长期施肥土壤腐殖质变化及其与土壤酸度变化的关系

Variation of soil humus under long-term fertilization andits relation to soil acidity

[目的]以吉林省黑土中具有代表性的草甸黑土为研究对象,分析长期施肥黑土腐殖质组成、胡敏酸类型及其与土壤酸度的关系。[方法]依据Kumada法提取土壤腐殖质,提取液经酸沉淀后,分离出胡敏酸(HA)和富里酸(FA),HA经稀碱溶解后,于波长400和600 nm处测定消光系数(K400和K600),并按高锰酸钾氧化滴定法分别测定HA和FA含量。[结果]长期单施化肥使游离态腐殖质的含量下降,添加有机物料后,游离态腐殖质含量随有机物料添加量的增加而升高。而结合态腐殖质含量在单施化肥以及配施有机物料的3组中均较CK下降。同一施肥处理下,长期配施有机物料,土壤游离态及结合态HA、FA含量均增加,土壤腐殖质总量升高。长期单施化肥使游离态HA类型由Rp型向P型转化;配施有机物料后,游离态HA的类型由P型向Rp型转化,组分发生变化。分析长期不同施肥土壤腐殖质与p H值、交换性H+、交换性Al3+、交换性酸的相关性,结果表明:土壤p H值与结合态HA含量呈显著正相关,土壤交换性H+、交换性酸与结合态HA含量呈极显著负相关。[结论]长期单施化肥土壤腐殖质含量下降,游离态HA类型向较高类型转化,腐殖化程度升高,腐殖质质量下降;配施有机物料后土壤腐殖质含量升高,游离态HA的类型向较低类型转化,腐殖化程度降低,腐殖质质量提高;土壤结合态HA含量的变化影响土壤腐殖质总量,缓解了施用化肥造成的土壤p H值变化,表明结合态胡敏酸对土壤酸度有一定的缓冲作用。

[Objectives]With the meadow black soil of Jilin test soil,the composition of black soil humus,different types of humic acid and its relationship with soil acidity under long-term fertilization were analyzed. [Methods]Extract soil humus was accorded to Kumada method. After adding acid to precipitate,the humic acid（ HA） and fulvic acid（ FA） were isolated. The HA was diluted withdiluent alkali to determine the extinction coefficient（ K400 and K600） at the wavelength of 400 and 600 nm. Then HA and FA were quantified according to the potassium permanganate oxidation titration method. [Results]Long-term single application of chemical fertilizer made the content of free humus decrease,and the content increased along with adding organic material. But in three groups the contents of combined humus by adding single application of chemical fertilizer or chemical fertilizers together with organic material decreased compared with CK. Under the same fertilizer treatments,and long-term adding combination of chemical fertilizer and different organic materials to the soil,the contents of free and combined HA and FA both increased. So did humus. Long-term single application of chemical fertilizer made the free HA transform type Rp into type P. The type of free humus had converted P into Rp after using organic material. Meanwhile the degree of humification declined,and the quality of humus increased. Analyzing the correlation among the p H value,exchangeable H＋,exchangeable Al3 ＋,exchangeable acid and humus under long-term different fertilizations,it showed： the p H value of soil was significantly positively correlated with the content of combined humic. The exchangeable H＋and exchangeable acid in soil had very significantly negative correlation with the content of combined humic. [Conclusions]Long-term single application of chemical fertilizer made the content of humus decrease and the type of free humic acid transform into higher type. Meanwhile,the degree of humification was improved and the quality of humus declined. After adding organic material,the content of humus increased and the type of free humic acid transformed into lower type. Meanwhile,the degree of humification declined and the quality of humus was improved. The change of content of combined humic acid affected the content of humus,and relieved the soil p H value changes caused by the chemical fertilizer. It showed that combined humic acid could alleviate soil acidity.