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The development of a crop specific drought index for corn
Abstract
The Palmer Drought Severity Index (PDSI) and the Crop Moisture Index (CMI) are the two indices most often used to characterize drought in the U.S. Although these indices have many inherent flaws, they continue to be used as primary tools for the assessment of drought conditions. From an agricultural point of view, it is well known that each crop responds differently to conditions of moisture stress. The PDSI and CMI, however, do not take into account different crops' response to drought. The purpose of this study was to develop and evaluate a drought index for corn (Zea mays L.). A principal components analysis showed that the PDSI and CMI related well to actual yield when precipitation was consistently above or below normal throughout the growing season. However, these indices were poor estimators of agricultural productivity during years that started out dry and turned wet, or vice-versa. A Crop Specific Drought Index (CSDI) for corn was developed such that, at any point during the growing season (following the 12 leaf stage) an estimate of potential yield could be generated. The model was derived using nine years of data, 1972-1980, from one climatic division in each of the following states: Nebraska, Missouri, Wisconsin, and Indiana. The model derives an index value based on the ratio of transpiration to potential evapotranspiration for the crop (T/ET$\sb{pc}$). The relative impact of moisture stress during each of these growth stages is defined by a sensitivity coefficient ($\lambda$). The model fit resulted in D-index of agreement values of 0.995 for Nebraska, 0.975 for both Missouri and Wisconsin, and 0.941 for Indiana. Model validation was examined through a statistical analysis using an independent data set from the 1981-1988 growing seasons. Model-predicted CSDI values were systematically low due to poor partitioning of ET into its evaporation and transpiration components. An improved repartitioning scheme led to improved model-predicted CSDI values.
Subject Area
Agronomy
Recommended Citation
Meyer, Steven J, "The development of a crop specific drought index for corn" (1990). ETD collection for University of Nebraska-Lincoln. AAI9030138.
https://digitalcommons.unl.edu/dissertations/AAI9030138