长期不同施肥下黑土和红壤团聚体氮库分布特征

摘要

为阐明长期不同施肥下土壤氮库的演变特征，揭示氮库稳定性不同的团聚体对不同施肥的响应，为化肥和有机物的合理施用提供科学依据。本研究通过对黑土和红壤22年的田间肥料定位试验，研究了长期不同施肥模式对土壤全氮、微生物氮以及各级团聚体中氮贡献率的影响。结果表明，长期不施肥（CK）和施用化肥（NPK），黑土土壤全氮含量以0.015 g/（kg· a）的速率显著下降（P＜0.05）；而长期化肥配施有机肥（NPKM），黑土全氮含量以0.025 g/（kg· a）的速率显著上升（P＜0.05）。在CK、NPK、NPKM和秸秆还田（NPKS）处理下，红壤全氮含量均没有显著变化。施肥22年后，NPKM处理下黑土和红壤微生物氮含量较NPK处理下分别增加了15％和43％，全氮含量分别增加了43％和45％，差异均达到显著水平（ P＜0.05）。氮素在黑土上主要积累在253μm微团聚体中，达到0.731.21 g/kg，在红壤上主要积累在＜2μm微团聚体中，达到0.460.98 g/kg。与NPK相比，NPKM处理下黑土和红壤2502000μm大团聚体中氮素贡献率均显著提高，分别增加了4.3％和5.1％。与NPK相比， NPKM和NPKS处理下，红壤253μm微团聚体中氮贡献率分别降低了5.9％和9.7％，而黑土除大团聚体外的各级团聚体氮贡献率均没有显著变化。可见，不同土壤类型对施肥响应不同，主要是253μm微团聚体中氮素的响应不同，化肥配施有机肥可提高土壤2502000μm大团聚体中氮的贡献率，进而增加土壤对作物的氮素供给能力，是有助于提高土壤肥力和生产力的农业生产可持续性施肥模式。%In order to study the change dynamics of soil nitrogen and effect of long-term fertilization on N distribution in soil aggregates , the total nitrogen ( TN ) , soil microbial biomass nitrogen ( SMBN ) and nitrogen accumulation in four size aggregates were analyzed in black soils and red soils based on 22 year long-term fertilization experiments .The results show that the TN contents decrease at a rate of 0.015 g/( kg· a) for both the CK and the NPK treatments in black soil , while the contents increase at 0.025 g/( kg· a) for the NPKM treatment ( P<0.05 ) .The TN contents of red soils do not changed significantly for all treatments over the fertilization period.Compared with the NPK treatment , the NPKM treatment increases SMBN by 15% and 43% and TN by 43% and 45% in black soils and red soils ( P <0.05 ) , respectively .The highest nitrogen concentrations are detected in 2-53 μm microaggregates in black soils (0.73-1.21 g/kg) and <2 μm microaggregates in red soils (0.46-0.98 g/kg ) among the four sizes aggregates .Compared with the NPK treatment , the NPKM treatment results in 4.3 and 5.1 percentage increases for the ratio of N contribution in 250-2000μm macroaggregates to total N, in black soils and red soils , respectively .The nitrogen contribution in 2-53 μm aggregates of red soils are significantly decreased by 5.9 and 9.7 percentages under the NPKM and NPKS treatments , respectively , compared with the NPK treatment.However, there is no significant change for the N contribution in black soils except 250-2000 μm macroaggregates .It suggests that it is 2-53 μm aggregates N which lead to different soil N amounts between the two soil types under the long-term fertilization .Combination of chemical fertilizer with manure improves the N distribution in 250 -2000 μm macroaggregates , which has higher ability to apply N to crop than to microaggregates.Therefore, chemical fertilizer in combination with manure is a strongly recommended fertilization to improve soil fertility and develop sustainable agriculture .