长期不同施肥对红壤Cu和Cd含量及活化率的影响

Effect of long-term fertilization on content and activity index of Cu and Cd in red soil

对始于1990年的红壤旱地施肥长期定位试验的6个处理包括对照(不施肥,CK)、施氮(N)、氮磷(NP)、氮磷钾(NPK)、氮磷钾+有机肥(NPKM)和有机肥(M)的历年耕层土壤重金属Cu和Cd全量和有效态含量进行分析,以阐明长期不同施肥条件下红壤Cu、Cd含量及活化率变化特征。结果表明,16a连续不施肥或施用化肥(N/NP/NPK)条件下土壤Cu、Cd全量和有效态含量基本保持不变;Cu活化率随施肥时间变化不显著,但Cd的活化率在施肥后期(1996-2006)呈明显上升趋势,在施氮处理上高达95.7%;不施肥和配施化肥下Cd的活化率与土壤pH值呈极显著负相关。化肥配施有机肥(NPKM)和单施有机肥处理(M)的土壤中Cu、Cd全量和有效态含量及其活化率随时间均呈显著上升趋势;土壤Cd含量从1990年的0.12mg·kg-1上升为2006年的1.31～1.48mg·kg-1,平均年上升0.08～0.09mg·kg-1;土壤有效态Cd含量2006年达到0.53～0.58mg·kg-1,为1990年的18.0～19.9倍;Cd活化率与土壤有机质含量呈显著正相关。长期施用有机肥红壤Cu、Cd含量超标严重,土壤Cu和Cd全量之间达极显著相关(r=0.887**,n=30),其来源具有一致性,有机肥为环境带来的风险应予以重视。

The changes of contents and availabilities of Cu and Cd were studied under a long-term experiment with six fertilization treatments （CK, N, NP, NPK, NPKM and M） in red soil and the variation characteristics of contents and activity index of Cu and Cd were discussed. The results indicated that the contents and availabilities of Cu and Cd were not changed under no fertilizer（CK） and chemical fertilizer （ N, NP and NPK ） treatments from 1990 to 2006. The activity index of Cu didn＇t change significantly with time. The activity index of Cd increased significantly in the last 10 years under no fertilizer and chemical fertilizer treatments. Moreover, the activity index of Cd was 95.7% in the N treatment in 2006. Activity index of Cd was negatively correlated to pH of soil （P〈0.005） under no fertilizer and chemical fertilizer treatments. However, the contents and activities index of Cu and Cd in the manure treat- ments （NPKM and M） were increased significantly during 16 years. The contents of Cd changed from 0.10-0.12 mg.kgl in 1990 to 1.31-1.48 mg.kg-1 in 2006 and increased annually by 0.08-0.09 mg-kgq in the manure treatments. During 16 years of fertilization, the contents of available Cd were 0.53-0.58 mg.kg-1 in the manure treatments, being 18.0-19.9 times of the background value. Ac- tivity index of Cd was positively correlated to soil organic matter （P〈0.05） in manure treatments. The study indicated that the corre- lation coefficient of Cu and Cd content was 0.887（superscript＊＊） and significant at 1% level. Tong-term manure fertilization lead to high level of Cu and Cd in red soil, which exceeded the national standard of Cu and Cdin soil. The source of the Cu and Cd was from applied manure. Therefroe, harm of manure to the environment should be considered seriously.