October 2017

Recycling fertilizer? South Dakota State researchers test ways to reduce and reuse runoff from farms

October 17th, 2017

What if you could capture the fertilizer that washed away with the rain and reuse it on your field? A pair of South Dakota State University professors is studying a way to do just that.


Dr. Laurent Ahiablame, from the department of agricultural and biosystems engineering, teamed up with Dr. Srinivas Janaswamy, from the department of dairy and food science.


Ahiablame has worked with edge-of-field nutrient removal methods, namely the woodchip-filled pits known as bioreactors. Bioreactors use microbes and a carbon source to “eat away” the nitrogen that moves with the runoff through the field’s tile drainage system. “They’re a proven technology to improve water quality,” Ahiablame said.


The microbes release nitrogen into the air as a gas and keep it from polluting lakes and rivers, but Ahiablame wondered if there was a way to capture the nutrient and take it back to the field.


Janaswamy had an idea from the food industry. He believes products used to thicken foods such as salad dressings and ketchup could be used to absorb nutrients like nitrate and phosphorus.


The thickeners in the form of beads – fully biodegradable polysaccharides – would help clean runoff water, but they have another major benefit beyond what bioreactors do today. The tiny beads could be spread across the field where it would release the fertilizer again, this time for the plants’ benefit.


“Humans have been using polysaccharides as gelling and thickening agents for generations,” Janaswamy said.


He’s encouraged at the thought that these biomaterials could be used to help farmers feed the world in a way that’s friendlier to the environment and less expensive for producers.


“That is what we are dreaming,” he said.


The professors aren’t sure it will work like they hope, but studies on the beads over the coming years will help determine if it’s possible. The project recently received funding through a new state program.


Money for the project comes from a 50-cent increase in the fertilizer inspection fee. The Legislature approved the new program in 2016, and the South Dakota Nutrient Research and Education Council (NREC) awarded its first round of funding this summer. It’s meant to help improve environmental and water quality through better agricultural practices.


“The main driver is sustainability,” said Bill Gibbons, interim director of the South Dakota Agricultural Experiment Station, which helps administer and manage funding for the NREC. “Farmers are very interested in precise placement of nutrients. If any get lost to groundwater or surface water, it’s money out of their pocket.”


The state money funded three other fertilizer-related studies in its first round. One will come up with new nutrient recommendations for oats, updating 2005 guidelines. Another will compare manure and synthetic fertilizer used on cover crops, studying how they each impact soil fertility, water quality and yields. A third study will assess how microorganisms can be used to minimize nitrogen leaching after cover crops are killed by frost.


More funding will be awarded by the end of the year. So far, all projects are being conducted by South Dakota State University researchers, but the funding is open to any university, state, commodity or non-government organization. Gibbons said there’s preference given to South Dakota-based projects.


It’s important to have money dedicated to precise placement of nutrients because it impacts the environment, which affects everyone, he said.


“Farmers – they’re doing their best,” Ahiablame said. But there’s not a perfect way for farmers to control how much nutrients they’re losing, he said.


The beads could be placed in a plastic-lined bioreactor and be used to clean subsurface drainage. They could also be placed in a shallow trench at the edge of the field to capture surface runoff. Once they absorb the nutrients, the hope is that the beads would be applied to the field like fertilizer. The beads would dissolve and leave the nutrients behind.


“They are completely environmentally friendly,” Ahiablame said.


Studies will begin this year in a lab setting. It will be two to three years before they move to the field.


The study’s first step is to learn how much of the nutrients the beads can absorb. There are many other questions after that: How will the water-soluble beads retain their form? At what rate should they be applied to field when it comes time to reuse the fertilizer? How long will it take them to release nutrients in the field?


The professors are looking forward to finding out.


“We really see a bright future for research in this area,” Janaswamy said.


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Discovery of New Step in Nitrogen Cycle To Fundamentally Alter Fertilizer Use

October 9th, 2017

Fertilizers form the backbone of many agricultural processes worldwide. Decades worth of work has been poured into understanding the way in which fertilizers function and the ways in which they can affect the environment. In fact, the process by which bacteria break down nitrogen products in fertilizers to help provide plants with nutrients has found its way into high school textbooks, often accompanied by easy to understand diagrams.


A study led by Prof. Kyle Lancaster, chemistry, however, sheds light on a new found process that suggests that there is more to this nitrogen cycle than previously known.


According to Lancaster, existing biochemical models state that bacteria convert ammonia into an inorganic compound, Hydroxylamine, before turning that into nitrite. Nitrite can then be converted by other bacteria to form nitrate, a vital plant nutrient. Lancaster’s work, however, demonstrates that this conversion from Hydroxylamine to nitrite does not happen in one step. Instead, bacteria create an intermediate compound known as nitric oxide.


The issue with this previously unknown conversion is that nitric oxide, under imperfect conditions, is converted into the greenhouse gas nitrous oxide. Some nitric oxide accumulates in the soil while the remainder is washed off by rain or through irrigation channels into freshwater bodies. As the compound reacts with oxygen, it forms nitrous oxide.


Though the Environmental Protection Agency says that nitrous oxide accounts for only 5 percent of all greenhouse gases, it has 300 times the warming potential than carbon dioxide. The gas is also a primary ingredient in the formation of acid rain, which can severely damage foliage.


“Understanding how the model works is the key to finding a solution that maximizes crop production without much environmental consequence,” Lancaster said.


The new discovery has immense implications for the fertilization industry. A better understanding of the process of nitrification helps us pinpoint inefficiencies in current agricultural practices. Because the formation of nitric oxide reduces the amount of time that plants have to absorb nitrogen compounds, Lancaster points to future research that could create inhibitors to slow the process by which the compound is created.


Lancaster also highlighted a number of practical implications of the study. Because producers are now aware of this intermediary step, they can tweak their fertilizer application schedule to provide crops with more time to uptake vital nutrients.


On a larger scale, the study also points to the importance of revisiting the nitrogen cycle as a whole in an attempt to better understand each step. A better view of the nitrogen species that form in wastewater could, for example, be used to make water treatment methods more effective and efficient.


For now, Lancaster and his team are trying to understand the particulars of the conversion from nitric oxide to nitrate, specifically if there are other enzymes involved.


“We have spent most of our attention on carbon dioxide because our nitrogen footprint is much more complicated. There are so many different forms of nitrogen and all have dire consequences to the environment,” Lancaster said. “Nitrite, nitrate, nitrous oxide. You count them all. It’s hard to talk about nitrogen in a condensed way because all species of it are important.”


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