温室番茄冠层和叶片光谱特征分析及营养诊断

通过温室基质栽培,利用ASD光谱仪和傅里叶光谱分析仪测量了四种营养水平下温室番茄冠层和叶片的光谱反射曲线,并检测了对应叶片的水分含量、叶绿素含量和氮含量,分析了不同营养水平下番茄冠层和叶片的反射光谱变化,并对番茄叶片含水量的敏感波长以及冠层反射光谱的红边波长进行了研究。结果表明:温室番茄冠层反射光谱曲线在可见光550nm左右均有叶绿素的强反射峰,近红外区反射率高于可见光区。在同一生长期,随基质营养水平的提高,番茄冠层反射率在可见光波段不断减小,在近红外波段不断增大,且红边波长位置出现"红移"现象。利用530和760nm特征波长得到的归一化颜色指标NDCI与叶片氮含量有较好相关性,R2为0.7511。

The canopy and leaf spectral characteristics and nutrition diagnosis of tomato in greenhouse

A green house experiment was conducted to research the characteristics of tomato canopy spectral reflectance and leaf spectral reflectance under different nutrition treatments, and the relationships between spectral reflectance and the water content, chlorophyll content, as well as nitrogen content were analyzed. Substrate cultivation method was used to grow the plants. The substrate was made from a mixture of peat and vermiculite. Test area was prepared for four levels of nutrition to form nutritional stress. There were 12 seedlings under each nutritional condition and a total of 48 seedlings were planted for the experiment. The canopy reflectance and leaf reflectance were measured by an ASD handheld spectroradiometer and a FT-NIR spectrometer respectively. It was observed that the trend of tomato canopy reflectance was similar to each others. There was a reflection peak at about 550 nm, and the reflectance in the visible light region was lower than that in near-infrared region. The results of analysis also indicated that under different nutrient conditions, canopy spectral reflectance characteristics of tomato took on disciplinary change. At near-infrared bands, the reflectance gradually increased with adding nutrition, while reduced at visible light bands. The leaf spectral reflectance characteristics at near-infrared bands had the similar change with the canopy reflectance. There were four sensitive wavelengths of water at near-infrared bands: about 980, 1450, 1 930, and 2 210 nm, and the results of single linear regression (SLR) and multi-linear regression (MLR) indicated that the reflectance at these sensitive wavelengths could be used to estimate the water content in tomato leaves. R2 were 0.5903 and 0.7437 respectively. NDCI as one of the most important spectral parameter was calculated by the spectral reflectance of 530 and 760 nm, and the result indicated that there existed a good correlation between NDCI and the nitrogen content, with R2 = 0.7511. Meanwhile, red edge inflection points were analyzed under four nutrition treatments based on the first derivative of canopy spectral reflectance. The analysis results illustrated that red edge inflection position moved to direction of red light (long wavelength) with the nutrition supply.