Biofertilizers and Organic Manures in Marigold: FYM, Vermicompost, Azotobacter, PSB, Doses per Acre and an Integrated Nutrient Plan

Marigold responds well when manure and biofertilizers replace part of the chemical fertiliser, not when they are added on top of a full dose. Most Indian sources put well-rotted FYM at 25 to 30 tonnes per hectare (roughly 10 to 12 tonnes per acre), mixed in at the last ploughing. TNAU gives Azospirillum and phosphobacteria at 2 kg per hectare each, mixed with FYM. Trials from Saharanpur, Faizabad and Raipur found the best flower yield with about 50 to 75 percent of the chemical dose plus vermicompost or FYM and Azotobacter, Azospirillum or PSB. Keep biofertilizers away from fungicides, and use Trichoderma as a preventive soil treatment, not a cure.

Marigold flowers for two to three months and is picked every few days, so it pulls nutrients out of the soil all season. Organic manures rebuild soil structure and feed slowly; biofertilizers add living bacteria and fungi that fix nitrogen or free up locked phosphorus. Together they let you cut chemical fertiliser without losing flowers.

The Indian Farming article from KVK Birauli calls marigold a short-duration crop that needs plenty of fertiliser for a good yield. That is true, and it is why a field planted after marigold often looks tired. The Saharanpur authors frame the problem the same way: indiscriminate chemical fertiliser alters soil fertility, and the gap has to be closed with organic and biological sources used alongside chemicals, not instead of them.

For the wider crop plan (varieties, sowing windows, spacing, picking), our pillar guide on marigold flower farming has the full picture. This article goes deep on the organic and bio inputs only.

Organic manures such as FYM, vermicompost and neem cake are bulky materials that carry nutrients and organic matter. Biofertilizers are small packs of living microbes, such as Azotobacter or PSB, that work around the root. Manure feeds the soil; biofertilizer feeds the crop through microbes. They do different jobs and work best together.

The Saharanpur trial defines biofertilizers in the same way: microbial inoculants that help fix nitrogen from the air, solubilise insoluble nutrients, make small amounts of growth hormones and speed up the breakdown of residues.

Most Indian sources give 25 to 30 tonnes of well-rotted FYM per hectare, which is roughly 10 to 12 tonnes per acre. TNAU says 25 t/ha, its organic package says 30 t/ha, and the Indian Farming article says 15 to 20 t/ha. Mix it in at the last ploughing, not on top of the soil.

Why the spread? The sources are for different systems. TNAU's 25 t/ha is the standard package. The organic package pushes the dose up because no chemical fertiliser backs it. The Indian Farming rate is for a Bihar system that also applies 200 kg N per hectare. If you are also giving chemical fertiliser, the lower end is the sensible start.

Three practical points from the TNAU manure page. First, FYM takes about 4 to 5 months to mature in a pit, so raw, half-rotted dung is a mistake. Second, only about 30 percent of its nitrogen reaches the first crop, with 60 to 70 percent of the phosphorus and 70 percent of the potassium. Third, for high rates apply at least 15 days before planting to avoid nitrogen lock-up while the material finishes decomposing.

Average FYM carries only about 0.5 percent N, 0.2 percent P2O5 and 0.5 percent K2O (TNAU). So 10 tonnes of FYM brings roughly 50 kg N, a useful but not complete supply, and most of it arrives slowly over the season. Its real value is soil structure and the food it gives soil microbes.

There is no single official rate. Trials used small amounts: 10 quintals (1 tonne) per hectare of vermicompost in the Pusa Arpita trial, which is about 400 kg per acre. Our vermicompost product label lists 500 to 1,000 kg per acre for vegetables. Use vermicompost to replace part of the chemical nitrogen, not as an add-on.

The Muzaffarnagar trial (2021-22, Pusa Arpita) used vermicompost at 10 q/ha as a single treatment and half of that dose in the best combination, which also had half the chemical dose and half the PSB dose. Plant height at 85 days was 57.47 cm in that best treatment against 40.62 cm in the untreated control, and the first flower opened at about 41 days (see the Plant Archives paper).

For a field, the Katyayani Enriched Vermicompost page gives 500 to 1,000 kg per acre for vegetable crops, and says flower crops can be given 500 g per plant. Do the arithmetic before you use the per-plant figure. At the traditional TNAU spacing of 45 x 35 cm there are roughly 25,700 plants per acre (our calculation), and 500 g each would be about 12.8 tonnes, which is no longer a top-up. For a field crop, work from the per-acre number. The per-plant number suits beds and pots.

The same page says vermicompost has 30 to 40 percent organic matter, and it lists no N, P or K percentages. We therefore give none. Check the pack label for the nutrient analysis of the lot you buy.

Yes, neem cake is a common soil amendment in flower crops. TNAU says nutrients from oilcakes become available 7 to 10 days after application and that the cake should be well powdered. The dose depends on the soil and the disease problem, so follow your state agriculture university recommendation.

The TNAU manure page describes neem cake as a non-edible oilcake used as manure for horticultural crops, and gives no N-P-K figure for it. For disease management, the TNAU organic package advises neem cake at 250 kg/ha to reduce soil inoculum in a chilli and tomato damping-off schedule. That is a different crop, so read it as a pointer to the practice, not as a marigold rate.

• Powder it. Lumpy cake breaks down slowly and unevenly.
• Apply early. The 7 to 10 day release window means it should go in at land preparation, not at flowering.
• Do not stack it with raw FYM. Both tie up nitrogen while they decompose, so keep a gap before transplanting.
• Keep it away from pesticide claims. Neem cake here is a soil amendment. Spray-grade neem oil is a separate product.

Azospirillum, Azotobacter and phosphate-solubilising bacteria (PSB) have the most marigold evidence, from TNAU recommendations and several Indian trials. KMB and mycorrhiza are sensible additions, but we found no marigold field data for them. Trichoderma belongs in the disease-prevention column, not the nutrition column.

The comparison for pulses is simpler because Rhizobium does the nitrogen job. Marigold is not a legume, so it relies on free-living nitrogen fixers such as Azotobacter and Azospirillum. If you grow pulses in rotation, our post on Rhizobium, PSB and KMB for chana explains the pulse side.

TNAU gives Azospirillum and phosphobacteria at 2 kg per hectare each (about 0.8 kg per acre) for soil application, mixed with FYM. For liquid Azotobacter, the Pusa Arpita trial used 700 ml per hectare, while our product page lists 1 to 2 litres per acre for soil. The two are different formulations, so follow your pack label.

The TNAU marigold page gives two ways. For seed, mix 200 g of Azospirillum in 50 ml of rice gruel and coat the seed before sowing. For soil in the precision system, apply 2 kg each of Azospirillum and phosphobacteria per hectare at planting, mixed with 100 kg of FYM. The TNAU precision production note puts the same 2 kg per hectare before the last ploughing.

Do not read the 280 ml and the 1 to 2 litre figures as a contradiction to fix. Trial rates come from small plots with a specific product and often a different cell count. Labels are written for the commercial product. When you buy, use the label dose for that exact product and treat the trial dose as evidence that the practice works.

One more gap to know about: the Azospirillum page on our site gives two different soil doses (1 to 2 litres per acre in one section and 1 litre in another), so we do not link it here until the product team fixes it.

PSB converts locked phosphorus in the soil into a form roots can absorb. KMB does the same job for potassium. Both reduce the amount of chemical P and K you need only when the soil already holds reserves. On a soil test with very low P or K, you still have to supply fertiliser.

Our Soluphos PSB page gives three methods. For seed, mix 250 ml in 2 to 3 litres of water to coat 50 to 60 kg of seed, then shade-dry. For transplants, mix 250 ml in 4 to 5 litres of water and soak seedling roots for 20 to 30 minutes. For soil, use 300 to 400 ml per acre, mixed with 50 to 100 kg of soil, sand or compost, and spread before the last ploughing or 24 hours before sowing. Marigold seedlings are transplanted, so the root soak is the method that fits.

The K-MOB page lists 1 to 2 litres per acre for soil. For seed, drench and timing, follow the pack. KMB is an optional extra, so judge it with a side-by-side strip in your own field.

PSB did show up in marigold trials. The Faizabad trial's best treatment combined Azotobacter, PSB and FYM with half the recommended nitrogen and phosphorus (the control was 200:100:100 kg/ha NPK). In the Raipur trial, Azospirillum plus PSB plus cow urine plus half the nitrogen through vermicompost plus half the NPK gave the highest flower yield and benefit-cost ratio.

In one pot study, marigold with mycorrhiza grew taller and flowered better than plants without it, especially under drought. We found no marigold field trial that shows a yield gain in rupees. So mycorrhiza is a reasonable add-on for low-phosphorus or dry soils, not a replacement for a fertiliser plan.

The Saudi greenhouse study used Glomus constrictum on marigold cv. Jubilee in pots of low-phosphorus sandy loam. Under full water, flower diameter was 5.22 cm with the fungus and 4.62 cm without. Under the driest treatment it was 3.34 cm against 2.86 cm. The authors found the response was stronger under severe drought. It is a pot study with one species of fungus, so we do not carry any of its numbers over to a field in India.

The Bhumiraja Mycorrhiza page says 4 to 8 kg per acre at sowing, or 4 to 10 kg mixed with 50 to 80 kg of FYM, compost or vermicompost, placed in the planting pit or furrow. It says gains are largest in soils low in available phosphorus. Its composition, benefits and cautions sections are blank at the moment, so it is a product-team gap, and we avoid quoting any claim beyond the dose.

Phosphorus Fertiliser And Mycorrhiza: Do not put a heavy dose of soluble phosphorus fertiliser right on top of a mycorrhiza application and expect both to work. Apply them at different times and test on a small strip first.

Marigold is raised in a nursery and transplanted, so the best fit is a seedling root dip, with a soil application mixed into FYM before the last ploughing. Seed treatment works for nursery beds. Apply in the evening or on a cloudy day, keep soil moist, and never let the product touch fungicide.

1. Seed treatment (nursery). Coat seed with the product in a thin slurry (TNAU uses rice gruel as the sticker for Azospirillum), then shade-dry before sowing.
2. Seedling root dip. Mix the product in water, dip roots for 20 to 30 minutes (Soluphos label), and transplant at once. This puts bacteria exactly where the root will grow.
3. Soil mix with FYM. Blend the product with well-rotted FYM or compost and spread it before the last ploughing, as in the TNAU 100 kg FYM mix. Moisture helps the bacteria survive.
4. Drip. Several liquid labels allow 1.5 to 2 litres per acre through drip. Use clean, filtered, non-chlorinated water.

TNAU also dips marigold seedlings in Pseudomonas fluorescens at 0.5 percent in its precision system, which is a disease-prevention step, not a nutrient step. Pseudomonas and nutrient biofertilizers are generally compatible, but check each label before mixing in one tank.

Put FYM or compost in at the last ploughing, 15 days or more before transplanting. Biofertilizers go in at or just before transplanting. Chemical top dressing follows at about 30 to 45 days. Foliar sprays, if any, come at 30 and 45 days after transplanting. Plan back from the planting date.

Sowing windows from the Indian Farming article give the base dates: for flowers in the late rains, sow in mid June and transplant in mid July; for winter flowers, sow mid September and transplant mid October; for summer, sow January to February and transplant February to March. Add your biofertilizer step to each of those transplant dates. Our post on winter flowers in pots covers the container version.

Spacing changes how much each plant gets. Plant at 40 x 40 cm for African marigold and 30 x 30 cm for French marigold per the Indian Farming article, or 45 x 35 cm in the TNAU standard system. Closer spacing means more plants per acre and a higher total manure and biofertilizer need, so base the dose on the area, not on the plant count.

The most reliable pattern from the trials is to cut the chemical dose to about 50 to 75 percent and make up the difference with FYM or vermicompost plus a nitrogen-fixing and a phosphate-solubilising biofertilizer. Do not stack full organic inputs on top of a full chemical dose. Adjust with a soil test.

In per-acre terms the TNAU standard schedule is roughly 18 kg N, 36 kg P2O5 and 30 kg K2O basal, plus 18 kg N at 45 days (our conversion from the per-hectare figures). The TNAU precision plan, at 75 percent of the dose, is about 27 kg N, 27 kg P2O5 and 23 kg K2O per acre in total through drip (also our arithmetic).

The TNAU precision note reports 32.5 t/ha of flowers in the precision system against 25 t/ha in the conventional one, with xanthophyll at 1.99 g/kg against 1.42 g/kg. That system changes several things at once: drip, raised beds, micronutrients and biostimulants as well as biofertilizers. Do not credit the whole 7.5 t gain to the biofertilizer.

A soil test makes this concrete. If your soil health card shows low organic carbon or very low available phosphorus, lean harder on manure and PSB. Our post on how to read your soil health card shows which lines to read. For why a nutrient can be present and still unavailable, see soil pH and nutrient lock.

Where the line sits between organic and chemical, our comparison bio vs chemical inputs is a short read. If you are fertigating, water-soluble vs granular fertiliser explains when that choice pays.

Across four Indian trials, plots with biofertilizers plus manure and a reduced chemical dose matched or beat full chemical doses. The strongest numbers come from Saharanpur: 185.1 q/ha with 75 percent RDF plus vermicompost plus Azotobacter, against 94.3 q/ha in the reference. Results are site-specific and cannot be added together.

The Muzaffarnagar paper also reports 402 q/ha for its best treatment. That is far above every other figure in this article and above the TNAU yield range, so we do not repeat it as a yield promise and list it for checking.

Expect modest returns, not miracles. The TNAU organic package gives 11 to 18 t/ha for African marigold and 8 to 12 t/ha for French marigold, and a biofertilizer will not lift a poorly managed crop out of that range. What it does is hold yield while the chemical bill falls.

In the Saharanpur trial, the largest flowers came from the lowest chemical dose: 50 percent RDF plus vermicompost plus Azotobacter gave 7.32 cm flowers weighing 7.06 g, against 5.19 cm and 4.91 g in the reference. The Raipur trial also reported the longest shelf life under a combined bio-organic treatment.

Look closely at that Saharanpur result. The treatment that won on flower number and total yield (75 percent RDF) was not the one that won on flower size (50 percent RDF). The 50 percent plot had 137 q/ha total yield, compared with 185 q/ha at 75 percent. So there is a trade-off between more flowers and bigger flowers. A grower selling by weight to a garland trader wants total yield; a grower selling large blooms by count to a decorator may prefer the larger flower.

Shelf life is a quality point for garland and temple markets. The Raipur abstract lists shelf life among the traits that improved with the full bio-organic treatment, but gives no hours or days. We therefore say it improved and put no number on it.

Trichoderma is a beneficial fungus that colonises roots and competes with disease fungi. It works as prevention: apply it to the nursery and the planting soil before damping-off, root rot or wilt appears. It will not rescue a plant that is already wilting. Pair it with good drainage and rotation.

The Katyayani Trichoderma viride 1.5% WP page lists 1 to 2 kg per acre as a soil drench in 200 litres of water, 8 to 10 g per kg of seed for seed treatment, a 30 minute dip of seedlings in 500 g in 50 litres of water, and for the nursery 500 g mixed with 10 kg of well-decomposed manure per acre. It names wilt, root rot, damping-off and seedling wilt, but does not list marigold among its target crops, so the doses are label rates and not a marigold recommendation.

The TNAU precision note uses Pseudomonas fluorescens, not Trichoderma, in marigold: a 0.5 percent seedling dip, and a 2.5 kg/ha soil application followed by a 0.5 percent foliar spray for leaf spot. The TNAU marigold page gives chemical options too: a Bavistin drench at 1 g per litre for root rot, and mancozeb or hexaconazole sprays for leaf spot. Where the disease is already established, those chemical routes are the tested ones.

• Enrich the manure. Mixing Trichoderma into dried FYM and leaving it moist under shade for a few days before applying is a common method. Our pillar post cites a KAU mix with neem cake; quantities there need checking against KAU's own page.
• Treat the nursery first. Damping-off starts in the seedbed. Treating beds and seed is cheaper than rescuing a transplanted field.
• Rotate and drain. Marigold also acts as a nematode-suppressing trap crop in other farmers' rotations (the Indian Farming article), but it can suffer root rot itself in wet, heavy soil.
• Do not apply the biofungicide and a chemical fungicide together. Keep a gap as per the label.

For more on using bio-agents in small plots and pots, see our post on Trichoderma and Beauveria for gardeners. You can also browse the bio-fungicides collection for other options.

Biofertilizers are living cultures, so heat, sun, fungicide and chemical contact kill them. Store them cool and shaded, use before the expiry date, apply in the evening to moist soil, and keep a gap from any fungicide or seed dressing. Never expect a visible rescue within days.

• Keep them away from fungicide and chemical seed dressing. Treat seed with the fungicide first, dry it, then use the biofertilizer, or choose a biological seed dressing.
• Do not leave an opened pack in the sun. Heat is the usual reason a product 'did not work'.
• Do not mix strong chemical fertiliser with the biofertilizer slurry. Keep fertiliser and inoculant separate.
• Apply to moist soil. Dry soil kills the bacteria before they reach the root.
• Check the batch. Buy a pack with a visible manufacturing and expiry date, and read the dose on that pack.

Neither the Azotobacter nor the PSB page we opened gave a storage or shelf-life figure, and the K-MOB page says detailed instructions come in the pack. Treat the pack insert as the final word on storage.

Yes. For pots and beds, mix well-rotted compost or vermicompost into the potting soil rather than using field-scale rates. Our vermicompost page lists 5 to 10 kg per 10 square feet for kitchen gardens and 100 g per plant for potted plants, with a repeat every 60 days. Add a pinch of biofertilizer at planting.

A vermicompost-heavy mix can stay wet. One of the pot studies we saw ran 40 to 60 percent vermicompost by volume, but we have not opened it, so stay at the product page's 30 to 35 percent and watch drainage. Our posts on a terrace garden soil mix and a kitchen garden fertilizer schedule show full mixes.

The usual errors are using half-rotted FYM, applying manure too close to transplanting, dosing biofertilizers on top of a full chemical dose and expecting extra yield, mixing biofertilizer with fungicide, and treating Trichoderma as a cure. Most of these waste money and some burn roots.

The pH row deserves a note. Container mixes do best around pH 5.8 to 6.2, and a soil test tells you your own field pH. Saline soils are unsuitable, and the TNAU marigold page and Indian Farming both call acidic soil unsuitable.

For identifying yellowing, purpling or poor flowering once the crop is in the ground, see the companion article on nutrient deficiencies in marigold (identification and correction), published with this one. It covers how to tell a nutrient shortage from a disease or a watering problem.

Conclusion

Marigold does best when organic manures and biofertilizers share the load with a trimmed chemical dose. Start with well-rotted FYM (about 10 to 12 tonnes per acre by the TNAU rates) at the last ploughing, add a nitrogen-fixing and a phosphate-solubilising biofertilizer at transplanting by root dip or mixed with FYM, and keep chemical NPK at roughly 50 to 75 percent of the recommended dose. Use Trichoderma early as prevention. Because sources and labels differ, use your state recommendation and the pack label, and test one strip against your usual practice before changing the whole field.