The future climate for Indiana is projected to become wetter and warmer during the winter/spring as well as hotter and drier in the summer with more intense precipitation events. This contributes to greater water export through subsurface drainage and associated nutrient loads, which can overwhelm local drainage systems, increase export of nutrients to receiving streams and delay field operations. The direct effects on agriculture lie at this intersection where crops experience both excess water and deficit water stresses with increasing frequency and magnitude (Bowling et al., 2018). The potential for greater intra-annual variability is also evident in the occurrence of extreme drought years followed by years with high rainfall and flooding (Loecke et al., 2017).
Although irrigation is not widespread in Indiana, in many years supplemental irrigation later in the growing season can provide a small yield advantage. According to the Indiana values reported in the four USDA Farm and Ranch Irrigation Surveys completed between 1998 and 2013, irrigated soybean yields were 9.9% higher, on average than non-irrigated yields. Following the 2012 drought, there was a surge in investment in irrigation infrastructure for Indiana farms. Most of these systems rely on a groundwater source tied to an overhead sprinkler system, but there are some locations in Indiana with very limited access to groundwater.
The overall goal of this research is to establish if additional research is warranted to quantify the potential crop yield and water quality benefits and ultimately the economic viability of utilizing recycled drainage water to irrigate soybeans in West Central Indiana, based on one year of data collection. This will be accomplished utilizing a small demonstration drainage water recycling system installed at the Agronomy Center for Research and Education (ACRE) in West Lafayette, IN. This system makes use of an existing three-acre wetland area located on the ACRE property, which has been modified to receive subsurface drainage from approximately 175 acres of the farm. To address this goal, we will complete three specific objectives.
First, we need to establish the irrigation infrastructure at the Oaks’ Woods Wetland. A water control structure at the wetland outlet is scheduled for installation in Fall 2020, with funding through the USDA Transforming Drainage program, to manage water levels for water quality and ecosystem benefits. With this project, we propose to install a surface sprinkler irrigation system which pumps stored drainage water from the wetland to irrigate a soybean experiment. The second objective is to monitor differences in soybean growth and water stress for different levels of irrigation. In-situ measurements of crop phenology will be coupled with bi-weekly unmanned aerial systems (UAS) surveys to quantify differences in above-ground biomass and crop water stress for different growth stages in irrigation plots. These measurements will contribute to analysis of the contribution of irrigation to potential yield differences between the plots. Soil water and evapotranspiration will be monitored to guide the irrigation events and differences in treatments.
In addition, it is necessary to quantify the reduction in downstream nutrient loads out of the Oaks’ Wood Wetland. The wetland receives drainage water from ACRE through two culverts and water is discharged through an outlet channel to a tributary to Indian Creek. Discharge and nitrate and soluble reactive phosphorus have been monitored for the last ten years. Continued monitoring of these inlet and outlet channels during irrigation will allow us to calculate the annual reduction in nitrate and SRP load associated with this practice. Given the challenges Indiana producers and drainage districts face in managing excessive spring drainage needs and summer dryness, the idea of capturing excess drainflow and storing it for summer use makes a certain logical sense. As an added advantage, reusing this nutrient-rich drainage water allows producers to increase nutrient use efficiency by reapplying it to their fields, enhancing environmental stewardship. Unfortunately, construction of storage reservoirs is very expensive. This project will allow us to begin to quantify the feasibility of implementing DWR for soybeans in Indiana to facilitate future investment in this practice.