Mono Ammonium Phosphate, better known to many chemists and farmers as MAP, didn’t appear overnight. A hundred years ago, few outside the world of chemistry gave much thought to phosphorus or ammonium salts. Agricultural expansion pushed folks to look for better ways to feed crops, and during the early-to-mid twentieth century, research labs ramped up interest in salts like MAP. Companies got behind rock phosphate mining, sulfuric acid production, and the chemical blending that would lead to modern MAP. By the 1960s, MAP had its own shelf at the feed and seed store, signaling a shift from small-scale phosphate use to global trade. There’s a good reason the old chemical industry magazines are thick with ads for phosphate—this stuff transformed modern agriculture in ways earlier fertilizers never managed.
MAP carries the formula NH4H2PO4. In the chemical supply closet, it’s a reliable, easy-to-identify powder or crystal. It enters the scene as both fertilizer and fire retardant, so it occupies a tough spot: doing hard field work on one hand and defense against wildfire on the other. Compared to Di-Ammonium Phosphate (DAP), MAP packs a little less nitrogen but delivers more phosphorus per unit, which gives farmers flexibility, especially on phosphorous-hungry soils. Its solubility means it doesn’t stick around forever when exposed to rain—good for quick root uptake, but you have to watch for runoff.
MAP shows up as a white, odorless crystalline powder. Grains crunch fine between your fingers and dissolve quickly in water. Water solubility stands strong—about 370 grams per liter at room temperature. At high heat, it starts melting around 190°C, but what’s more interesting is the decomposition: above 200°C, it kicks off ammonia fumes and leaves behind phosphoric acid. For someone working in the plant lab, these traits make MAP a good fit for fast-dissolving fertilizers or as part of firefighting powders. The blend of ammonium and phosphate ions, both common in living things, means nature knows what to do with this compound once it enters the ecosystem.
On fertilizer bags, MAP is sold under the N-P-K formula: 11-52-0, which shows the strong punch of phosphorus. Any technical data sheet counts on the purity and particle size. Particle sizing matters less to big factories churning out hundreds of tons, more to folks using precision agriculture gear. Most national guidelines require labeling of moisture content (usually kept below 2%), presence of heavy metals (every serious manufacturer should post a cadmium limit), and batch analysis for ammoniacal nitrogen. Trace impurities—like iron or silica—often show up, sometimes due to the original phosphate ore, and product managers need tight process controls to keep them low.
Factories approach MAP production by reacting ammonia (NH3) gas with orthophosphoric acid (H3PO4). This sounds simple on paper but tells you plenty about why big maps of fertilizer factories dot the riverbanks of the US Midwest and Chinese industrial zones. You see towers venting white clouds; those clouds come from the exothermic heat of neutralization, where ammonia meets acid and churns out MAP crystals. After reaction, manufacturers cool the mixture, let MAP crystallize out, and then dry it before bagging. Few operations can do this well without tight control since excess ammonia or acid changes the final product’s chemistry.
Reactive MAP isn’t just stuck in its original form. Manufacturers sometimes tweak it for special roles. Blended with urea or potassium chloride, you create other fertilizers with a broader nutrient mix. MAP itself can act as a starting point for forming polyphosphates under heat and pressure, or react with calcium compounds, resulting in different phosphate salts. In fire retardants, chemical additives help MAP cling to foliage and resist washing away, key for wildland firefighting. Researchers have found ways to microencapsulate MAP—trapping it in coatings that slow its release, so farmers don’t have to reapply after every rain shower.
Don’t expect every chemist or agronomist to call it MAP. Some refer to it as Ammonium Dihydrogen Phosphate, Acid Ammonium Phosphate, or just NH4H2PO4. Brand names pop up depending on the manufacturer and region: PhosAgro, Mosaic MAP, Haifa MAP, and so on. In fire safety, you mostly see “Monoammonium Phosphate Powder” listed on fire extinguisher labels. The fertilizer aisle tends to lead with the N-P-K values, and MAP’s distinctive ratio makes it easy to spot.
Handling MAP rarely worries folks the way pesticides do, but safety protocols are no afterthought. Large-scale operations require dust masks, eye protection, and ventilation, since inhaled particles or splashes in the eye cause irritation. Long-term bulk storage in damp places encourages caking and compaction, which damages product quality. MSDS (Material Safety Data Sheets) always call out its incompatibility with strong alkalis or oxidizing agents—mix those and you risk unwanted chemical reactions. For transport, MAP falls under the non-hazardous materials code, but spills near waterways create real phosphorus pollution concerns, so spill plans matter.
Agriculture leads the demand for MAP, since both food crops and ornamentals count on phosphorus for cell function, root growth, and increased yield. Anyone who’s worked on a row crop farm likely spread MAP just before planting, either by surface broadcasting or banding it in rows. Commercial greenhouses use it for precise feeding systems, since the high solubility makes it ideal for drip irrigation. But MAP isn’t limited to food: it’s the main fill in the famous “ABC” fire extinguishers you see in offices and kitchens, where it smothers flames by cutting off air and breaking chemical combustion chains. Specialty markets depend on the chemical’s compatibility with polymers, so you sometimes see it in flame-retardant tapes, cements, and paint primers.
Researchers haven’t lost interest in MAP after a century of use. Some agricultural scientists chase smarter fertilizer formulations, blending MAP with microscale coatings to slow down nutrient leaching. Others aim for ways to recycle phosphorus from waste streams—urban wastewater or manure plants—into MAP, closing the loop in fertilizer supply. Fire science labs try to improve its stickiness and weather resistance, searching for retardants that last longer between storms during wildfire season. Even outside the farm or firehouse, polymer scientists adapt MAP to suit new composite boards and nano-materials needing better flame resistance without harsh fumes. Each innovation pushes the chemical past its old limits.
Toxicity sits at the center of chemical debates, and MAP has drawn stacks of studies. For most humans, it counts as low-toxicity—exposure leads to mild irritation, not chronic illness, when handled properly. Drinking water standards set phosphorus and ammonium limits far below what a MAP granule delivers; incidents usually come from over-application or factory runoff. The big concern comes down to ecosystems, not people. Excessive phosphorus pollutes rivers, drives algae growth, and triggers fish die-offs. Because MAP’s nutrients dissolve fast, you need stewardship: keeping it out of waterways, timing application before plant growth periods, and promoting buffer zones. Animal tests rarely link MAP to lasting toxicity, but research continues on build-up in soil and long-term groundwater exposure.
Anyone watching global trends sees MAP demand climbing as new regions chase higher farm yields. Sustainability stands as the challenge that will shape its future. Producers and farmers have to improve both phosphorus use efficiency and recycling. Urban waste recovery, precision fertilizer placement, and nutrient-stabilizing coatings point toward a low-impact road ahead. As fire risk zones enlarge thanks to climate change, expect continued investment in next-generation MAP-based fire retardants—maybe even bio-based blends or smarter “sticky” formulations that perform better with less. Regulatory frameworks will need to keep up, protecting waterways and mandating safer manufacturing, storage, and use protocols. If history says anything, MAP will evolve: not because it’s “ideal” or “universal,” but because people push chemicals to work harder, safer, and cleaner in a world with tight margins and growing demand.
Mono Ammonium Phosphate, or MAP, shows up in almost every serious farming operation I’ve seen, whether folks are growing row crops or putting in a backyard patch of veggies. MAP delivers two things every plant needs in big doses: nitrogen and phosphorus. For a lot of soils, phosphorus slips right through, and plants struggle to grab it. MAP puts both nutrients in reach, helping seeds set roots and seasons produce some real heft. Most places with heavy planting – from the cornfields in the Midwest to rice paddies in Asia – rely on a steady supply.
Big yields aren’t just about luck or fancy machines. They need a recipe, and good fertilizer plays a starring role. MAP kicks off early growth, gives seedlings a push, and supports blossoms and grains as crops mature. In my experience, places short on phosphorus always look duller and deliver less, rain or shine.
MAP is best known as a plant booster, but that’s not where the story stops. It helps out in fire extinguishers, where its powder smothers flames quickly. If you’ve ever watched firefighters handle an electrical blaze, you might’ve seen that pale dust settle and keep sparks from reigniting. Factories also use MAP to keep equipment safe, and it often lines the shelves in supply rooms for emergencies.
Some folks use it for a clean-up job, since the phosphate can help break down and clear away certain metals from water in mining operations. You don’t hear much about it, but wastewater plants sometimes treat water with compounds like MAP before letting it back into rivers. If the job calls for locking up heavy metals, this fertilizer steps in outside the field.
Farmers want their crops lush, but using too much MAP brings trouble. The excess can run off in heavy rain, washing nutrients into rivers and lakes. That sparks big algae blooms, drains oxygen, and chokes out fish. The Gulf of Mexico sees these “dead zones” grow almost every year, mainly from the stuff washing off Midwestern fields.
Phosphorus doesn’t just vanish. Once in the water, it hangs around. That puts pressure on everyone upstream to rethink what and how much gets put down. Companies making MAP try offering formulas with more precise nutrients. Precision agriculture turns the tide, letting farmers map soil, test for gaps, and give only what’s needed. It takes work, but cutting back on blunt spreading keeps crops healthy and waters clearer.
As demand grows, the world pays more attention to how these nutrients move. I’ve seen communities tie conservation efforts to grants or price breaks for smarter fertilizer use. Farmers talk with local co-ops and conservationists, aiming for full yields with less impact. Old timers remember when fields didn’t glow so green, but most agree the payoff comes from working smart, not loading up the bag.
MAP keeps food shelves full and fires at bay, but the best uses take a steady hand and a mind for tomorrow’s rivers and lakes. Every scoop tossed on the soil means a chance to do it right – not just for crops, but for everyone connected down the line.
Fertilizers hit the market with numbers front and center, and a lot of folks stare at those N-P-K ratings confused or just plain uninterested. Mono Ammonium Phosphate, or MAP, usually wears the numbers 11-52-0 on its bag. This ratio matters a whole lot more than people might think.
The first value, nitrogen (N), sits at 11%. This part gives plants a boost early in their life, helping green shoots and fresh leaves jump up out of the soil. Out here, cold spring gardens won’t get going without a little help from nitrogen. Getting that kick right can mean brighter fields and fuller harvests.
The phosphorus (P) content gives us the ‘52’. That’s a big leap from the nitrogen side. It means MAP delivers phosphorus in a way roots can use fast and easily. Phosphorus plays a big role in root development, flower setting, and fruiting. Ask a farmer who’s faced yellowing leaves or slow-growing seedlings, and they’ll often talk phosphorus. This makes MAP a favorite each year for getting seeds off to the right start, especially in soils that test low or cool spring conditions that tend to lock phosphorus away.
Zero potassium (K) might jump out in that trio. For some crops, and in many soils, there’s already enough potassium hanging around. Fields tend to build up K over time, so growers often find they don’t need more in every application. This is why MAP leaves out potassium and focuses on what’s needed most at planting time.
The numbers on the MAP label came out of decades of farm seasons. Soil tests guide growers to fertilizers that match actual needs, not just tradition. Walk into any co-op in the spring and talk to the seasoned hands behind the counter. They’ll say, 11-52-0 is about delivering starter phosphorus in a form crops can grab, no matter if you’re running big field corn or patching up a patch of carrots out back.
It’s not about pushing out more and more of each nutrient. Too much phosphorus actually locks up other nutrients; run-off puts a strain on rivers and lakes, too. Small grains especially call for a balanced hand. Overusing anything, even the right stuff, backfires over time.
Growers who treat fertilizer as a tool, not a cure-all, wind up saving money and yield. Soil testing tells you whether the 11-52-0 MAP formula fits or if you need to adjust. Blending MAP with other sources helps fill gaps when potassium or extra nitrogen is short. Some farms use banding at planting to help the root zone grab that phosphorus just as the plant needs it.
Keeping an eye on those three numbers opens the door to healthier plants, cleaner water, and more resilient operations. Any time the budget gets tight, fertilizers with clear, reliable N-P-K profiles like MAP help avoid guesswork, waste, and unwanted surprises down the line.
Monoammonium phosphate, or MAP, pops up often in farm supply stores. Its two main draws? A reliable dose of phosphorus and a good boost of nitrogen. Cornfields across the Midwest eat it up. Vegetable growers chasing root growth turn to it, too. The quick-hitting phosphorus helps kickstart seedlings and gives roots a strong launchpad.But just because MAP gets shelf space everywhere, doesn’t mean every plant thrives with it.
From my own experience walking through wheat fields and fruit orchards, not every crop wants the same recipe. Cereals like wheat, corn, and barley are often restless in soils with a phosphorus shortage. Spreaders carting MAP across these fields can sometimes work wonders. I watched a neighbor’s oats shift from pale green to a rich forest shade by midseason, just from a timely MAP application before planting.
Leafy greens and many legumes don’t always demand such phosphorus-heavy support. Nitrogen-hungry vegetables, like lettuce and spinach, may get the same spark from a balanced fertilizer. Overdoing phosphorus here can lock out micronutrients, like zinc or iron, leading to yellowing and weak growth. I’ve seen spinach plants stall from over-fertilization. Sometimes the worst stunting comes from too much enthusiasm, not too little.
Soil isn’t just a blank slate. Clay-heavy farms hold on to phosphorus, releasing it slowly, so MAP benefits don’t always roll in all at once. Sandy fields leach nutrients fast, so plants might use MAP more fully. Warm, moist climates make nutrients available quicker, but cooler, damp spring soils can keep phosphorus locked out of reach. My own patch of black prairie ground, high in natural phosphorus, showed little difference adding more MAP. But just half a mile away on lighter soil, neighbors swear by it.
Soils with high pH, such as alkaline patches out west, are notorious for fixing phosphorus in forms plants can’t use. Piling on more MAP only fattens the fertilizer bill. Switching strategies, like applying chicken litter or using a phosphorus-solubilizing bacteria, stretches dollars further. Watching a friend’s alfalfa respond better to compost than chemical fertilizer opened my eyes to these alternative routes.
Not every solution on the farm starts with a fertilizer truck. Farmers and gardeners often get more mileage from a trusty soil test than guesswork. Spending a little time on soil sampling pays for itself fast. Once you know what’s missing, you can dial in the mix. Sometimes a blend with less phosphorus, or timed applications, works better for crops like potatoes, beans, or berries.
It’s easy to get caught up in the one-product-fixes-all cycle, but field results push back against that idea. In places with phosphorus-rich soils, rotating with legumes or tapping into natural sources can free up stuck nutrients. In phosphorus-poor regions, MAP or alternating organic sources can give crops the lift they need, without building up a stubborn surplus that hurts future plantings.Smart farming is about tweaking and observing, not just repeating what worked for the neighbor.
Mono Ammonium Phosphate shows up in so many places: farming fields hungry for nutrition, warehouses stockpiling fire extinguishers, and even some workshops. It comes across as a powder or a granule, and both types can draw moisture like a magnet. Over the years, I've watched bags harden into blocks and containers leak, all for one reason—ignoring proper storage. This isn't something to push down the priority list.
Dampness spells trouble. In a humid storage room, Mono Ammonium Phosphate clumps up before you know it. That lump stops spreading in a field and can ruin fertilizer spreaders or jam machinery. I once saw a small flood creep into a storeroom and half a pallet turned rock-solid within days. Keeping the chemical dry makes all the difference.
Storage rooms deserve close attention. Simple fixes, like pallets and thick plastic sheeting on the floor, stop small leaks from reaching the product. Using moisture-absorbing packets between bags offers another layer of protection. I’ve seen even big operations forget plastic liners or leave doors open in rainy weather—minor negligence that causes major waste.
Though it doesn’t catch fire on its own, Mono Ammonium Phosphate can release toxic gas if burned. Many people assume that fertilizers can't be dangerous until someone leaves a bag next to a heater or a hot piece of equipment. Storing it far from any sources of heat isn’t just a safety precaution; it’s a necessity.
Clear separation helps. Designating a room or a corner that’s cool, dry, and out of the sun helps prevent problems. Just as important, label everything clearly; confusion breeds carelessness.
Mixing Mono Ammonium Phosphate with other fertilizers or chemicals leads to problems that few want to discover. Some things, like urea or strong acids, react badly when piled together. I’ve watched people stack bags high to save space, only for cross-contamination to create headaches such as color changes or odd smells. Separate storage beats dealing with ruined shipments.
Product left open absorbs water straight from the air. If a bag rips or a lid cracks, even the cleanest warehouse can’t stop the humidity from sneaking in. Transferring opened bags to airtight, rigid bins preserves their quality and keeps critters out as well. Metal drums with rubber seals, heavy-duty buckets with snap-on lids—these are investments that pay off.
Having clear records on stock, location, and date matters. I’ve run into more than a few situations where a forgotten bag expired, or a shipment got lost for months at the back of a crowded shed. Tracking everything avoids misplacement and makes rotating old product easier, helping prevent waste and hidden safety risks.
Storing Mono Ammonium Phosphate properly boils down to common sense and consistency. Whether stocking a garden shed or a commercial warehouse, every step—protecting from water, heat, and contamination—lets this valuable chemical do its job. The most frequent hazards I’ve seen come from shortcuts. Taking a little time saves money, prevents headaches, and keeps people safe.
Everywhere crops grow, someone faces choices out in the shed: what blends in the tank, and what turns into a gummy mess? Monoammonium phosphate—most folks call it MAP—offers plenty of phosphorus and a bit of nitrogen in one bag. A tight margin season means not just picking the right fertilizer, but making sure it works well with everything else going into the soil, whether that’s urea, potash, or something to keep bugs and fungi away.
MAP blends with a lot of other dry fertilizers—urea and potash being two of the most common. Farmers like this because it saves on passes and fits well with variable-rate plans. Toss MAP and urea together, they hold up. No caking, no chemical fireworks, and both get to the root zone where plants use them. Same goes with potash—mixing broadens the nutrient package without risking fertilizer “burn.” These combos land on fields from Australia to Brazil, and over decades, results say the math adds up.
Soil folks always remind you—mixing MAP with lime doesn’t do anyone favors. Phosphorus locks up, turns into forms plants can’t grab, and dollars end up wasted. Gypsum creates a bit less pain, but you’ve still got to watch application timing. Tossing MAP straight onto very alkaline or calcareous soils? That’s another way to lose the value you paid for. Maybe a better split—one material on, rain comes, then layer the next—keeps each input working hard.
Dry fertilizer blends aren’t the only concern. Every ag retailer fielded the question: “Can I tank-mix MAP with my herbicides or fungicides?” The answer usually circles back to form and pH. Straight MAP won’t dissolve easy enough to toss in with most sprayers—the stuff’s meant for the ground, not the nozzles. On the foliar side, there’s MAP in some specialty sprays. Growers find value on certain broadleaves, but the trick lies in checking labels and small-scale tests first. No one likes clogging sprayer lines or toasting leaves because something settled in the bottom of the jug.
Weed and disease programs use more than just fertilizer—water conditioners, oils, and soil boosters fill up the shelf. That’s where experience counts. Not all commercial water conditioners get along with MAP, and mixing in the wrong order runs up the bill for new parts or even lost crops. Calling local extension or the ag rep may save a field’s worth of headaches.
Field edges and test strips still sort out more questions than the shiniest university study. Mix a small batch before hitting big acreage. Add one new ingredient at a time. Listen to a neighbor who’s been in the same battle. That willingness to double-check avoids mistakes that don’t show until weeks later, when the best response costs more than fixing it up front.
This whole business of matching MAP with other products always circles back to one idea: make sure every dollar you spend turns into more bushels in the bin. Whether it’s a physical blend or a tank-mix, the right moves take work and curiosity, and leave room for checking and learning. Agriculture’s always changing, but smart combining sticks around as long as folks put their hands in the dirt.
| Names | |
| Preferred IUPAC name | Ammonium dihydrogen phosphate |
| Other names |
Ammonium dihydrogen phosphate Ammonium phosphate monobasic MAP Monoammonium orthophosphate |
| Pronunciation | /ˌmɒn.oʊ.əˈmoʊ.ni.əm ˈfæsfət ɛm ɛf eɪ ɛl ɛm ˌɛm eɪ ˈpiː/ |
| Identifiers | |
| CAS Number | 7722-76-1 |
| Beilstein Reference | 2708730 |
| ChEBI | CHEBI:63006 |
| ChEMBL | CHEBI:63031 |
| ChemSpider | 77436 |
| DrugBank | DB11336 |
| ECHA InfoCard | 03c9f6e3-352b-44e6-9c3c-2fbc515a487d |
| EC Number | 226-575-2 |
| Gmelin Reference | 85638 |
| KEGG | C00221 |
| MeSH | D018778 |
| PubChem CID | 101441 |
| RTECS number | SB1875000 |
| UNII | 2WQY37749N |
| UN number | UN2061 |
| Properties | |
| Chemical formula | NH4H2PO4 |
| Molar mass | 115.03 g/mol |
| Appearance | White crystalline powder |
| Odor | Odorless |
| Density | 1.8 g/cm³ |
| Solubility in water | 370 g/L (20°C) |
| log P | -2.1 |
| Vapor pressure | Negligible |
| Acidity (pKa) | 5.5 |
| Basicity (pKb) | 8.8 |
| Magnetic susceptibility (χ) | −61·10⁻⁶ cm³/mol |
| Dipole moment | 1.52 D |
| Thermochemistry | |
| Std molar entropy (S⦵298) | 100.7 J·mol⁻¹·K⁻¹ |
| Std enthalpy of formation (ΔfH⦵298) | -1287 kJ/mol |
| Std enthalpy of combustion (ΔcH⦵298) | -1282 kJ/mol |
| Pharmacology | |
| ATC code | V06DF |
| Hazards | |
| Main hazards | May cause respiratory irritation. Causes eye irritation. Causes skin irritation. |
| GHS labelling | GHS02, GHS07 |
| Pictograms | GHS07, GHS09 |
| Signal word | Warning |
| Hazard statements | H315: Causes skin irritation. H319: Causes serious eye irritation. H335: May cause respiratory irritation. |
| Precautionary statements | Keep container tightly closed. Keep only in original container. Store in a dry place. Avoid breathing dust. Wash hands thoroughly after handling. Do not eat, drink or smoke when using this product. Wear protective gloves/eye protection/face protection. |
| Autoignition temperature | > 400°C |
| Lethal dose or concentration | LD₅₀ (oral, rat): > 2,000 mg/kg |
| LD50 (median dose) | LD50 (median dose): > 2000 mg/kg (oral, rat) |
| NIOSH | SF7580000 |
| PEL (Permissible) | PEL (Permissible Exposure Limit) for Mono Ammonium Phosphate (MAP): "15 mg/m³ (total dust), 5 mg/m³ (respirable fraction) as OSHA PEL (particulates not otherwise regulated) |
| REL (Recommended) | 30 kg/ha |
| IDLH (Immediate danger) | 300 mg/m3 |
| Related compounds | |
| Related compounds |
Diammonium phosphate Ammonium sulfate Urea Single superphosphate Triple superphosphate Potassium phosphate |
