农作模式对冀西北坝上寒旱区土壤不同粒径团聚体氮形态及氮库管理指数的影响

Effects of Farming Patterns on Nitrogen Forms of Soil Aggregates with Different Particle Sizes and Nitrogen Pool Management Index in Cold and Arid areas of Bashang,Northwest Hebei Province

为了研究不同农作模式下土壤团聚体结构对氮素的稳定机制影响,以冀西北坝上不同农作模式的土壤为研究对象,采用野外调查取样和室内试验分析相结合测定土壤的总氮(TN)、溶解性总氮(DTN)、铵态氮(NH_(4)^(+)-N)和硝态氮(NO_(3)^(-)-N)含量,计算可溶性有机氮(DON)含量及氮库管理指数(NPMI),分析不同粒径团聚体中土壤氮素分布及NPMI变化规律。结果表明:土壤氮素主要贮存在中等粒径(1.00耀2.00 mm)的团聚体中。施用有机肥促进氮素向超大粒径(跃5.00 mm)团聚体分布,进而提高大粒径团聚体NH_(4)^(+)-N的含量和NPMI。施用无机肥提高中等粒径团聚体TN的含量和分配比例,增加微粒径(约0.25 mm)团聚体NO_(3)^(-)-N的NPMI和大粒径(2.00耀5.00 mm)团聚体NO_(3)^(-)-N的活度指数。充分灌溉能够促进小粒径(0.25耀0.50 mm)团聚体TN和NH_(4)^(+)-N含量的增加及分配,提高各粒径团聚体的NPMI。粗放管理促进小粒径和微粒径团聚体NH_(4)^(+)-N的含量增加及分配,降低土壤的NPMI。对农作模式最敏感的是大粒径团聚体,施用有机肥通过增加大粒径团聚体的氮素含量和活度,提高土壤肥力供给和土壤保护能力;施用无机肥通过增加中等粒径团聚体氮素的含量及活度,促进氮素利用率的提高;粗放管理和还林还草通过增加小粒径团聚体的氮素含量,增强固氮能力。冀北坝上寒旱区可通过增施有机肥以增加团聚体数量,并进行适度灌溉,达到保肥供肥的目的。

In order to study the effect of soil aggregate structure on nitrogen stability mechanism under different farming patterns,soil samples from different farming patterns in Bashang,northwest Hebei were taken as the research objects.A combination of field investigation sampling and indoor experimental analysis were used to determine the total nitrogen(TN),dissolved total nitrogen(DTN),ammonium nitrogen(NH_(4)^(+)-N),and nitrate nitrogen(NO_(3)^(-)-N)content of soil.The soluble organic nitrogen(DON)content and nitrogen pool management index(NPMI)were calculated,and the distribution of soil nitrogen in aggregates with different parti cle sizes and NPMI changes were analyzed.The results showed that soil nitrogen was mainly stored in medium-sized aggregates(1.00-2.00 mm).The application of organic fertilizer promoted the distribution of nitrogen towards oversized aggregates(>5.00 mm),thereby in creasing the content of NH4+-N and NPMI in large-sized aggregates.Applying inorganic fertilizers increased the content and distribution ratio of TN in medium-sized aggregates,increased the NPMI of NO_(3)^(-)-N in aggregates(<0.25 mm),and increased the activity index ofNO_(3)^(-)-N in large-sized(2.00-5.00 mm)aggregates.Adequate irrigation can promote the increase and distribution of TN and NH_(4)^(+)-N content in small-sized aggregates(0.25-0.50 mm),and improve the NPMI of aggregates of various particle sizes.Extensive management promoted the increase and distribution of NH_(4)^(+)-N content in small and micro-sized aggregates,and reduced NPMI.The most sensitive to agricultural practices was large aggregates.Applying organic fertilizer increased the nitrogen content and activity of large aggregates,improving soil fertility supply and soil protection capacity.The application of inorganic fertilizers promoted the improvement of nitrogen utilization efficiency by increasing the content and activity of nitrogen in medium-sized aggregates.Extensive management and returning forests and grasslands enhance nitrogen fixation capacity by increasing the nitrogen content of small-sized aggregates.In the cold and arid areas of northern Hebei,increasing the application of organic fertilizer can increase the number of aggregates,and moderate irrigation can be carried out to achieve the goal of maintaining fertilizer supply.