Where Does Your Nitrogen Go? And What PGA Can Do About It

Every grower knows the feeling: you put down a full rate of nitrogen, and the crop still looks a little short of where you'd expect it to be by mid-season. That's not your imagination, and it's not bad math on the fertilizer bag. It's the nitrogen cycle doing what it does - and it turns out that cycle is far less efficient than most of us assume.

A Bigger Loss Than It Looks

Across the world's major cereal systems - the crops where this has been studied most closely - only 30% to 50% of the nitrogen fertilizer applied in a given season is actually taken up by the crop that year ^[1]. A large review pulling together more than 3,500 field observations across rice, wheat, and corn put the average even more precisely: about 39% ^[2]. Put plainly, well over half of the nitrogen you apply is not ending up in the plant.

That's not a niche problem confined to a handful of poorly managed fields - it shows up at scale. One analysis of roughly eight million corn fields across the U.S. Midwest put the value of nitrogen lost from those fields, in a single year, at approximately $485 million ^[3]. Multiply that pattern across every nitrogen-fertilized acre in the world, in every crop, and the scope of the issue becomes clear: this is one of the largest sources of inefficiency in modern agriculture.

Where It's Actually Going

Applied nitrogen doesn't just vanish - it moves along three main pathways, and understanding them is the first step toward managing them:

Ammonia volatilization. Some of the nitrogen sitting in the soil as ammonium converts to ammonia gas and drifts off into the air. Globally, this pathway alone accounts for an average of 18% of applied nitrogen, though it swings widely depending on soil, weather, and application method ^[4].

Nitrate leaching. Once soil microbes convert ammonium into nitrate, that nitrogen loses its positive charge and becomes highly mobile. If rain or irrigation moves through the soil before the crop's roots can take it up, it washes past the root zone and into groundwater.

Denitrification. In waterlogged or low-oxygen pockets of soil, microbes convert nitrate into nitrogen gas - and, along the way, into nitrous oxide, a long-lived greenhouse gas.

These three pathways share a common root cause: a mismatch in timing. Nitrogen is often most available in the soil precisely when the crop's demand for it is lowest - early in the season - and by the time the crop is actively growing and pulling hard on the nitrogen supply, much of it has already been lost.

A Biological Way to Close the Gap

This is where polyglutamic acid (PGA) comes in. PGA is a naturally occurring biopolymer produced through microbial fermentation - the same basic process behind cheese, yogurt, and natto. This series focuses specifically on the linear, water-soluble form of PGA, not the chemically distinct crosslinked, super-absorbent version sold for water retention. What makes linear PGA agronomically interesting is its structure: every building block of the molecule carries a free, negatively charged carboxyl group, giving the whole polymer an unusually dense negative charge in the soil.

That single structural feature drives three complementary mechanisms that intervene directly in the nitrogen cycle described above:

1. It acts like a nutrient magnet. The negatively charged polymer electrostatically holds on to positively charged ammonium, keeping it in the root zone longer and reducing how much escapes as ammonia gas or converts too quickly into leachable nitrate.

2. It works like a microbial time-release system. Soil microbes are drawn to PGA as a food source, and in doing so they temporarily lock up ("immobilize") mineral nitrogen in their own biomass early in the season - precisely the window when the crop's demand is lowest and leaching risk is highest. As the season progresses, that nitrogen is gradually released back into the soil, tracking more closely with the crop's actual uptake curve.

3. It supports stronger root development. A larger, more active root system covers more soil volume, intercepting nitrogen and water before either has a chance to move out of reach.

What the Research Shows

The evidence for these mechanisms isn't limited to one crop or one lab. In paired field and greenhouse wheat trials, purified PGA raised nitrogen recovery efficiency by roughly 11% to 14% and lifted grain yield by about 7% over the untreated control ^[5]. A separate two-year field study in corn found yield gains ranging from about 5% to 22%, alongside an 8% to 19% drop in ammonia volatilization ^[6]. And in a greenhouse trial with Chinese cabbage, cutting the nitrogen rate by 30% and adding PGA didn't just hold yield steady - it matched or beat full-rate conventional fertilization outright ^[7].

Taken together, these results span cereals, fiber crops, and vegetables, under both open-field and greenhouse conditions - which matters, because it suggests the underlying mechanism is about soil chemistry and microbiology, not something specific to any one crop's genetics.

Worth Saying Plainly

In the interest of giving growers and agronomists a straight picture: most of the published research on linear PGA to date comes out of China, with a smaller but growing body of independent trials - including a recent grassland study in Poland - beginning to test the same effects in other geographies and soil types. That's a genuine, current limitation of the evidence base, not a reason to dismiss it, and it's one of several open questions we lay out candidly in the full technical review.

The Bigger Picture

Nitrogen loss isn't a flaw unique to any one farming system - it's a byproduct of the same basic soil chemistry wherever fertilizer meets soil, whether that's a broadacre cereal field, a raised vegetable bed, or a greenhouse bench. The good news is that the mismatch driving most of that loss - nitrogen available before the plant is ready for it - is exactly the kind of problem a biological tool like PGA is built to help address.

This post is the first in a series exploring the science behind polyglutamic acid's role in the soil nitrogen cycle. For the full technical breakdown - including the complete evidence review, mechanism-by-mechanism detail, and an honest look at where the research still has gaps - download our whitepaper, The Role of Polyglutamic Acid in the Soil Nitrogen Cycle.

References

1. Ladha JK, Pathak H, Krupnik TJ, Six J, van Kessel C. Efficiency of fertilizer nitrogen in cereal production: retrospects and prospects. Adv Agron. 2005;87:85-156.

2. Yu X, Keitel C, Zhang Y, Wangeci AN, Dijkstra FA. Global meta-analysis of nitrogen fertilizer use efficiency in rice, wheat and maize. Agric Ecosyst Environ. 2022;338:108089.

3. Basso B, Shuai G, Zhang J, Robertson GP. Yield stability analysis reveals sources of large-scale nitrogen loss from the US Midwest. Sci Rep. 2019;9:5774.

4. Pan B, Lam SK, Mosier A, Luo Y, Chen D. Ammonia volatilization from synthetic fertilizers and its mitigation strategies: a global synthesis. Agric Ecosyst Environ. 2016;232:283-289.

5. Xu Z, Wan C, Xu X, Feng X, Xu H. Effect of poly(γ-glutamic acid) on wheat productivity, nitrogen use efficiency and soil microbes. J Soil Sci Plant Nutr. 2013;13(3):744-755.

6. Zhai Z, Shi W, Liu L, Jing B. Poly-γ-glutamic acid enhances corn nitrogen use efficiency and yield by decreasing gaseous nitrogen loss and increasing mineral nitrogen accumulation. Soil Tillage Res. 2025;249:106480.

7. Bai N, Zhang H, He Y, et al. Effects of Bacillus subtilis A-5 and its fermented γ-polyglutamic acid on the rhizosphere bacterial community of Chinese cabbage. Front Microbiol. 2022;13:954489.