Fertilizer Schedule for Soybean: Stage-Wise Dose per Acre for Seed Treatment, Basal, Sulphur, Zinc, Boron, Molybdenum and Flowering Sprays

Soybean makes much of its own nitrogen, so the schedule is mainly about seed treatment, phosphorus, potash, sulphur and a few micronutrients. Treat seed with Rhizobium and PSB, put the full basal dose in the furrow below the seed at sowing, and spray DAP or urea at 20 g per litre at flowering and again 15 days later. TNAU gives 20:80:40 kg N:P2O5:K2O per hectare plus 40 kg sulphur and 25 kg zinc sulphate for irrigated soybean (about 8:32:16 kg per acre, 16 kg S, 10 kg zinc sulphate), and a blanket 20:40:20:20 for rainfed soybean (about 8:16:8:8 per acre) when no soil test is available. Assam Agricultural University recommends 20:60:40 per hectare. Your soil test and state recommendation decide the final dose.

• TNAU irrigated basal dose is 20 kg N, 80 kg P2O5, 40 kg K2O and 40 kg S (as 220 kg gypsum) per hectare, plus 25 kg zinc sulphate. That is about 8, 32, 16 and 16 kg per acre, with about 89 kg gypsum and 10 kg zinc sulphate.
• TNAU rainfed blanket dose, used only if there is no soil test and moisture is adequate, is 20:40:20:20 kg N:P2O5:K2O:S per hectare, all applied as basal (about 8:16:8:8 per acre).
• Assam Agricultural University recommends 20:60:40 kg N:P2O5:K2O per hectare as 45 kg urea, 375 kg SSP and 70 kg MOP, placed in furrows 5 to 7 cm below the seed, with lime at 2 t per hectare where soil pH is below 6.0.
• The ICAR Indian Farming article of August 2026 gives N 20 to 30, P2O5 60 to 80 and K2O 40 to 60 kg per hectare, sowing from mid to end June and a seed rate of 55 to 65 kg per hectare.
• Seed treatment: TNAU uses 600 g per hectare (3 packets, about 240 g per acre) each of Rhizobium and phosphobacteria with rice kanji, applied at least 24 hours before sowing. ICAR gives thiram or carbendazim at 2 g per kg of seed one day before sowing.
• Foliar: DAP or urea at 20 g per litre once at flowering and again 15 days later (TNAU). Assam recommends one MOP spray (3 percent, 400 litres per hectare) at 30 to 35 days after sowing in low-potash soils.
• A Punjab Agricultural University trial in the Indian Journal of Agricultural Sciences found 30 kg S per hectare gave the best soybean yield on sulphur-deficient soil, and SSP, gypsum and bentonite-S worked equally well at that rate.
• ICAR-IISS Bhopal says basal zinc beats foliar zinc and 5 kg Zn per hectare (about 24 kg zinc sulphate heptahydrate, calculated) lasts 2 to 3 cropping cycles in soybean-wheat on medium to deep Vertisols.
• ICAR gives rainfed soybean yields of 1.5 to 2.0 t per hectare and irrigated yields of 2.5 to 3.0 t, about 0.6 to 0.8 and 1.0 to 1.2 t per acre (calculated).

Soybean is a legume, so its schedule is built around seed treatment with Rhizobium and PSB, a basal dose of phosphorus, potash and sulphur placed at sowing, zinc and other micronutrients where the soil is short, and a flowering spray. The table puts each step against the crop stage.

The ICAR article lists soybean varieties maturing in about 90 to 120 days, so the whole nutrient plan has to be in place early. There is little time to correct mistakes.

It depends on rainfed or irrigated conditions, soil test and state. TNAU irrigated soybean works out to about 8:32:16 kg N:P2O5:K2O plus 16 kg sulphur per acre, and TNAU rainfed to about 8:16:8:8. Assam recommends about 8:24:16 per acre. ICAR gives ranges. Treat these as a range, not a promise.

The spread in phosphorus (40 to 80 kg P2O5 per hectare) reflects different soils and moisture. TNAU's higher dose is for a managed irrigated crop; its rainfed dose is half that for P2O5 and K2O. If your field is rainfed, start from the lower rows, then adjust to the soil test.

The Soil Health Card is the cheapest way to adjust. Our post on how to read your soil health card shows where phosphorus, potash, sulphur and zinc status are printed, so you can cut or raise the basal dose instead of copying a blanket rate.

Only a small starter dose. Soybean fixes atmospheric nitrogen in root nodules, which is why ICAR notes it reduces the need for chemical fertiliser. The sources list 20 to 30 kg N per hectare, about 8 to 12 kg per acre, and TNAU and Assam both apply it at sowing.

The ICAR Indian Farming article gives 20 to 30 kg N per hectare, TNAU gives 20 and Assam gives 20. All three are small compared with cereals, and TNAU applies all of it as basal.

• You may not need urea. About 70 kg of DAP per acre supplies roughly 32 kg of P2O5 and about 12.7 kg of nitrogen (calculated at 18 percent N and 46 percent P2O5; check your bag). That already covers the TNAU 8 kg N per acre.
• Do not top dress heavy urea on a nodulating crop. The recommended N is small by design.
• Short on DAP? Our post on DAP alternatives like SSP covers swaps, and for supply problems see DAP and urea shortage in India.

Mix Rhizobium and phosphobacteria (PSB) culture with a sticky binder such as rice kanji, coat the seed, shade dry it for about 15 minutes and sow. TNAU uses 600 g per hectare of each, about 240 g per acre, applied at least 24 hours before sowing.

The TNAU nutrient page says to treat seed at least 24 hours before sowing with 3 packets (600 g per hectare) each of Rhizobium culture and phosphobacteria, using rice kanji as the binder, then shade dry for 15 minutes. If seed treatment is skipped, it gives a fallback of 10 packets (2 kg per hectare) of each, mixed with 25 kg FYM and 25 kg soil and applied before sowing. The Assam package takes a different route: Rhizobium culture at 15 g per kg of seed after moistening the seed lightly, so that a thin coat sticks, and the inoculated seed must not be exposed to the sun.

Check that the pack names soybean. Katyayani's rhizobium biofertilizer page lists soybean among the legumes it is meant for, and its phosphate solubilizing bacteria page says it is particularly beneficial for pulses. Follow the label for the product dose and method. Our post on Rhizobium, PSB and KMB for chana explains the same biofertiliser logic for another pulse, and the bio fertilizer collection lists the range.

ICAR gives thiram or carbendazim at 2 g per kg seed one day before sowing. TNAU says fungicides and biocontrol agents are incompatible, and that where a biocontrol agent and a biofertiliser are both used, the biocontrol agent goes on first, then Rhizobium.

One Rule To Remember: Do not mix a chemical fungicide and a live culture in one slurry. If you are unsure how long a gap to leave between a fungicide dressing and the Rhizobium coat, ask your KVK; none of the opened ICAR or university pages states the gap.

The basal dose is the full phosphorus, potash and sulphur, plus the small nitrogen share, applied at sowing. The Assam package places it in furrows 5 to 7 cm below the seed and covers it with 3 to 4 cm of soil; if placement is not possible, it is broadcast and incorporated.

The bag figures are calculated from standard grades (DAP 18-46-0, MOP 60 percent K2O, urea 46 percent N, SSP 16 percent P2O5, which matches the Assam table of 375 kg SSP for 60 kg P2O5). Check the percentages on your own bag before buying.

Convert the per-hectare dose to per acre by dividing by 2.471, then to bags using the nutrient percentage on the label. The list below is an example built on the TNAU doses only. It is not a replacement for a soil test.

If you buy SSP instead of DAP for phosphorus, it also brings sulphur, so the gypsum line shrinks. Work from the S percentage printed on the SSP bag. The detailed trade-off between bagged and soluble grades is in our post on water-soluble vs granular fertiliser.

TNAU recommends 20 kg N, 80 kg P2O5, 40 kg K2O and 40 kg sulphur (as gypsum) per hectare as basal dressing, 25 kg zinc sulphate per hectare under irrigation, and DAP or urea sprays at flowering. That is about 8, 32, 16 and 16 kg per acre, with about 10 kg of zinc sulphate.

Irrigated soybean is usually the summer or protected crop. The ICAR article says a summer crop needs 5 to 6 irrigations, timed at germination, flowering, pod initiation and seed filling. Kharif soybean needs no scheduled irrigation. The NAA and salicylic acid sprays are growth regulators, not nutrients, so treat them as optional.

TNAU says to apply NPK on soil test recommendation where possible. Without a soil test, apply a blanket 20:40:20:20 kg N:P2O5:K2O:S per hectare, about 8:16:8:8 per acre, entirely as basal, provided adequate moisture is present. Treat seed with Rhizobium and phosphobacteria, 3 packets of each per hectare.

Rainfed soybean is the majority of the crop, and its biggest risk is moisture, not nutrients. The ICAR article gives rainfed yields of 1.5 to 2.0 t per hectare against 2.5 to 3.0 t under irrigation, about 0.6 to 0.8 t and 1.0 to 1.2 t per acre (calculated). A heavy fertiliser load in a dry spell does not pay.

• Sow on time. The ICAR article recommends mid to end June, with 55 to 65 kg of seed per hectare (about 22 to 26 kg per acre, calculated).
• Raised bed or ridge and furrow. The ICAR article says broad-bed and furrow or ridge-furrow systems can raise rainfed yield by 8 to 30 percent over flat sowing, by conserving water and improving drainage.
• Keep the basal at the TNAU rainfed level unless the soil test says otherwise.

ICAR trial data points to 30 kg sulphur per hectare (about 12 kg per acre) on sulphur-deficient soil, and SSP, gypsum and bentonite-S worked equally well at that rate. TNAU recommends 40 kg S per hectare for irrigated soybean and 20 kg for the rainfed blanket dose. Choose the cheapest source.

The Indian Journal of Agricultural Sciences study (Punjab Agricultural University, three years) compared single super phosphate, gypsum and bentonite-S at 0, 20, 30 and 40 kg S per hectare. Yield rose significantly up to 30 kg S, the three sources were equal at 30 kg S, and the average seed-yield gain over the control was 0.257 t per hectare for SSP, 0.253 for gypsum and 0.280 for bentonite-S. Returns per rupee rose as S went from 20 to 30 kg.

A separate on-farm trial in the Malwa region of western Madhya Pradesh (Vertisols, rainfed, variety JS 95-60, 2011-12 and 2012-13) tested 0, 20 and 40 kg S per hectare added to the recommended dose; the 40 kg level gave the best yield and net return in that soil. The right level depends on the soil, which is one more reason to use the Soil Health Card.

For gypsum itself, our post on gypsum in agriculture explains the difference between using it as a sulphur and calcium source and using it to reclaim sodic soil.

Apply zinc sulphate to the soil at sowing where the soil test shows zinc is low. TNAU gives 25 kg of zinc sulphate per hectare, about 10 kg per acre, for irrigated soybean. ICAR-IISS says basal soil zinc works better than foliar spray, and 5 kg Zn per hectare lasts 2 to 3 cropping cycles.

The ICAR-IISS Bhopal article says zinc sulphate heptahydrate (21 to 22 percent Zn) is the most efficient and cheapest source for most crops and soils, and that 5 kg Zn per hectare enhanced soybean-wheat productivity for 2 to 3 cropping cycles in medium to deep Vertisols. At 21 percent Zn, 5 kg Zn is about 24 kg of heptahydrate (calculated), which lines up with the TNAU figure of 25 kg.

For a ready product, see Katyayani's zinc sulphate page, which lists pulses and oilseeds among its crops but does not name soybean. Use the ICAR and TNAU rates above as the reference and follow the product label for the pack you buy. Zinc locks up in high-pH soils; if your Soil Health Card shows a high pH, read why fertiliser does not work in high-pH soil before adding more bags.

Not on every field. They matter where the soil is short. ICAR-IISS lists soybean responses of 0.08 to 0.19 t per hectare to molybdenum, and suggests a 0.2 percent boric acid or borax spray before flowering where boron deficiency is hidden. Decide with a soil test.

For ready products, Katyayani's ammonium molybdate page names soybeans among the legumes it is meant for, and its boron 20 fertilizer page lists soybean among its crops. Use the ICAR rates above as the reference and follow the label for the pack you buy.

TNAU lists DAP or urea at 20 g per litre of water once at flowering and again 15 days later. In low-potash soils the Assam package adds one MOP spray at 30 to 35 days after sowing. Boron goes in before flowering if the field is short of it.

The Assam MOP rate works out to about 4.9 kg of MOP in about 162 litres of water per acre (calculated). None of the opened sources gives a separate dose for the pod-fill stage; the second TNAU spray, 15 days after the first, is the nearest guidance. The ICAR article stresses that water stress at flowering causes flower and pod abortion and that, under a moisture deficit, irrigation should go first to the flowering through seed-filling period.

Katyayani sells a soybean flowering combo for the flowering stage; its page lists a mixed micronutrient pack and a bloom booster. Follow the pack label for dose and timing. A growth regulator is not a fertiliser; our post on plant growth promoters and the rules around them explains where they fit. For the full range, see Katyayani's soybean combo kits.

Dose changes with soil, rainfall and the state package. Tamil Nadu and Assam both start from 20 kg N, but TNAU uses 80 kg P2O5 for irrigated crops and Assam uses 60, and only Assam lists lime. Start from your own state package and soil test, not a national average.

The Indian Farming article lists high-yield varieties by state, for example JS 23-03 and JS 22-12 in Madhya Pradesh (about 2.1 to 2.3 t per hectare), KDS 992 and KDS 753 in Maharashtra (2.5 to 2.7 t), and DSb 21 in Karnataka (3.0 t). A higher yield potential asks for a steadier nutrient plan, so match the dose to the variety as well as the district.

For the soils behind these differences, see our guide to the soil types of India and the crops they suit. A department dose sheet for Madhya Pradesh or Maharashtra could not be opened, so ask your KVK for the current one.

Use the soil test for three decisions: cut phosphorus and potash where the soil is already high, add sulphur and zinc where they are low, and fix pH or salinity first. TNAU itself says to apply NPK per the soil test recommendation wherever possible. A blanket dose is the fallback.

Salty patches often cause poor stands that look like a nutrient problem. Our guide to soil salinity: causes, symptoms and fixes covers EC readings and reclamation. If the crop is already pale, the diagnosis belongs in our planned post on soybean NPK requirement and deficiency symptoms (soybean-npk-requirement-and-deficiency-symptoms); for the wheat parallel see sulphur, zinc and urea timing in wheat.

Water at germination, flowering, pod initiation and seed filling decides whether the basal dose is used. The ICAR article lists exactly these four stages, says kharif soybean needs no scheduled irrigation, and gives priority to the flowering through seed-filling period when water is short.

• Germination. A light irrigation after basal application helps seedlings establish, and waterlogging should be avoided (ICAR).
• Flowering. Water stress here leads to significant flower and pod abortion (ICAR). This is also when the TNAU DAP or urea spray goes on.
• Pod initiation and seed filling. Excess moisture at pod maturity promotes seed discolouration and quality loss, so irrigate to need, not by calendar (ICAR).
• Drainage. Soybean is highly sensitive to prolonged saturation; the Assam package asks for surface drains with a gentle slope.

The ICAR article puts rainfall need at 600 to 650 mm, well distributed. In a dry kharif, a rescue irrigation at flowering is worth more than an extra bag.

The common ones are heavy nitrogen on a legume, a blanket dose with no soil test, ignoring sulphur, wrong micronutrient sources, waterlogging, and mixing fungicide and culture in one slurry. Each costs money or yield without benefit. Fix these before adding a new product.

• Heavy urea. The sources list only 20 to 30 kg N per hectare.
• Blanket dose for every field. TNAU says to use the soil test recommendation wherever possible.
• No sulphur. DAP and MOP carry no sulphur; use SSP or gypsum and read the S percentage on the bag.
• Wrong micronutrient carrier. ICAR-IISS found zincated urea and boronated SSP inferior to zinc sulphate or chelates in highly deficient soils.
• Waterlogging. The ICAR article calls soybean highly sensitive to prolonged saturation.
• Fungicide and culture together. TNAU calls fungicides and biocontrol agents incompatible.

Conclusion

A good soybean fertilizer schedule is short and early. Treat the seed with Rhizobium and PSB, keep fungicide and culture apart, place a modest basal dose of phosphorus, potash and sulphur in the furrow below the seed, add zinc where the soil test says so, and spray DAP or urea at 20 g per litre at flowering and again 15 days later. Use TNAU's 20:80:40:40 irrigated and 20:40:20:20 rainfed doses and the Assam 20:60:40 package as reference points, convert them to per-acre bags, and let the Soil Health Card and your state recommendation have the last word.