Excessive use of agro-chemicals (such as mineral fertilizers) poses potential risks to soil quality. Application of organic amendments and reduction of inorganic fertilizer are economically feasible and environmentally sound approaches to develop sustainable agriculture. This study investigated and evaluated the effects of mineral fertilizer reduction and partial substitution of organic amendment on soil fertility and heavy metal content in a 10-season continually planted vegetable field during 2009-2012. The experiment included four treatments: 100% chemical fertilizer (CF100), 80% chemical fertilizer (CF80), 60% chemical fertilizer and 20% organic fertilizer (CF60+OM20), and 40% chemical fertilizer and 40% organic fertilizer (CF40+OM40). Soil nutrients, enzyme activity and heavy metal content were determined. The results showed that single chemical fertilizer reduction (CF80) had no significant effect on soil organic matter content, soil catalase activity and soil heavy metal content, but slightly reduced soil available N, P, K, and soil urease activity, and significantly reduced soil acid phosphatase activity. Compared with CF100, 40% or 60% reduction of chemical fertilizer supplemented with organic fertilizer (CF60+OM20, CF40+OM40) significantly increased soil organic matter, soil catalase activity and urease activity especially in last several seasons, but reduced soil available P, K, and soil acid phosphatase activity. In addition, continuous application of organic fertilizer resulted in higher accumulation of Zn, Cd, and Cr in soil in the late stage of experiment, which may induce adverse effects on soil health and food safety.

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This letter addresses several key issues in the process of model-based optical metrology, including three dimensional (3D) sensing, calibration, registration and fusion of range images, geometric representation, and visualization of reconstructed 3D model by taking into account the shape measurement of 3D complex structures,and some experimental results are presented. CLC number: TP206+.1 Document code: A Article ID: 1673-1905(2007)02-0115-04 DOIThe characterization of three dimensional (3D) objects with complex geometry and topology is one of good examples in model-based optical metrology. The visualization of 3D model of complex objects is another significant aspect, which involves the geometric representation and shading or texture mapping of the 3D structures which enable the end-user could not only obtain the geometric and topological information regarding a 3D object under the inspection but also the appearance of the object surface, perhaps a piece of useful information to characterize the test object. The visualization as a complementary feature of digitization can offer timely feedback to guide the digitizing process in order to maintain high quality 3D sensing and therefore permit an accurate modeling afterwards. The geometric representation technique would be probably useful for comparative measurement and 3-D model transmission via the network environment, which is particularly useful for tele-metrology.Full-field optical metrology incorporated with the image processing provides a powerful alternative as a non-contact, fast, and accurate measurement tool. For the specific application of 3-D topography, the measurement data are also referred to as a range image with 2.5-dimensions in terms of computer/machine vision. Among a number of optical fullfield techniques, the fringe projection with coherent or incoherent illumination would be one of the most popular optical methods to acquire the range images of 3-D structures [1][2][3] . Two different prototypes of 3-D digitizers were developed in our laboratory, respectively. One prototype was based on the fringe projection using white light (incoherent) [4] while the other was constructed with dual acousto-optic deflectors by using coherent illumination [5] . With both setups one is able to acquire range images of complex 3-D objects with help of automatic fringe pattern analysis. Particularly a sophisticated phase unwrapping technique was applied to extract range image from modulated fringe patterns in a multiresolution manner [6] . In addition to fringe projection, 3-D sensing mechanisms based on other active pattern illumination were also explored by our group [7][8] . The conversion of a continuous phase map to a range image is a crucial step to allow accurate shape measurement. This involves the 3-D calibration of the digitizer used for the measurement. A comprehensive discussion on this issue can be found elsewhere, e.g. Ref. [ 9].Nevertheless, any optical equipment for the shape measurement may have limited field of view (FOV) and depth of field (DOF...

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