长期不同施肥对旱地小麦土壤氮素供应及吸收的影响

【目的】评价长期不同施肥处理土壤中氮素固持、供应和损失情况。【方法】以连续19年不施肥（NF）、施用化学氮、磷、钾肥（NPK）和有机肥与化学氮、磷、钾配施（MNPK）田间定位试验处理为对象，设置施氮和未施氮微区，研究了小麦生长期间土壤矿质态氮、土壤微生物量氮（SMBN）及小麦氮素吸收的动态变化。【结果】施用氮肥显著提高长期不施肥土壤（NF）矿质态氮含量（P＜0.05），小麦拔节期、开花期和收获期增幅分别为239%、70%和62%，在小麦收获时施用的氮肥约50%淋溶到30 cm土层以下。氮肥施用使NPK处理土壤小麦拔节期和开花期矿质态氮含量分别显著增加46%和90%（P＜0.05），但对MNPK处理土壤矿质态氮含量无显著影响。施用氮肥对NF处理SMBN无影响，使拔节期NPK和MNPK处理土壤SMBN含量分别显著增加1.8和3.4倍（P＜0.05）。从拔节期到开花期，施用氮肥处理NPK和MNPK土壤SMBN显著降低49%和63%（P＜0.05）。MNPK处理土壤小麦氮肥的利用率（69%）显著高于NF、NPK处理土壤（分别为5%和40%）。【结论】有机无机长期配施增强了土壤对氮肥的缓冲能力，协调了土壤中氮素固持、释放与作物吸收之间的关系，提高氮肥利用率。

Effects of Long-Term Different Fertilization Managements on Changes of N in Soil and Its Uptake by Wheat on Dryland

【Objective】Organic fertilizer application can improve the biological function and affect the fates of inorganic N in soil.【Method】 The microplot method was used to compare the effects of 19-year different fertilization managements(NF,no application of fertilizer;NPK,inorganic NPK fertilizer;MNPK,manure plus inorganic NPK fertilizer) on changes of mineral N and soil microbial biomass N(SMBN) and its uptake by wheat on dryland.【Result】 Addition of urea-N significantly(P<0.05) increased mineral N content in the NF soil by 239%,70%,and 62% at elongating,flowering,and harvesting stage,respectively;and about half of added N was leached below 30 cm soil layers after harvesting wheat.Addition of urea-N also enhanced the mineral N in the NPK soil at elongating and flowering stage,but had no effect on mineral N in the MNPK soil.Addition N had no effect on SMBN in the NF soil,but significantly(P<0.05) increased SMBN by 1.8 times in the NPK soil and 3.4 times in the MNPK soil at elongating stage.Soil microbial biomass N in the NPK and MNPK soils at vigorous stages of wheat(from elongating stage to flowering stage) decreased by 49% and 63%,respectively.The use efficiency rate of added N in the MNPK soil was 69%,which was significantly(P<0.05) higher than in the NPK(40%) and NF(5%) soils.【Conclusion】 It was concluded that long-term application of manure plus chemical fertilizers increased the buffer capacity of soil to N fertilizer,and synchronized N retention in soil and take up by crops.