AMMONIA VOLATILIZATION FROM NITRIC-ACID-TREATED CATTLE SLURRY SURFACE-APPLIED TO GRASSLAND

Much research is being done to lower NH3 volatilization from animal ma nure. In this study, reduction in NH3 loss from HNO3 treated cattle sl urry, surface applied to grassland, was measured on different soil typ es throughout the Netherlands from 1989 to 1992. In total, 13 micro-me teorological mass balance and 10 small wind tunnel experiments were ca rried out. Amounts varying between 7-17 and 10-30 m(-3) ha(-1) were ap plied, respectively. Measurements were performed for 4 and 10 days, re spectively. The pH of treated slurry ranged from 3.9 to 6.6. Acidified slurry was always compared with untreated slurry. A mean total of 60% (range: 29-98%) of the NH4-N from untreated slurry was volatilized in the mass balance experiments. A reduction in NH3 volatilization of 85 , 72 and 55% was achieved for acidified slurry with a respective pH of c. 4.5, 5.0 and 6.0. Approximately 55% (range: 7-91%) of the total lo ss from acidified slurry was measured on the day of application. A mea n total of 66% (range: 21-90%) of NH4-N from untreated slurry volatili zed in the tunnel experiments. The reduction in NH3 volatilization was 73% for slurry with pH 4.5. Approximately 27% (range: 6-91%) of the t otal loss from acidified slurry was measured on the first day. The low er reduction and the different pattern in NH, volatilization observed in the wind tunnel experiments might be the consequence of different c limatic conditions in and outside the tunnels or they might be related to the higher rates of slurry application in these experiments. Regre ssion analysis indicated that high temperature, slurry pH, potential w ater evaporation and NH4+ concentration stimulated NH3 loss in the mas s balance experiments (R(2) = 87%). It is suggested that the results o btained with acidified slurry were independent of the grassland soil t ype at the application levels employed.