"Professor Tom Fernandez is improving the efficiency of water resource management in greenhouses and nurseries."

Jack Falinski describes this event in a press release from Michigan State University.

Tom Fernandez, a horticulture professor at Michigan State University, has dedicated much of his 25-year career to studying effective water resource management in greenhouses and nurseries to improve water use efficiency and reduce nutrient leaching.

Fernandez developed management strategies to ensure that agricultural resources such as fertilizers and pesticides do not infiltrate the environment and degrade water quality.

According to the US Environmental Protection Agency, around half a million tons of pesticides, 12 million tons of nitrogen, and 4 million tons of phosphorus fertilizers are introduced into the soil annually. The runoff of these substances has a negative impact on water quality.

In greenhouses and nurseries, many plants are easily leached due to the characteristics of their containers, which allow water to flow freely. Fernandez found that using plant-based water consumption as a basis can reduce irrigation by 30-80% depending on the species, helping farmers conserve water and reduce nutrient leaching from the soil.

In addition to reducing nutrient leaching from fertilizers such as nitrates and phosphates, Fernandez also studied how to reduce the movement of pesticides from the soil to non-target areas.

Pesticides are typically sprayed onto plant surfaces, leading to their penetration into interspaces between plants or ground cover crops in greenhouses and nurseries. When overhead irrigation occurs, pesticides can move with water and negatively affect water quality.

Fernandez notes that supplying less water to plants can help reduce the movement of pesticides in the soil. For instance, micro-irrigation of individual pots using sprinkler stakes significantly reduces pesticide runoff.

"We have enough time regarding nutrients and pesticides. The longer we prevent their entry into water systems, the more opportunities the biological environment has to correct potential problems," Fernandez said.

These strategies provide a better understanding of how to water container plants without causing leaching. Currently, Fernandez is studying water purification methods used in agricultural production to assess the amount of nutrients and pesticides in water after application.

Since 2018, Fernandez and Gemma Reger, deputy dean of the College of Natural Sciences at Michigan State University and professor of microbiology, genetics, and immunology, have been researching how nutrients from fertilizers interact with bioreactors and how well bioreactors remove nutrients from water used in greenhouses. The study started with former Fernandez graduate student Damon Abdi, who is now an assistant professor in horticulture at Louisiana State University.

Externally, bioreactors are large barrels filled with wood shavings. Fernandez notes that in the first stage of the bioreactor, wood shavings convert nitrates into nitrogen in gaseous form, while in the second stage, clay provides a larger surface area for binding phosphorus from phosphates.

Studies have shown that over 95% of nitrates and 80-87% of phosphates can be removed as water passes through the bioreactor. Fernandez and his team found that most of the activity occurs in the wood shavings, so the second stage of the bioreactor using clay was discontinued.

Many greenhouses and nurseries operate with closed water supply systems where water is stored and reused. Fernandez reports that bioreactors can remove 90-100% of nutrients from water for reuse in production and reduce pesticide levels in water by 30-75%, depending on their mobility.

"In our laboratory experiments, we found that by reducing the time water spends in the bioreactor, we can retain nutrients and reduce the amount of pesticides in the water," Fernandez notes.

Amy Appleton, Executive Director of the Michigan Nursery and Landscape Association, notes that Fernandez's research results help agricultural and nursery businesses market their products based on ecological practices. Fernandez’s team also provides practical demonstrations for evaluating and implementing these technologies.

Research has been ongoing for the third year, monitoring the operation of bioreactors in a large-scale greenhouse operation.

Fernandez notes that they use 300 and 600-gallon tanks as bioreactor containers, and the breakdown of pesticides in anaerobic and aerobic conditions is currently being studied.

“As far as I know, this is the first instance of using such systems in commercial greenhouses,” Fernandez said, expressing hope that the information obtained will help improve the efficiency of pesticide removal from water.