Kelsey Kolars is an M.S. graduate student in the Agricultural and Biosystems Engineering (ABEN) program at North Dakota State University (NDSU). She holds a Bachelors of Science degree in Mathematics from NDSU. Kelsey is researching the relationship of water tables to crop water consumption by measuring water table levels, soil moisture, irrigation and drainage variables, and weather data. She will incorporate her findings into a new application for subsurface drainage and subirrigation water management.
Development of a Model for Subsurface Drainage and Subirrigation Water Management Decisions
Fellow: Kelsey Kolars
Advisor: Xinhua Jia, Ph. D., P.E., Associate Professor, Department of Agricultural and Biosystems Engineering, North Dakota State University.
Degree Progress: M.S. in Agricultural and Biosystems Engineering, expected graduation in fall 2014.
In the Midwest, shallow water tables caused by excess precipitation and poor drainage conditions have the potential to increase soil salinity and water logging, and make field trafficability difficult (Guitjens et al., 1997; Skaggs et al., 2010). Lately, the negative impacts of shallow water tables have been seen in the Red River Valley (RRV), which is in large part due to a wet weather cycle since 1993 (Jia et al., 2012). This wet weather cycle has encouraged the installation of subsurface drainage systems (SSD), which help to remove excess water from the soil profile and make trafficability with heavy machinery easier during planting and harvest.
However, these SSD systems have been shown to have a negative impact on water quality by increasing the amount of nitrates and soluble salts in the outflow compared to surface runoff alone (Jia et al., 2012; Skaggs et al., 2010). Thus, an emphasis has been put on controlled drainage (CD) and subirrigation (SI) systems for their ability to not only reduce outflow by keeping water in the field in late spring, but also allow for subirrigation when it is needed by crops. Even though a CD + SI system has many benefits, its success relies heavily on proper management. One potential management option involves the inclusion of SSD, CD, and SI in the Checkbook Method for Irrigation Scheduling.
The Checkbook Method for Irrigation Scheduling is a popular and relatively simple method developed at NDSU and used in the upper Midwest to help with irrigation management decisions (Steele et al., 2010). However, the Checkbook Method is meant for use with an above ground sprinkler irrigation system and does not consider drainage outflow through a SSD system. Thus, the development of irrigation efficiency for a SI or CD + SI system would be helpful when it comes to determining the time and amount of irrigation water needed to reach field capacity. The introduction of SI and SSD in the Checkbook Method would allow the landowner to better manage the soil moisture deficit so that the field remains at optimal moisture conditions. In the end, the results of this study will allow a better understanding on the effects of a shallow water table on crop water consumption and, as a result, assist in the development of better management plans using the modified Checkbook method for a CD + SI system. Benefits of a better management plan for a CD + SI system consist of increased yields, improved water quality, and reduced pumping costs.
The research project will focus on subsurface drainage and subirrigation water management by modifying the Checkbook irrigation method. The specific objectives of the study are to:
A CD and CD + SI system was installed in the spring of 2012 and both systems were used over the 2012 growing season. In the CD and CD + SI fields, 12 piezometers were installed in the fall of 2011 and water level loggers have been placed in each well during the 2012 growing season. In the CD + SI field, an eddy covariance and wireless weather stations have been set up and collect soil moisture, ET, wind speed, soil temperature, relative humidity, air temperature, and rain/snowfall data. In the CD field soil moisture sensors have been installed at six different depths to record soil moisture changes with respect to different water management practices and varying weather conditions. In 2013, the CD and CD+SI fields switched (i.e. the CD field became CD + SI and the CD + SI field became CD) as well as their associated instruments.
Over the summer of 2013, Kelsey presented a poster and wrote a conference paper titled “Using eddy covariance, soil water balance, and photosynthetically active radiation methods for corn evapotranspiration measurements in the Red River Valley” for the 2013 ASABE Annual International Meeting in Kansas City, MO. The paper not only presents comparisons among the three evapotranspiration (ET) methods (Photosynthetically Active Radiation (PAR), Eddy Covariance (EC), and Soil Water Balance (SWB)), but also ET comparisons among four water management practices (WMP) and two corn varieties. It was found that ET estimates through PAR and EC methods were well correlated with a coefficient of determination (R2) of 0.94 and root mean square error (RMSE) of 0.02 mm/30min. On the other hand, the ET estimates through SWB and EC methods showed little to no correlation. When comparing ET estimates among four different WMP’s it was found that ET rates were similar over all WMP’s. This was partially due to the abnormally dry growing season in which the water table remained below 6 ft the entire season, hence subsurface drainage systems had little effect on the water balance. In addition, no visible difference was seen among ET estimates for the two corn varieties.
Currently, the research has continued through the 2013 growing season. There has already been markedly different field conditions between the 2012 and the 2013 growing seasons, with 2013 being much wetter than 2012. Hence, 2013 data should provide good comparisons between dry and wet growing seasons along with varying WMP’s.
Regular updates on field activities/progress can be found at http://aben-saregrant-ndsu.blogspot.com/
The application and installation of SSD, CD, and SI systems in the RRV has dramatically increased over the last decade. With this increase also comes an increased need for a better understanding of how to optimally manage these systems. An increase in yield is seen along with a decrease in nitrate loadings and soluble salts to surrounding surface waters with these systems. By incorporating net irrigation and drainage into the Checkbook method, the landowner is given a simple, familiar, and effective tool to manage their system.
Xinhua Jia, Ph.D., P.E.