Ammonia volatilization from enhanced-efficiency urea on no-till maize in brazilian cerrado with improved soil fertility

Abstract

High nitrogen losses by ammonia volatilization are expected when urea is used as the source of N. The use of controlled-release urea and urease inhibitors are possible strategies to reduce such losses and increase nitrogen use efficiency. This study aimed to evaluate nitrogen losses by ammonia volatilization from stabilized, slow and controlled release urea and its absorption by maize grown under no-till in an improved Cerrado soil. Four N sources were used: conventional urea, urea + N-(n-butyl) thiophosphoric triamide (NBPT), urea + Cu and B and urea coated by sulfur + polymers. These N sources were surface applied along the rows using three N doses of 100, 150 and 200 kg ha -1 . No N was added to the control. Data were collected regarding N losses by volatilization, the N contents accumulated in the stubble and grains, and the yields of the stubble and grains. Stabilized urea and slow release urea were efficient for postponing the ammonia volatilization peaks. The urease inhibitors postponed the peaks for up to two days, reducing the accumulated volatilization by 18% when compared with common urea. Polymer sulfur coated urea resulted in a 37% reduction in ammonia volatilization. Increasing the N application rate to 200 kg ha -1 resulted in 16% greater yields and 37% greater N accumulation in the plants relative to the control. However, the stabilized and slow-release urea did not improve the N accumulation or yield. Consequently, the nitrogen use efficiency of maize was not improved relative to the use of conventional urea.Index terms: Nitrogen fertilizers; NH 3 -N losses; polymer sulfur coated urea; urease inhibitors; Zea mays L. RESUMOA aplicação de ureia, frequentemente, gera grandes perdas de N por volatilização e o uso de revestimentos e inibidores de urease, podem reduzir essas perdas. Neste estudo, objetivou-se avaliar as perdas de nitrogênio pela ureia estabilizada e de liberação lenta ou controlada e sua absorção pelo milho cultivado em plantio direto, em solo de Cerrado, com fertilidade construída. Quatro fontes de N foram utilizadas: ureia convencional, ureia + N-(n-butyl)thiophosphoric triamide (NBPT), ureia + Cu + B e ureia revestida por enxofre e polímeros. Essas fontes de N foram aplicadas em superfície nas doses de 100, 150 e 200 kg ha -1 . Não houve aplicação de N no controle. Avaliaram-se as perdas de N por volatilização, o acúmulo de N nos grãos e palhada e produção de grãos e de palhada. A ureia estabilizada e de liberação controlada foi eficiente em atrasar os picos de volatilização de amônia. Os inibidores de urease atrasaram os picos de volatilização em até dois dias, reduzindo a volatilização acumulada em até 18%, quando comparado à ureia comum. A ureia revestida por enxofre e polímeros resultou em uma redução de 37% na volatilização de amônia. O aumento da dose de N até 200 kg ha -1 resultou em aumento de 16% na produtividade e 37% no acúmulo de N em relação ao controle. Entretanto, a ureia estabilizada e de liberação controlada não aumentou o acúmulo de N ou a produtividade...

Ammonia and carbon dioxide emissions by stabilized conventional nitrogen fertilizers and controlled release in corn crop

“…As illustrated in Figures 3a, 3b and 3c, it is observed that urea coated with 16% S 0 presented no cracks. Similar evaluation was carried out by Cancellier et al (2016) with urea coated with 7.9% S 0 + polymers. The difference between the two types of coatings is that the additional layer of polymers serves as water passage control and as dissolution of the urea present innner granules.…”

“…In a study carried out by Cancellier et al (2016)the largest daily N-NH 3 loss of the urea occurred on the 2 nd day after fertilization, and was 12% of total N applied in topdressing. Blend of PSCU and urea (5.6% of the applied N) and urea treated with NBPT (7% of the applied N) promoted daily peaks of N-NH 3 emission on the 3 rd and 4 th day after its application to the soil surface, respectively.…”

“…Prilled urea presents mostly spherical-shaped particles, with diameter between 1 and 2 millimeters. The characterization by scanning electron microscopy (SEM) was carried out by Cancellier et al (2016). Granular urea: conventional urea fertilizer (45% N).…”

“…Fertilizers samples were divided into four parts, and the selected granules were cut using a scalpel; samples were set in "stubs", metallized in a carbon evaporator device model Union CED 020, and observed in in the Scanning Electron Microscope model LEO EVO 40 XVP Zeiss. Samples were qualified, quantified, and mapped regarding the chemical composition by Spectroscopy Energy Dispersive X-Ray using the Quanta X Flash 5010 Bruker device, according to the methodology described by Cancellier et al (2016). …”

“…Between 20 to 70% of conventional urea applied escapes to the environment through ammonia volatilization and denitrification (Nauz;Sulaiman, 2016). In agricultural systems, several factors, such as humidity, temperature, pH, organic matter, cultivation system, nitrogen (N) availability, and the N rates applied influence ammonia loss (Denmead;Dunin, 2008;Rochette et al, 2014;Cancellier et al, 2016) and C-CO 2 losses (Al-Kaisi et al, 2008).…”