Si-sang Deng

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Changes in soil microbial community structure and diversity may reflect environmental impact. We examined 16S rRNA gene fingerprints of bacterial communities in six agroecosystems by PCR amplification and denaturing gradient gel electrophoresis (PCR-DGGE) separation. These soils were treated with manure for over a century or different fertilizers for over(More)
This study was carried out to investigate the effect of tillage and residue management on activities of phosphatases (acid phosphatase, alkaline phosphatase, phosphodiesterase, and inorganic pyrophosphatase) and arylsulfatase. The land treatments included three tillage systems (no-till, chisel plow, and moldboard plow) in combination with corn residue(More)
Studies were conducted to investigate the effects of long-term management practices on level and distribution of soil P and enzyme activities involved in P transformations in soil. Treatments included manure, P, NP, NPK, and NPK plus lime. Cattle manure was applied every 4 years at 269 kg N ha–1 for over a century and chemical fertilizers were applied every(More)
A simple and sensitive method was developed to detect and quantify N-acetyl-b-D-glucosaminidase (EC 3.2.1.30) activity in soil. This enzyme is also listed as b-hexosaminidase (EC 3.2.1.52) in Enzyme Nomenclature. The optimum pH and temperature for the enzyme were approximately pH 5.5 and 638C, respectively. The Km and Vmax values were calculated from three(More)
Recent interest in soil tillage and residue management has focused on low-input sustainable agriculture. In this study we investigated the effect of three tillage systems (no-till, chisel plow, and moldboard plow) and four residue placements (bare, normal, mulch, and double mulch) on the activities of four amidohydrolases (amidase, L-asparaginase,(More)
 Studies were conducted to evaluate the relationships among different active N pools of organic matter in soils at two long-term cropping systems in Iowa. Results indicated that multi-cropping systems, particularly meadow-based systems, enhanced bioactivities of soils. Mono-cropping systems, particularly soybean, reduced soil microbial biomass and enzyme(More)
Studies were conducted to evaluate microbial populations and community structures in soils under different management systems in a long-term continuous winter wheat experiment. These soils had been treated with cattle manure for over a century, and P, NP, NPK, or NPK plus lime for over 70 years. Cattle manure application promoted the growth of bacteria, but(More)
 Understanding the effect of cropping systems on N mineralization in soils is crucial for a better assessment of N fertilizer requirements of crops in order to minimize nitrate contamination of surface and groundwater resources. The effects of crop rotations and N fertilization on N mineralization were studied in soils from two long-term field experiments(More)
An automated clean up and concentration method by column switching is described for the assay of gliquidone, a hypoglycemic agent, in plasma. The system uses Merck Lichroprep RP2 (25-40 microns) as short precolumn packing material for on--line clean up and concentration. A Shimpack CLC--ODS (5 microns) is used as analytical column. Water is used as the(More)
Androgen plays critical roles in vertebrate reproductive systems via androgen receptors (ARs). In the present study, the full-length spotted scat (Scatophagus argus) androgen receptor (sAR) cDNA sequence was cloned from testis. The sAR cDNA measured 2448 bp in length with an open-reading frame of 2289 bp, encoding 763 amino acids. Amino acid alignment(More)