The Wisconsin Central Sands (WCS) exemplifies the scientific and political trajectory that the expansion of irrigated agriculture will take in the Midwest, especially in regions with unconfined glacial aquifers, prized aquatic ecosystems, and coarse agricultural soils. The WCS irrigates 80,000 hectares of corn, potato, pea, and bean crops, which require over 335 billion liters of groundwater to support a $450 million industry. WCS residents and tourists value these surface waters as ecosystems that support fishing, swimming, biodiversity, and spirituality. Prophetic hydrological studies in the late 1960s warned of future impacts to WCS surface waters if aquifer development for agriculture persisted, but these warnings went unheeded and the number of high-capacity wells in Wisconsin increased exponentially from less than 50 in 1960 to over 3800 in 2013, with the majority located in the WCS.
There is a great need to manage consumptive groundwater use in the WCS in order to maximize crop water use efficiency (WUE), while maintaining healthy aquatic resources. Growers currently have two relatively untapped resources available to improve their WUE and reduce consumption of groundwater for irrigation: precision irrigation and irrigation scheduling.
Central Wisconsin’s need to increase crop WUE and protect its water resources in the face of a changing climate has outgrown the mainstream practice of subjectively irrigating based on intuition and experience alone. With projected changes in climate, precipitation will be distributed as sparser, heavier rain events that are less likely to be captured by the crop root zone. To build more resilient agricultural and freshwater ecosystems in a changing climate, WCS growers need evidence-based tools to face the challenge of growing more food with less water.
This research project, through a combination of grower participation, irrigation scheduling, field measurements and two numerical models, will address the following questions: (1) how much groundwater savings and WUE improvement occur through implementing precision and irrigation scheduling strategies? (2) How accurate is the Wisconsin Irrigation Scheduling Program (WISP) at simulating water loss below the root zone, and do more complex agroecosystem models (Agro-IBIS) perform better? (3) Given that many fields in the WCS have similar sandy soils with high hydraulic conductivity and low plant available water, how much intrafield delineation is required for precision management? We are in a uniquely qualified position to address these questions given the following recent accomplishments: (1) We can directly measure coupled water and carbon budgets in the WCS through a network of 25 lysimeters already installed (2013) and field tested in a companion project; (2) We have a long-term collaboration with a grower (Isherwood Farms) who is highly enthusiastic about implementing the best irrigation management practices; (3) We have previously mapped apparent soil electrical conductivity (EC), delineated intrafield water management zones, performed soil particle size analysis (PSA), and collected biophysical data from six fields to inform our proposed experimental design, objectives, and hypotheses; and (4) our research group is at the forefront of agroecosystem model development and implementation.
Lead scientists: Mallika Nocco, Kevin Masarik, Elizabeth McNamee, Cadan Cummings, and Chris Kucharik.