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通过对美国长期和短期实行土壤保护计划 (CRP)的土地 (5～ 10cm土层范围内 )进行土壤质量检测 ,结果发现 :土壤全氮、全碳含量均低于天然草原的土壤含量 ,长期实行CRP的土壤微生物生物量中的碳氮含量分别比短期实行CRP的土壤增加了 141%和 93 %。由于天然草原中硝酸盐含量较少 ,土壤无机氮含量非常低。实行 10aCRP后 ,土壤无机氮含量明显降低。研究表明 ,实行CRP能促进土壤质量的恢复 ,但 10a时间并不足以使土壤全碳全氮含量恢复到开垦前的水平。
Soil quality testing of long-term and short-term soil conservation programs (CRP) in the United States (within the range of 5 ~ 10cm soil layer) showed that soil total nitrogen and total carbon content were lower than that of natural grassland, The carbon and nitrogen contents of soil microbial biomass in CRP increased by 141% and 93% respectively than the soil with short-term CRP. Due to the low nitrate content in natural grasslands, the soil inorganic nitrogen content is very low. After the implementation of 10aCRP, the soil inorganic nitrogen content decreased significantly. Studies have shown that the implementation of CRP can promote the restoration of soil quality, but the 10a time is not enough to make the soil total carbon content return to pre-reclamation levels.