Section 05 · Fertilisers
Feed the crop what your soil lacks
Work out the bags for your crop and field with whatever fertiliser your shop has. Then read what is in each bag, what your soil test means, and what the leaves are telling you.
For 1 acre of Wheat
What to buy
DAP
1
bag · 53 kg
Urea
2.5
bags · 111 kg
MOP
0.5
bags · 27 kg
Nutrients in it: N 61 kg · P₂O₅ 24 kg · K₂O 16 kg
Also add farmyard manure or compost: 4 t
- Don't put it all in at once: follow the timing on the Wheat page. Full Wheat guide
- Your Soil Health Card can raise or lower these amounts. If you have one, follow it.
- The dose is counted in nutrients. Change the products above to what your shop has, and the amounts change to match.
General dose for North India, not yet checked against a package of practices. Choose your state, or confirm the dose with your KVK.
Nutrients by weight, at least: DAP: 18 % N, 46 % P₂O₅ · Urea: 46 % N · MOP: 60 % K₂O
Urea comes in 45 kg bags, DAP and MOP in 50 kg. For the other products, check the weight printed on the bag.
Fertiliser facts: Press Information Bureau, Ministry of Chemicals and Fertilizers, MRP of DAP and MOP fertilizers to come down with immediate effect (4 July 2016)
What's in the bag
Nutrients in each fertiliser
Minimum nutrients by weight, as the Fertiliser Control Order requires. A 50 kg bag of DAP, for example, holds at least 9 kg of nitrogen and 23 kg of P₂O₅.
| Fertiliser | N | P₂O₅ | K₂O | S |
|---|---|---|---|---|
| Urea | 46 | – | – | – |
| Ammonium sulphate | 20.6 | – | – | 23 |
| CAN (calcium ammonium nitrate) | 25 | – | – | – |
| DAP (diammonium phosphate) | 18 | 46 | – | – |
| SSP (single superphosphate) | – | 16 | – | 11 |
| NPK 12:32:16 | 12 | 32 | 16 | – |
| NPK 10:26:26 | 10 | 26 | 26 | – |
| 20:20:0:13 (ammonium phosphate sulphate) | 20 | 20 | – | 13 |
| MOP (muriate of potash) | – | – | 60 | – |
| Zinc sulphate (heptahydrate)Zinc (Zn): 21 % | – | – | – | 10 |
| Zinc sulphate (monohydrate)Zinc (Zn): 33 % | – | – | – | 15 |
Your soil test
Reading a soil test report
PAU's ratings for Punjab soils and how much to change the dose for each. Your Soil Health Card may use other units: where it gives its own advice, follow the card.
Nitrogen, judged by organic carbon
- Lowbelow 0.4 %→ 25 % more nitrogen
- Medium0.4–0.75 %→ the recommended dose
- Highabove 0.75 %→ 25 % less nitrogen
Phosphorus, available P
- Lowbelow 5 kg per acre→ 25 % more phosphorus
- Medium5–9 kg per acre→ the recommended dose
- High9–20 kg per acre→ 25 % less phosphorus
- Very highabove 20 kg per acre→ no phosphorus for 2–3 years, then test again
Potassium, available K₂O
- Deficientbelow 55 kg per acre→ give potash
- Sufficientabove 55 kg per acre→ no potash
Reading a soil test report
- Organic carbon also changes the phosphorus. At 0.4–0.6 % organic carbon, PAU cuts phosphorus by a quarter on medium-P soil and by half on high-P soil. Above 0.6 %, by half on medium-P soil and to none on high-P soil.
- Zinc below 0.6 kg per acre: 10–25 kg zinc sulphate (21 %) per acre, depending on the crop. In a rotation, give it to the kharif crop.
- Manganese below 3.5 kg per acre: spray wheat with 0.5 % manganese sulphate 2–4 days before the first irrigation, then 3 more times at weekly intervals.
- Alkali soil (pH above 9.3) and saline soil (EC above 0.8 mmhos/cm) need 25 % more nitrogen. Never put gypsum on saline soil.
Taking a soil sample
- Take samples after the harvest, from the empty field. In a standing crop (not rice), take them between the rows.
- Scrape away the litter on top and dig a V-shaped cut 6 inches deep with a spade or khurpa.
- Cut a 1 inch slice of soil from one side of the cut.
- Do this at 7 to 8 places in a field of the same soil, and mix it all in a clean bucket or cloth.
- Put about half a kg in a cloth bag, labelled with the field number, your name and address, and the date. If the soil is wet, dry it in the shade first.
Reading the leaves
What yellow wheat is telling you
Where the yellowing starts tells you which nutrient is short. These are PAU's signs for wheat; other crops can look different.
Nitrogen
Signs: Yellowing starts on the older, lower leaves.
PAU's fix: If the full urea dose is already in and the crop still looks short of nitrogen, spray 3 % urea (9 kg urea in 300 litres of water per acre), criss-cross.
Sulphur
Signs: The young top leaves fade to light yellow, except their tips, while the lower leaves stay green. Common on sandy soil, worse in long winter rains.
PAU's fix: 100 kg gypsum per acre, even in the standing crop. Before sowing, 100 kg gypsum or 18 kg bentonite-sulphur (90 %) per acre where DAP was used instead of SSP.
Zinc
Signs: The crop is stunted and bushy; leaves go pale in the middle, then break and hang down.
PAU's fix: 25 kg zinc sulphate (21 %) per acre, enough for 2–3 years. In the crop: 2 or 3 sprays of 0.5 % zinc sulphate, 15 days apart (1 kg zinc sulphate and half a kg of unslaked lime in 200 litres of water per acre).
Manganese
Signs: On light soil after rice, the middle leaves get grey-yellow to pinkish-brown specks between the veins, which join into streaks while the veins stay green.
PAU's fix: Spray 0.5 % manganese sulphate (1 kg in 200 litres of water per acre) 2–4 days before the first irrigation, then 3 more at weekly intervals on sunny days. Spraying works; putting it in the soil doesn't pay.
Rules that save fertiliser
- Each tonne of well-rotted farmyard manure gives about as much N, P and K as 4 kg urea, 10 kg superphosphate and 6 kg MOP. Cut the fertiliser by that much.
- Wheat: on kallar (salt-affected) soil give 25 % more nitrogen; for wheat sown after mid-December, 25 % less.
- Put phosphorus on wheat rather than on the kharif crop after it: wheat responds more.
- If DAP and SSP can't be had, PAU allows 13:33:0:15 or 12:40:0:10:1 for wheat's phosphorus, though they cost more.
- For raya and gobhi sarson, PAU prefers SSP for the phosphorus, because it also brings sulphur.