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Can New Microbes Lower Nitrogen Rates in Corn?

Tony J. Vyn
Professor, Cropping Systems
Henry A. Wallace Chair in Crop Sciences
Agronomy Department, Purdue University

Recent high fertilizer prices have prompted huge farmer interest in the possibility of lowering nitrogen (N) rates with commercial microbial supplements that claim to fix N from the atmosphere. Environmental concerns about N losses in corn production only add to the impetus to apply less N per unit of yield.


In this presentation, Dr. Tony Vyn will highlight his team’s experiences, and that of other universities in the Mid-West United States, from the results of recent public-institution trials with corn produced with commercial microbial products like Envita, PROVEN and PROVEN 40. In each case, the preliminary public institution trials were conducted with a full range of nitrogen (N) fertilizer rates. Public data on possible reductions from the economic N rate when farmers utilize microbial supplements are, unfortunately, limited.  Nevertheless, Dr. Vyn addresses some of what is known from public replicated trials in Indiana and other Corn Belt states. He also provides perspectives on the daunting challenges in conducting field research to arrive at a reliable number for a N fertilizer rate reduction, if any, with N-fixing microbial supplements.


The title of his presentation is “Finding Proof for Recommending Less N with Microbial Supplements: Research Challenges in Corn”. This talk was first presented at the Indiana Certified Crop Adviser Conference in mid-December, 2021, and then modified. However, even then, these tentative conclusions are based on a public-data set that is too small. New financial resources, and considerably more private-public cooperative research, are needed to expand research station and on-farm trials with present and evolving microbe strains that may help meet corn’s N requirements with less N fertilizer per bushel. 

Welcome to Vyn Labs!

Here we share who we are, what we've been learning, and the latest updates on our research. 

The primary mission of the Cropping Systems Lab is to critically evaluate potentially sustainable agricultural technologies for field crop production from the relevant perspectives of genotype by environment by management system interactions that farmers encounter. In pursuit of that overall mission, our research group endeavors to use our talents and resources to

(a) advance the scientific understanding of plant response mechanisms to specific crop inputs,

(b) enhance the sustainability of crop production practices in the Eastern Corn Belt,

(c) train great students who can contribute to the future growth of even more sustainable crop production practices.


Congratulations to Lia B. Olmedo Pico for her successful Ph.D defense:

Nitrogen’s Role in Changing Kernel Weight in Maize: Relevant Physiological Mechanisms During Reproductive Stages

Although grain yield (GY) in maize (Zea mays L.) is the product of both kernel number (KN) per unit area and kernel weight (KW), the latter has usually been considered the least variable component. However, sink strength enhancement by genetic improvement has meant that KW itself is more likely to limit yields in modern hybrids. This research studied the physiological mechanisms underlying KW by evaluating the effects of N availability on: 1) the sources of dry matter (DM) and N assimilates; 2) the determination of potential KW; and 3) the realization of final KW. To investigate how N availability affected source capacity, a 2-year field study (2016-2017) that combined N timing and N rate treatments was conducted. DM and N sources were calculated separately for the lag phase (R1-R3) and the linear phase (R3-R6). In the lag phase, substantial DM gains in leaves and stems occurred in both years, while N content gains were mostly detected in reproductive tissues. GY differences were consistently and mainly explained by KW variability, with reproductive tissues proving to be relatively stronger sinks for N than for DM during the lag phase. To understand how N availability affected both the determination of potential KW in the lag phase and the realization of final KW in the linear phase, three field experiments testing N rates, plant densities and N timing applications on a single hybrid were conducted (2017-2019). Average GY gains from zero N to the maximum N rate tested exceeded 8 Mg ha-1. Endosperm cell number (ECN), an indicator of potential KW, was determined at different timings (from 9 to 17 days after silking -DAS-), and plant component biomass plus N samples were taken at V12, R1 and R3. Low N treatments consistently reduced ECN at 9, 10, 13, and 17 DAS. Positive KW responses at R6 to N rates were always explained by higher ECN. Each year, ECN was highly correlated with ear N allocation rate during the lag phase. Potential KW was not associated with plant growth rate per kernel during the critical period, and a positive relationship (rather than a trade-off) was found between KW and KN. Additionally, since kernels accumulate both DM and N assimilates during the linear phase, kernels were sampled weekly over a 9-10-week interval from the early R3 stage. Linear plateau models were then fitted to the resulting kernel DM and N data to obtain characterizing parameters. Increases in N supply improved all four parameters: effective grain-filling rate, grain filling duration, kernel N accumulation rate (KNAR) and duration. KNAR was strongly correlated with both final KW (r=0.96) and with whole-plant N uptake by R3 (r=0.80). Overall, this dissertation provides new evidences for the distinct indirect and direct roles that N plays in the physiological mechanisms that determine final KW in maize at high potential GY.


We are located at Purdue University in West Lafayette, IN in the Department of Agronomy in the College of Agriculture.

Learn more about the Department of Agronomy here.


2022 Indiana Certified Crop Adviser Conference
December 13-14, 2022