The contents of nitrogen and organic carbon in an agricultural soil were analyzed using reflectance measurements （n = 52） performed with an ASD FieldSpee-Ⅱ spectroradiometer. For parameter prediction, empirical mod...The contents of nitrogen and organic carbon in an agricultural soil were analyzed using reflectance measurements （n = 52） performed with an ASD FieldSpee-Ⅱ spectroradiometer. For parameter prediction, empirical models based on partial least squares （PLS） regression were defined from the measured reflectance spectra （0.4 to 2.4 μm）. Here, reliable estimates were obtained for nitrogen content, but prediction accuracy was only moderate for organic carbon. For nitrogen, the real spatial pattern of within-field variability was reproduced with high accuracy. The results indicate the potential of this method as a quick screening tool for the spatial assessment of nitrogen and organic carbon, and therefore an appropriate alternative to time- and cost-intensive chemical analysis in the laboratory.展开更多
A new laboratory method was proposed to establish an easily performed standard for the determination of mobile soil water close to real conditions during the infiltration and redistribution of water in a soil. It cons...A new laboratory method was proposed to establish an easily performed standard for the determination of mobile soil water close to real conditions during the infiltration and redistribution of water in a soil. It consisted of applying a water volume with a tracer ion on top of an undisturbed ring sample on a pressure plate under a known suction or pressure head. Afterwards, soil water mobility was determined by analyzing the tracer-ion concentration in the soil sample. Soil water mobility showed to be a function of the applied water volume. No relation between soil water mobility and applied pressure head could be established with data from the present cxperiment. A simple one- or two-parameter equation can be fitted to the experimental data to parameterize soil water mobility as a function of applied solute volume. Sandy soils showed higher mobility than loamy＂ soils at low values of applied solute volumes, and both sandy and loamy soils showed an almost complete mobility at high applied solute volumes.展开更多
基金Supported by National Natural Science Foundation of China(20577055,31201689)Chinese Academy of Sciences-DAAD(German Academic Exchange Service)Joint Scholarship Programme Doctoral Research in Germany,and China Postdoctoral Science Foundation(20110490630)
文摘The contents of nitrogen and organic carbon in an agricultural soil were analyzed using reflectance measurements （n = 52） performed with an ASD FieldSpee-Ⅱ spectroradiometer. For parameter prediction, empirical models based on partial least squares （PLS） regression were defined from the measured reflectance spectra （0.4 to 2.4 μm）. Here, reliable estimates were obtained for nitrogen content, but prediction accuracy was only moderate for organic carbon. For nitrogen, the real spatial pattern of within-field variability was reproduced with high accuracy. The results indicate the potential of this method as a quick screening tool for the spatial assessment of nitrogen and organic carbon, and therefore an appropriate alternative to time- and cost-intensive chemical analysis in the laboratory.
基金Coordenacao de Aperfeicoamento de Pessoal de Nível Superior (CAPNS), Brazil and Deutsche Forschungsgemeinschaft (DFG), Germany-Bilateral Cooperation Project 017/04
文摘A new laboratory method was proposed to establish an easily performed standard for the determination of mobile soil water close to real conditions during the infiltration and redistribution of water in a soil. It consisted of applying a water volume with a tracer ion on top of an undisturbed ring sample on a pressure plate under a known suction or pressure head. Afterwards, soil water mobility was determined by analyzing the tracer-ion concentration in the soil sample. Soil water mobility showed to be a function of the applied water volume. No relation between soil water mobility and applied pressure head could be established with data from the present cxperiment. A simple one- or two-parameter equation can be fitted to the experimental data to parameterize soil water mobility as a function of applied solute volume. Sandy soils showed higher mobility than loamy＂ soils at low values of applied solute volumes, and both sandy and loamy soils showed an almost complete mobility at high applied solute volumes.
