Paddy Soil And Dryland Soil Enzyme Activities And Organic Matter, Ft-ir Characteristics Of A Comparative Study

Typical agricultural soils along the East side of China were sampled from provinces of Hainan, Jiangxi, Zhejiang, Jiangsu, Henang, Liaoning and Jiling. At each sampling site, at least one paddy soil and a corresponding upland soil were chosen based on their sources of parent materials, texture and geological locations. Selected soil enzyme activities and characteristic peaks of Fourier transform infrared spectroscopy (FT-IR) of organic matter were compared between upland and paddy soils. In Zhejiang sampling site, the historic records are available for dating back the duration of agricultural uses of soils, and thus the soils allow the comparison of the effects of cultivation duration on the soil properties. Purpose of present study is to examine the impact of anthropogenic activities on soil enzyme activities and chemical structure of soil organic matter. Particular attention is directed to comparison between upland and paddy soils.Results showed that four enzyme activities were mostly higher in paddy soils with the duration of soil cultivation ranging from 50 to 700 years than those in upland soils. There was no clear trend of arylsulfatase, acidic phosphatase, alkaline phosphatase, belta-glucosidase and dehydrogenase activities in upland soils. Arylsulfatase activities in paddy and upland soils ranged, respectively, from 0.2 to 0.4 and from 0 to 0.2 mg p-nitrophenol g-1 h-1. Based on the results from present study, it was concluded that soil enzyme activities were useful parameters in evaluating soil fertilities.Enzyme activities examined showed significant correlation among themselves except for alkaline phosphatase activities. The correlation efficiency (R) was as high as 0.834 between arylsulfatase and belta-glucosidase activities, and was 0.541 between arylsulfatase and acidic phosphatase activities.FT-IR peak patterns between the organic matters extract from upland and paddy soils with sodium pyrophosphate were largely the same, with some variation of peak heights, indicating that the chemical structure of organic matter was not profoundly altered by cultivation of rice. However the height of peak signifying C=O group was increased as the increase of cultivation duration of rice (paddy soils). There was no obvious difference of other peaks between the organic matters from upland and paddy soils.The peak of 630-846 cm-1 in the organic matter extracted with pyrophosphate was undetectable under the present experiment conditions. However the peaks of 1640 cm-1 and 1392 cm-1 were strong, the former of which signifies C=O group. In contrast to pyrophosphate treatment, HF-treated soil organic matters showed stronger peak of 1392 cm-1 but weaker and broaden peak of 1029 cm-1. Soils without subjection to extraction procedures showed week peaks within the range of detectable spectrums. Based on the data stated above, it was concluded that HF-treatment was inferior to pyrophosphate-treatment in characterizing structure of soil organic matter.