MANAGEMENT OF IRRIGATION AND NITROGEN FERTILIZERS TO REDUCE AMMONIA VOLATILIZATION

Fernando Viero,Cimélio Bayer,Renan Costa Beber Vieira,Eduardo Carniel

doi:10.1590/01000683rbcs20150132

Abstract

ABSTRACT Nitrogen losses by ammonia (NH3) volatilization can be reduced by appropriate irrigation management or by alternative N sources, replacing urea. The objective of this study was to evaluate the efficiency of irrigation management and N source combinations in decreasing NH3 volatilization from an Argissolo Vermelho Distrófico típico cultivated for 28 years with black oat (Avena strigosa) and maize (Zea mays), under no-tillage in the region of Depressão Central, Rio Grande do Sul, Brazil. The experiment was arranged in a randomized block design with split plots with three replications, where the main plots consisted of irrigation systems: no irrigation; irrigation immediately before and irrigation immediately after fertilization. The subplots were treated with different N sources: urea, urea with urease inhibitor and slow-release fertilizer, at an N rate of 180 kg ha-1, broadcast over maize, plus a control treatment without N fertilization. Ammonia volatilization was assessed using semi-open static collectors for 1, 2, 4, 6, and 10 days after N fertilization. In general, more than 90 % of total NH3-N losses occurred until three days after N fertilization, with peaks up to 15.4 kg ha-1 d-1. The irrigation was efficient to reduce NH3 losses only when applied after N fertilization. However, reductions varied according to the N fertilizer, and were higher for urea (67 %) and slightly lower for urea with urease inhibitor (50 %) and slow-release fertilizer (40 %), compared with the mean of the treatments without irrigation and irrigation before fertilization. The use of urea with urease inhibitor instead of urea was only promising under volatilization-favorable conditions (no irrigation or irrigation before N fertilization). Compared to urea, slow-release fertilizer did not reduce ammonia volatilization in any of the rainfed or irrigated treatments.

Highlights

Urea is the most widely used nitrogen fertilizer for broadcasting on maize in Brazil
N losses by ammonia volatilization depend on the environmental conditions, i.e., they can be lower in dry soil and higher when N fertilizer is applied to moist soil (Cantarella et al, 2008), and intensified at high temperatures (Tasca et al, 2011)
The occurrence of three rainfall events (1, 3 and 5 days after fertilization), with a total of 25 mm certainly had a restrictive effect on NH3 losses (Fontoura and Bayer, 2010), in particular the 19 mm rain on the third day after fertilization

Summary

Introduction

Urea is the most widely used nitrogen fertilizer for broadcasting on maize in Brazil. High N losses, mainly by ammonia (NH3) volatilization, may decrease the fertilization efficiency, limiting maize yields (Fontoura and Bayer, 2010) These losses are highly influenced by environmental conditions in the days following N application (Duarte et al, 2007; Holcomb et al, 2011). OH ions are released, raising the pH in surrounding granules, favoring N conversion to ammonia and volatilization (Bouwmeester et al, 1985) In this way, NH3 losses are usually highest in the first days after N fertilization, reaching values between 28-37 % of total losses in the first three days after fertilizer application. N losses by ammonia volatilization depend on the environmental conditions, i.e., they can be lower in dry soil and higher when N fertilizer is applied to moist soil (Cantarella et al, 2008), and intensified at high temperatures (Tasca et al, 2011)

Objectives

Methods

Results

Conclusion