Study On Composing And Structural Characteristics Of Soil Humin

Soil humus is an important part of soil, and it plays important role in soil fertility, environmental protection, agricultural developement and other aspects. Humin accounts for 50-80% of soil humic substance, but most studies focused on humic acid and fulvic acid in previous, and litte on humin (HM).The effects of continuous NaOH and NaOH+Na₄P₂O₇ extraction times on contents and characteristics of soil humus fractions extracting from dark-brown soil in Jilin Province of China were studied in this paper. We also studied the effect on contents and characteristics of humus of black soil with long-term fertilization, and it was divided by Pallo method. The contents and characteristics of different fractions were also studied. The objects were to clarify the effect on humus in long-term fertilization conditions, and provided scientific basic of humin effect on soil fertility. It had an active meaning in keeping a high output and improving soil quality. The main results were as follows:The results showed that the total organic carbon (TOC) content of soil humus fractions extracted by using the above two extractants was not quite different, and TOC content of humic acid (HA) fraction was higher than that of fulvic acid (FA) fraction. With the continuous extraction times, the absolute content of HA, FA and HM all decreased, the relative content of HA and FA also decreased, but the relative content of HM increased. A higher relative proportion of FA was obtained in the last extractable humus fractions when NaOH was used as extractant. During the course of continuous extraction,â–³logk and activity degree of HA and FA generally appeared an increasing tendency while relative chrorna (RF) decreased, indicated that the condensation degree of theirs declined while aliphaticity increased. RF is a more properly index for describing the characteristic change of HA and FA with extraction.Generally speaking, the humus contents could increase with fertilizing. Only inorganic fertilizer application was favorate to accumulate FA. Compared with inorganic fertilizer, organic + inorganic fertilizer application could increased humus contents obviously, and high proption of organic fertilizer + inorganic fertilizer application could enhance the yield of crops.As a rule, organic fertilizer was in favor of increasing the absolute content of different fractions of soil humus. About the effeciveness, inorganic+organic fertilizer was superior to inorganic fertilizer, and inorganic+high quantity organic fertilizer was better than inorganic+low quantity organic fertilizer. For the treatments of inorganic+ organic fertilizer, the relative contents of humin linked to iron (HMi) and humin linked to clay (HMc) decreased with the increasing of organic fertilizer quantity, while the ratio of HMi/HMc decreased. For the treatments of organic fertilizer, the relative content of HMi increased with the increasing of organic fertilizer quantity, and the relative content of HMc decreased slightly. The contents of extractable humic substance (HE) decreased with the increasing of organic fertilizer quantity, and inorganic+organic fertilizer was more effective. Compared with unfertilized control plot, the extracting rate of TOC (HE/TOC) with single inorganic fertilizer application was lower. This might result from the contents of soil organic matter increased by long-term organic fertilization. Relatively, it maybe means that the amounts of humin increased.Fertilization had no obviously effect on free fulvic acid (FFA) and fulvic acid extracted with sodium pyrophosphate (FAp). The results of hue coefficient (â–³logk) of different fractions of soil humus indicated that the structure of different fractions became simpler with increasing organic fertilizer, while inorganic+organic fertilizer applied. For the treatments of inorganic+organic fertilizer, the activation degree (AD) of FA increased with the increasing of organic fertilizer quantity, but HA decreased slightly which needed to be validated again. Compared with unfertilized, the effect of HMi and HMc with only using inorganic fertilizer had no difference, and organic fertilizer was favorate to simplify the structure of HMi and HMc.From the anlysis of difference thermal analysis (DTA), the complicated sequence of molecue structure was black carbon (BC)＞HM＞FA. In the fractions of humin, the complicated sequence of molecue structure was superstratum of humin linked to clay (HMcu)＞substratum of humin linked to iron (HMid)＞substratum of insoluble humin residates (HMrd).¹³C Nuclear magnetic resonance (¹³C-NMR) spectroscopy of soil humus indicated that aliphatic contents of HM was more than HA and FA. The structure of HMi was familiar with HA and FA, and the structure of FA had more carbohydrates.