Most Ugandan farmers who buy a single bag of fertilizer buy DAP, and they buy it for planting day. DAP is diammonium phosphate, 18 percent nitrogen and 46 percent phosphate in one granule, and it is stocked in almost every input shop in the country. Its job is to put phosphorus within reach of a seedling's first roots. That is why where you place it matters more than how much you use.
The bag prints the analysis as a ratio joined by dashes. This page writes the same ratio with colons, so 18:46:0, which reads more cleanly on a phone. The three numbers are nitrogen, phosphate and potash in that order, and the zero means DAP carries no potassium at all.
What DAP Fertilizer Is and What Is in the Bag
DAP is made by reacting ammonia with phosphoric acid, which is why it ends up carrying both nutrients. The granules are hard, roughly spherical and pour freely when dry. It dissolves fast, faster than most granular fertilizers, which is part of its appeal for a crop that needs phosphorus in its first fortnight.
Of the two nutrients, phosphate is the one you are really buying. Forty six percent phosphate is a high analysis by any standard, and at that concentration a 50 kg bag carries about 23 kg of phosphate and 9 kg of nitrogen. The nitrogen is a genuine bonus rather than a full nitrogen programme. It will carry a maize seedling through its first few weeks and no further, which is why DAP at planting is followed by a nitrogen top dressing later.
In Ugandan input shops DAP and urea are the two highest volume products. Market assessment work by IFDC found six granulated fertilizers account for 74 percent of granulated fertilizer traded in the country, with DAP and urea leading. On quality, that same work found the nitrogen content of Ugandan DAP samples fully compliant with the label, while phosphate fell short of tolerance in 6 percent of samples by around two and a half percent. DAP is, in other words, one of the more reliably honest bags on the Ugandan market.
Phosphorus Does Not Move Through Soil, and That Changes Everything
Here is the fact that governs everything else about DAP. Nitrogen moves. Dissolve nitrogen in soil water and it travels, up to a plant root, down past it, sideways with a rainstorm. Phosphorus does not. It binds to clay particles and to iron and aluminium oxides within a centimetre or two of where the granule dissolved, and there it stays.
The practical consequence is that a root has to grow to the phosphorus, because the phosphorus will not come to the root. Broadcast DAP across the surface of a field and most of the phosphate ends up in soil no seedling root reaches during the weeks it needs feeding. The nutrient is not lost from the field. It is simply parked out of reach at the exact moment it is wanted.
Ugandan soils make this worse than average. Phosphorus binds harder as soil turns acid, and a great deal of Ugandan cropland tests below the pH range crops prefer. On that kind of land, applied phosphate gets locked up quickly. The crop recovers a minority of it in the season you apply it, with the rest joining a slowly available reserve that later crops can draw on.
So the phosphorus question is never only how much. It is how much, placed where.
How to Place DAP Fertilizer at Planting Without Burning the Seed
Two things are true at once. Phosphorus has to be close to the seed to be useful. And DAP close to the seed can kill it. Working between those two is the skill.
The damage mechanism is the alkaline pocket described above. As the granule releases ammonium, a little of it converts to free ammonia, and ammonia in contact with a germinating seed or a new root tip scorches the tissue. What you see afterwards is patchy germination, seedlings that emerge and then wilt, or a row that comes up thin for no obvious reason. Farmers usually blame the seed.
Placement that works is a band to the side of and below the seed, close enough that the roots reach the phosphate within a week or two, far enough that nothing touches. Two or three centimetres of earth between the two keeps the ammonia off, and the separation extension officers usually name is about 5 cm sideways and a little deeper than the seed. Where a jab planter or a two wheel planter with a fertilizer box is available, it does this automatically, which is the main agronomic reason to use one.
For hand planting, which is how most Ugandan smallholders plant, the workable method is to open the hole, drop the fertilizer, cover it with a scrape of soil, then place the seed on top of that soil and cover. The thin layer of soil between the two is what protects the seed. Dropping seed and granule into the same hole together is the single most common way to lose a stand.
Broadcasting DAP and then ploughing it in is better than broadcasting and leaving it, but it is still a long way behind banding. You dilute the phosphate through the whole plough layer, and a young root system meets very little of it.
DAP Application Rates Per Acre and What Decides Them
Rates are where a lot of money gets wasted in both directions, and where honest guidance has to stay honest. The rate that is right for your field depends on how much phosphorus the soil already holds, how acid it is, what crop is going in and what yield you are aiming for. No page can give you a number that is correct for your plot, and any page that does is guessing.
Uganda does have its own answer, and it is more useful than the figures in general circulation. The Uganda Fertilizer Use Optimizer, a set of zone by zone sheets built from Ugandan response trials and published for extension agents, sets rates for each crop in each farming region, graded by what the household can lay out. DAP and urea are the products it deals in, which are the ones Ugandan farmers really buy. Its uppermost grade is labelled on the sheet itself as the setting that returns the most profit from an acre, not the most grain, and it states on the face of each sheet the fertilizer price and grain price it assumed, so when those move the recommendation moves with them.
The DAP rates it gives for planting are a lot lower than the figure most people quote. For Central Uganda, maize gets 15 kg per acre of DAP at the middle spending tier and 20 kg per acre at the profit maximising tier. In the Western Highlands above 1800 m, the profit maximising maize option is 10 kg per acre of DAP. Beans run from about 13 to 27 kg per acre, bananas 20 to 31 kg per acre, upland rice 13 to 31 kg per acre, groundnuts 26 to 40 kg per acre, and Irish potato in the highlands is the heavy feeder at 40 to 72 kg per acre. No zone and no tier reaches the 50 kg per acre figure that circulates widely in trade and extension material for maize. That figure is roughly two and a half times what Uganda's own optimiser recommends at its most generous maize setting.
Two details from those sheets are worth carrying to the field. Rates below about 10 kg per acre are not worth applying, because the response does not cover the trip. And the sheets calibrate doses by things a farmer already owns: a drinking water bottle cap holding 7.5 ml carries roughly 8.25 g of DAP, and a bottle cut off at 2 cm holds about 65 g. That is how a 20 kg per acre rate becomes a cap of granules per few plants rather than an abstraction, and it is the difference between a recommendation that gets followed and one that gets guessed.
Treat those as the best available Ugandan starting point, not as your answer. What definitely changes the rate:
Soil phosphorus status. A plot that has been fertilized for years may be holding a phosphorus reserve and need a maintenance rate. A hillside garden cropped for three decades with nothing returned needs more. Only a test tells you which you have.
Soil pH. On acid soil a larger share of what you apply gets locked up, so the same rate does less. The answer is not to pile on more DAP. It is to lime first and then apply a sensible rate.
The crop. Legumes like beans and groundnuts fix their own nitrogen but still want phosphorus, particularly for nodulation, and they want less total fertilizer than maize. Fruiting vegetables want phosphorus early and potassium later, which points towards a compound rather than straight DAP.
What your money buys. A half rate placed correctly beats a full rate broadcast on the surface. If the budget is tight, spend it on placement before you spend it on quantity.
Use the fertilizer requirement calculator to turn a recommendation into bags for your actual acreage, since most published rates are given per hectare and most Ugandan plots are measured in acres.
| Crop | When DAP goes in | What decides the rate |
|---|---|---|
| Maize | At planting, banded | Soil test and pH |
| Beans | At planting, banded | Soil test, lower than maize |
| Groundnuts | At planting | Soil test, phosphorus only |
| Tomato | In the planting hole | Soil test, then a compound |
| Coffee | At planting out | Soil test and leaf analysis |
Crops in Uganda That Respond to DAP at Planting
Maize is the big one, and the response is usually visible. A maize seedling that meets phosphate in its first two weeks builds a deeper root system, which then carries it through a dry spell later in the season that would otherwise cost yield. That knock on effect is easy to miss and it is often worth more than the immediate growth difference.
Beans and other legumes want phosphorus for nodule formation. The rhizobia bacteria that fix nitrogen in bean roots are themselves phosphorus hungry, so a phosphorus short soil gives you poor nodulation and then a nitrogen shortage that looks like something else entirely. On legumes, DAP's nitrogen is largely surplus to requirements, which is the argument for a straight phosphate instead.
Vegetable transplants respond well to a little phosphate in the planting hole, because a transplant has lost most of its root system and needs to rebuild fast. Tomato, cabbage and pepper growers commonly do this. The quantity is small and the placement rule still applies, so cover the granules with soil before the roots go in.
Coffee and bananas are longer conversations. Both want phosphorus at planting out, when the young plant is building roots, and both then shift towards needing potassium and nitrogen as they come into bearing. DAP is a planting input for these crops, not a maintenance one. Our maize fertilizer application guide and bean fertilizer guide set out full season programmes where DAP is only the first step.
DAP and Soil Acidity on Ugandan Land
This is the part the product literature skips, and it matters here more than in most countries.
The alkaline pocket around a fresh DAP granule is temporary. Bacteria in the soil take the ammonium apart and turn it into nitrate, shedding hydrogen ions as they go. The net effect of applying an ammonium bearing fertilizer, season after season, is that the soil gets more acid. This is not a fault in DAP alone. Every ammonium forming nitrogen source does it, and ammonium sulphate does it faster. Nitrate based sources such as CAN do it far less, partly because they supply less ammonium and partly because CAN carries calcium carbonate in the granule.
Where Uganda comes in is the starting point. MAAIF's guidance puts the best soil pH for maize at 6.0 to 7.0, and a large share of Ugandan cropland already sits below that, particularly on the older, more weathered soils and on land that has been cropped hard for decades. Pushing already acid soil further down costs you twice: the crop struggles, and the phosphorus you are paying for binds up faster.
The fix is not to stop using DAP. It is to know your pH and manage it. MAAIF's own sequence is to test the soil, lime at the recommended rate, and wait at least three months before planting, because lime needs time to react. Liming and fertilizing in the same week wastes both.
Why a Soil Test Beats a Blanket DAP Rate
A blanket rate is a compromise built for a field you have never seen. It will be roughly right on some plots, wasteful on others, and too low on the ones that need help most.
A phosphorus test tells you whether the soil is holding a reserve or genuinely short. A pH reading tells you whether the phosphate you apply will stay available or bind up, and whether you need lime before you need fertilizer. Together those two results change both the product and the rate, and they are the cheapest agronomic information you can buy.
There is a money argument too. Phosphorus is the expensive nutrient in a fertilizer bag, and phosphate rock is imported. Applying a full phosphate rate to a plot that already has phosphorus is money spent on nothing. Applying nothing to a plot that is short of it costs you the yield. Read our page on soil testing before fertilizer application for how sampling actually works and where tests can be done.
One footnote worth knowing. Phosphate fertilizers carry trace cadmium from the phosphate rock they are made from, and the amount depends on the deposit. IFDC measured cadmium in Ugandan phosphate fertilizers and found the highest value in a DAP sample at 23 parts per million, or 10.7 mg per kg of phosphate, which sits below both the Kenyan tolerance limit of 30 ppm and the European limit. It is not a reason to avoid DAP. It is a reason the origin of the phosphate rock is worth monitoring, and one more argument against applying phosphate the soil does not need.
DAP, TSP or NPK as Your Planting Fertilizer
DAP is not the only planting fertilizer, and it is not always the right one.
TSP, triple superphosphate, is straight phosphate with no nitrogen. On a legume crop that fixes its own nitrogen, the nitrogen in DAP is largely surplus, so TSP delivers the nutrient you want without the one you do not. TSP is also less acidifying than DAP for the simple reason that it contains no ammonium to nitrify. It turns up less often in Ugandan shops, which is usually what decides the matter.
NPK compounds add potassium to the mix. On bananas, coffee, fruiting vegetables and any soil that tests short of potassium, a compound at planting does a job DAP cannot. NPK 17:17:17 is the general purpose grade in Uganda. The trade off is that you get less phosphate per bag than DAP gives you, so a plot with a serious phosphorus deficit is better served by DAP plus a separate potassium source. Our guide to reading NPK grades and what the numbers mean works through the arithmetic, while the map of what fertilizer types Uganda actually stocks lines every option up together.
After planting, the conversation moves to nitrogen, and DAP is finished. That stage belongs to urea or CAN, and which of those two you pick is a separate decision with its own logic.
Storing and Handling DAP Fertilizer on the Farm
DAP stores better than urea, which is a low bar but a real advantage. The granules are harder and less prone to pulling moisture out of the air. Ugandan market work found caking in 15 percent of fertilizer bags examined, and the worst of it was in urea rather than DAP.
Even so, the conditions in a typical Ugandan store work against you. Median relative humidity inside the shops and warehouses surveyed was 55 percent, high enough that several fertilizers begin absorbing moisture once the temperature climbs past 30 degrees. Bags sat under stacks ten high in 22 percent of stores, and 38 percent had few or no pallets, so sacks rested on concrete and drew damp from below. At home you can beat that easily. Get the sacks up on poles or a pallet, leave a gap to the wall, put a roof over them, keep the pile short, and finish the lot inside the season.
On handling, treat DAP as the concentrated ammonium salt it is. Gloves when you are placing granules by hand, which is how most of it gets applied here. Rinse hands before eating. Granules or dust in an eye need flushing with clean water immediately. Breaking up a caked bag produces dust that irritates airways, so do it outside and stand upwind.
Where the bags live matters as much as how you carry them. A phosphate sack stored next to a feed store or a seed tin is an accident waiting for a torn corner, and livestock that get into spilled fertilizer can die of it. Lock the store or put the bags up high, because granules look like sweets to a small child. A sleeping room is not a store. Sacks that have held fertilizer should be burned or binned rather than repurposed for grain or water. And park the pesticides somewhere else entirely, so nobody grabs the wrong container in a rush.
DAP Fertilizer Questions Ugandan Farmers Ask
Can DAP be used as a top dressing instead of urea? It is a poor substitute. DAP carries only 18 percent nitrogen, so you would need well over twice the weight to match a urea dressing, and you would be paying for phosphate that a growing crop cannot reach anyway, since surface applied phosphorus stays where it lands. Use DAP at planting and a proper nitrogen source for top dressing.
What happens if DAP touches the seed? The granule dissolves into an alkaline pocket and releases a little free ammonia, which scorches germinating seed and new root tips. You get gaps in the row, or seedlings that emerge and then collapse. Put a scrape of soil between the fertilizer and the seed and the problem disappears.
Does DAP work on acidic soil? It works, but less of it reaches the crop, because phosphorus binds harder as pH falls. Worse, DAP itself adds to the acidity over time as its ammonium converts to nitrate. On land testing below the range maize prefers, the sequence that pays is a soil test, then lime at the recommended rate at least three months before planting, then a sensible DAP rate.
Can I use DAP on coffee and bananas? At planting out, yes, when the young plant is building roots. For established coffee and bananas the limiting nutrients are usually potassium and nitrogen rather than phosphorus, so a compound or a straight nitrogen source fits better. Base the decision on a soil test and, for coffee, on leaf analysis where you can get it.
How long does DAP stay available in the soil? The nitrogen is gone within weeks, either taken up or converted and leached. The phosphorus behaves differently: a minority of it feeds the crop in the season you apply it and the rest joins a slowly available reserve that later crops draw on. That is why phosphorus status builds up on regularly fertilized land and why a soil test is the only way to know what you already have.
How much does a bag of DAP cost in Uganda? It moves week to week, because DAP is imported and the landed price tracks the exchange rate, international phosphate prices and freight, then varies again between Kampala and upcountry dealers. Compare current fertilizer prices in Uganda rather than working from a figure you read months ago. When you compare bags, compare cost per kilogram of phosphate rather than cost per bag, because DAP at 46 percent phosphate and a compound at 17 percent are not carrying the same amount of what you are actually buying.
Placement and timing are entirely in your hands, and they matter more than the rate. What is worth shopping around for is the bag itself, since the same 50 kg of DAP carries different prices from one dealer to the next and the spread grows with distance from Kampala. Find out which input suppliers stock fertilizer near you, look at the price page before committing, and get the sack onto a scale before money changes hands. More guides sit on the farm inputs hub.