Diammonium Phosphate didn’t show up overnight. Its story winds back to the times when folks realized their fields needed more than just cow manure to thrive. DAP came out of the 20th century’s search for fertilizers that deliver both nitrogen and phosphorus in a single bag. The rise of chemical fertilizers mirrored bigger farms and a growing demand for reliable crop yields, especially after war-era research gave chemical companies a chance to experiment at scale. By the 1960s and 70s, DAP had found its way from laboratory benches into the hands of farmers across North America, Europe, and expanding economies. Mass producers turned to a process involving ammonia and phosphoric acid, and the fertilizer market hasn’t looked back since.
Diammonium Phosphate serves as a granulated, off-white fertilizer. Each granule carries both nitrogen and phosphorus—and that's a big deal for staple crops like wheat, rice, and maize. DAP also finds a place on ships hauling fire retardants, in brewing, and even in physics laboratories as a kind of buffer. Its granules pour smoothly, making spreading in the field less of a hassle. Farmers know it for its kick-start to young seedlings, helping roots anchor and grow in soils that often lack available phosphate. Companies often sell it under names like “DAP 18-46-0," which tells you this stuff packs 18% nitrogen, and 46% phosphorus pentoxide.
DAP’s structure centers on the NH4+ and H2PO4- ions. It doesn’t stay rock solid forever—moisture in the air can dissolve it back into its ions. At room temperature, those sugar-sized crystals stay stable, free-flowing, and surprisingly tough for everyday handling. The melting point sits stubbornly at 155°C, a reminder this fertilizer won’t catch fire or break down during transport. In water, the pH jumps to 7.5–8.0, so it falls just slightly alkaline, which matters when mixing with other chemicals or spreading on soils sensitive to pH swings.
Walk into any agricultural supply store, and DAP shows up with strict tags. Regulatory agencies push for clear labels, spelling out nutrient percentages along with safety warnings and batch tracking numbers. Industry plays by international codes—ISO and FAO both have their eyes on nitrate and phosphate standards, and shipping bags need durable printing. Weight and purity must hit benchmarks: manufacturers test for heavy metal contaminants, particle size, and solubility, and anything sold under the DAP name must line up with both local and international rules. The numbers—often 18-46-0—aren’t just decoration. Those figures drive fertilizer blending, and they help the farm manager avoid under- or over-shooting field requirements.
Plant operators keep things moving around the clock. They charge big reactors with anhydrous ammonia and concentrated phosphoric acid. The acid reacts with the ammonia, heating up and releasing steam, which needs careful handling to avoid dangerous bursts or accidental releases. The result—after cooling—are crystals. This DAP then heads to dryers, granulators, and screens before bagging. The process bats away contaminants, but the real skill lies in balancing raw material quality with process conditions to make fertilizer that flows smoothly and doesn’t clump in bags for months. It’s more panel controls and lab samples than test tubes and textbooks.
DAP enters the soil as a soluble salt but doesn’t stick around in its original form for long. Rain or irrigation breaks it into ammonium and phosphate ions. In acidic soils, ammonium can release more hydrogen ions, raising pH locally; in calcareous soils, free ammonia may escape, wasting nitrogen. Soil bacteria speed up the changes, often making nitrogen available to crops within days. Blenders sometimes tweak DAP’s makeup with conditioning agents to keep dust down during spreading, and researchers are always on the hunt for coatings or additives that might boost nutrient uptake or slow release, cutting losses in wet climates.
Apart from its technical title, DAP goes by aliases like ammonium phosphate dibasic or ammonium hydrogen phosphate. In trade, it picks up names like “CropKing DAP,” “Agrium’s 18-46-0,” and generic descriptors like “starter fertilizer.” Each region might flag it differently on customs lists. Labeling clarity matters since the world’s fertilizer market sees plenty of substitutions and blends, and buyers look for the N-P-K numbers first, letting the chemistry take a back seat.
DAP holds a solid track record compared with more volatile fertilizers, but it’s no lunch ingredient. Inhalation irritates the throat, dust can stick to skin, and high exposure eyes sting. Facilities rely on dust suppression, protective gloves, and regulators enforce permissible exposure levels. Storage calls for dry conditions, with good ventilation and careful stacking. Spill response plans emphasize containment and cleanup—no one wants groundwater phosphate spikes. Out in the field, instructions aim to prevent accidental over-application that runs off into waterways, stoking algae blooms. Regulators in the EU, US, and China all press for documentation and regular inspection.
DAP started by feeding grains, but its use spreads way beyond the farm gate. Flame retardant recipes rely on its phosphorus backbone; the forest fire folks use it in air drops. Brewing industries tap into DAP to fuel fermentation, especially in wine and beer, keeping yeasts humming. Aquaculture crowds sometimes spike tanks with it to spark algal blooms—the base of many fish food chains. Even water treatment plants dose out DAP to balance nutrient cycles in municipal systems, tapping into its adjustability and predictability.
University researchers and fertilizer makers race to make DAP more efficient and less polluting. Plenty of effort goes into “smart” coatings, aiming to time nutrient release with plant growth stages. Lab teams measure runoff losses after heavy rain, or test plant tissue to see how much DAP actually ends up in the food we eat. Engineers examine how manufacturing tweaks—like different acid sources or ammonia concentrations—change crystal structure and, by extension, how well DAP mixes in the field. Increasingly, work moves toward recycling phosphorus from wastewater and old mines, looking for ways to create DAP alternatives before natural phosphate runs out.
While DAP scores low toxicity by most measures, scientists keep tabs on its effects in fresh water and soil. Oversized doses leach phosphate into rivers and lakes, where algae feasts and fish suffocate under the resulting blooms. The ammonium component, though less persistent than nitrate, can still stress aquatic life at high concentrations. Long-term studies look at subtle impacts—say, what years of rising phosphorus mean for wildlife or downstream drinking water quality. Most safety sheets warn workers about dust exposure and call out the value of prompt clean-up in both field and warehouse settings.
With global farmland under strain and a shrinking pool of accessible mineral phosphate, DAP faces tough questions ahead. Will farmers shift toward recycled phosphorus, or lean on precision agriculture to get more from each granule? New blends might pair DAP with micronutrient boosters, or use nanotechnology coatings that promise savings on total fertilizer bills. There’s also an active push for regulations that cap phosphorus emissions, and companies see opportunity in “green” certification labels and smarter logistics. Judging by the sheer volume of research and investment, this isn’t a product headed for retirement—its forms will evolve, and the way we handle it must keep pace with farming and environmental priorities.
Walk through any major agricultural region and you’ll spot big bags marked DAP stacked in storage sheds or laid out near the fields. Diammonium phosphate isn’t some trendy new invention; it’s been around for decades. Farmers have come to depend on it, and for good reason.
Crops need the right blend of nutrients to thrive, and DAP delivers two that are absolutely essential: phosphorus and nitrogen. A standard bag packs about 18% nitrogen and 46% phosphorus in one shot. Most soils turn up short on phosphorus, especially after years of heavy harvests. Plants struggle to fix roots, grow strong stems, or produce full grains if phosphorus lags. Nitrogen keeps plants green and lush, pushing the kind of leafy growth you see in healthy, high-yielding fields.
That double boost makes DAP an all-star for everything from corn and wheat to rice and vegetables. Where I grew up, neighbors nearly always gave their wheat fields a DAP starter dose. Yields dropped if they tried to skip it. The reason’s simple: without phosphorus at sowing, young plants start off weak and don’t recover later.
DAP comes as hard granules. You toss it on by hand, spread it with a broadcast spinner, or drop it right in the seed row. Granules dissolve fast when rain arrives, putting nutrients right where roots start searching. In areas with unpredictable rain, this speed matters. Crops get a head start, even if the sky holds off for a week or two after planting. On smaller farms, simple spreading beats mixing up slurries or specialized equipment for liquid fertilizers. Less fuss means fewer delays during sowing.
On thousands of farms worldwide, DAP has built food security season after season, but it hasn’t solved everything. Sometimes folks spread too much, not thinking about the soil’s actual needs. Phosphorus overuse doesn’t vanish—it runs off into streams and lakes, leading to murky water and algae blooms that choke out fish. I once visited a rice-growing region where the water was green from top to bottom. Locals knew fertilizer runoff played a part, but getting folks to use just the right amount takes education and better soil testing, not just more regulation from the outside.
The other thing that crops up is price. Since DAP relies on ammonia and phosphate rock, spikes in fuel costs or political disruptions overseas can send prices straight up. Farmers in countries without homegrown raw materials feel the pinch the most. It’s a reminder that, in feeding the world, local solutions and diverse supplies matter as much as big, centralized factories.
Some folks now use soil sensors, drone technology, or precision maps to figure out exactly how much DAP to spread—no more, no less. This can cut back waste and pollution, protecting watersheds and making crops just as healthy. Governments and farm groups push for more soil testing and subsidized lab access, especially for small-scale growers.
No single product can solve every challenge in agriculture. Still, DAP has earned its place by giving farmers a reliable, straightforward way to supply phosphorus and nitrogen when and where they matter. Using it wisely, with an eye toward both yield and the planet, marks the real way forward.
DAP, or Diammonium Phosphate, pops up on store shelves and in farm supply catalogs every season. Its bag doesn’t hide what’s inside: a stamp showing 18-46-0. These three numbers matter more than folks realize. They tell us the percentage by weight of nitrogen (N), phosphorus (P), and potassium (K) in the fertilizer. So, DAP contains 18 percent nitrogen, 46 percent phosphorus (as P₂O₅), and not a bit of potassium.
That middle number, 46, draws attention right away. Crops rely on phosphorus not just to get going but to build roots deep enough to chase moisture and nutrients. High phosphorus in DAP lines up with what young plants crave. Nitrogen, at 18, offers a steady boost to early growth but doesn’t go overboard. Farmers who add DAP before planting see quick results from that nitrogen, while the phosphorus lingers and keeps fueling root systems as the season stretches on.
Pitching bags of fertilizer on a wagon might look simple, but getting the mix right is trickier. My father never just reached for any random sack. We checked the N-P-K numbers like checking the oil in a truck. Too much nitrogen burns seedlings. Too little phosphorus leaves plants small and weak, especially if your soil tests hint at a phosphorus shortage. DAP’s blend punches up germination, kickstarts growth, and lowers the stress on new roots. That’s one reason corn and wheat growers swear by it, especially in areas where soil phosphorus runs low.
The high phosphorus counts bring up some honest concerns. Spreading DAP every season in the same spots loads the soil with phosphorus, and extra nutrients end up in streams and lakes after a big rain. This runoff issue isn’t a problem on just one farm; it affects whole watersheds. It clouds water, fuels algae blooms, and messes up fish habitats. So, while DAP makes wheat jump out of the ground, it’s also part of the need for fertilizer plans that balance results with environmental care.
Solving these runoff problems isn’t about banning DAP or pointing fingers at farmers. Soil testing matters. My own small patch out back taught me that. Before scattering anything, I use a soil probe and send samples to a co-op lab. That way, I learn exactly what’s missing and avoid wasting fertilizer or letting it wash away. Banding DAP close to seed rows instead of broadcasting it can keep nutrients where roots can reach them, cutting down on runoff. Local extension offices bring advice on which fields need phosphorus and which ones get by with less.
DAP’s reputation for jumpstarting crops keeps it in the fertilizer shed year after year. The 18-46-0 formula fits many common row crops and vegetable patches. But wise use and routine soil checks make the difference between bumper harvests and unintended harm downstream. Farmers and gardeners alike get to draw on old hands’ experience and new science to use DAP better, getting food out of the ground while keeping rivers and streams in good shape.
Diammonium phosphate, known by most as DAP, stands out for a reason. It supplies both phosphorus and nitrogen, making it a popular pick for fields across the world. On my family’s farm, we relied on DAP to jumpstart everything from wheat and corn to tomatoes. Every season, timing and method separated so-so crops from the ones that made us proud.
Too many folks skip soil testing, maybe out of habit or cost, but this move saves money and protects water and soil. I remember an older neighbor spreading DAP every spring, no matter what. His yields started dropping. The soil didn’t need all that extra phosphorus, just more careful management. Testing lays out a clear picture, showing how much DAP to use without risking runoff or waste.
Crops crave phosphorus early on, especially right after planting, when roots are small and looking for nutrients. If DAP sits too long before seeds go in, heavy rain can wash valuable nutrients into rivers rather than into hungry plants. I found the best results dropping DAP just before sowing, then mixing it lightly into the soil. Plants sprouted with more vigor, and root systems dug deep.
Broadcasting DAP across the entire field works, but too often, the edges of the field collect extra fertilizer, and a lot of it never reaches young roots. Band placement, where strips of fertilizer drop right beside the seed row, shows better results on our ground. This way, the young plant roots have a buffet set right in front of them. I usually shoot for two inches to the side of the seed and a couple inches below. Corn and wheat especially take to this approach.
Too much surface-applied DAP just waits for the next rainstorm to move it, often somewhere you don’t want it. If a big weather system looms, hold off. Work the fertilizer into the soil or wait until things dry out. Just last year, I lost nearly a quarter of a bag to heavy runoff during a crazy spring downpour. Lesson learned: soil incorporation beats risking runoff every time.
Plants grow strong with a balance of nutrients. Tossing DAP out without thinking about nitrogen or potassium misses the mark. Over the years, I started mixing DAP with urea or potash when fields showed holes in their nutrient profile. This stopped weak growth patches and boosted overall yield. Local extension services offer good advice on this front.
Nothing replaces walking fields and checking plants. If leaves look pale or fall behind, there’s a message in that. Over-application, though, shows up as burned roots and stunted plants, something I’ve kicked myself for watching. Adjust as you go; soil is alive and changes each season with crop rotation, weather, and rainfall.
New gear, like precision drills and GPS-guided applicators, can boost DAP efficiency. These tools let you target strips or specific zones, cutting both waste and cost. Some years, custom applicators know more about local soil quirks than anyone, and I lean on their advice. Innovation keeps input bills down, and fields healthier for the next generation.
DAP stands for diammonium phosphate, a fertilizer that contains two main nutrients: nitrogen and phosphorus. It comes as small granules, fairly easy to handle, and dissolves quite fast under moisture. Commercial growers and home gardeners reach for it a lot since it bumps up plant growth quickly. In my earliest gardening days, I put DAP under nearly all my vegetables. The spinach and cabbages took off like rockets. That type of visible growth can get addictive, yet I noticed some patches struggled or turned yellow around the edges. Digging a little into what DAP actually does, its high phosphorus content started to stand out as both an asset and a stumbling block, depending on what you want to grow.
Not all plants love abundant phosphorus. Some, like beans and most native wildflowers, prefer soils with little-to-no fertilizer added. DAP tilts the scale on soil pH, making it a bit more alkaline. Acid-loving plants—blueberries, azaleas, and camellias for example—often look stunted or faded when you use DAP close to their roots. My aunt used DAP around her rhododendrons once, thinking more food is always better. Leaves dropped, flowers shriveled, and she had a mess that took a season to bounce back. That bunch favors more acidic soil and milder feeds.
Young seedlings or freshly-transplanted crops burn fast if you pile on DAP granules. I’ve seen ugly blackened root ends in tomato starts because folks sprinkled fertilizer directly in contact with roots. The high salt content in DAP can suck moisture out and kill tissue. Instead, it helps to scatter the granules some inches away—or, even better, scratch them lightly into the surface and water thoroughly. This way, roots reach out for nutrients as they need them without getting torched at the start.
A soil test saves loads of trouble. Most garden store workers can guide you through a basic kit. In one local community plot, the soil phosphorus measure came back off the charts after years of annual DAP use. Vegetables still set leaves but no fruit formed well. Too much phosphorus locks out other nutrients like zinc and iron, which leads to stunted or discolored foliage in many garden staples. Corn, tomatoes, and peppers demand steady feeding, but abundance of one nutrient can throw others out of reach.
There are plenty of situations where compost or lower-phosphate blends do the job just fine, especially in long-used soils. Green leafy crops—lettuce, arugula, herbs—often need more nitrogen than phosphorus. Building healthy soil with regular mulching, companion planting, and crop rotation keeps plants thriving with less risk. DAP works best when the soil truly needs a phosphorus boost, not just as a ritual spring dumping before every seed packet hits the dirt.
I keep DAP in the shed for the heavy feeders—onions, garlic, spring brassicas—always following up with a mulch layer to seal in water and keep granules from running off with the first strong rain. I’ve dropped broadcast feeding in favor of target-spot applications, driven by what my soil reports say and the previous year’s harvest sizes. That small shift brings healthier plants and fewer dramatic swings. Picking the right fertilizer means knowing what lives below the surface as much as what grows above it.
Any farmer who has stacked bags of DAP (Diammonium Phosphate) in the shed understands it’s not as simple as just keeping a stack dry. The stuff works wonders for crops, but can cause real headaches if it’s not looked after right. Years back, I learned this the hard way. A neighbor kept his fertilizer bags in a leaky corner of his barn. Pretty soon, clumps formed, sacks started to rip, and he lost more of his investment to spoilage than the plants ever saw.
Moisture is DAP’s silent enemy. Exposed to steam, drizzle, or even the humidity hanging in the air, those pellets start to break down. Lumps form and caking starts. At worst, the fertilizer gets sticky and you end up with a solid block instead of easy-to-spread granules. This isn’t just a nuisance—it actually lowers the nutrient value, making those hours spent spreading across the field less worthwhile. Keeping DAP indoors, away from leaks or groundwater, and off a cold slab is critical if you want your money’s worth.
I’ve seen plenty of storage sheds with DAP bags stacked eight-high, packed into a hot metal box in the summer. Heat speeds up chemical changes in fertilizer, encouraging ammonia to drift off and lowering quality. Even worse, that heat and lack of ventilation can spark a fire if someone’s careless and chemicals mix the wrong way. Dealers and co-ops need more than just a roof—they need airflow. Stacking bags on pallets rather than the floor, spacing stacks apart, and cracking a vent or window actually makes a difference.
In too many rural supply stores, I’ve seen DAP stacked right next to gasoline, grease, and piles of seeds or feed. This isn’t just messy—it’s risky. Any contact with combustible materials ups fire danger. DAP reacts with certain chemicals and acids, so it’s best to keep it isolated. Fertilizer and chemical labels don’t get read as often as they should, but they always warn about this. Keeping different fertilizers in their own section, away from animal feed and fuel, keeps surprises to a minimum.
Anyone moving around bags of DAP should know what they’re handling. Clear labels on every stack cut down on accidents—no one wants to see what a mix-up between ammonium nitrate and DAP looks like. In bigger warehouses, keep an up-to-date list of your stock, keep a record of which delivery went where, and always check for torn or leaking sacks every week. I’ve learned to sweep up spills quickly and log every issue because a single spill can lead to contamination that hurts animals, water supplies, and the bottom line.
Many mishaps happen because a new hand on the farm didn’t know any better. Training every worker—seasonal or full time—about what goes where, what to look for in spoiled fertilizer, and what to do if something goes wrong takes half an hour, and can save thousands. Local ag extension offices host safety demos for good reason. There’s no substitute for experience and good habits. Those who take care of every bag like it’s money in the bank rarely lose a crop—or their peace of mind.
| Names | |
| Preferred IUPAC name | diammonium hydrogen phosphate |
| Other names |
Ammonium hydrogen phosphate Ammonium phosphate dibasic DAP Diammonium hydrogen phosphate Phosphoric acid diammonium salt |
| Pronunciation | /daɪˌæm.oʊˈniː.əm ˈfæʃ.feɪt/ |
| Identifiers | |
| CAS Number | 7783-28-0 |
| Beilstein Reference | 1721266 |
| ChEBI | CHEBI:63042 |
| ChEMBL | CHEMBL1201540 |
| ChemSpider | 85804 |
| DrugBank | DB11448 |
| ECHA InfoCard | 03b7de09-6d5f-425c-949b-39c02d7e050c |
| EC Number | 231-987-8 |
| Gmelin Reference | Gm. 153 |
| KEGG | C01250 |
| MeSH | Ammonium Compounds |
| PubChem CID | 24456 |
| RTECS number | BQ9610000 |
| UNII | 49J2KH2VD3 |
| UN number | UN2061 |
| Properties | |
| Chemical formula | (NH4)2HPO4 |
| Molar mass | 132.06 g/mol |
| Appearance | White or off-white crystalline solid |
| Odor | Odorless |
| Density | 1.62 g/cm³ |
| Solubility in water | Soluble |
| log P | -2.0 |
| Vapor pressure | Negligible |
| Acidity (pKa) | pKa1 = 2.12, pKa2 = 7.21 |
| Basicity (pKb) | 11.7 |
| Magnetic susceptibility (χ) | Diamagnetic |
| Dipole moment | 6.28 D |
| Thermochemistry | |
| Std molar entropy (S⦵298) | 217.1 J·mol⁻¹·K⁻¹ |
| Std enthalpy of formation (ΔfH⦵298) | -2837 kJ/mol |
| Std enthalpy of combustion (ΔcH⦵298) | –2030 kJ/mol |
| Pharmacology | |
| ATC code | S01XA04 |
| Hazards | |
| Main hazards | May cause respiratory irritation. Causes serious eye irritation. |
| GHS labelling | GHS07, Warning, H319, P264, P280, P305+P351+P338, P337+P313 |
| Pictograms | GHS07 |
| Signal word | Warning |
| Precautionary statements | Keep out of reach of children. Read label before use. 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 (752°F) |
| Explosive limits | Not explosive |
| Lethal dose or concentration | LD50 (oral, rat): 6500 mg/kg |
| LD50 (median dose) | LD50 (oral, rat): 6,180 mg/kg |
| NIOSH | SB8225000 |
| PEL (Permissible) | Not established |
| REL (Recommended) | 18 kg/ha |
| IDLH (Immediate danger) | Not established |
| Related compounds | |
| Related compounds |
Monopotassium phosphate Monocalcium phosphate Monoammonium phosphate Ammonium sulfate Urea |
