Fertilizer amount·Compound NPK 17-21-17 · 100 m²
Compound NPK 17-21-17
4.76 kg
100 m² · P₂O₅ 10 g/m²
Content 21%

Compound NPK 17-21-17 on 100 m² — 4.76 kg for 10 g/m² of P₂O₅

To put 10 g/m² of P₂O₅ on 100 m² with Compound NPK 17-21-17, spread 4.76 kg — that is 47.62 g per m². At 21% content it is simply the 1 kg of nutrient you need divided by that figure.

Fertilizer to spread

Urea is only 46% nitrogen, so putting 10 g of N down means spreading 10 ÷ 0.46 = 21.74 g of urea. Multiply instead and you get 4.6 g, a number that looks plausible enough to pass unnoticed. Whenever the content is below 100%, the fertilizer weight is always larger than the nutrient weight — that is the fastest check that you have the division the right way round.

  • P₂O₅ 5 g/m² · 23.81 g/m²2.38 kg
  • P₂O₅ 10 g/m² · 47.62 g/m²4.76 kg
  • P₂O₅ 15 g/m² · 71.43 g/m²7.14 kg
  • P₂O₅ 20 g/m² · 95.24 g/m²9.52 kg

Comes along with it

Matching 10 g/m² of N with a 21-17-17 puts the fertilizer at 47.62 g/m², and those 47.62 g carry 8.1 g of P₂O₅ and 8.1 g of K₂O with them. You do not get to choose: once the fertilizer weight is fixed, the other two are dragged along in proportion to their content. That is why one compound bag rarely hits all three targets. The order of work is to match one, then top up or accept the surplus with straight fertilizers.

  • N 17% · 8.1 g/m²809.5 gN 809.5 g
  • K₂O 17% · 8.1 g/m²809.5 gK 671.9 g
Fertilizer
Compound NPK 17-21-17 (17-21-17)
Area
100 m²
Nutrient matched
P₂O₅
Content
21%
Nutrient needed
1 kg
Per m²
47.62 g

Nearby cells

Compound NPK 17-21-17
9.52 kgP₂O₅ 21%
Compound NPK 17-21-17
23.81 kgP₂O₅ 21%
Compound NPK 17-21-17
47.62 kgP₂O₅ 21%
Compound NPK 20-20-20
50 gN 20%

Same fertilizer, other areas

1 m²
47.6 gP₂O₅ 21%
5 m²
238.1 gP₂O₅ 21%
10 m²
476.2 gP₂O₅ 21%
20 m²
952.4 gP₂O₅ 21%
50 m²
2.38 kgP₂O₅ 21%
100 m²
4.76 kgP₂O₅ 21%
200 m²
9.52 kgP₂O₅ 21%
500 m²
23.81 kgP₂O₅ 21%
1000 m²
47.62 kgP₂O₅ 21%

Same area, other fertilizers

Urea
2.17 kgN 46%
Ammonium sulfate
4.76 kgN 21%
Ammonium nitrate
2.94 kgN 34%
Calcium nitrate
6.45 kgN 15.5%
Diammonium phosphate DAP
2.17 kgP₂O₅ 46%
Monoammonium phosphate MAP
1.92 kgP₂O₅ 52%
Triple superphosphate TSP
2.17 kgP₂O₅ 46%
Potassium chloride MOP
1.67 kgK₂O 60%
Potassium sulfate SOP
2 kgK₂O 50%
Potassium nitrate
2.17 kgK₂O 46%
Monopotassium phosphate MKP
1.92 kgP₂O₅ 52%
Compound NPK 21-17-17
4.76 kgN 21%
Compound NPK 17-21-17
4.76 kgP₂O₅ 21%
Compound NPK 20-20-20
5 kgN 20%
Compound NPK 10-10-10
10 kgN 10%

Worth knowing

  • Fertilizer to spread = nutrient needed ÷ (content ÷ 100). It is a division, never a multiplication.
  • Nutrient needed = area × target rate, so twice the area means twice the fertilizer.
  • A fertilizer with half the content takes twice as much for the same nutrient — inverse proportion.
  • With a compound, matching one nutrient drags the other two in at their content ratio.

Common questions

Q. How much Compound NPK 17-21-17 goes on 100 m²?

At 10 g/m² of P₂O₅, 4.76 kg — that is 47.62 g per m². It is the 1 kg of nutrient needed divided by the 21% content.

Q. If I double the target, do I double the fertilizer?

Yes. Target and fertilizer weight are directly proportional — 5 g/m² takes 2.38 kg and 20 g/m² takes 9.52 kg. Area behaves the same way: twice the area, twice the fertilizer.

Q. What else goes in along with it?

Matching P₂O₅ to the target also puts in N 809.5 g, K₂O 809.5 g. That is not a choice — those amounts are dragged in at their content ratio.