石羊河中下游不同退耕年限次生草地土壤理化及生物学特性研究

测定并分析了石羊河中下游不同退耕年限次生草地土壤理化(含水量、有机碳、硝态氮、铵态氮、全磷、有效磷、全钾、速效钾、缓效钾)及生物学(微生物量碳、氮、磷及真菌、细菌、放线菌数量)特性。结果表明,随退耕年限的延长,各土层(0~10 cm,10~20 cm,20~30 cm,30~40 cm)土壤铵态氮及全磷呈下降趋势;土壤含水量、有机碳、硝态氮、有效磷、有效钾及缓效钾呈上升趋势;全钾与速效钾随退耕年限的变化不显著;除30~40 cm土层外,各土层土壤微生物量碳在退耕较短年限内(从1 a到5 a)呈下降的趋势,在退耕较长年限内(从8 a到31 a)呈上升趋势;土壤微生物量氮呈先上升(从1 a到4 a)再下降(从4 a到8 a)最后趋于稳定(从8 a到31 a)的趋势;除0~10 cm土层外,各土层土壤微生物量磷呈先下降(从1 a到2 a)再上升(从2 a到8 a)最后下降(从8 a到31 a)的趋势;不同年限退耕地土壤三大类微生物数量均表现为细菌>放线菌>真菌。

Effects of different years of cultivation abandonment on soil physical,chemical and microbial characteristics in the midstream and downstream of Shiyang River area

Soils have been investigated in midstream and downstream areas of the Shiyang River that had been previously cultivated but abandoned for different numbers of years.The research investigated physical and chemical properties (water content,organic carbon,nitrate nitrogen,ammonium nitrogen,total phosphorus, available phosphorus,total potassium,quick-available potassium,slow-available potassium )and microbes (microbial biomass C,N,P and the number of microorganisms).Results showed that soil ammonium nitrogen and total phosphorus content decreased the longer the land had been abandoned,while water content,organic carbon,nitrate nitrogen,available phosphorus,available potassium and slow-available potassium increased. There were however no significant differences in total potassium and quick-available potassium over the years. Microbial biomass C decreased in 30-40 cm soil layers in land abandoned for shorter periods (1 -5 yrs),but increased for longer periods (8-31 yrs).The variability of microbial biomass N increased initially (1-4 yrs), then decreased (4-8 yrs)and finally stabilized (8-31 yrs).Except for 0-10 cm soil layers,the variability of soil microbial biomass P decreased at first (1-2 yrs),then increased (2-8 yrs)and finally decreased (8-31 yrs).Bacteria were the most frequent,followed by actinomycetes,and fungi were the least numerically signifi-cant during all stages.