By Terry Julesgard, Water Department Manager, UBBNRD

It all started with two questions–

“What does the NRD do with the information we gather from producers on the Phase II and III and Water Use Reports?” The answer - in the beginning the data was compiled and archived to give the district a snapshot of the year the data was collected. Now, using the data provided over the past eight years, located in our Beehive platform, we can provide meaningful trends in yield, water use, nitrogen applied, residual soil nitrates and nitrogen use efficiency. The first report provided back to the producer was water use by pooled fields to help the producer plan water use by field if the district needs to move into a time of allocation. The second report provided back to the producers was the nitrogen use efficiency by field to show the producer what their nitrogen use efficiency is by field or if changes in nitrogen application could improve their bottom line. The data collected also helps the district track trends in crop rotation and timing of nitrogen application to help the district develop education programming around best management practices.

“Is what the district doing helping lower the nitrate levels in the groundwater?” This question is a little more complex to answer and one with many answers and maybe just as many questions. The short answer is “yes,” with the help of our partners like UNL Extension, the Nature Conservancy and the Natural Resource Conservation Service, producers are provided a constant stream of practice improvement and learning opportunities to improve their soils and their nitrogen use efficiency. With this education the district is seeing trend lines of nitrates in the groundwater begin to flatten out in some management zones and even decrease in one zone. The data collected over the last eight years shows what we would consider “normal increases”. The district has seen:
•Average yields increases of 11%, to 227 bushels per acre in Phase II and III areas.
•Applied nitrogen increases of 15% to 200 pounds per acre (lbs/A) average for corn-on-corn fields and 4% to 184 lbs/A average for corn/bean rotations.
•Average nitrogen use efficiency rate of 0.9 pounds of nitrogen per bushel of corn grown.
The numbers that stand out are the residual nitrate nitrogen in the soil:
•Corn-on-corn field increases from 33 lbs/A average to 86 lbs/A, an increase of 202%.
•Corn/bean rotation field increases from 32 lbs/A average to 86 lbs/A, a 212% increase.

Why is the data showing these dramatic increases in residual nitrate nitrogen in the soil? Is there an elephant in the room? Is there something being overlooked or not taken fully into consideration? And if so, what is it?
While trying to answer those questions, I came across the article below, published by Purdue University in July of 2019. The article points out what I believe most producers already know but maybe have not taken the time to fully investigate themselves.

Simultaneous gains in grain yield and nitrogen efficiency over 70 years of maize genetic improvement

By Sarah M. Mueller, Carlos D. Messina & Tony J. Vyn

WEST LAFAYETTE, Ind. – During the past 70 years, hybrid corn varieties have increased both yield and nitrogen use efficiency at nearly the same pace, largely by preserving leaf function during grain filling. The Purdue University study’s findings offer strategies for corn breeders who want to continue to improve yields and nutrient efficiencies.

Decades of genetic improvements in corn have led to a fourfold increase in grain yield since the 1930s, before hybrids were widely used. But those yields also required increases in nitrogen application, and loss of excess nitrogen can damage water and air quality as well as wildlife.

Tony Vyn, the Corteva Agriscience Henry A. Wallace Chair in Crop Sciences and a professor in Purdue’s Department of Agronomy, wanted to know how corn plants have historically utilized nitrogen – especially in reproductive growth – so that breeders can make informed decisions with future hybrids. He and his former doctoral student, Sarah Mueller, obtained seed and grew seven commercially important Pioneer hybrids, approximately one from each decade between 1946 and 2015. They were grown side by side under a range of nitrogen managements and analyzed at several stages of growth through maturity to understand nitrogen uptake and distribution throughout plant tissues.

“There’s been a progressive improvement in nitrogen use efficiency in corn hybrids. That’s coming about as yields have increased while modern hybrids were able to capture more and more of the fertilizer nitrogen applied,” said Vyn, whose findings were published in the journal Scientific Reports. Over the last 70 years, genetic improvements have led to an 89 percent increase in grain yields and a 73 percent increase in nitrogen use efficiency from early hybrids to today, the study finds.

“There’s been a plateau in nitrogen fertilizer rates applied to corn in the U.S. since the 1980s,” Vyn said. “But we’re capturing more of the fertilizer we apply so that less is lost while more of the nitrogen captured by the plant is creating grain. In our case, we’ve documented progression from creating 42 pounds of grain per pound of nitrogen taken up in the plant to 65 pounds of grain. “That essentially means that we’ve not necessarily sacrificed the environment in realizing much higher yields now than we did 50 or 70 years ago.”

Vyn’s team found that more modern hybrid corn kernels get much of their nitrogen from corn stems. That’s key, he said, because it’s important to keep as much nitrogen as possible in leaves so that plants can meet the assimilate requirements inherent in the increased corn kernel numbers and kernel size that are foundational in achieving higher grain yields.

“Kernels are going to pull nitrogen from somewhere in the plant. Stems contribute almost nothing to photosynthesis, but keeping nitrogen concentrations in the leaves higher for more of the growing season allows for more photosynthesis and improved
yields,” Vyn said. He added that the findings offer breeders suggestions for how to continue to make improvements in yield and nitrogen use efficiency, focusing on the timing and movement of nitrogen through stems and into kernels.

Corteva Agriscience, of which Pioneer Hybrid International is a part, donated seeds for the research, blindly analyzed tissue samples and provided funding to hire undergraduate student workers and for field and laboratory supply and equipment rental expenses. Sarah Mueller’s doctoral studies at Purdue were supported by a scholarship from the Indiana Corn Marketing Council. Vyn was funded through a U.S. Department of Agriculture Hatch grant. Writer: Brian Wallheimer, 765-532-0233, bwallhei@purdue.edu Source: Tony Vyn, 765-496-3757, tvyn@purdue.edu

Though this article has a different focus, it highlights a very important fact—corn hybrids are becoming more efficient in nitrogen use efficiency (NUE) with each new hybrid developed. So, what do we know about NUE?
According to David Meyer, who grew up near Dodge NE, and has a Ph.D. in plant breeding and genetics for UNL along with a 40-year career with Corteva AgriSciences in plant breeding, provided the follow in site into NUE. “NUE is a complex genetic trait with many interdependencies that make it difficult to select for per se in a breeding program. What makes NUE tricky is there are two distinct paths.

One being, how well can the plant extract nitrogen from the soil. The second being how well can the plant move it into the kernel which determines yield. Thus, by historically selecting for the highest yielding variety across a wide range of environments in breeding programs, both aspects of NUE was inherently improved”. Dr. Meyer adds, “Modern Varieties that are much improved on their ability to both absorb Nitrogen from the soil and convert it into yield once it’s in the plant. Producers and their advisors need to take this into account when deciding how much N to apply.” So, with the new hybrids and their ability to uptake and use nitrogen efficiently, a serious look needs to be taken at how much nitrogen does a corn plant actually need?

Looking at this from a 30,000-foot view it begs the question, do we—hybrid developers, producers, educators, natural resources managers, regulators— truly understand how efficient the new hybrids are at using nitrogen? Is over application taking place because we do not allow these new hybrids to reach their full potential of nitrogen use efficiency? I fully agree with the statement I hear from all producers, “we cannot afford to over apply nitrogen”, but if one doesn’t know the actual efficiency of the seed they are planting, and use the same old way to determine nitrogen application rate, how does one know if an over application has occurred? There are technologies currently being developed and used to feed the plant only what it needs, when it needs it and are achieving nitrogen use efficiencies (NUEs) of 0.6 lbs of nitrogen per bushel raised and in some cases even lower NUEs. These technologies are proving to be very good at reaching nearer to the maximum efficiency of a corn plant, and not decreasing yields, but have they found it? Or is there more we need to know?

So, in attempting to answer, “Is what the district’s doing helping lower the nitrate levels?”, more questions have risen. It becomes more of a we question. We need to ask ourselves some questions: As a hybrid developer, am I making known the potential NUE of my product? As a producer, am I asking what the NUE potential is for the hybrid being planted and applying nitrogen accordingly or just doing what has worked in the past? As an educator, am I empowering us to move forward and ask the right questions? As a natural resources manager, am I providing all the data needed to support long-term sustainability and improvement of the resources? As a regulator, am I developing a path that promotes improvement and sustainability?

Maybe the starting question is “What can I, or we, do to help lower the nitrate levels?” A wise person once told me “An individual can make a small change, but it takes a community to make a real change.” Let us be that community.