NUE Explained: What Does NUE Mean for Sustainability?

We’ve covered what an NUE score is, how to use it, and what to do to improve your NUE. Now, we’re zooming out to look at what your NUE score means for sustainability, both on the farm and off. 

With expertise provided by Zoe Thorsland, Business Development Associate at Sound.

Nutrient use efficiency, or NUE, refers to the relationship between the amount of a nutrient applied to fields (usually nitrogen or phosphorus) and the amount of yield growers achieve at the end of the season. The less nutrient required per bushel of yield, the better a grower’s nutrient efficiency and the lower their input costs. By paying attention to their NUE, growers can directly improve not only their own sustainability, but the sustainability of the agricultural industry more broadly.

Sustainability is a concept that is easily thrown around, sometimes at the risk of becoming simply a buzzword, untethered from a grower’s daily concerns. 

Zoe Thorsland, Business Development Associate at Sound, says that because the term has become somewhat political, it can sound like a high-minded goal rather than what it’s really about — efficiency.

“We have a food crisis on our hands, globally,” she says. ​“Ultimately, sustainability is about figuring out how to best use our resources to nourish our plants and our population — taking care to create an efficient system that serves the farmer and the environment for years to come,” she explains.

In addition to an ever-rising global population, other factors like extreme weather events, supply chain disruptions, lingering impacts of the COVID-19 Pandemic, and the conflict in the Ukraine have impacted access to critical inputs and overall yields, making it harder and harder to meet our agricultural output demands. 

To meet the growing demand for food, Zoe says the productivity of existing acres needs to increase while avoiding land-use change. If we increase output by changing acres of forest or grasslands into agricultural land, we not only release carbon through that land use change but also lose the important wildlife habitat those natural resources provide.

“If we can help already nutrient-efficient farmers meet their yield goals, that helps prevent land use change while also avoiding potential emissions,” she says.

Improving NUE and fertilizer efficiency can have significant financial benefits for individual growers and their operations, but also helps address the larger environmental impacts of the agriculture industry. Recent research from the Universities of Exeter and Turin suggests the global synthetic nitrogen industry represents over 10% of agricultural emissions and 2% of greenhouse gas emissions globally. 

“The production of fertilizer is extremely energy intensive and more polluting than the global aviation industry, and that’s all before we talk about nutrients lost to the environment, which is when NUE comes in,” says Zoe. Production and transportation of synthetic nitrogen fertilizer account for about 40% of its total emissions, while field emissions account for nearly 60%. 

When growers apply fertilizer to their fields, a good deal is lost to the environment. For nitrogen, up to 40% is lost via volatilization, denitrification, and runoff; only between 50 and 70% of applied nitrogen is actually absorbed by the crop. For phosphorus, the numbers are even worse: between 75 and 85% is lost to leaching and runoff or becomes tied up in the soil. Both phosphorus and nitrogen can have serious impacts in downstream watersheds, causing massive algae blooms that deplete the dissolved oxygen available to other aquatic life and damaging water quality. 

“Hypoxia and algae blooms from agricultural runoff are causing damage to natural ecosystems and human health,” says Zoe. ​“EPA task forces and local water quality initiatives are trying to mitigate the damage by limiting nutrient application.” 

That’s why improving NUE matters; higher efficiency means growers can be sure the nutrients they applied are being used by the plants instead of lost to the environment in runoff or as a greenhouse gas. 

Trying to reduce greenhouse gas emissions isn’t just a thing growers do to benefit the rest of the world, though; growers themselves are some of those people most directly affected by climate, weather and environmental shifts. 

“Agriculture and climate are closely tied. As weather events get more extreme, it is important to help agricultural communities adopt practices that make their farm and business more resilient,” Zoe says. ​“We have a vested interest in reducing greenhouse gas emissions because growers are already experiencing climate volatility and having to adapt their operations to meet the challenges of a changing climate.” 

On the level of individual farms, a core element of sustainability includes making sure growers can produce high-quality crops for years to come. This means not only making sure they have healthy soils and are giving their plants access to the nutrients they need, but that their operation is profitable. 

“The cold, hard fact for a grower is that nutrient loss is money washing away from the field,” says Zoe. 

That’s especially true when input costs are high; improving NUE can have direct and significant benefits on a grower’s ROI and profitability, and that matters when it comes to financial sustainability. By applying only the inputs needed to optimize output, growers improve the overall efficiency of their farm without wasting money.

“When you optimize your nutrient application to meet crop needs, your money benefits your plants instead of causing damage downstream,” says Zoe.

For Zoe, one of the most exciting parts of the interaction between NUE and sustainability is that growers can have a big impact through small changes on their own farm. 

“A grower can focus on their financial sustainability as the North Star and the positive environmental outcomes take care of themselves,” she says. ​“It’s not about trying to tackle global challenges, it’s just deciding to make sure your plants have access to the inputs you’ve put on your fields. Local action can have global reach. With lower application and demand for fertilizer, hopefully we will see less fertilizer produced and lower nutrient pressure on watersheds, resulting in healthier ecosystems and wetlands. Growers have agency when it comes to nutrient efficiency, which starts with financial sustainability and ripples out into positive environmental outcomes.” 

When considering how to approach sustainability through NUE, the steps a grower should take will depend on their specific situation and whether they’re overapplying fertilizers. Once growers have dialed in their nutrient applications, they can start looking at other factors that may be limiting yield, such as pest pressures, weather, soil characteristics or nutrient form. 

Growers may also face region-specific challenges to nutrient applications as some states have begun implementing phosphorus and nitrogen limits to try and reduce the flow of nutrients into local waterways. In Maryland, for example, the state is required to reduce phosphorus pollution by 48% by 2025. The idea is that soils in the area are already phosphorus rich, so introducing limitations on how much phosphorus growers can apply aims to prevent over-application. 

In these situations, it becomes even more important to ensure the nutrients in the soil and applied by growers are actually making it into the plants. For example, a farm in the mid-Atlantic region using chicken manure for fertilizer recently found that despite having phosphorus-rich soils, they were still seeing phosphorus deficiency in their plants. Since local regulatory bodies limit how much phosphorus the grower can apply, he needed to help his crops take up the existing phosphorus in the soil. 

“They’re limited in how much phosphorus they can apply, but even if there’s high phosphorus content in the chicken litter they’re putting down, it’s not necessarily in a form accessible to the plant,” Zoe explains. 

In cases like this, the challenge is getting plants access to an already abundant nutrient. SOURCEⓇ, Sound’s microbiome activator, helps the biology in the soil unlock the nutrients like nitrogen and phosphorus that are already there. For growers who use manure, especially in regions where nutrient runoff is a concern and phosphorus applications are limited, that can have big benefits. 

“Manure is a cost-effective fertilizer for a lot of growers,” says Zoe. ​“SOURCE actually increases both soil availability and plant uptake of phosphorus, reducing the need for the application of an additional synthetic source. Unlocking manure benefits also contributes to on-farm efficiency — if I’m raising chickens and using that waste to fertilize my crops, I’m creating a circular system.” 

Many different regional organizations, federal regulatory bodies and task forces are trying to address nutrient runoff and water quality, and Zoe says growers may feel like they’re stuck between a rock and a hard place.

“You may be seeing corn leaves that are yellow and phosphorus deficient, but have regulations that limit how much additional phosphorus you can apply,” she says. The first place to start is simple, though; nutrient efficiency. 

“Nutrient management and NUE just means having a better idea of the nutrients you apply and how your plants are taking that up,” she says. ​“Nutrient management is the solution that different regional bodies have converged on. Understanding NUE and developing a plan enables growers to make financially sustainable decisions.”