【作者】 夏拥军；

【导师】 丁为民；

【作者基本信息】 南京农业大学 ， 农业机械化工程， 2004， 硕士

【摘要】 土壤机械阻力是土壤的一个重要力学性质，与土壤容重、含水量、塑性指数、圆锥指数等土壤的物理特性之间有着密切的关系，对农作物的生长和农业机械的作业能耗有很大的影响。因此，应当重视对其测定方法和应用的研究。目前，普遍使用的测量装置是使用土壤圆锥仪或硬度计非连续测定的方法，该方法操作方便、效率较低；但因测点相对较少，用于评价土壤或探索其与其它土壤特性参数、植物生长参数的关系时，精度受到影响。在实施精确农业的发展趋势下，需要实时、在线连续测定土壤机械阻力，并探索其在土壤-植物生长模型中的作用，非连续测定的方法已经不能适应这种需要。为此，本研究中设计了一套由硬件和软件组成的连续测定系统。试验表明，该系统能够高效的连续测定土壤机械阻力，与GPS、GIS、DSS等结合起来符合精确农业的发展趋势和要求。 在对测试系统进行了标定的基础上，进行了田间试验。对田间试验结果进行频谱分析和滤波处理后，分析表明土壤机械阻力是低频随机信号，主频集中在2Hz以内；通过对土壤机械阻力连续测定的结果与硬度计在同一位置的平均土壤硬度的相关系数计算，经显著性检验发现高度相关，从而确定了连续测定的方法可以用于评价土壤的强度；利用滤波后的数据，初步探讨了土壤机械阻力的空间变异性和分形特征：(1) 通过计算自相关函数，得出自相关距离，表明在一定范围内土壤机械阻力存在着空间相关性，可以利用自相关范围内的点来插值估计未测点的值。(2) 利用半方差法和功率谱密度法分别计算土壤机械阻力的分维数，用半方差法得出的分维为1.78845～1.9124、用PSD方法得出的分维为2.12～2.296。分维数均接近2，说明在本试验区域不同采样线路上土壤机械阻力的变化程度是同样复杂的，具有随机性和不规则性。更多还原

【Abstract】 Soil mechanical resistance is an important mechanics property of soil. The relationship between soil mechanical resistance and several soil physical parameters (such as soil dry bulk densities, soil moisture content, plasticity index, cone index and so on) is closely, and soil mechanical resistance is unfavourable to corn growing and soil tillage. So, we should appreciate researching on its measuring and applying. Amongst the numerous instruments developed to measure soil mechanical resistance, penetrometer is widely used to measure stop-and-go. The method is convenient but labour-intensive, time-consuming. In addition, soil mechanical resistance data is limited to a few discrete points within a field, relationship between soil mechanical resistance and several soil property parameters or crop growing from point data have an accuracy limitation due to a relatively small achievable measurement density. In the context of precision agriculture, soil mechanical resistance should be on-line and on-time measured, and used to build the model of soil-crop. Measuring stop-and-go do not meet the need. Therefore, a set of continuous testing system was developed, which was consisted of hardware and software. The designed dynamometer and the associated measurement chain is efficient, it will suit to precision agriculture if it is integrated with GPS, GIS and DSS.A laboratory calibration of the sensor showed good linear relationship between the applied solicitations and the output electrical tensions of the Wheatstone bridge. The experiment in this study was performed in a field. After spectrum analysis and filtering, the results showed that soil mechanical resistance is lower frequency signal and the lower spectrum density occurs at 2Hz; the soil mechanical resistance at a constant depth was correlated to the cone penetrometer measurements for the same depth, so, the continuously measurement could be used to evaluate soil strength; spatial variability and fractal dimension of soil mechanical resistance was primary studied: (1) autocorrelation function was calculated, autocorrelation length was found, the results showed that existed spatial correlation phenomenon in a limited range, value of undetected points could be interpolated by points from neighbor area. (2) the fractal dimension of soil mechanical resistance were estimated in semi-variograms (1.78845-1.9124) and power spectral densities(2.12-2.296), which were all very close to 2, and it showed that the variation of soil mechanical resistance in all measuring routings were the same complex, random and irregular.更多还原