This is a paper on NH3 modelling that was originally submitted to Nutrient Cycling and Agroecosystems using only data from a Ballance funded Master's project from 2013. Following the initial review we were asked to include an additional dataset for model validation and resubmit the paper. For this additional dataset we used the urine only treatment from the experiment "Effects of N transformation inhibitors (NTIs) and gibberellic acid on N2O emissions" that was conducted as part of Objective 6.6