Methane and N2O emissions, nitrate concentrations of drainage water, and zinc and copper uptake by rice fertilized with anaerobically digested cattle or pig slurry

We have examined the effects of different types of slurry on CH₄ and N₂O emissions, Zn and Cu contents of rice, and nitrate content of the drainage water. The experiment included four treatments: (1) anaerobically digested cattle slurry (ADCS), (2) ADCS filtered to remove the coarse organic matter fraction, (3) anaerobically digested pig slurry (ADPS), and (4) chemical fertilizer (CF). The application rate was 30?g?NH₄?CN?m^?2. Different amounts of C were incorporated with fertilization: 725?g?C?m^?2 in ADCS, 352?g?m^?2 in filtered ADCS, and 75?g?m^?2 in ADPS. The average CH₄ emissions during a growing period were 304, 359, 452, and 579?mg?m^?2?day^?1 in the CF, ADPS, filtered ADCS, and ADCS treatments, respectively. The CH₄ emission was significantly higher in ADCS than in CF and ADPS. Negligible N₂O emissions were observed during the growing period. Comparable concentrations of Zn and Cu were observed in the rice grain among the treatments. In contrast, their concentrations in the stems and leaves were significantly higher in ADPS than in CF treated rice, although the values were lower than the upper limit of feed additives. Nitrate concentrations in the drainage water were consistently low (0.5?mg?N?L^?1). The present study suggested that ADPS, containing a lower amount of C than ADCS, might be an organic fertilizer in paddy field with comparable environmental impacts to chemical fertilizers (CF), but long-term field studies are needed to better understand the effects of these organic fertilizers.