Is CAN the best top-dressing fertilizer in Kenya? When to use CAN, Urea, or Ammonium Sulphate
Walk through any Kenyan farming area at top-dressing time and you will see the same product going into the soil: CAN. Most farmers reach for it out of habit, because their neighbour does. And on much of Kenya's acidic land, that habit is actually sound. But "always CAN" is not always the best choice — on some soils Urea gives you more nitrogen for the same money, and on others a hidden sulfur shortage means Ammonium Sulphate would do more for your yield. This guide explains what each product does, and how to know which one your soil needs.
The three top-dress options, side by side
Top dressing means feeding nitrogen after the crop is up and growing — the nutrient it needs most for leaf, stem, and grain. In Kenya you have three realistic choices at the agrovet. They differ in nitrogen strength, what else they carry, and — crucially — what they do to your soil pH.
| Property | CAN (26:0:0) | Urea (46:0:0) | Ammonium Sulphate (21:0:0) |
|---|---|---|---|
| Nitrogen (%) | 26% | 46% | 21% |
| Sulfur (%) | None | None | 24% |
| Calcium | ~8% Ca | None | None |
| Effect on soil pH | Neutral — does not acidify | Acidifying | Strongly acidifying |
| Price per 50 kg bag (KES, 2026) | ~4,000–4,800 | ~4,800–5,800 | ~3,800–4,800 |
| Cost per kg of nitrogen | Higher | Lowest | Moderate — value is the sulfur |
| Best for | Acidic and calcium-poor soils | Non-acidic soils on a budget | Sulfur-deficient soils |
| Watch out for | Costs more per unit of N | Loses 20–30% if not watered in; acidifies | Strongly acidifies — pair with lime |
Why CAN became the Kenyan default — and where the habit is right
The tradition of top-dressing with CAN is not cargo-cult farming. It fits a real feature of Kenyan soils: a large share of them are acidic. Across the highlands and much of western Kenya, soil pH sits below 5.5, and acidity is one of the biggest silent limits on yield.
CAN (Calcium Ammonium Nitrate, 26% N) suits that situation for three reasons:
It does not acidify
CAN carries calcium carbonate, so it feeds the crop without pushing pH lower. Urea and Ammonium Sulphate both make acidity worse.
It adds calcium
The ~8% calcium is a small bonus on calcium-poor soils and supports cell-wall strength.
It acts fast
Half its nitrogen is nitrate, taken up immediately, so the crop responds quickly after application.
So on acidic soil — which describes a majority of Kenyan farms — CAN really is a sensible default. The problem is applying the same habit to every soil, regardless of what that soil actually is.
When Urea is the smarter buy
Urea is 46% nitrogen — nearly double CAN's 26%. Because you are really paying for nitrogen, that matters: even though a bag of Urea costs a little more, per kilo of actual nitrogen it works out cheaper than CAN. On a soil that is not acidic (near-neutral pH, as in parts of the Rift and the drier eastern zones), CAN's anti-acidity advantage is wasted — and defaulting to it out of habit means paying more for the same nitrogen.
The one catch with Urea
Urea loses 20 to 30 percent of its nitrogen to the air (volatilisation) if it is left on a hot, dry soil surface. To capture the cost saving, water it in, apply it before rain, or lightly incorporate it. Do that, and on non-acidic soils Urea delivers more usable nitrogen per shilling than CAN.
When Ammonium Sulphate wins: the hidden sulfur gap
Sulfur is the nutrient nobody talks about, and Kenyan soils are increasingly short of it — the result of years of cropping with fertilizers that contain no sulfur (like CAN, Urea, and DAP). A sulfur-deficient crop looks nitrogen-starved even when you have applied plenty of nitrogen: pale, yellowing younger leaves and poor protein in the grain.
Ammonium Sulphate (Sulphate of Ammonia, 21% N + 24% S) fixes both at once. If a soil test shows sulfur is low, switching your top-dress from CAN to Ammonium Sulphate corrects the sulfur while still supplying nitrogen — often a bigger yield gain than adding more nitrogen ever would. It is also usually the cheapest of the three per bag.
The acidity trap — read this before switching from CAN
Here is the subtlety that trips people up. Both Urea and Ammonium Sulphate acidify the soil — Ammonium Sulphate strongly so. On a soil that is already acidic, switching to either of them to save money or add sulfur can quietly make your pH problem worse over seasons.
The fix is simple: if you use Urea or Ammonium Sulphate on acidic land, pair it with agricultural lime. Lime corrects the acidity; the fertilizer supplies the nutrient. And remember — CAN itself is not a liming material. It won't acidify your soil, but it won't cure existing acidity either. Only lime does that.
Which top-dress for your situation
| Your situation | Best top-dress | Why |
|---|---|---|
| Acidic soil (pH below 5.5) | CAN | Won't push pH lower; adds calcium |
| Near-neutral soil, tight budget | Urea (watered in) | Cheapest nitrogen per shilling |
| Sulfur-deficient soil | Ammonium Sulphate | Fixes nitrogen and the sulfur gap together |
| High-rainfall zone | CAN or Urea, split-applied | Two smaller doses cut nitrate leaching |
| Beans, cowpeas, other legumes | None — inoculate the seed | Legumes fix their own nitrogen; N top-dress suppresses it |
The honest takeaway: CAN is a good default for Kenya, but the best top-dress is the one matched to your soil's pH and sulfur — not the one everyone else is buying.
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