A simple and easy method to measure ammonia volatilization: Accuracy under field conditions

Field studies on soil ammonia (NH₃) volatilization are restricted in many countries owing to the high costs commonly demanded for accurate quantification. We assessed the accuracy of a simple, open chamber design to capture NH₃ under field conditions, as affected by different chamber placement schemes. Urea-¹⁵N was surface applied to lysimeters installed in the spaces between maize rows. Open chambers made from plastic bottles were installed on each lysimeter with variations in i) N rates (3, 8, 13, and 18 g m^-2), ii) the height of the chamber above the soil surface (0, 5, and 10 mm), and iii) chamber relocation (static vs. dynamic). Reference lysimeters without chambers were used to measure NH₃ losses by ¹⁵N-balance. Losses of NH₃-N accounted for more than 50% of the applied N. Relocation of the chambers had no impact on their NH₃-trapping efficiencies, proving to be an unnecessary procedure. Variation in the height of the chambers above the soil surface affected the capture of NH₃, but the results still maintained high linearity with the NH₃ losses quantified by the reference method (R² > 0.98). When the same placement scheme used in the introductory study describing the chamber was utilized (static and touching the soil surface), we found a trapping efficiency of 60%, which was very similar to that (57%) obtained in the previous study. Our results show that this simple, open chamber design can be used with satisfactory accuracy under field conditions, provided that simple, standardized procedures are warranted.