Mark D. Rath

Document Type

Thesis - University Access Only

Award Date

1994

Degree Name

Master of Science (MS)

Department / School

Agricultural Engineering

First Advisor

Darrell W. DeBoer

Abstract

Combination subsurface irrigation/drainage (irridrain) systems represent a water management concept that has potential application in areas where crop stress is primarily caused by a lack of soil water. An aspect that needs to be considered in determining this potential is the economic feasibility of this system. DRAINMOD, a computer model, was modified to simulate crop water use in semi-arid environments and used to simulate the water balance of corn for irridrain scenarios in the northeastern and southeastern parts of South Dakota. A relationship between corn grain yield and a water stress index (Percent Yield Reduction= 5.07 * Water Stress Index, R2 = 0.81) was developed from field data and was combined with potential and actual evapotranspiration (ET) values, as calculated by the modified DRAINMOD, to estimate corn yields. The relationship was checked against reported field data from Spink County in northeastern and Union County in southeastern South Dakota. Predicted dryland yields corresponded closely with actual dryland yields for Spink County where the relationship data were collected. Actual and predicted yield responses were not highly correlated for Union County when a remote climatic data set from Concord, NE was used to simulate crop yield response. Irridrain system simulations were made utilizing the modified DRAINMOD computer model and data sets for four soils and the Redfield, SD climatic data. The percent yield reduction relationship was used to determine tile line spacings for the different soils which produced minimal yield reductions. Estimated acceptable tile spacings were < 9.1 m (30 ft) for the Pierre Clay, ≤ 18.3 m (60 ft) for the Great Bend silt loam, ≤ 54.9 m (180 ft) for the McPaul silt loam and ≤ 91.4 m (300 ft) for the Ulen fine sand. Economic analyses were performed for a combination subsurface irrigation/drainage system, a center pivot sprinkler irrigation system and a dryland (non-irrigation) system. A comparison of the two irrigation systems showed the subsurface irrigation/drainage system to be economically competitive under certain conditions. Some conditions shown to be favorable for the subsurface irrigation/drainage system were: low interest rates of 8 percent; low tile installation costs of $1.64 per meter ($0.50/ft) and installation into coarse silt loam or fine sandy loam soils, where wider drain line spacings (> 18.3 m (60 ft)) could be utilized, rather than finer textured soils. A subsurface irrigation/drainage system was found to be competitive with a dryland system particularly when higher yield levels, ≥ 11.0 t/ha (175 bu/ac), would be realized by the subsurface irrigation drainage system. Other conditions that were indicated as being favorable to the subsurface irrigation/drainage system were: low interest rates of 8 percent, low tile costs of $1.64/m ($0.50/ft) and wide tile spacings, ≥18.3 m (60 ft), as allowed with coarse soil types such as McPaul silt loam and Ulen fine sands. Fine silt loams could be utilized when other favorable factors were also considered such as low interest rates of 8 percent, high corn prices of $94.54/t ($2.40/bu) and low tile installation costs of $1.64/m ($0.50/ft).

Library of Congress Subject Headings

Irrigation -- South Dakota -- Management -- Computer simulation
Drainage -- South Dakota -- Computer simulation
Water table -- South Dakota -- Management -- Computer simulation
DRAINMOD

Format

application/pdf

Publisher

South Dakota State University

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In Copyright