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Crop Response to Soil Water Potential and Drip Irriagation System Design
|dc.contributor.author||Thomas, Jureerat K.|
|dc.description.abstract||Models of water movement for drip irrigation have been proposed as a means of incorporating soil hydraulic properties into the design of drip irrigation systems (Bresler, 1978; Warrick et.al., 1979). The crop component of these models has been represented by an arbitrary choice of the soil water potential at a point near the soil surface, midway between irrigation lines or emitters. The purpose of this research was to evaluate the use of the single midway soil water potential value or, alternatively, spatially integrated potential values in the root zone, by correlation with crop yield response. Another objective was to examine the adequacy of the Warrick model (1981) for prediction of wetting patterns. The field experiment was conducted on a silty-clay (Typic Torrox) soil in Hawaii. Three treatments were subjected to different soil water potential distributions, which resulted from line-source spacing of 50, 100 and 150 cm. Sweet corn (Zea mays L.) was planted in rows spaced at 50 cm in all treatments. Soil water potential was measured at four depths and four distances from the line source using tensiometers and a pressure transducer. Three methods of integrating the soil water potential over space and time were used to calculate the representative values of soil water potential. Results showed the impact of line source spacing on soil water potential distributions and crop yield. The soil water potential and crop yield decreased with increasing line source spacing. The integrated values of soil water potential using simple averaging and the Taylor (1952) method were highly correlated with crop yield, as compared to the Karamanos (1980) method. The single midway soil water potential and the representative value at the 15-cm depth were well correlated with crop yield, suggesting that this simple representation of crop water requirement may be useful in practical irrigation system design. The integrated values of soil water potential over all depths and over time also correlated well with crop yield. The Warrick model predicted narrower ranges of soil water potential variation in comparison with field-measured potentials. Even so the model represented soil water potential distributions sufficiently well to be useful in drip irrigation system design.|
|dc.title||Crop Response to Soil Water Potential and Drip Irriagation System Design|
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Ph.D. - Agronomy and Soil Science|
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