The variation in background ammonia (NH₃) concentrations in agricultural regions is of increasing interest due to the difficulty in determining agriculture-specific NH₃ emissions. Understanding these variations will increase the accuracy of emissions estimates from agricultural lands throughout the United States. In this study, integrated two week samples of atmospheric NH₃ concentrations were obtained from the Ammonia Monitoring Network (AMoN) and measurements of diurnal NH₃ concentrations by a Tunable Diode Laser (TDL) were conducted in June 2014 at the Purdue Agronomy Center for Research and Education (ACRE) to determine the annual and diurnal variability in NH₃ background concentrations. Passive NH₃ concentration measurements and landscape analyses for AMoN sites CO13, IL11, IN99, KS98, MI96, MN18, NY67, OH02, OH27, OK99, SC05, TX43, and WI07, were conducted to determine the influence of the number of farms (sources) near a site on NH₃ concentrations. Drier climates tended to have higher background NH₃ concentrations than wetter climates (Fig. 1): higher background NH₃ concentrations can be explained by the reaction in the soil NH₃ + H₂O ↔ NH₄⁺ + OH^-. In wetter climates, NH₃ will gain a hydrogen proton to become NH₄⁺ and is not detected by NH₃ instruments. Background TDL NH₃ concentrations and the time of day was studied to determine diurnal cycles of NH₃. Maximum and minimum concentrations for each day ranged from 45 to 90 ppb. Diurnal NH₃ concentrations tended to display temperature dependence: higher NH₃ concentrations corresponded with higher temperatures (Fig. 2). Further analysis of diurnal and annual cycles of background NH₃ dependence on temperature and soil moisture will be discussed.