Date of Award
Master of Science
Agricultural and Biosystems Engineering
Crop models have emerged as a method to evaluate different crop management practices such as irrigation without costly and time-consuming onsite experiments. A decision support system called APOLLO has been developed in past years to assist researchers in using the CERES-Maize crop model to simulate precision farming methods for corn. Past experiments have used APOLLO to develop precision population and nitrogen application prescriptions for maximum yield. In this work, an additional module was created for APOLLO to automate spatially variable irrigation scenarios. This module has the capability of simulating blanket scheduled uniform irrigations or precision irrigations based on percent of available soil water. In a Windows-based interface, the user can input desired irrigation application efficiency, irrigation amount, and threshold and management depth used for automatic applications. The module was successfully tested using several years of data and various schedules, application thresholds, irrigation amounts, and management depths. This simulation may be a very powerful tool in studying irrigation feasibility, deficit irrigation, and varying irrigation management strategies. Few studies have been done considering the possibility of irrigation systems in Iowa or other humid regions. Recent technological progress in precision agriculture may allow irrigation in these areas to become more economically feasible. In this study, the newly developed irrigation module in the APOLLO program was used to evaluate potential improved yield in a central Iowa cornfield on a spatially and temporally variable basis. Five years of historical yield and weather data were used to calibrate the model for the 20.25 ha field over 100 spatially variable grids. This calibrated model then used 28 years of historical weather data to simulate three irrigation scenarios: no irrigation, scheduled uniform irrigation, and precision irrigation. 30 mm irrigations were applied when the percent of available soil water fell below 50 percent. Irrigation improved yield by at least 1000 kg ha−1 in half of the years simulated, and also showed to have less variability both spatially and temporally. Precision irrigation showed slightly higher yields than scheduled uniform irrigation. Spatial variability of yield was most influence by topography, with the largest improvements occurring on steep sideslopes and hilltops. Assuming use of a center pivot irrigation system, irrigation showed economic returns in only three of the 28 years included in the study. High capital costs were the leading restrictor of economic feasibility.
Kendall Craig DeJonge
DeJonge, Kendall Craig, "Development and utilization of irrigation simulation with CERES-Maize in a central Iowa cornfield" (2006). Retrospective Theses and Dissertations. 19391.