Ammonia Volatilization and Nitrogen Retention: How Deep to Incorporate Urea?

Abstract

Incorporation of urea decreases ammonia (NH) volatilization, but field measurements are needed to better quantify the impact of placement depth. In this study, we measured the volatilization losses after banding of urea at depths of 0, 2.5, 5, 7.5, and 10 cm in a slightly acidic (pH 6) silt loam soil using wind tunnels. Mineral nitrogen (N) concentration and pH were measured in the top 2 cm of soil to determine the extent of urea N migration and the influence of placement depth on the availability of ammoniacal N for volatilization near the soil surface. Ammonia volatilization losses were 50% of applied N when urea was banded at the surface, and incorporation of the band decreased emissions by an average of 7% cm (14% cm when expressed as a percentage of losses after surface banding). Incorporating urea at depths >7.5 cm therefore resulted in negligible NH emissions and maximum N retention. Cumulative losses increased exponentially with increasing maximum NH-N and pH values measured in the surface soil during the experiment. However, temporal variations in these soil properties were poorly related to the temporal variations in NH emission rates, likely as a result of interactions with other factors (e.g., water content and NH-N adsorption) on, and fixation by, soil particles. Laboratory and field volatilization data from the literature were summarized and used to determine a relationship between NH losses and depth of urea incorporation. When emissions were expressed as a percentage of losses for a surface application, the mean reduction after urea incorporation was approximately 12.5% cm. Although we agree that the efficiency of urea incorporation to reduce NH losses varies depending on several soil properties, management practices, and climatic conditions, we propose that this value represents an estimate of the mean impact of incorporation depth that could be used when site-specific information is unavailable.

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

“…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).…”

“…In addition to the conventional alternatives already known to reduce N-NH 3 losse, such as: incorporation of urea (mechanically or by the water from irrigation and rain); (Holcomb et al, 2011;Rochette et al, 2014), and the supply of Nin the form of nitrate or ammonium sulfate Ciência e Agrotecnologia, 41(5):494-510, Sep/Oct. 2017 (Fontoura;Bayer, 2010), it should be mentioned the use of stabilized and of slow and controlled release nitrogen fertilizer (Azeem et al, 2014;Timilsena et al, 2014;Nauz;Sulaiman, 2016) which are within the scope of the "4C" practices -four management practices that promote the efficient use of fertilizer: to apply the right N source at the right dose, at the right time and the right place (Fixen 2007;Chien;Prochnow;Cantarella, 2009;IFA, 2009).…”

Urease Inhibitor and Irrigation Management to Mitigate Ammonia Volatilization from Urea in No-Till Corn

“…Therefore, soil moisture sufficed to hydrolyze urea in both treatments, but irrigation after fertilization significantly reduced NH 3 -N losses -probably through its effect of incorporating fertilizer into the soil (Rochette et al, 2013). Adsorption of NH 4 + by negative soil charges and buffering of a rise in soil pH around granules (Holcomb III et al, 2011) strongly decreased volatilization rates: from 17 to 2 kg ha -1 d -1 on the second day after N fertilization ( Figure 2a).…”

Nitrogen Related Diffuse Pollution from Horticulture Production—Mitigation Practices and Assessment Strategies

“…The same applies to the formulations used to control the soil reaction, e.g., the use of (NH 4 ) 2 SO 4 to acidify the soil can contribute to N losses through volatilization [105].…”

“…• Fertilizer application method When urea is spread at the surface, the NH 3 volatilization losses can be as high as 50% of the applied N [105]. Moreover, incorporating urea at depths higher than 7.5 cm can result in negligible NH 3 emissions and maximum N retention.…”