A comparison of methods of estimating ammonia volatilization in the field
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Accurate estimation of the potential for NH3 volatilization from urea-based fertilizers is an important step in attaining optimum N-use efficiency from these fertilizers. Published estimates of NH3 volatilization losses from urea vary widely. Much of this variability may be due to the method of estimation and the degree of influence of the method on NH3 loss. This study compared two field methods of estimating NH3 volatilization in the field; a microplot-forced draft method, and a micrometeorogical method. Loss of NH3 was estimated in three experiments following urea solution application to bare soil, and in two experiments following urea-ammonium nitrate solution application to wheat stubble residue. Both methods were found to be sensitive to soil and climatic variables influencing NH3 volatilization. Cumulative N loss from the bare soil experiments ranged from 7 to 8 kg N ha-1 for the microplot method and from 5 to 20 kg N ha-1 for the micrometeorological method. Cumulative loss from wheat stubble residue ranged from 2 to 2.2 kg N ha-1 for the microplot method and from 15 to 33 kg N ha-1 for the micrometerological method. Loss of NH3 was especially influenced by soil or residue water content and the influence of water content on the rate of urea hydrolysis. Maximum rates of loss were generally observed near midday, when water content at the soil surface was just beginning to decline and the surface temperature was rapidly rising. The microplot method was found to have a greater potential for affecting the environment and thus influencing NH3 loss measurements than the micrometeorological method. Windspeed and mixing at the soil surface was influenced by the presence of the microplot cylinder and lid, especially in the wheat residue experiments. It is likely that the micrometeorological method, with its minimal influence on the field environment, more accurately reflects actual levels of ammonia loss. The primary advantage of the microplotforced draft method is its ability to easily compare relative NH3 losses from different treatments. 1988 Martinus Nijhoff Publishers.
author list (cited authors)
Ferguson, R. B., McInnes, K. J., Kissel, D. E., & Kanemasu, E. T.
complete list of authors
Ferguson, RB||McInnes, KJ||Kissel, DE||Kanemasu, ET