Effects of Biogas Slurry on Yield of Pennisetum and Inorganic Nitrogen and Enzymatic Activities in Soil

To explore the potential of utilizing slurry from biogas-producing fermentation beds for fertilization, 'Fujian 6' grass (Pennisetum americanum P. purpureum CV. Minmu 6) was used in a turf experiment. Varied quantities of slurry application (i.e., N₁ as control, and N₂ through N₅ as treatments) on the grass were executed. The plant height and yield of the grass, as well as the ammonium nitrogen, nitrate nitrogen and the activities of urease, protease, glutaminase and asparaginase in the soil, were determined. The results showed that the applications improved the plant height over N₁, but no significant differences among the treatments (P>0.05). The grass yield was also significantly increased (P < 0.05) reaching 174 754 kg·hm^-2, a level 119.0% higher than that of N₁. In the 0-20 cm or 20-40 cm soil layers, there was no significant change on the ammonium nitrogen content (P>0.05), but the nitrate nitrogen increased with increasing slurry application. Compared to N₁, N4 and N5 significantly increased the nitrate nitrogen content in the 0-20 cm soil (P < 0.05). The effects of biogas slurry on the activities of urease, protease, glutaminase and Asparaginase were not significant during T₁(May, 7, 2015) period (P>0.05). A correlation analysis on the data re-confirmed a significant correlation between the biogas slurry applications and the plant height of the grass (P < 0.05), and an extremely significant correlation between the applications and the nitrate nitrogen in 0-20 cm layer of soil and the yield of the grass (P < 0.01) at all time periods, but none on the enzymatic activities during T₁ period.