Substitution Effect of Pig Manure for Nitrogen Fertilizer on Nitrogen-Use Efficiency

Pot experiments using a N-15 isotope technique were conducted to quantify the substitution effect of pig manure (PM) for chemical fertilizer (CF) nitrogen (N) on N-use efficiency. Treatments include a control, 100% CF N, 100% PM N, and portions of PM N (25-75%) substitution for CF N. With an increase portion of PM, N in wheat and maize plants derived from the CF (%Ndff) significantly (P < 0.05) decreased from 76.6 to 35.1% and 79.8 to 40.9%, whereas N derived from PM (%Ndfm) increased from 13.1 to 57.0% and 5.4 to 47.1%. Plant availability of PM N was equivalent to 33% and 28% of CF N for wheat and maize, and 10-17% and 12-20% of PM N were recovered by wheat and maize plants, respectively. The PM N could substitute for 33% CF N. Combinations of PM with CF did not improve N efficiency compared with equivalent rate of CF alone.