Evaluation of Aerated Cow Slurry as a Nutrient Source to Orchardgrass

Abstract

We attempted to elucidate the change in the form and content of nitrogen (N) in cow slurry under different aeration periods and its effect on dry matter production of orchardgrass (Dactylis glomerata) in a pot experiment. Aeration treatments of the slurry were conducted at three levels : a) no aeration for 4 weeks, b) short-term aeration (aeration for i week after no aeration for the first 3 weeks) and c) long-term aeration (aeration for 4 weeks). We applied these slurries as a nutrient source to grass grown in pots. The application rate was 80 g pot^<-1> (4 kg m^<-2>). Aeration treatment resulted in slurries with a high pH. The content of total N and NH_4-N in the slurry decreased with the length of aeration period. NO_3-N was slightly detected in the long-term aerated slurry. It appeared that the decrease in total N of the aerated slurry was due to the gaseous loss of NH_4-N in the slurry. These results showed that the application rate of N derived from the slurry to the pots was different among the treatments because of the difference in the content of NH_4-N in the slurry. We then calculated the efficiency of dry matter production per unit N in the slurry applied. The efficiency of the non-aerated slurry was the highest among the treatments, and the efficiency of the aerated slurry decreased with the aeration period. The difference in the amount of N accumulated in the grass among the treatments showed a similar tendency to the results described above. From the results, we concluded that the nutritive value of the aerated slurry was less than that of the non-aerated slurry because aeration caused the gaseous loss of NH_4-N from the slurry.