Understanding Nutrient Use Efficiency

Are you making the most of your soil? Understanding your NUE score is pivotal to understanding not just nitrogen use efficiency, but also your soil’s overall potential.

Effectively and efficiently managing inputs is one of the best ways growers can lower operating costs, maintain yield and reduce waste, but with so many factors impacting the production of each bushel, it can be hard to tell what effects inputs like nitrogen fertilizer actually have on yield.

A grower’s last pounds of nitrogen are often negative in terms of profitability. Not only are yield increases often not enough to offset the input cost, but depending on soil and weather conditions, nitrogen can often be lost to the environment. Understanding how well the nitrogen is being used can help growers assess which on-farm practices are providing the best ROI and track their progress towards reducing inputs and improving soil health.

A nutrient use efficiency (NUE) score is one way growers can track their operation’s efficiency. By observing the relationship between the amount of nitrogen applied and yield achieved, growers can find opportunities to reduce input costs and improve soil health.

NUE is simply the ratio of nitrogen applied per bushel of yield, and the lower the ratio, the more efficient a growers nutrient use. The less nitrogen a grower can use per bushel, the lower their costs and the higher their return. 

To calculate NUE, a grower just divides the pounds of nitrogen applied by the number of bushels produced; the results show how much nitrogen went into each bushel. For example, if a grower applied 200 pounds of nitrogen and got 160 bushels, 1.25 pounds of nitrogen went into each bushel. 

“Some growers know exactly how much nitrogen they’re putting out while others can give a ballpark but don’t necessarily have a finger on the pulse of exactly how much nitrogen they’re using,” says Zach Carlson, Sales Agronomist with Sound. When talking to growers, Zach says figuring out a grower’s current NUE is the first step to improving that efficiency and cutting back on input costs. 

Whether a grower has an exact figure or a range for pounds of applied nitrogen, keeping their NUE score in mind can support a holistic understanding of their farm’s strengths and limits, especially when it comes to soil.

While a lower NUE is generally better, a good NUE score will look different for every grower based on their farm’s unique traits. 

Soil characteristics like organic matter, pH, and CEC can have a significant impact on how much applied nitrogen can be held and used. Because CEC measures the soil’s holding capacity, a grower relying on fertilizers to boost yield may find their ability to lower their NUE score limited by how much nitrogen the soil can hold. Growers with higher organic matter soils also have a stronger potential for nitrogen mineralization and may have more carryover nitrogen between seasons. 

“Not all NUE scores are the same,” says Zach. ​“Considering NUE is the start of a conversation about whether a grower can be more efficient with their nitrogen, and we know many growers are over-applying nitrogen, compared to what they could be using efficiently.”

Rather than thinking about NUE as a static end-goal, growers should consider it a plan that can be reevaluated and adjusted as needed based on weather, soil, and other environmental factors beyond their control.