Applying Liquid Manure through Subsurfce Drip Irrigation to Reduce N2O Emissions in Dairy Forage Production.

Flood-irrigated (FI) forage production systems fertilized with liquid dairy manure emit large amounts of nitrous oxide (N₂O), while subsurface drip irrigation (SDI) could lower these emissions. However, liquid manure has previously not been applied via SDI. The SDI system capable of delivering liquid manure to crops was developed by Netafim. The study was conducted in collaboration with Sustainable Conservation in the California Central Valley. The soil type was Pachappa fine sandy loam. We measured N₂O emissions, crop yields and N uptake in SDI and FI silage wheat and corn systems fertilized with liquid dairy manure applied with the irrigation water. During the irrigation season, N₂O emissions were lower in the SDI system by an order of magnitude, but corn yields were lower in SDI than FI. To our knowledge, this is the first SDI system in commercial agriculture to deliver liquid manure. This approach reduces direct N₂O emissions in dairy systems during the irrigation season, but risk management of liquid manure storage during the rainy season needs to be improved.