Characterizing A Crop Water Stress Index For Predicting Yield in Corn

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Title: Characterizing A Crop Water Stress Index For Predicting Yield in Corn
Author: Meijer, Alan David
Advisors: John W. Van Duyn, Committee Member
Hugh A. Devine, Committee Co-Chair
Ronnie W. Heiniger, Committee Chair
Abstract: The purpose of this research was to develop a Crop Water Stress Index (CWSI) for conditions in North Carolina and use it to study the spatial characteristics of water stress and predict grain yield in corn (Zea mays L.). CWSI readings were taken from plots in two locations throughout the growing season in 2001. Due to lack of water stress, an upper water-stressed baseline could not be calculated and a published baseline of +4.6oC was used. Lower non water-stressed baselines were calculated from the data for each date. A seasonal baseline was also calculated from the pooled data. Analysis showed that the individual baselines for each date were not significantly different from the seasonal baseline in most cases. Also, the seasonal baselines for each location were not significantly different from each other. Variography analysis was performed on data from 2001 and 2002 to study the spatial characteristics of water stress at a field scale. Spatial models were fit to the data in most cases. The range tended to increase late in the season, while the proportion of variability due to location tended to decrease. To accurately capture the spatial variability of water stress prior to the sidedress nitrogen application, samples would have had to be taken at intervals of 15 m or less. However, slightly larger intervals would be required when soil water was limiting. A location by water interaction tended to influence CWSI, as did a main nitrogen treatment effect. Plants with preplant nitrogen applied had lower CWSI values than plants without. Plants with 0 kg N ha-1 before planting that received 224 kg N ha-1 at sidedress, showed a significant drop in CWSI. Grain yield was negatively correlated to CWSI, showing that as CWSI increased, grain yield decreased. At Lewiston in 2002, CWSI measured on 26 June was able to account for 86% of the variability in corn yields.
Date: 2005-03-01
Degree: MS
Discipline: Crop Science

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