Ammonia losses from urea applied to winter wheat over four consecutive years and potential mitigation by urease inhibitors

Abstract

Urea is not only the most important mineral nitrogen (N) fertilizer worldwide, but it is also the mineral N fertilizer with one of the highest potential for ammonia (NH3) losses. The European emission inventory guidebook estimates an average loss of 16% of the applied urea as NH3. For mitigating NH3 losses from urea, the best option would be to immediately incorporate the fertilizer. However, the addition of a urease inhibitor (UI) represents a potent alternative. In a multi‐year experiment from 2002 to 2005, 17 measurement periods were conducted in winter wheat (Triticum aestivum L.) and on bare soil in Southern Germany to evaluate the extent of NH3 losses following the application of urea and to determine the mitigating effect of urease inhibitors. In all measurement periods, 80 kg N ha−1 as urea without or with the UI N‐(n‐butyl) thiophosphoric triamide (nBTPT) 0.3% w/w or N‐(isopropoxycarbonyl) phosphoric acid triamide (IPAT) 0.4% w/w were applied. For 6–24 d following fertilizer application, NH3 emissions were continuously measured using a dynamic chamber system. Generally, low NH3 emissions were detected from urea, varying between 0.1 and 2.7% of the N applied to winter wheat and between 2.6 and 16.3% of the N applied on bare soil. Addition of the UIs IPAT and nBTPT had a significant effect on the course of NH3 emissions and reduced losses on average by 32% and 24%, respectively.

Ammonia volatilization, nitrous oxide emissions, and corn yields as influenced by nitrogen placement and enhanced efficiency fertilizers

“…A multi-year, multi-site NH 3 volatilization study in corn conducted in Tennessee showed a positive correlation with total NH 3 volatilization loss and mean temperature in the 20 d after application (Liu et al, 2019). Similar conclusions were found in a multi-year volatilization study in winter wheat in Germany, with greater losses during measurement campaigns with higher temperatures (Schraml, Weber, Heil, Gutser, & Schmidhalter, 2018).…”

Direct and Indirect Effects of Urease and Nitrification Inhibitors on N2O-N Losses from Urea Fertilization to Winter Wheat in Southern Germany

“…However, the major reasons leading to low NH3 emission in southern Germany may be due to low pH values of the investigated soils together with increased cation exchange capacity, and low temperature prevailing in April and frequent precipitation events after N application. However, the 7.7% of the applied urea N from NH3-N losses was higher than the 0.1-2.7% in southern Germany reported by Schraml et al [6]. This discrepancy may be attributable to the higher pH at the experimental site of this study (pH = 6.7).…”

“…Furthermore, our long-term studies on N 2 O emissions have shown that averaged N 2 O emissions over many years were consistent (back to the 1990s, e.g., [23][24][25][26]). In particular, NH 3 emission from U from 2001 to 2010 were much less variable with years and were limited to a small range of 1-3.4% of urea-N applied during the growing seasons of winter wheat [6,[25][26][27][28][29]. A simulation study on modeling NH 3 emissions across Germany [30] showed that NH 3 emissions (% urea N applied) were in a range of 0-10% in strong contrast to the averaged 24% for European arable soils assumed by EMEP/EEA [31].…”

“…In addition to incorporating U into soil, the addition of UIs is another best practice to avoid NH 3 volatilization, and had a significant effect on NH 3 emissions and reduced NH 3 losses by 26-83% and 24-32%, respectively, of the applied urea-N on average [5,6]. Starting from 2020, the new German fertilizer ordinance requires the application of either UIs or the immediate incorporation of U into soils.…”

“…The main working principle of UIs is slowing down the hydrolysis of U, and thus giving more time for the U to increase its dispersion into the soil [6].…”