Episode 44 - The Vadose Zone - A critical indicator for Nebraska groundwater quality

The vadose zone is the area between crop roots and the water table, and is a critically important region for storage, transport and transformation of chemicals that can impact groundwater quality. In this episode of the Water for Food Podcast, host Frances Hayes talks with Arindam Malakar, a researcher with the Nebraska Water Center (NWC, a part of DWFI) who studies Nebraska’s vadose zone and monitors the impacts of irrigation and fertilizer on groundwater.

Hayes is also joined by Marie Krausnick, assistant general manager for Nebraska’s Upper Big Blue Natural Resources District (NRD). The Upper Big Blue NRD and other NRDs across the state have partnered with the University of Nebraska-Lincoln and the Nebraska Water Center in researching nitrate concentration in their districts. While nitrate levels in some areas have decreased in the Upper Big Blue NRD, there has been an overall increase of 54% in the district.

In Nebraska, as in many parts of the world, one of the key chemicals monitored in the vadose zone is nitrate. Nitrogen is a critical plant nutrient, but once it sinks below the roots and enters the vadose zone, it becomes a liability: both an economic loss for the farmer and a potential public health risk for some rural communities where wells have not been recently tested. Excess nitrate in drinking water can cause adverse health effects, particularly in infants and vulnerable populations, as too much nitrate in the body makes it harder for red blood cells to carry oxygen. Contaminants, like nitrates, present in the vadose zone can eventually appear in the underlying aquifers. NWC takes soil cores all the way down to the groundwater table, sometimes over 100 feet, and tests them for nitrate and other contaminants. These cores are crucial for understanding how water and chemicals move through the soil and potentially reach groundwater. They can also be useful in predicting water quality issues. The Nebraska Water Center Water Sciences Lab has collected vadose cores for decades. To increase the usability of all this data, they launched the Nebraska Vadose Zone Program online portal in 2015 with funding from the Nebraska Environmental Trust, Nebraska Department of Environment and Energy (now the Nebraska Department of Water, Energy, and Environment), and several Natural Resources Districts (NRDs).

In the 43rd episode of the Water for Food Podcast, host Frances Hayes speaks with Claudia Ringler of the International Food Policy Research Institute (IFPRI) about the crucial link between irrigation and global health, expanding on Ringler's recent Heuermann Lecture as part of the 2025 Water for Food Global Conference and previous episodes in this podcast. Together they explore how irrigation can improve health outcomes while also addressing potential unintended negative impacts and how to avoid them when designing irrigation solutions. The conversation highlights successful irrigation projects, strategies for ensuring access to irrigation for beneficial outcomes like decreased malnutrition and improved hygiene, and necessary policy changes and international collaborations to maximize positive health impacts globally.

This special episode of the Water for Food Podcast commemorates the 15th anniversary of the Daugherty Water for Food Global Institute by sharing the story of its origin. Read the full historical account here.

The 15th anniversary year will be highlighted by a celebration reception at the upcoming 2025 Water for Food Global Conference, held in Lincoln, Nebraska, April 28-May 2. Learn more at waterforfood.nebraska.edu.