Date of Award

1991

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Engineering Science (Interdepartmental Program)

First Advisor

Richard L. Bengtson

Abstract

A study was conducted to determine the actual evapotranspiration of sweet corn in a warm, humid climate. Sweet corn was grown in six lysimeters at Louisiana Agricultural Experimental Station's Ben Hur Research Farm located 6 km south of Louisiana State University, Baton Rouge, Louisiana. A water balance was measured over three corn growing seasons for the following three soil moisture regimes: No irrigation or drainage (SMR1); No irrigation but drainage as needed (SMR2); and irrigation or drainage as needed (SMR3). The average actual evapotranspiration from SMR1, SMR2, and SMR3 over three seasons were 192 mm, 202 mm, and 304 mm respectively. The maximum total actual ET under soil moisture treatment SMR3 was 352 mm. Irrigation increased actual evapotraspiration during a dry season. Potential evapotranspiration was estimated using the Modified Penman model, Hargreaves model, Thornthwaite model, and evaporation pan. By comparing the potential evapotraspiration of these three models with pan evaporation based on monthly values, mean monthly values for the period Jan 1981-Sept 1990, it was concluded that Modified Penman model was the most reliable model for estimating potential evapotraspiration for Southern Louisiana. A pan coefficient of 0.92 was calculated with $\pm$0.032 std. error. A crop growth stage coefficient curve for sweet corn was developed for Southern Louisiana. This curve did not differ significantly from the already published USDA-SCS curve 5 (1970). Actual evapotranspiration (ET$\sb{\rm act}$) can be determined at any growth stage of sweet corn by applying the following relationship: ET$\sb{\rm act}$ = 0.92 * Kc * E$\sb{\rm pan}$ where Kc is crop coefficient, and E$\sb{\rm pan}$ is pan evaporation in mm/day. Irrigation significantly increased the growth (height), dry matter yield (kg/ha) and marketable yield (number of ears/ha) during a dry season. Also, a linear relationship was found between the dry matter yield (kg/ha) and the total actual ET (mm) which shows that dry matter increased 57.32 kg/ha for each 1.0 mm increase in actual ET.

Pages

265

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