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土壤氮库由多种形态氮组成,不同形态N素的季节变化是影响土壤氮素植物利用效率的重要因素.在国家紫色土肥力定位监测点,研究了全氮、碱解氮和微生物生物量氮在不同大小团聚体中的季节动态变化.结果表明,原土全氮(TN)季节性波动不显著,变异系数为2.31%;而碱解氮(MN)、微生物量氮(MBN)在原土与不同粒径团聚体中具有相似的季节变化模式,原土中碱解氮在秋季最高为131.8 mg/kg,而原土微生物量氮在冬季最低为21.9mg/kg.不同粒径团聚体中全氮、碱解氮、微生物量氮均具有明显的季节变化.秋季(10月)和夏季(7月)团聚体土壤中微生物量氮较低,而冬季(1月)和春季(4月)微生物量氮较高.2007年秋季土壤大团聚体(2.0～0.25mm)中MBN最高为24.2mg/kg,其余粒径之间差异不显著,为12.2～17.0mg/kg.春季(4月)和秋季(10月)团聚体土壤中全氮(TN)和碱解氮(MN)相对较高,冬季(1月)和夏季(7月)相对较低.2008年冬季土壤小团聚体(0.25～0.053mm)中TN最低为1.10g/kg,其余粒径之间差异不显著,为1.40～1.45g/kg,而粉砂和粘粒(<0.053 mm)中MN最高为136.7 mg/kg,其余粒径之间差异不显著,为105.5～112.5mg/kg.微生物量氮的季节变异系数是全氮和碱解氮的2倍左右.研究认为微生物生物量氮的季节性变化大于全氮和碱解氮,不同粒级团聚体中微生物量氮、全氮和有效氮量具有相似的季节变化模式;土壤全氮的季节变化主要受温度和水分的影响,而土壤碱解氮的变化则和作物生长,秸秆分解有关,气候变化和作物生长周期则是土壤微生物量氮季节变化的主要因子.
The soil nitrogen pool is composed of a variety of forms of nitrogen, seasonal changes of different forms of nitrogen is an important factor affecting the soil nitrogen plant utilization efficiency in the national purple soil fertility monitoring points, the study of total nitrogen, available nitrogen and microbial biomass The seasonal dynamics of nitrogen in aggregates of different sizes showed that the seasonal variation of total nitrogen (TN) in native soil was insignificant with a coefficient of variation of 2.31%, whereas the contents of alkaline nitrogen (MN) and microbial biomass nitrogen (MBN) Similar to the pattern of seasonal variation in aggregates with different particle sizes, the maximum nitrogen content in native soil was 131.8 mg / kg in autumn, while the lowest in native soil was 21.9 mg / kg in different size aggregates Total nitrogen, available nitrogen and microbial biomass nitrogen all had significant seasonal changes.The microbial biomass nitrogen was lower in the soil aggregates in autumn (October) and summer (July) than in winter (January) and spring (April) In the autumn of 2007, the highest MBN was 24.2 mg / kg in soil macroaggregates (2.0 ~ 0.25 mm), and the difference was not significant (12.2 ~ 17.0 mg / kg) (TN) and alkali-hydrolyzable nitrogen (MN) in the aggregates of autumn (October) and autumn (October) were relatively higher than those in winter (January) and summer (July) (TN) was 1.10g / kg in the small soil aggregates (0.25-0.053mm) in winter of 2008, and the difference was not significant (1.40-1.45g / kg) 0.053 mm), the highest MN was 136.7 mg / kg, and the difference between other particle sizes was not significant (105.5-112.5 mg / kg) .The seasonal variation coefficient of microbial biomass nitrogen was about 2 times of that of total nitrogen and alkali-hydrolyzable nitrogen The seasonal variation of microbial biomass nitrogen was greater than that of total nitrogen and available nitrogen. The patterns of seasonal variation of microbial biomass nitrogen, total nitrogen and available nitrogen in different size fractions were similar. The seasonal variation of soil total nitrogen was mainly affected by temperature and water content While the change of soil available nitrogen was related to crop growth and straw decomposition. Climate change and crop growth cycle were the main factors that affected the seasonal variation of soil microbial biomass nitrogen.