Title: Understanding and simulating spatial soil water and yield variability in an irrigated soybean field
Full Citation
Permanent Link: http://ufdc.ufl.edu/UF00100707/00001
 Material Information
Title: Understanding and simulating spatial soil water and yield variability in an irrigated soybean field
Physical Description: xvi, 151 p.
Language: English
Creator: Nijbroek, Ravic, 1973- ( Dissertant )
Jones, J. ( Thesis advisor )
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 1999
Copyright Date: 1999
Subjects / Keywords: Agricultural and Biological Engineering thesis, M.E   ( lcsh )
Dissertations, Academic -- Agricultural and Biological Engineering -- UF   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
bibliography   ( marcgt )
theses   ( marcgt )
non-fiction   ( marcgt )
Abstract: When investigating how agricultural profits can be maximized while minimizing the impact on the environment, it may be necessary to study management practices from a systems approach. In this research, five different irrigation management strategies were analyzed using the CROPGRO-Soybean crop simulation model. The 12.6 ha irrigated soybean research site was located in Crestview, Georgia. One of the most critical factors when using simulation models is the accuracy of input parameters used. The most yield-limiting factor for soybeans in many locations is drought stress. Therefore, the most critical model input parameters are the soil water holding limits and amounts of water applied during the growing season. In a selected location the soil water holding limits were measured using time domain reflectometry and 1500 kPa pressure plate chambers. The time domain reflectometry time series data were used to estimate the drained upper limits in the middle of the growing season when plant roots were actively removing soil water. This new method was based on nighttime drainage rates in consecutive soil layers. The pressure plate analysis was used for the estimation of the lower limits. The field observations were used to select a soil parameter estimation method that best predicted the soil water holding limits. This method was used to estimate the water holding limits in five predetermined management zones in the remainder of the field. The simulated irrigation schedules of those management zones with the earliest sign of stress, largest area, and highest yield were used to simulate irrigation over the entire field. In addition, the field was irrigated according to an optimal irrigation for each zone. The total field production, water used, water drained, and gross margins were calculated to compare the irrigation management options. The time domain reflectometry data were successfully used with the pressure plate analysis to estimate 84 mm of plant available soil water in the soil profile. The Rawls soil parameter estimation method best approximated these results (78 mm of plant available water). The 25-year field scale simulations indicated that spatially variable irrigation resulted in the highest average field production (33.5 metric tons). Irrigation management according to the highest yielding zone used the least amount of irrigation water and had the lowest drainage as well (23.4 and 14.6 million liters respectively). The spatially variable irrigation management strategy resulted in the highest average gross margin ($6919 using $6 per bushel and $2 per hectare-cm). However, this gross margin value was statistically different from the other management options for this field.
Subject: spatial variability, plant available soil water, soil water, precision farming, precision agriculture, variable rate irrigation, time domain reflectometry, TDR, CROPGRO, CROPGRO-soybeans, soil water limits, drained upper limit
Thesis: Thesis (M.E.)--University of Florida, 1999.
Bibliography: Includes bibliographical references (p. 148-150).
System Details: System requirements: World Wide Web browser and Adobe Acrobat Reader to view and print PDF files.
System Details: Mode of access: World Wide Web.
Statement of Responsibility: by Ravic Nijbroek.
General Note: Title from first page of PDF file.
General Note: Document formatted into pages; contains xvi, 151 p.; also contains graphics.
General Note: Vita.
 Record Information
Bibliographic ID: UF00100707
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 45261190
alephbibnum - 002531481
notis - AMP7403


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