SOIL BACKGROUND EFFECTS ON REFLECTANCE-BASED CROP COEFFICIENTS FOR CORN
SOIL BACKGROUND EFFECTS ON REFLECTANCE-BASED CROP COEFFICIENTS FOR CORN
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DOI：
10.1016/0034-4257(93)90096-g
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发表时间：
1993-11-01
影响因子：
13.5
通讯作者：
BAUSCH, WC
中科院分区：
文献类型：
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作者：
BAUSCH, WC
先前开发的基于反射率的玉米作物系数（K（cr））是根据归一化差异植被指数（NDVI）估计的，已被证明在与深色土壤一起使用时高估了玉米的基础作物系数（K（cb））24%或更多。这种高估的发生是因为在黑暗的背景下，对于相同的植被数量，NDVI产生更大的指数值。因此，本文的目的是调查新的植被指数，已开发的土壤背景效应最小化，并开发一个基于反射率的作物系数，适用于广泛的农业土壤反射率的玉米。两种土壤（浅色和深色）的红色反射率分别为31%和13%，分别被选为这项研究。玉米冠层的反射率数据与四种组合的这些土壤（光，干;光，湿;黑暗，干，黑暗，湿）在托盘插入在同一个地方的玉米冠层下面。土壤调整植被指数（SAVI），调整因子（L）设置为0。5，发现充分减少土壤背景的影响，从稀疏到密集的植被条件。使用玉米的K（cb）和SAVI之间的线性变换将SAVI转换为K（cr）。该K（cr）在光照、干燥土壤背景和黑暗、潮湿土壤背景（极端情况）之间的最大差异小于6%。基于SAVI的K（cr）校正了湿润土壤表面，并且不需要额外的校准来估计在大多数农业土壤上生长的玉米的基础作物系数。
A previously developed reflectance-based crop coefficient (K(cr)) for corn, estimated from the normalized difference vegetation index (NDVI), has been shown to overestimate the basal crop coefficient (K(cb)) for corn by 24 % or more when used with a dark-colored soil. This overestimation occurs because the NDVI produces larger index values for the same vegetation amount over dark backgrounds. Thus, the purpose of this article was to investigate newer vegetation indices that have been developed to minimize soil background effects and to develop a reflectance-based crop coefficient for corn that applies over a wide range of agricultural soil reflectance. Two soils (light- and dark-colored) with red reflectance of 31 % and 13 %, respectively, were selected for this study. Reflectance data of the corn canopy were acquired with four combinations of these soils (light, dry; light, wet; dark, dry, and dark, wet) in trays inserted at the same place beneath the corn canopy. The soil adjusted vegetation index (SAVI), with an adjustment factor (L) set to 0. 5, was found to adequately minimize soil background influences from sparse to dense vegetation conditions. A linear transformation between the K(cb) for corn and the SAVI was used to convert the SAVI into the K(cr). The maximum difference for this K(cr) between the light, dry soil background and the dark, wet soil background (extreme cases) was less than 6 %. The K(cr) based on the SAVI corrects for a wet soil surface and requires no additional calibration to estimate the basal crop coefficient for corn grown on most agricultural soils.