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Effect of polymer-coated urea and tillage on the dynamics of available N and nitrous oxide emission from Gray Luvisols

Soon, Y.K., Malhi, S.S., Lemke, R.L., Lupwayi, N.Z., Grant, C.A. (2011). Effect of polymer-coated urea and tillage on the dynamics of available N and nitrous oxide emission from Gray Luvisols, 90(2), 267-279. http://dx.doi.org/10.1007/s10705-011-9428-2

Abstract

Two field experiments were conducted to assess the effectiveness of polymer-coated urea (PCU) vs. conventional urea (urea) in minimizing nitrate accumulation in soil and nitrous oxide (N2O) emission while optimizing available N supply. The trials were located on Dark Gray Luvisols (Typic Cryoboralf) near Beaverlodge, Alberta (2004-2007) and Star City, Saskatchewan (2004-2006), in the north western Canadian Prairies. The treatments comprised of combinations of two tillage systems (conventional and no tillage), the two forms of urea (applied at commercial rates, 50-60 kg N ha-1), and time of application (side-banded in spring or fall). Tillage had little effect on the measured soil variables. Available N at the anthesis growth stage was higher with spring- than fall-banded N in three of four site-years, and with PCU than urea in two site-years. At seeding, nitrate in the soil layers to 60-cm depth, especially the top 15 cm, was mostly higher for fall- than spring-banded treatments but differed less between the forms of urea. Fall application, therefore, has greater potential for gaseous N and leaching losses early in the growing season when crops have low N requirements, and hence is not advisable. Nitrous oxide emission from spring to fall was higher with the fertilized treatments in three of five site-years and not different between fertilized and unfertilized treatments in the other site-years. At Beaverlodge, N2O loss was low in 2 years and showed few significant treatment effects. At Star City, N2O loss was 1.5- to 1.7-fold higher from urea than PCU treatments, and up to 1.5-fold lower from spring than fall application. It is concluded that although PCU can increase available N during the growth period and reduce N2O loss in some years compared with urea, the time of N application had a consistently greater effect than the type of urea in enhancing crop N recovery and reducing N loss to the environment. © 2011 Springer Science+Business Media B.V.

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