Nitrogen mineralization of soil and soil particle f ractio ns with long term annual combined application of manure and chemical
fertilizer in a wheat/rice rotation system was monitored during a 112 day laboratory incu bation NH 4 + and NO 3 - in leachates were measured after soil samples we re incub ated for 1, 2, 4, 6, 8, 10, 12, 14 and 16 weeks at 25℃ Nitrogen minera lizatio n potential (N 0) and mineralized rate constant (k) were fitted using a first order equation N 0 value of soil and
soil particle fractions was s ignificantly increased after 14 year incorporation of pig manure and stra w, how ever, there was no significant effect on k value The N mineralizability in different soil particle fractions increased in the order: 0～2 μm>2～10 μm> 50～100 μm>10～50 μm A pot experiment was also conducted to determine the b asic nitrogen supply of the soil and soil particle fractions during 16 week gro wth of ryegrass The results showed that the amount of N mineralized during the
incubation was greater than those taken up by ryegrass, suggesting that it is w orthwhile making some modifications when we make comparison of the results obtai ned from incubation and pot experiments