosum L.) à l'aide du traçage isotopique 18O, 2H et 15N et d'un échantillonnage représentatif de la microtopographie
Quantifying nitrogen fertilizer leaching in order to reduce environmental losses in the potato (Solanum tuberosum L.) production on sandy soils is a major issue of current research. The general objective of the thesis was to address this problem in three parts. The first part aimed to follow the fate of rainfall and snowmelt in the soil during an entire year with water stable isotopes (18O and 2H) since nitrates follow water pathways. Rainfall and snow melt percolation rate was approximately 1.5±0.5 months. Water percolates at slower rate in the upper soil layer than in sublayers. Finally, a perceptual model considered two periods of nitrate leaching: the first period from previous harvest to seeding and the second during the cropping season. In the second part, we followed the nitrogen fertilizer pathway through soil and estimated fertilizer recovered by plants after fortification with nitrogen 15. Soil profiles were sampled on the same days as for the oxygen 18 and deuterium samplings. Results show that the fertilizer remained in the hill until the occurrence of rainfall events exceeding 70±10 mm. Nitrates are leached away mostly during the fall, as was the case for oxygen 18 and deuterium. At harvest, the tuber took up 47% of the nitrogen from fertilizer, leaving the remainder susceptible to leaching. Until maximum foliage coverage, the plant took up nitrogen more from fertilizer than mineralized organic nitrogen, but the reverse occurred thereafter. The third part was to simplify the sampling procedure of soil nitrate within the hill for budgeting nitrate. The hill was sampled across a 0-50 cm soil profile at four places and at five moments during the cropping season. A reliable relationship with a slope of 0.78 related soil nitrate content sampled at the centre of the hill to that of the entire hill for the 0-50 cm soil profile.
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Advisor:Anctil, François; Parent, Léon-Étienne
School Location:Canada - Quebec / Québec
Source Type:Master's Thesis
Date of Publication:12/01/2007