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

Field studies on soil ammonia(NH_(3))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 NH_(3)under field conditions,as affected by different chamber placement schemes.Urea-15 N 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 NH_(3)losses by^(15)N-balance.Losses of NH_(3)-N accounted for more than 50%of the applied N.Relocation of the chambers had no impact on their NH_(3)-trapping efficiencies,proving to be an unnecessary procedure.Variation in the height of the chambers above the soil surface affected the capture of NH_(3),but the results still maintained high linearity with the NH_(3)losses quantified by the reference method(R^(2)>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.