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Tillage and straw incorporation are important agricultural practices that can break plough layer and improve black soil fertility. The effects of tillage and straw incorporation on straw humification coefficient, soil organic carbon (SOC), and maize yield were investigated in a field experiment. Subsoil combined with straw incorporation in 20-35 cm soil layer (ST+S) could break plough layer and decrease the bulk density by 5.7%, 3.3% and 5.7% compared with traditional til-lage (TT), subsoil (ST) and traditional tillage combined with straw incorporation (TT+S) in six experimental years, respectively, and the best effects were observed in ST and ST+S treatments in the first expe-rimental year. The rate of straw decomposition was higher in 0-20 cm (72.0%) than in 20-35 cm (59.2%), and the straw humification coefficient in 0-20 cm and 20-35 cm soil la-yers reached the peak in first experimental year with 15.9% and 12.7%, respectively. Compared with initial soil sample, SOC and light fraction organic carbon (LFOC) of TT, ST and ST+S treatments in 0-20 cm soil layer was decreased in experimental years, but was increased by 2.9% and 12.4% within TT+S, respectively. SOC and light fraction organic carbon (LFOC) of ST+S in 20-35 cm soil layer was increased by 9.2% and 9.9%, respectively. The effect of field treatments on maize yield showed in a decreasing trend of ST+S>TT+S>ST>TT, effects of tillage and straw incorporation on maize yield could continue 3 and 6 years, respectively, indicating that tillage and straw incorporation had time effect. Therefore, straw incorporated into 20-35 cm soil layer based on tillage was an effective, sustainable agricultural practice of improving black soil quality.

Change in soil organic carbon between 1981 and 2011 in croplands of Heilongjiang Province, northeast China.

BACKGROUND: Soil organic carbon (SOC) is fundamental for mitigating climate change as well as improving soil fertility. Databases of SOC obtained from soil surveys in 1981 and 2011 were used to assess SOC change (0-20 cm) in croplands of Heilongjiang Province in northeast China. Three counties (Lindian, Hailun and Baoqing) were selected as typical croplands representing major soil types and land use types in the region. RESULTS: The changes in SOC density (SOCD) between 1981 and 2001 were -6.6, -14.7 and 5.7 Mg C ha(-1) in Lindian, Hailun and Baoqing Counties respectively. The total SOC storage (SOCS) changes were estimated to be -11.3, -19.1 and 16.5% of those in 1981 in the respective counties. The results showed 22-550% increases in SOCS in rice (Oryza sativa L.) paddies in the three counties, but 28-33% decreases in dry cropland in Lindian and Hailun Counties. In addition, an increase of 11.4 Mg C ha(-1) in SOCD was observed in state-owned farms (P < 0.05), whereas no significant change was observed in family-owned farms. CONCLUSION: Soil C:N ratio and initial SOCD related to soil groups were important determinants of SOCD changes. Land use and residue returning greatly affected SOC changes in the study region. To increase the topsoil SOCD, the results suggest the conversion of dry croplands to rice paddies and returning of crop residue to soils.

Nitrous oxide emissions from Mollisols as affected by long-term applications of organic amendments and chemical fertilizers.

A field experiment was conducted to evaluate the influences of long-term applications of organic amendments and chemical fertilizers on nitrous oxide (N2O) emissions from Mollisols in northeast China and to relate soil N2O fluxes to soil moisture and temperature. A closed-chamber method was used to determine soil N2O flux during the maize growing season in 2011. In the entire maize growing period, cumulative N2O emissions were significantly (all P<0.05) increased by 66, 86 and 83% under the applications of 4.5 Mg ha(-1) maize straw combined with NPK, 7.5 and 22.5 Mg ha(-1) pig manure combined with NPK, respectively, compared with the control (0.64±0.01 kg N2O-N ha(-1)), whereas NPK fertilizer alone and 2.25 Mg ha(-1) maize straw combined with NPK had no remarkable influences (P>0.05). Nonetheless, even increasing nitrogen inputs, the cumulative microbial N2O emission over 126 days had an upper threshold around 1.2 kg N2O-N ha(-1). Approximately 25-44% of N2O was emitted from the applied organic amendments, and the emission factor (EF) of applied organic amendments as N2O based on 126 days was between 0.07 and 1.52%, higher than NPK fertilizer-induced EF (0.03%). Soil temperature explained 38-96% of the seasonal variation in soil N2O fluxes using exponential models, with a Q10 of 2.01-3.48. Our results suggest that the influences of organic amendments on soil N2O emissions from Mollisols primarily vary with the type of the applied organic amendments, whereas great nitrogen inputs at maximum asymptotically double baseline cumulative emissions.

Treatment of children with femoral subtrochanteric fracture with advanced elastic intramedullary nail technology / 中国骨伤

<p><b>OBJECTIVE</b>To explore curative effects of advanced elastic intramedullary nail technology in treating children with femoral subtrochanteric fracture.</p><p><b>METHODS</b>Form March 2009 to December 2010, 16 children with femoral subtrochanteric fracture were treated with advanced elastic intramedullary nail technology. There were 12 males and 4 females ranging in age from 7 to 15 years old with a mean of 9.8 years old. According to fracture classification, 9 cases were stable fractures (traverse or short oblique type) and 7 cases were unstable fractures (comminuted or long oblique type). Radiographs and complications were retrospectively reviewed. Fracture healing were evaluated according to Flynn criteria.</p><p><b>RESULTS</b>All children were followed up from 11 to 32 months with an average of 21 months. No incision infecton,bone nonunion and breakage of screw occurred. The fracture healing time was from 8 to 16 weeks with an average of 10.1 weeks. According to Flynn criteria, 14 cases got excellent results, 1 moderate and 1 poor.</p><p><b>CONCLUSION</b>Advanced elastic intramedullary nail technology for the treatment of children with femoral subtrochanteric fracture is a safe and effective fixation, which is good for early mobilization, shorter the duration of hospital stays and reduce complications.</p>