Ammonia volatilization and yield of corn fertilized with different nitrogen sources in the Brazilian semiarid

Wadson De Menezes Santos,Heraldo Namorato De Souza,Claudia Pozzi Jantalia,Marcelo Ferreira Fernandes,Bruno José Rodrigues Alves,Edson Patto Pacheco,Inácio De Barros,Josimar Nogueira Batista,Segundo Urquiaga,Eduardo Pires Bender

doi:10.1590/s1678-3921.pab2020.v55.01036

Abstract

Abstract: The objective of this work was to evaluate the effect of the use of different nitrogen fertilizers on N losses by NH3 volatilization and on the grain yield of a corn (Zea mays) crop grown in the semiarid region of the state of Sergipe, Brazil. Corn was managed under rainfed conditions and conventional tillage. The fertilization treatments were: sulfur-coated urea (SU) and organo-mineral-coated urea (OMU). Regular urea and ammonium sulfate (AS) were also included as a reference of N sources of high and low NH3-volatilization potential, as well as a control without N fertilization. The N sources were applied to the soil surface at a rate of 150 kg ha-1 N as side-dressing at the V5 growth stage of corn. The experiment was carried out in 2015 and repeated in 2016. Losses of N through NH3 volatilization differed among the N sources in the two study years, with AS presenting the lowest N losses and regular urea, the highest. In the area treated with OMU, losses by NH3 volatilization were consistently controlled, showing a reduction of 74 and 67% in relation to that of regular urea in both years. SU, however, only mitigated NH3-N losses in 2015, increasing them in 2016, compared with regular urea. Corn plant grain yield and N status, assessed by the index leaf, did not clearly reflect N losses by NH3 volatilization. For the semiarid of Sergipe, OMU is the best urea-based fertilizer to mitigate N losses by NH3 volatilization, and the use of AS is an alternative to increase corn yield and eliminate N losses as NH3.

Highlights

For most Brazilian soils, the natural availability of nitrogen to the plants is low, making N fertilization a countrywide strategy for improving crop yield (Cancellier et al, 2016)
The urea-based fertilizers – regular urea, organomineral-coated urea (OMU), and sulfur-coated urea (SU) – had NH3 volatilization rates well above those of the control, while ammonium sulfate (AS) was virtually inert to this N-loss process
The process of NH3 volatilization is primarily dependent on the dissociation of NH4+ into NH3 and H+, whose magnitude will vary with NH4+ and H+ availabilities in the soil

Summary

Introduction

For most Brazilian soils, the natural availability of nitrogen to the plants is low, making N fertilization a countrywide strategy for improving crop yield (Cancellier et al, 2016). Almost 4.4 million tons of N are applied to cropped soils, mainly to those with corn and sugarcane (Heffer & Prud’homme, 2016). Urea is the main agricultural N source used, corresponding to 48% of the 107 million tons of N fertilizer applied in 2017 (IFA, 2019). In Brazil, urea has been widely used, representing about 50% of the total N applied in agriculture in the last two to three decades, which is likely related to its high N concentration (±45%), allowing reductions in transport and application costs (Alves at al., 2016). For the corn crop in Brazil, seedbed fertilization is followed by the application of urea, after 25 to 30 days of plant emergence, as the main N source, at rates varying from 80 to 160 kg ha-1, depending on yield expectation and cropping system management (Coelho et al, 2008). Urea hydrolysis into NH4+ and CO2 results in an increase of up to 8–9 in soil pH around the fertilizer granule and in the shift of NH4+ ions to the volatile NH3 form (Sommer et al, 2004)

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Results