Ammonia volatilization following application of pig slurry increases with slurry interception by grass foliage

Abstract

Efficient liquid manure application systems that minimize ammonia volatilization are required for use on perennial forage grasses. Ammonia volatilization was monitored using wind tunnels for 10 d after three pig slurry applications using four boom-mounted applicators: a broadcast splash-plate system, a trailing-shoe system and a drag-hose system with and without previous soil aeration. Average losses of 32, 20 and 15% of the total ammonia-N (TAN) applied to plots were observed for the splash-plate, the trailing-shoe and the drag-hose systems, respectively. The grass canopy intercepted, on average, 14% of pig slurry TAN using the splash-plate system compared with 4% for the trailing-shoe and 5% for the drag-hose systems. Reductions in canopy interception explained 58% of differences in volatilization rates among the application systems. On two of three application dates, NH3 volatilization was lower using the drag-hose than the trailing-shoe system. This was attributed to the sealing of the soil surface by the passage of the trailing-shoe, which decreased slurry infiltration rate. Ammonia volatilization was not reduced by soil aeration prior to slurry application using a drag-hose system likely because aeration did not increase slurry infiltration into the soil. Producers could be advised to reduce volatilization losses by using a simple drag-hose system to avoid application of slurry to leaf canopies.