The microplot method was used to compare soils under'different long-term (19 years) fertilization treatments i. e. NF (no fertilizer) ;NPK (inorganic NPK fertilizer) and MNPK (manure plus inorganic NPK fertilizer) in retention ,crop uptake,and leaching of applied N. Results show that application of N significantly increased mineral N in the soil of Treatment NF,but had no such effect in the soils of Treatments NPK and MNPK. However, it increased soil microbi-al biomass N ( SMBN) by 4. 3 and 0. 8 times in the soils of Treatments NPK and MNPK at the elongating stage of wheat, but did not in the soil of Treatment NF. From the elongating stage to the flowering stage,soil microbial biomass N in the soils of Treatments NPK and MNPK dropped by 51% and 56% . In Treatments NPK and MNPK,the crop of wheat used up 36% and 45% ,respectively,of applied N, while in Treatment NF, wheat rarely absorbed any of the applied N,of which 34% was used up by the subsequent maize. By the time when wheat was harvested more than 50% of the applied N had been leached into the soil layers below 30 cm in Treatment NF, and a significant portion into the 30 - 50 cm soil layer in Treatment NPK,but little down the soil profile in Treatment MNPK. The findings demonstrate that long-term combined application of manure and NPK is an effective way of fertilization management that could strengthen N buffer capacity of the soil, harmonize the relationship between soil N retention and crop N uptake demand, improve N use efficiency and minimize the risk of environment pollution.%以长期不同施肥处理土壤为对象,研究了不同施肥土壤中施用氮肥后土壤氮素含量、微生物固持及释放和作物吸收及利用特性.结果表明,施用氮肥显著增加长期不施肥土壤(NF)矿质氮含量,对长期施用化肥土壤(NPK)和有机无机配施土壤(MNPK)矿质态氮含量无显著影响；施用氮肥对NF中土壤微生物生物量氮(SMBN)含量无显著影响,使拔节期NPK和MNPK中SMBN含量分别增加了4.3倍和0.8倍.从小麦拔节期到开花期,NPK和MNPK中土壤微生物生物量氮含量分别显著降低51％和56％.小麦收获时NPK和MNPK土壤氮肥的利用率分别为36％和45％；而NF土壤所施人的氮素几乎未被小麦吸收利用,但在玉米季有34％被吸收.小麦收获时,NF土壤施入的氮肥有50％以上淋溶至土壤30 cm以下土层,施氮也显著提高了NPK土壤30 ～ 50 cm土层硝态氮含量,但施用氮肥对MNPK土壤0～100 cm剖面硝态氮含量无显著影响.说明长期有机无机配施增强了土壤氮素的缓冲能力,协调了土壤氮素固持与作物吸氮间的关系,为提高氮素利用率,减少氮素对环境影响的有效手段.
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