Degree Type


Date of Award


Degree Name

Master of Science


Agricultural and Biosystems Engineering


Agr icultural and Biosystems Engineering

First Advisor

Matthew Helmers


Drainage water recycling is a sparsely studied agricultural management practice which has the potential to both improve yields and reduce adverse water quality effects of row crop agriculture. This practice captures and stores subsurface drainage from agricultural fields for supplemental irrigation. This study seeks to understand how drainage water recycling effects long-term continuous corn (Zea mays L.) yields in Central Iowa, and what economic impact those effects might have. The Agricultural Production Systems sIMulator (APSIM) was used to create a 40-year simulation. This was based on 6 years of field data and local historical weather data. Three annual irrigation water availability scenarios were modeled, each under both baseline and climate change weather conditions. Under baseline weather conditions, the practice resulted in average yield benefits between 19 and 22 bushels per acre. These values rose to 23 to 28 bushels per acre under climate change conditions. This shows drainage water recycling is capable of increasing long-term corn yields in Central Iowa. After determining ownership and operation costs (excluding the cost of land and construction for a storage reservoir), two corn price models were used to estimate profitability of drainage water recycling. These showed a wide range of returns (-$39/ac/yr to $0/ac/yr) in baseline weather conditions. The system becomes more cost effective ($-31/ac/yr to $23/ac/yr) in the modeled climate change scenario. Proper irrigation scheduling is also shown to be a critical factor in utilizing drainage water recycling to turn a profit. With proper design and management, drainage water recycling can add resiliency to continuous corn cropping systems in Central Iowa.


Copyright Owner

Samuel Phillips



File Format


File Size

49 pages