四川盆地酸性紫色水稻土硝化作用的类型及氧化锰的影响

Nitrification and Influence by Birnessite in Acidic Purple Paddy Soils of Sichuan Basin

酸性土壤中的硝化活性存在很大空间变异,并且其硝化类型也因土壤环境条件而异。锰氧化物作为土壤矿物的一种,可能通过其生物毒性及作用土壤氮矿化等影响硝化过程。本研究在四川盆地分别采集pH为4.6,4.9两种酸性紫色水稻土,通过添加乙炔或锰氧化物,探究四川盆地酸性水稻土硝化作用的主要类型以及锰氧化物对硝化作用的影响。结果表明:酸性水稻土中存在显著的硝化活性,加入乙炔后,pH4.9空白对照和pH4.9加硫酸铵处理的两种酸性紫色水稻土的净硝化速率均显著下降,分别从0.46 mg kg^(-1)d^(-1),0.58 mg kg^(-1)d^(-1)降至-0.08 mg kg^(-1)d^(-1),-0.15 mg kg^(-1)d^(-1),证明酸性水稻土的硝化作用主要以自养硝化作用为主;pH4.6,4.9土样加入锰氧化物后,净硝化速率分别从2.07 mg kg^(-1)d^(-1),3.17 mg kg^(-1)d^(-1)下降到0.60 mg kg^(-1)d^(-1),2.71 mg kg^(-1)d^(-1),表明锰氧化物对酸性水稻土硝化作用的净效应是抑制作用,可能的原因是酸性条件下锰氧化物对硝化微生物的毒性所致。

Great variations of nitrification were observed in acidic soils, which depended on biotic and abiotic factors. Nitrification dynamics may be changed by manganese oxide, probably due to nitrogen mineralization and toxicity to nitrifying microorganisms. Samples of two acid paddy soils with pH 4.6 and 4.9 were collected from Sichuan basin to study the occurrence and type for nitrification, and the effects of birnessite on nitrification in acid paddy soils were also studied. Results showed that there was a remarkable nitrification activity in acid paddy soils. After adding acetylene, the net nitrification rates in the acid purple paddy soil with pH 4.9 without and with ammonim sulfate application （Control and Ammonium treatments） were decreased significantly from 0.46, 0.58 mg kg^-1 d-1 to -0.08, -0.15 mg kg^-1 d-l, respectively, which concluded autotrophic nitrification played an important role in acid paddy soils. After addition of birnessite, the net nitrification rates in the two acid paddy soils with pH 4.6 and 4.9 were decreased from 2.07 and 3.17 mg kg^-1 d-l to 0.60 and 2.71 mg kg^-1 d-1, respectively, which indicated that nitrification was inhibited by birnassite in these acid soils and it may be due to the toxicity of manganese oxide on ammonia-oxidizing microorganisms.