Agronomy and Horticulture, Department of


Date of this Version

Fall 12-2010


A THESIS Presented to the faculty of The Graduate College of the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Master of Science, Major: Agronomy, Under the Supervision of Professors Drew J. Lyon and Timothy J. Arkebauer. Lincoln, Nebraska: December, 2011

Copyright (c) 2011 Juan Jose Miceli-Garcia


In the Central Great Plains, the predominant crop rotation is winter wheat (Triticum aestivum L.)-fallow. Producers are looking to add diversity and intensity to their cropping systems by adding summer crops, however, the elimination of summer fallow may increase crop production risk. The objective of this study was to use crop simulation modeling to compare the productivity of two fixed rotations [winter wheat-corn (Zea mays L.)-fallow and winter wheat-corn-spring triticale (X Triticosecale Wittmack)] with simulated flexible fallow rotations. The flexible fallow rotations made the decision to plant triticale or use summer fallow prior to winter wheat seeding based on available soil water in spring. Data from three years of field studies at two sites, Sidney, NE and Akron, CO, were used to calibrate and test the model, AquaCrop, for the crop simulation. Twenty-three years of historical weather data from each of the two locations were used to simulate crop production for each rotation. Average income was improved by replacing summer fallow with triticale (from 120 to 160 US $ ha-1 for Akron and from 126 to 199 US $ ha-1 for Sidney), but income variability (standard deviation) also increased (from 73 to 84 US $ ha-1 for Akron and from 93 to 115 US $ ha-1 for Sidney). Risk-averse growers are likely to always use fallow in their crop rotations prior to planting winter wheat, while non-risk-averse growers will likely eliminate fallow and substitute triticale or a similar early-planted spring forage. Flexible fallow rotations seldom improved profits compared to always using fallow without also increasing income variability. The exception was Sidney using the 400 mm soil water threshold, which lowered income variability compared to always fallowing (from 93 to 91 US $ ha-1) and increased average income (from 126 to 142 US $ ha-1). However, the economic benefits of flexible fallow compared to the two fixed cropping systems were minimal.

Advisers: Drew J. Lyon and Timothy J. Arkebauer.