玉米叶片高光谱反射率、吸收率与色素含量的关系比较分析

分析测定了大田试验条件下11个玉米品种的3个氮肥处理、2个密度处理和6个生育期的150张叶片在350～2500nm波段的反射率和吸收率及其叶绿素a、叶绿素b和类胡萝卜素的含量。玉米叶片在叶绿素吸收波段的最大吸收波长位于665nm附近,665nm处叶片的吸收率与反射率间呈高度负相关(R2=-0.7533,n=150),而吸收率较高(>92%)的叶片的相关性明显强于吸收率较低的叶片。基于近红外波段和叶绿素吸收波段(红波段)或叶绿素反射波段(绿波段)构建的8个高光谱参量只有以反射率为基础计算时才与色素含量间存在相关性。mSR705和mND705无论以反射率还是以吸收率为基础计算,均表现出与色素含量间的强相关关系,而以吸收率为基础计算的mSR705和mND705与色素含量间的相关性又稍强于以反射率为基础计算的mSR705和mND705。本研究结果暗示叶片的表面反射是干扰叶片光谱(尤其是吸收光谱)对色素浓度变化响应的主要因子。     

Quantifying nitrogen status of corn (Zea mays L.) in the field by reflectance measurements

Nutrient deficiencies can seriously reduce yield and economic returns to farmers. Tools that can rapidly quantify the nutritional status of plants are needed for efficient fertilizer management. Reflectance measurements have shown to be a useful tool to identify the nutritional status of different plant species. A set of calibration curves relating reflectance ratios to the nitrogen (N), phosphorus (P), magnesium (Mg), and iron (Fe) concentrations in corn leaves was established in greenhouse trials in a previous study. In this paper these calibrations were examined for their ability to identify nutrient deficiencies under field conditions. A 2-year field experiment was conducted to check and define the regions of the spectra that are influenced by leaf N concentration and to set up possible equations for quantifying the leaf N status in the field. The experiment was carried out on a loess derived soil in south-western Germany. Reflectance of corn leaves, from plants grown with six different N fertilization treatments ranging from 0 to 160 N kg ha⁻¹, was determined once a week from the beginning of June until the end of July. Reflectance measurements were performed at the 4th leaf of corn plants with a digital LEICA S1 Pro camera under controlled light conditions. Reflectance was measured in different wavelength ranges in the visible and infrared spectra. Leaf scans were evaluated within the L*a*b*-color system. Total N concentration of corn leaves was determined chemically and correlated with reflectance patterns. Significant correlations between corn N status and leaf reflectance changes were obtained at a nitrogen level of N<3.0%. Reflectance patterns at 510₇₈₀, 516₁₃₀₀, 540₁₃₀₀ nm were found most suitable to the corn N status in the field regardless of the year or sampling date. The results indicate that the spectral patterns and the defined calibration curves of N deficiency from greenhouse studies could be used in field studies. Thus, reflectance measurements may serve as a rapid, non-destructive approach to discriminate nitrogen deficiency in the field.     

双通道近地遥感图像采集处理系

利用2CCD多光谱相机设计了近地遥感图像采集平台,同步获取小范围区域作物的可见光和NIR图像,通过图像处理技术从作物图像获得反射光谱信息.采集平台包括一个2CCD多光谱相机,两个采集盒,一台具有两个千兆网口的田间计算机.图像处理部分通过2GRB灰度化、中值滤波和Otsu二值化,从背景中分割出作物图像,结合作物原始R分量灰度图像,提取出作物红光图像平均灰度值,利用建立的灰度值与反射率的线性模型,计算得到作物红光波段的反射率.试验结果表明,图像采集平台工作稳定,利用图像处理方法提取的反射率与ASD光谱仪测量结果有较好相关性,为从作物冠层图像探测生长状况提供了理论依据.     

棉花群体结构与棉田光量子传递特性关系的研究

棉花群体结构与棉田光量子的透射、 反射和吸收等传递特性有密切关系, 其中透射率与叶面积指数和群体叶片重关系最密切, 可用于估测叶面积指数和群体叶重的大小。 光的透射率与群体地上部分生物量和茎枝生物量也有很好的关系, 可用于活体农作物生物量间接测定。 反射率与叶面积和生物量也有一定关系, 采用反射遥感方法也可在     

Estimation of dye concentration in the cross section of polyamide rod using scanner data

The reflectance factors of the polyamide rods which were dyed with different concentrations of three commercial yellow, red, and blue disperse dyes are recovered from their RGB data obtained from scanning of the cross sections of rods with the desktop scanner. The RGB data are converted to device independent XYZ tristimulus values by simple polynomial regression technique. Then, the principal component analysis (abbreviated by PCA) technique is employed for the recovery of reflectance spectra from the tristimulus values by using three different datasets, i.e. using the reflectance factors of Munsell chips, MacBeth ColorChecker SG, and a dynamic dataset prepared from the reflectance factors of dyed rods samples. The first three eigenvectors of each dataset are extracted and employed in the reconstruction process of spectral reflectance from XYZ colorimetric data. Finally, the well known Kubelka-Munk function is implemented for estimation of concentration of dye from the recovered spectral reflectance. The root mean square (RMS) errors between the reconstructed and the actual reflectance data over the visible spectrum are calculated. According to results, the RMS errors for the reflectance recovery are within the acceptable range. Error of estimation of dye concentration in the rods varies for different hues as well as concentrations and changes with applied dataset.     

利用可见光/近红外-短波红外光谱预测土壤总氮含量的研究

利用航天遥感影像,分析了影像光谱值与土壤总氮含量之间的关系.利用多元统计方法,建立了总氮含量预测模型,并制作了总氮含量分布图.     

付里叶变换近红外漫反射光谱法测定谷子中赖氨酸含量

本文应用介绍付里叶变换近红外漫反射全谱分析谷物中的赖氨酸的方法,相关系数达0.96,标准差<0.004%,分析结果达到农业产品分析要求。这种方法还可推广应用于其它氨基酸的分析。     

Determination op fluoride in plant samples by a potentiometric method and near‐infrared reflectance spectroscopy

Abstract

The determination of fluoride in plant materials was studied using a specific ion electrode following extraction using either deionized water or 0.1 M perchloric acid.

When the extracting agent was water, the amount of fluoride determined was generally 37% less than that obtained using perchloric acid. However, a close relationship was observed between the amounts extracted by either procedure. When perchloric acid is used, the method was found to be precise (variation coefficient 0.74%), accurate (average recovery 98.67%) and sensitive enough to be used in the routine analysis of plant materials.

The determination of fluoride by near‐infrared reflectance analysis (NIRA) was also used which gave generally acceptable results.     

藏北地区土壤水分遥感反演模型的研究

土壤水分是反映地表土壤特性的重要表征参量,也是遥感反演领域的一个热点问题。利用MODIS卫星数据第7波段对水分变化较敏感的特点,构建了一种简单实用的土壤水分反演回归模型。结果表明,利用该模型计算的预测值与实地观测值间的相关性比较好,达到了显著水平(P0.001),可以作为研究区土壤含水量遥感反演回归模型。由于该方法具有简单实用的特点,为高原土壤水分遥感监测提供了可行的方法。