From The Air To The Field: What Zimbabwe Must Learn From The Global Nitrogen Squeeze
In a fertiliser shed outside Chinhoyi, 52-year-old maize grower VaGumbo stares at a half-empty stack of bags. Last season he applied the full 300kg per hectare his agritex officer recommended. This year, with prices climbing and stock in short supply, he’s wondering which field will go hungry.
On the other side of the world, Australian scientists are asking a related question: why does it take so much nitrogen fertiliser to grow our food — and what happens when the ships stop coming?
A new explainer from Australia’s national science agency, CSIRO, shows how dependent modern farming has become on synthetic nitrogen, and how fragile that dependence really is. For Zimbabwe, the lessons are uncomfortably close to home — and they point to a future where we must treat nitrogen not as something we simply buy, but as something we manage.
Why Nitrogen Fertiliser Is Suddenly A Food Security Issue
Every bag of AN, urea, or compound fertiliser starts in the air above us. The Haber–Bosch process, developed in the 1910s, captures nitrogen gas (N₂) and combines it with hydrogen under high heat and pressure to make ammonia. From there, factories turn it into fertilisers that pushed global yields high enough to feed billions.
But this miracle comes with a catch: only a small fraction of the nitrogen we apply actually ends up in food.
- Globally, about 100 teragrams (100 million tonnes) of synthetic nitrogen are applied to farmland each year.
- Only around 17 teragrams end up in the food people eat — the rest is lost to air and water. [SOURCE REQUIRED: confirm global nitrogen use figures]
- For every US$1 a farmer spends on nitrogen, only about 30–50 cents comes back as harvestable product.
Those losses are not just wasted money. They fuel water pollution, greenhouse gas emissions and, critically for a country like Zimbabwe, they represent imported dollars leaking into the ground.
Australia’s vulnerability looks different but rhymes with ours. As CSIRO’s Dr Alison Bentley notes, almost all of that country’s synthetic nitrogen now arrives by ship — while most of its grain also leaves by ship.
Supply chain shocks — from the Arab Spring to the war in Ukraine — have spiked fertiliser prices repeatedly. Australian researchers warn that because nitrogen doesn’t store well, you can’t build strategic reserves the way you might stockpile fuel. Farmers feel price and supply shocks almost immediately.
Zimbabwean producers know this in their bones. Input delays, forex shortages, and global price spikes have already forced many to cut back on fertiliser, risking yields. The CSIRO story simply spells out, in scientific language, what our fields have been telling us: fertiliser security is food security.
Nitrogen: Why Maize, Wheat And Soya Care So Much
Nitrogen is the engine-room nutrient. Plants use it to build proteins, chlorophyll, and the enzymes that drive growth and grain filling. Without enough nitrogen:
- Maize stays pale, stunted, and produces smaller cobs.
- Wheat and barley deliver poor grain protein, lowering milling quality and prices.
- Soya and other legumes may nodulate poorly if soils are badly depleted.
In Zimbabwe, where maize and wheat underpin both household food security and national politics, that makes nitrogen a strategic input on par with fuel or electricity.
FFA Explainer:
Haber–Bosch nitrogen gave the world a way to turn air into food. But it’s energy-hungry, relies on gas or coal, and ties farmers into volatile global markets. Over time, making our crops and soils use nitrogen more efficiently is as important as securing supply.
The Conversion Problem: Why So Much Nitrogen Is Wasted
CSIRO’s scientists highlight a core challenge: we have to apply a lot of nitrogen fertiliser to get the yield we want — and crops only convert a fraction of it into grain.
Losses happen because:
- Rain or irrigation can leach nitrate down beyond the root zone.
- Wet or compacted soils can push nitrogen off as gases (ammonia, nitrous oxide).
- Plants often can’t take up big pulses of nitrogen fast enough, especially early in the season.
As CSIRO’s Javier Navarro notes, farmers must “buy months before sowing” based on imperfect seasonal forecasts. If rains fail, crops use less nitrogen and the rest doesn’t wait obediently in the soil — it moves.
This is just as true on a wheat farm in Western Australia as it is on a communal maize field in Gokwe. “Careful” use (waiting for moisture, splitting applications) helps, but it’s not the same as efficient use.
What Zimbabwe Can Learn From Australia’s Nitrogen Rethink
CSIRO’s work points to three big shifts — and each has a Zimbabwean angle.
1. Breed Crops That Use Nitrogen Better
Instead of only asking, “How do we supply nitrogen?”, Australian researchers are asking, “How do plants use nitrogen?”
Dr Bentley’s research in the UK and now with CSIRO shows that different wheat and barley varieties vary surprisingly in how efficiently they take up and convert nitrogen. Grain itself sends signals to the rest of the plant about how much nitrogen to pull in.
Some varieties are simply better at turning each kilogram of applied nitrogen into grain. That’s a breeding opportunity.
For Zimbabwe, this suggests:
- Our maize, wheat, and barley breeding programmes — public and private — should start selecting lines for nitrogen-use efficiency, not just yield under high fertiliser.
- Variety trials under reduced nitrogen regimes (for example half the standard rate) can reveal which lines hold yield and quality when fertiliser is short.
- Seed companies can begin to market not just “high-yielding” hybrids, but high-return-per-bag-of-fertiliser hybrids — a message farmers will understand instantly.
Under NDS1 and Vision 2030, supporting local seed systems that deliver climate- and nutrient-smart varieties is low-hanging fruit for policy.
2. Let Roots Help Keep Nitrogen In The Soil
A second strand of CSIRO’s work looks at how plants themselves can slow nitrogen losses in the soil. Some crops and grasses release compounds from their roots that suppress the microbes responsible for turning plant-available nitrogen into leachable or gaseous forms. This is called biological nitrification inhibition (BNI).
BNI was first described in a tropical forage grass, but CSIRO notes that many major crops show at least some ability to do it.
FFA Explainer:
Biological nitrification inhibition (BNI) is a plant’s way of “holding” nitrogen in a form it can use. Root exudates slow down soil microbes that would otherwise convert ammonium into nitrate (which leaches) or gases (which escape). Stronger BNI means more nitrogen stays where roots can reach it.
For Zimbabwe, where soils are often sandy and rainfall comes in hard bursts, BNI is particularly relevant:
- Tropical grasses with strong BNI traits could be used more deliberately in pasture leys and rotations ahead of maize or wheat.
- Local research institutions could start screening existing varieties of sorghum, millets, and grasses for BNI strength, then prioritise those traits in breeding.
- Mixed systems – for example, maize intercropped with BNI-strong forages in certain strips – might reduce nitrogen losses while feeding cattle.
3. Give Seeds A ‘Lightning-Style’ Nitrogen Kick
The CSIRO piece closes with something that sounds like science fiction: using cold plasma to treat seeds before planting.
When lightning strikes, it briefly creates a plasma state in the air, splitting nitrogen molecules and forming reactive forms that fall in rain to the soil. Cold plasma technology mimics part of this process without the heat.
CSIRO scientists are exposing grain seeds to cold plasma before planting, aiming to unlock nitrogen that’s already bound inside the seed so that the seedling can use it during the first crucial weeks.
As Dr Bentley explains, the goal is a short, sharp “nitrogen burst” to fuel early growth before roots can tap soil fertiliser effectively — and before nitrogen can be washed or gassed away.
For Zimbabwe, this is future tech, not next-season practice. But it hints at a world where some of our nitrogen “input” is prepared in the seed store, not just in the fertiliser shed. Keeping an eye on such technologies will be important for research planners and seed companies alike.
Where Does Organic Matter And Manure Fit In?
The CSIRO piece is clear: organic fertilisers — manures, composts — can’t completely replace synthetic nitrogen at current production levels. They’re bulkier, less concentrated, and more variable.
Yet for Zimbabwe, they’re a critical part of the nitrogen picture:
- Every tonne of composted manure that goes back to fields improves soil structure and water-holding, making each kilogram of synthetic N work harder.
- Legume rotations (soya, sugar beans, cowpeas) fix biological nitrogen, cutting the need for imported fertiliser and improving following cereal crops.
- Integrated fish–livestock systems can recycle nutrient-rich pond sludge and water to irrigate fodder crops, effectively “stretching” nitrogen through the system.
Organic and synthetic nitrogen are not enemies; they are partners. The smarter we are with manure and crop residues, the less pressure we put on our foreign currency and on global fertiliser chains.
A Zimbabwe Nitrogen Strategy: From Crisis To Design
What would it look like if Zimbabwe took nitrogen as seriously as fuel or maize grain?
Borrowing from the Australian debate, a national nitrogen strategy could include:
- Supply security:
- Diversifying import sources and exploring regional production with SADC partners to reduce exposure to single regions.
- Encouraging private investment in small-scale ammonia or fertiliser blending plants, possibly powered by renewables in the long term. [SOURCE REQUIRED: feasibility studies]
- Demand efficiency:
- Training farmers in the “4Rs” of nitrogen: right source, right rate, right time, right place.
- Integrating nitrogen-use efficiency traits into national maize and wheat breeding targets.
- Promoting legume rotations and cover crops under Pfumvudza/Intwasa and other programmes.
- Innovation and research:
- Funding local studies on BNI traits in Zimbabwean crops and forages.
- Exploring algae-based fertilisers or supplements from fish ponds as part of integrated systems.
- Partnering with institutions like CSIRO and CGIAR centres on cutting-edge nitrogen management research.
Such a strategy would support NDS1 goals on import substitution, climate resilience, and higher yields, while aligning with SDG 2 (Zero Hunger) and SDG 13 (Climate Action).
Bringing It Back To VaGumbo’s Shed
None of this helps VaGumbo find cheap fertiliser in time for this season. But it does change how we answer his question: “Which field will go hungry?”
In the short term, agritex officers can help him triage — prioritising fields with better soil organic matter, splitting applications, leaning harder on legumes where possible, and choosing varieties known to perform under lower nitrogen.
In the longer term, CSIRO’s message is that farmers like him shouldn’t be left alone to gamble on global fertiliser markets every year. Through better varieties, smarter root systems, improved soil biology, and seed and manure innovations, we can tilt the odds.
When lightning cracks over a field in Hurungwe, it’s still quietly fixing nitrogen into the soil, just as it did before humans learned to bottle the air. The science coming out of Australia doesn’t suggest we can go back to relying on storms alone. But it does suggest a path where we ask plants and soils to shoulder more of the work — and where, one day, the pile of bags in VaGumbo’s shed doesn’t have to be quite so high for his family, or his country, to eat.
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