Apparent Nitrogen Recovery in Milk and Early Dry Season Nitrous Oxide Emission Factors for Urine Deposited by Dual-Purpose Cattle on Different Soil Types

Pasture conditions influence the nutrients use efficiency and nitrogen (N) losses from deposited excreta. Part of N is lost as nitrous oxide (N 2 O), a potent greenhouse gas. The objective this study was to characterize apparent recovery in milk dual-purpose cattle quantify O emissions urine they deposit following grazing on Megathyrsus maximus cv. Mombasa. content grass produced by urea (MUN) were quantified two contrasting regions Colombia (Casanare Atlántico). Dry matter intake (DMI) estimated using Cornell Net Carbohydrate Protein System. We used closed static chamber technique measure soils areas with without patches (21 days Atlántico 35 Days Casanare). Estimated DMI values 11.5 11.6 kg DM day −1 , production 6.5 5.9 L 24 23%, MUN 4.4 17.2 mg dl Casanare Atlántico, respectively. applied soil form corresponded at rates 20 64 g m −2 net cumulative 350 O-N Despite low digestibility offered diet, above reported dairy tropical conditions. High urine-N inputs site did not result high suggesting that default Tier 1 emission factor (EF) which based would have overestimated urine-based Atlántico. Comparing previous studies conducted Colombia, we observed inter-regional differences emissions. This observation suggests increase certainty estimating emissions, needs move toward more region-specific EF reduce its dependence IPCC EF. In addition, adoption sector will facilitate accounting for effect animal diets inventories.