Green Manure Guide: Best Crops, Timing and Nitrogen Gains

Quick answer Green manure is a fast-growing crop, usually a legume, that you grow and then plow into the soil while it is still green. Incorporated just before flowering, a good green manure crop adds 40 to 120 kg of nitrogen per acre, lifts organic matter, and can replace 2 to 5 bags of urea for the crop that follows.

Key Takeaways

• Green manure means burying a living crop in your own field. No carting, no heap, no waiting for compost to mature.
• Sesbania (dhaincha) is the strongest choice for the summer gap before rice. Berseem is the best winter option.
• Cut and mix the crop into the soil at early flowering, when it is soft, leafy and low in fibre.
• Wait 3 to 4 weeks after incorporation before you sow the main crop, or soil bacteria will borrow the nitrogen back for a while.
• Two cheap habits double your results: coat the seed with the right rhizobium strain, and drop one bag of SSP at sowing.
• The first season pays for itself. The real gain shows up in year two and year three, when the soil starts holding water and nutrients on its own.

Why Farmers Are Going Back to Green Manure

Fertilizer prices climb every season. Soil quality does the opposite. So it makes sense that a practice farmers used for thousands of years, long before a urea factory existed, is suddenly getting attention again.

Here is the part that surprises people. Seed for one acre of sesbania usually costs less than a single bag of urea, yet the nitrogen it leaves behind can be worth three to five bags. You are not buying fertilizer. You are growing it.

This guide walks through the whole practice: which green manure crop to pick, how much to sow, exactly when to plow it in, how long to wait, and the small mistakes that quietly cancel out most of the benefit. Every number below sits in the range reported in field trials and farmer records across South Asia. Your own soil, sowing date and water supply will shift the results, so treat them as planning figures rather than promises.

What Is Green Manure?

Green manure is a crop grown for the soil rather than for the market. You sow it, let it build leaf and root, then chop it and mix it into the topsoil while it is still green and soft, before it matures or sets seed.

Compost is made outside the field and then carried in. Green manure is made where it stands. That single difference is why it stays cheap even on a large area: no heaps, no loading, no transport.

Most green manure crops are legumes. Bacteria living in nodules on their roots pull nitrogen out of the air and fix it in a form plants can use. Bury the crop and that nitrogen goes to your next crop instead of leaving with a harvest. Cereal types such as oats and sorghum fix no nitrogen, but they produce a lot of bulk, and bulk is what builds lasting humus. You can size that bulk before you plant with the green manure biomass calculator.

Green Manure, Cover Crop or Compost: What Is the Difference?

Practice	Where it is made	Main job	Nitrogen supply
Green manure	In the field, then buried	Feed the next crop and build organic matter	High if a legume is used
Cover crop	In the field, often left on top	Protect the soil surface and stop erosion	Low to high, depends on species
Compost	In a heap outside the field	Balanced, slow release soil food	Low but very steady

The line between a cover crop and a green manure is thin. A cover crop becomes a green manure the moment you mix it into the soil rather than leaving it on the surface. If you are sizing seed for either job, the cover crop seeding rate calculator will get you close on the first try.

What Green Manure Actually Does for Your Soil

The nitrogen gets all the attention. In practice, farmers who stick with the habit for a few seasons usually talk more about how the soil feels and how it takes water.

• Free nitrogen. A legume crop leaves 40 to 120 kg of nitrogen per acre behind, which cuts straight into your fertilizer bill. Check what that means for your plan with the nitrogen balance calculator.
• More organic matter. Fresh green material feeds the soil life that builds stable humus. Track the change season by season using the soil organic matter calculator.
• Better structure and water entry. Roots open channels, water soaks in instead of running off, and hard setting topsoil loosens. That also eases the pressure shown by a soil compaction risk estimator.
• Fewer weeds. A thick sesbania or cowpea canopy shades the ground so completely that most weeds never get going.
• No bare soil. Ground that would have sat empty and baking between crops is covered instead, which slows erosion and water loss.
• Live soil. Earthworm counts and microbial activity climb quickly once fresh green material is going in every year.
• A break in pest cycles. Slotting a different plant family into the rotation interrupts diseases and soil pests. Sunn hemp goes further and suppresses root knot nematodes. Map the sequence with the crop rotation planner.

There is a climate angle too. Soil that holds more carbon and needs less manufactured nitrogen has a smaller footprint, which you can put numbers to with the farm carbon footprint calculator.

Best Green Manure Crops for Pakistan and South Asia

Pick by season first, then by soil. A crop that thrives in standing water is the wrong pick for a sandy field, no matter how much nitrogen it fixes on paper.

Sesbania (Dhaincha)

The best option for the summer gap, and the reason many rice growers try green manure at all. It reaches full size in 45 to 60 days, fixes 80 to 120 kg of nitrogen per acre, and shrugs off waterlogging that would kill most legumes. Sow 5 to 8 kg per acre in May or June and plow it in just before rice transplanting.

Mung Bean

The practical choice if you cannot give up a whole season to a crop you do not sell. Harvest the pods for income, then work the stalks and roots back in. Even after picking, the residues and nodules leave 20 to 50 kg of nitrogen per acre. Sow 6 to 8 kg per acre in Kharif, and if you are weighing the income against a pure green manure, run both through the crop profit comparison calculator.

Cowpea

Tough in heat, quick to cover the ground, and fixes 40 to 80 kg of nitrogen per acre. It handles sandy and light soils where sesbania struggles. Not sure which group your field falls in? A soil texture classifier sorts that out in a couple of minutes.

Berseem (Egyptian Clover)

The winter workhorse. Take two or three fodder cuts through the Rabi season, then incorporate the last flush in March or April. Over a full season it fixes up to 100 kg of nitrogen per acre while feeding your animals along the way, which is hard to beat for value.

Sunn Hemp (Jantar)

Fast, bulky, and the one to reach for if nematodes are the problem. It produces a heavy load of biomass in about 60 days and works well ahead of tomato, brinjal and other vegetables that suffer root knot damage.

Oats and Sorghum

These fix no nitrogen, so treat them as organic matter crops. Their value is sheer carbon rich bulk, which is exactly what a field with reasonable nitrogen but tired, low carbon soil needs. Sorghum in summer, oats through winter.

A quick way to compare your options at a glance:

Crop	Season	Days to incorporate	Nitrogen per acre	Seed rate per acre	Best fit
Sesbania (dhaincha)	Kharif	45 to 60	80 to 120 kg	5 to 8 kg	Before rice, wet and heavy soils
Mung bean	Kharif	45 to 55 or after pods	20 to 50 kg	6 to 8 kg	When you also want income
Cowpea	Kharif	45 to 50	40 to 80 kg	10 to 12 kg	Sandy and light soils
Berseem	Rabi	Last cut in March or April	60 to 100 kg	8 to 10 kg	Fodder plus fertility
Sunn hemp (jantar)	Kharif	50 to 60	70 to 100 kg	8 to 10 kg	Before vegetables, nematode fields
Oats or sorghum	Rabi or Kharif	55 to 70	None fixed	As per fodder rate	Low organic carbon soils

Seed rates shift with sowing method, seed size and germination percentage, so confirm your own figure with the seed rate calculator before you buy.

How Much Nitrogen Does Green Manure Add?

Three things decide the answer: the crop, how long it grew, and whether the root nodules were actually working. Dig up a few plants at 30 days. Healthy nodules are firm and pink or red inside. White or grey nodules mean the bacteria are not fixing much, and your nitrogen figure will land at the bottom of the range.

Green manure	Stage at incorporation	Nitrogen supplied per acre	Urea bags replaced
Sesbania	60 days, before flowering	80 to 120 kg	3 to 5
Mung bean residues	After pod harvest	20 to 40 kg	1 to 2
Cowpea	50 days, early flowering	40 to 80 kg	2 to 3
Berseem	Full season, final growth	60 to 100 kg	2 to 4
Sunn hemp	60 days	70 to 100 kg	3 to 4

One 50 kg bag of urea carries about 23 kg of actual nitrogen. So a strong sesbania crop genuinely stands in for three to five bags per acre. Before you cut your fertilizer plan, work the credit through the urea application rate calculator so the reduction lines up with what the next crop needs, and adjust the rest of the programme with the NPK fertilizer dosage calculator.

One caution worth repeating. Green manure supplies nitrogen generously, but very little phosphorus, potash or micronutrients. It is not a full fertilizer programme on its own. If your soil is short on potash or zinc, it will stay short, so run a check with the soil nutrient deficiency checker and keep covering those separately.

How to Use Green Manure Step by Step

Eight steps, start to finish. None of them are complicated, but the timing in steps 6 and 8 is where most of the value is won or lost.

1. Choose the right crop. Match it to your season, your soil and the crop that follows. Legumes before crops that need plenty of nitrogen, such as wheat, maize, rice and vegetables. Cereals such as sorghum or oats when organic matter is the real gap. The crop calendar generator helps you see whether the gap in your rotation is genuinely long enough.
2. Prepare a simple seedbed. Green manure crops are not fussy, but they germinate far better in a clean, level, weed free bed. Light tillage and levelling is plenty. Skip the deep plowing and save the fuel.
3. Sow at the right rate. Broadcast evenly or drill in rows. Rates sit in the table above. Add one bag of SSP per acre at sowing, because legume nodules cannot function without phosphorus, and size that dose properly with the phosphorus application calculator.
4. Inoculate the seed with rhizobium. This is the cheapest step and the one most often skipped. Buy the strain matched to your crop, because different legumes need different bacteria. Mix the inoculant with the seed in the shade, never in direct sun, and sow within 24 hours. Rates and handling are covered by the biofertilizer application calculator.
5. Irrigate once after sowing. One light irrigation gets germination away cleanly. After that most green manure crops ride out the monsoon or the cool season on very little water. If you are on tube well water and counting every turn, the soil moisture deficit calculator will tell you when a second irrigation is genuinely needed.
6. Incorporate at early flowering. This is the moment that matters. Just before or at the very start of flowering, the plants hold their highest nutrient content and their lowest ratio of carbon to nitrogen, so they break down fast and release nitrogen quickly. Leave it later and the stems turn woody. The compost carbon to nitrogen ratio calculator shows why that shift slows everything down.
7. Chop and mix properly. Run a rotavator, disc harrow or moldboard plow and work the material into the top 15 to 20 cm of soil. Finer pieces rot faster. If the crop is tall and thick, go over it twice rather than burying long stems in clumps.
8. Irrigate, then wait 3 to 4 weeks. Water starts decomposition. The wait is not optional. While bacteria multiply to break the material down, they lock up soil nitrogen temporarily, so a crop sown too soon can look pale and starved for its first two or three weeks even though plenty of nitrogen is on the way.

The timing rule to remember Incorporate at flowering. Sow the main crop 3 to 4 weeks later. Get those two right and everything else is detail.

The right window for each crop:

• Sesbania: 45 to 60 days after germination, before flowering opens up
• Mung bean: 45 to 55 days for pure green manure, or straight after pod harvest
• Cowpea: 45 to 50 days, at early flowering
• Berseem: final cut or full incorporation in March to April, before Kharif preparation
• Sunn hemp: 50 to 60 days, while stems are still soft enough to snap by hand

If your sowing date has already slipped, check the maturity window with the planting date and maturity calculator before you commit the field.

Five Mistakes That Waste a Good Green Manure Crop

Almost every disappointing result traces back to one of these.

• Sowing the main crop too soon after incorporation. This is the big one. Decomposing green material ties up nitrogen for a few weeks, so an early sowing shows deficiency in the very crop you were trying to feed. Always leave 3 to 4 weeks.
• Not inoculating the seed. Without the correct rhizobium strain, nodules either fail to form or form small and useless, and your legume behaves like a grass. You lose most of the nitrogen for the price of a sachet.
• Incorporating too late. Once flowering is over and seed is setting, the crop turns tough and carbon heavy. It then decomposes slowly and can pull nitrogen out of the soil instead of releasing it. Late is worse than a little early.
• Skipping phosphorus at sowing. Nodules run on phosphorus. One bag of SSP is a small cost against a large gain in fixation, and the organic fertilizer calculator helps if you prefer a rock phosphate or manure route.
• Expecting everything in year one. The first season gives you part of the benefit. The compounding shows up in the second and third year, as organic matter, water holding and soil life all step up together.

Green Manure in Real Cropping Systems

The Rice Wheat System

In the rice wheat rotation that covers much of Punjab, the window between wheat harvest in April or May and rice transplanting in June or July is close to perfect. Sesbania fills it exactly, growing in 45 to 60 days and going in just ahead of transplanting.

Farmers who make this a habit commonly report cutting nitrogen fertilizer for the rice crop by roughly a quarter to two fifths, and long running research on rice based systems in South Asia points the same way. Plan the whole sequence with the crop rotation planner, then budget the change with the crop cost of production calculator.

The Cotton Belt

After cotton comes off in October or November, berseem can run right through winter and go in before land preparation in April. Cotton soils are often the most depleted on the farm, so this is where the organic matter gain is easiest to see. On sodic patches, pair it with a gypsum dose sized by the gypsum application calculator, because green manure improves structure but does not fix sodicity by itself.

Vegetables and Kitchen Gardens

Intensive vegetable ground takes constant punishment, so short green manures between crops pay quickly. Mung bean or cowpea in summer, oats in winter, sunn hemp wherever nematodes are a problem. On a small plot a spade and fork do the job perfectly well. If you are working out what a home plot saves you, the kitchen garden planner and savings calculator is a useful starting point.

Does It Pay? A Simple Way to Check

Run the numbers for one acre of sesbania before you commit. Costs vary by district and season, so use your own local prices, but the shape of the sum stays the same.

Line item	What to count
Costs	Seed for 5 to 8 kg, one rhizobium sachet, one bag of SSP, one or two irrigations, one to two rotavator passes
Returns	Value of 3 to 5 bags of urea saved, plus organic matter and structure gains that carry into later seasons
Hidden cost	The field is occupied. On a genuine gap between crops this is zero. If it displaces a cash crop, count that income
Break even	Most farmers cover the cost in the first season on saved urea alone, before counting any yield response

For a full picture across the year, drop the figures into the farm budget planner. The soil benefits are real but slow, so the honest way to judge green manure is over three seasons, not one.

Frequently Asked Questions

What is green manure in simple words?

Green manure is a crop you grow and then plow into the soil while it is still green, before it sets seed. Instead of harvesting it, you feed it to the soil. Legumes are used most often because they add free nitrogen along with organic matter.

Which green manure crop is best in Pakistan?

Sesbania, known locally as dhaincha, is the strongest choice for the Kharif gap before rice. It fixes 80 to 120 kg of nitrogen per acre in 45 to 60 days and tolerates waterlogging. For the Rabi season, berseem gives you fodder cuts and up to 100 kg of nitrogen per acre.

How much nitrogen does green manure add per acre?

Most legume green manures supply 40 to 120 kg of nitrogen per acre, depending on the crop and how long it grew. Since a 50 kg bag of urea holds about 23 kg of nitrogen, a good sesbania crop replaces roughly three to five bags per acre.

When should green manure be plowed in?

Just before or at the start of flowering, usually 45 to 60 days after sowing. At that stage the plants are soft, nutrient rich and low in fibre, so they break down fast. After flowering the material turns woody and releases its nitrogen much more slowly.

How long should I wait before sowing the main crop?

Wait 3 to 4 weeks after incorporation. Bacteria breaking down the fresh material use soil nitrogen while they multiply, so a crop sown too early can show yellowing and stunting for two to three weeks. Irrigating after incorporation speeds decomposition and shortens the wait.

Is green manure better than compost?

They do different jobs. Green manure is cheaper at field scale and supplies its own nitrogen, but you can only use it when a gap in the rotation allows. Compost is more balanced, applies any time and lasts longer in the soil. Used together they work best.

Can I use green manure in organic farming?

Yes. It is one of the core practices of organic farming and often the most cost effective way to meet nitrogen needs without synthetic fertilizer. Pair it with compost or vermicompost for a balanced supply, and see the organic farming calculators for rates.

Do I need special equipment for green manure?

No. A rotavator or disc harrow does the job well on field scale, and a spade or garden fork is fine on small plots. What matters is chopping the material small and mixing it into the topsoil rather than leaving whole plants lying on the surface.

Does green manure waste water?

It uses some, but far less than most people expect. Sesbania and cowpea grow through the monsoon on rain plus one or two irrigations, and the extra organic matter improves water holding, so later crops usually need less irrigation than before.

Final Thoughts

Green manure is one of the few farm practices that gets cheaper and more effective the longer you keep at it. Nothing about it is complicated: pick the right crop for the season, inoculate the seed, add a little phosphorus, plow it in at flowering, and wait three or four weeks.

Start small. One field, one season. Sesbania in the Kharif gap or berseem through Rabi. Watch how the soil crumbles when you turn it and how the following crop colours up, and you will not need convincing for the second year.

Next step: size your own crop with the green manure biomass calculator, then plan the season with the soil and land calculators and the fertilizer and nutrient calculators. For crop by crop practice notes, browse the Foods Farming crop guides.