Abstract
Anaerobically digested cattle slurry made mainly from the liquid portion of cattle's dung urine was examined for the effect on the growth and yield of paddy rice (Oryza sativa) Koshihikari. The rice plant was cultivated using the digested slurry as basal application,whose ammonium nitrogen accounted for 67% of total nitrogen, and ordinary chemical fertilizer as supplemental application. In small scale field experiments, carried out in the area of 10m^2, the application of the slurry which was equivalent to chemical fertilizer on amount of ammonium nitrogen basis followed by immediate plowing resulted in growth and yield similar to those under standard cultivation. This result indicated that the organic nitrogen which accounted for the rest of total nitrogen had slight effect on the growth of the plant. Two types of application methods, application before flooding and the inflow application, were carried out. In the former method, the application of two days before flooding led to growth and yield similar to those in small scale field experiments as described above. In contrast, the application of nine days before flooding resulted in 40% nitrogen uptake by the plant originated from the liquid. For the latter method, the plowing of three days after inflow application produced corresponding values of 48%. A possible explanation of the extreme decrease in efficiency of nitrogen is that aerobic condition may have caused prompt nitrification followed by denitrification. Ammonium nitrogen was potentially dissipated by volatilization because the pH of the slurry was 8.4. Whether or not the pH was adjusted, the growth and yield, however, were approximately the same in both the plots, indicating that the loss of ammonium nitrogen by volatilization would be negligible.
