Fractionnement de la fertilisation azotée dans la production du bleuet nain sauvage et suivi de l’azote du sol

Abstract

In wild lowbush blueberry production, fertilizers are applied in the spring of the vegetative year. To increase fertilizers efficiency and to reduce environmental losses, fertilizer split applications between vegetative and production year have been proposed. The objectives of this project were to determine the effect of split application of the nitrogen (N) in the vegetative and production year on the wild blueberry production and on soil mineral N in six blueberry fields located in Saguenay-Lac-Saint Jean (Quebec, Canada). Four rates of ammonium sulfate were applied in the spring of the vegetative year (0, 30, 60 and 90 kg ha-1). These same rates were applied in the spring of the vegetative (50%) and production (50%) years. The 30 kg N ha-1 rate was also applied only in the production year. For all sites, maximum fruit yields (3800 kg ha-1) were obtained with 62 kg N ha-1. However, the maximum rate ranged from 25 to 90 kg N ha-1 according to the sites. Applying N in the vegetative and production years had comparable fruits yields to those obtained with the fertilizer applied only in the vegetative year. One month after N application, the amount of N-NH4 in the soil profile increased by 4 to 38 kg ha-1 compared with the control. Split N application reduced by 55 to 76% the amount of NH4-N in soil layers only in the vegetative year. Soil nitrate increased with N rates at the end of the growing season, indicating that a part of NH4-N was nitrified and can be potentially leached the under root zone. According to the various maximum N rates obtained and N fertilizer impacts on soil N mineral, there would be no agronomic or environmental benefit to splitting low rates (<30 kg ha-1). However, with higher rates, splitting N between vegetation and production years would maximize fruit yields and reduce environmental risk.Key words: Maximum N rate, ammonium, nitrate, Vaccinium angustifolium Ait., split fertilization

Biodisponibilité de l'azote et du phosphore dans les sols de bleuetières du Québec

“…Des e´tudes ante´rieures ont e´galement de´montre´que l'extraction au KCl, a`l'eau et l'utilisation des membranes d'e´change cationique aient e´te´aussi performantes pour e´valuer la biodisponibilite´du N du sol (Ziadi et al 1999(Ziadi et al , 2006. L'accroissement rapide en N-NH 4 dans le sol apre`s l'application des engrais azote´s a e´te´e´galement mesured ans des e´tudes ante´rieures portant sur la fertilisation azote´e dans la production du bleuet sauvage (Eaton et Patriquin 1988;Gagnon et al 2003;Lafond 2010b). Les diminutions en N-NH 4 du sol mesure´es aux e´chantillonnages suivants indiquent que l'azote a e´te´pre´leveŕ apidement par la culture (Eaton et Patriquin 1990).…”

“…L'application de fertilisants complets apportant de l'azote (N), du phosphore (P) et du potassium (K) est recommande´a`chaque de´but de cycle de production pour assurer le de´veloppement de la culture et maintenir sa productivite´ (MAPAQ 2000;Lafond 2010a). Plusieurs e´tudes ont de´montre´que la culture de bleuet re´pondait positivement a`la fertilisation azote´e (Penney et McRae 2000;Eaton et Nams 2006;Starast et al 2007;Lafond 2010b;Lafond et Ziadi 2011). Toutefois, les re´sultats ont e´te´contradictoires quant a`la re´ponse de la culture a`la fertilisation phosphate´e.…”

“…De plus, sous des conditions de pH de sol acide, le taux de nitrification demeure relativement faible (Eaton et Patriquin 1988). Toutefois, des apports importants d'engrais azote´sous forme de sulfate d'ammonium peuvent engendrer une accumulation de nitrates sous la zone racinaire en fin de saison (Lafond 2010b). Le plant de bleuet est e´galement caracte´rise´par une association avec un champignon mycorhizien de type e´ricoı¨de (Goulart et al 1993).…”

“…L'azote mine´ral est ge´ne´ralement de´termine´a`la suite d'une extraction au KCl (Maynard et al 2007). Cette me´thode est particulie`rement sensible pour suivre l'e´volution du N-NH 4 dans le sol a`la suite d'application d'engrais dans la culture du bleuet (Lafond 2010b). L'extraction a`l'eau est e´galement utilise´e et la fraction de l'azote soluble a`l'eau est habituellement conside´re´e comme la fraction la plus facilement et rapidement disponible (Cordovil et al 2007).…”

Boundary-Line Approach to Determine Minimum and Maximum Leaf Micronutrient Concentrations in Wild Lowbush Blueberry in Quebec, Canada

“…The average temperature was 14 • C for May to August (Environment Canada, 2012). The trials are described in previous studies by Lafond (2010a) and Lafond and Ziadi (2011). Those trials were selected to ensure a wide range of data on fruit yields and leaf micronutrient concentrations.…”