%0 Journal Article
%T Volatiliza£¿£¿o de am£¿nia da ureia alterada por sistemas de preparo de solo e plantas de cobertura invernais no Centro-Sul do Paran¨¢
%A Rojas
%A Carlos Andr¨¦s Leguizam¨®n
%A Bayer
%A Cim¨¦lio
%A Fontoura
%A Sandra Mara Vieira
%A Weber
%A Mirla Andrade
%A Vieiro
%A Fernando
%J Revista Brasileira de Ci¨ºncia do Solo
%D 2012
%I Sociedade Brasileira de Ci¨ºncia do Solo
%R 10.1590/S0100-06832012000100027
%X nitrogen losses from urea by ammonia volatilization are higher from no-tillage than from conventional tillage. the objective of this study was to evaluate the magnitude of this process under cool and wet spring conditions in the south-central region of the state of paran¨¢ and to evaluate the influence of two winter cover crops (black oat and common vetch) on ammonia volatilization in no-tillage. the tillage systems were compared in a long-term tillage experiment (28 years) and the cover crops tested separately in a long-term (> 15 yr) no-tillage area. maize was grown in both experiments. urea was applied at rates of 0, 80 and 160 kg ha-1 n in a single application in the tillage experiment and at rates of 0, 100 and 200 kg ha-1 n, split in two applications, in the cover crop experiment. volatilization of nh3 was measured for 20 days after urea application in a semi-open static system. urease activity was evaluated in both experiments. the nh3 loss rates were highest 5 days after urea application. cumulative ammonia losses reached 18% of the applied n in no-tillage and 3% in conventional tillage. the higher losses from no-tillage may be partially related to the greatest urease activity in the soil surface layer. ammonia volatilization was not affected by cover crops. as an isolated practice, split surface n fertilization does not ensure a decrease of nh3 losses, which are primarily related to rain events immediately after urea application.
%K no-tillage
%K urease.
%U http://www.scielo.br/scielo.php?script=sci_abstract&pid=S0100-06832012000100027&lng=en&nrm=iso&tlng=en