【摘要】 对海拔2600～3000m农牧交替带不同退化程度的草原、草原开垦后土壤磷素变化进行了系统研究。退化草原包括:轻度(LDP),中度(MDP)和重度(HDP)3种类型,耕种土壤开垦年限从1至50年不等,土壤样品取自甘肃省7县市18个地点,主要土壤类型为黑钙土。通过进行磷的分级发现,草原开垦后土壤有机磷组分明显下降。种植8、16、41年后土壤有机磷分别下降8%、20%和36%;区域性土壤分析结果亦表明,耕种30年以上的土壤有机磷平均下降35%。有机质矿化,土壤侵蚀后由于耕作措施造成的底土与表土混合,以及无机磷肥的施用使得耕种土壤中Ca P明显增加。NaOH浸提的潜在活性有机磷,随着草原退化程度的增加和耕作年限的延长有递减的趋势。活性有机磷与总有机磷显著相关(R2=0 63),而活性有机磷的多寡与耕种和施肥明显相关。更多还原

【Abstract】 This study, conducted on transitional areas of grasslands and crop fields in Gansu, China, deals with the impacts of land use on soil P dynamics. Land uses include three magnitudes of pasture degradation, lightly (LDP), moderately (MDP), and heavily degraded pasture (HDP), and cultivated fields varying 1 to 50 years of cultivation. Soil samples were collected from 18 sites at seven locations lying between 2,600 to 3,000 m above sea level. The dominant soil samples were Chernozem. The objective of this study was to understand soil P dynamics under different land uses. 　　Phosphorus fractionation showed that proportion of soil organic phosphorus decreased sharply when pasture was put into crop production. Cultivation of grassland resulted in a decrease of organic phosphorus by 8%, 20%, and 36% after 8, 16, and 41 years cultivation, respectively. Regionally, 35% of organic phosphorus was lost within 30 to 50 years cultivation. Cultivation and fertilization significantly raised labile P and calcium associated inorganic phosphorus (CaPi) levels. Mineralization of organic P, incorporation of subsoil by tillage following erosion, and fertilization were major sources of increased CaPi in topsoil of cultivated fields. In general, Fe and Alassociated Pi was higher after pasture was cultivated. Soil organic P, especially the potentially labile fraction extracted by NaOH, declined with pasture degradation and cultivation. Labile organic P, extracted by NaHCO3, is highly correlated with total organic P (R2=063).更多还原