Ammonia volatilization from nitrogen fertilizers in no-till wheat and maize in southern Brazil

Sandra Mara Vieira Fontoura,Renato Paulo de Moraes,Fernando Viero,Cimélio Bayer

doi:10.1590/s0100-06832014000500017

Abstract

Crop residues on the soil surface of no-till systems can intensify ammonia volatilization from N fertilizers applied to cereal crops. This study assessed the magnitude of N losses through ammonia volatilization from urea applied to no-till winter (wheat) and summer crops (maize) on a Typic Hapludox in the south-central region of Paraná, southern Brazil. In addition, the potential of alternative N sources (urea with urease inhibitor, liquid fertilizer, ammonium nitrate and ammonium sulfate) and different urea managements (fertilizer applied in the morning or afternoon) were evaluated. Two experiments with maize and wheat were carried out for two years, arranged in a randomized block design with four replications. Nitrogen volatilization losses were assessed with a semi-open static collector until 21 days after fertilization. In winter, the losses were low (<5.5 % of applied N) for all N sources, which were not distinguishable, due to the low temperatures. In the summer, volatilization rates from urea were higher than in the winter, but did not exceed 15 % of applied N. The main factor decreasing N losses in the summer was the occurrence of rainfall in the first five days after fertilization. Urea with urease inhibitor, nitrate and ammonium sulfate were efficient to decrease ammonia volatilization in maize, whereas the application time (morning or afternoon) had no influence.

Highlights

Maize and wheat are among the major grain crops produced in Brazil, grown on about 13 and 2 million hectares, respectively, mostly in the no-till (NT) system (CONAB, 2012)
Nitrogen fertilization is one the technologies for which optimization is being sought in order to increase crop yields, in view of the estimated efficiency of around 60 % (Fontoura & Bayer, 2009)
Recently the suitability of urea has been questioned, due to the possibility of its reduced efficiency by volatilization losses, which is increased under notillage management systems (Rojas et al, 2012), with losses ranging from 35 to 78 % of the N applied in warm climate, as in southeastern Brazil (Lara Cabezas et al, 1997b; Costa et al, 2003; Lara Cabezas & Souza, 2008; Pereira et al, 2009)

Summary

Introduction

Maize and wheat are among the major grain crops produced in Brazil, grown on about 13 and 2 million hectares, respectively, mostly in the no-till (NT) system (CONAB, 2012). One of the important forms of N fertilization is the surface application of urea (Fontoura & Bayer, 2010). This is the most commonly used N source in grain crops, due to its lower cost per nutrient unit, for its availability and accessibility, being more competitive, in situations where lower volatility losses are expected, e.g., in the driest and coldest months (Cantarella et al, 2008). Recently the suitability of urea has been questioned, due to the possibility of its reduced efficiency by volatilization losses, which is increased under notillage management systems (Rojas et al, 2012), with losses ranging from 35 to 78 % of the N applied in warm climate, as in southeastern Brazil (Lara Cabezas et al, 1997b; Costa et al, 2003; Lara Cabezas & Souza, 2008; Pereira et al, 2009)

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