What's in the bag
Australian and New Zealand labels give nitrogen, phosphorus and potassium as elemental percentages by weight. Two typical products from the same maker:
| Product type | N | P | K | Label rate, vegetables |
|---|---|---|---|---|
| Blood and bone with composted poultry manure | 4.8 % | 3.0 % | 1.3 % | 100 g/m² every 6 weeks |
| Composted chicken manure pellets | 3.5 % | 1.1 % | 1.6 % | 100 g/m² every 6 weeks |
Both labels also list calcium, magnesium, sulfur and a little iron. Note what the first product is made of: composted poultry manure with blood and bone added. Products sold as blood and bone vary, so read the analysis rather than the name. The same labels give 70 g/m² for lawns, and 500 g per fruit tree for each year of its age, up to 2.5 kg.
The US publication used below lists blood meal on its own at 12 % nitrogen, and dried, pelleted poultry manure at about 4 %. US labels express phosphorus and potassium as oxides, so compare their P and K figures with care. The fertiliser calculator explains the conversion.
Raw manures and composts
Manure straight from the animal carries a lot of water and bedding, so its nutrients per kilogram are low. These are the typical values in Fertilizing with manure and other organic amendments (PNW 533), from Washington State, Oregon State and Idaho universities. They are converted to percentages of the manure as it comes, the same way Australian labels are written:
| Manure, as it comes | N | P | K | Dry matter | N released, first season |
|---|---|---|---|---|---|
| Poultry, broiler litter | 2.8 % | 1.35 % | 1.95 % | 68 % | 40–60 % |
| Poultry, laying hens | 1.95 % | 1.4 % | 1.45 % | 39 % | 40–60 % |
| Rabbit | 1.0 % | 0.55 % | 0.6 % | 35 % | 20–40 % |
| Sheep | 0.85 % | 0.35 % | 0.75 % | 32 % | 20–40 % |
| Beef cattle | 0.7 % | 0.2 % | 0.6 % | 28 % | 15–30 % |
| Dairy, stockpiled | 0.9 % | 0.3 % | 1.75 % | 50 % | 10–20 % |
| Horse, no bedding | 0.4 % | 0.15 % | 0.4 % | 25 % | 0–15 % |
| Horse, with bedding | 0.5 % | 0.15 % | 0.5 % | 35 % | −5 to 10 % |
| Beef manure compost | 0.9 % | 0.35 % | 1.1 % | 64 % | 0–10 % |
The last column is the share of the total nitrogen that becomes available to plants in the first growing season. A negative figure means the manure takes nitrogen from the soil for a while: microbes breaking down the woody bedding use it up. The rest of the nitrogen is released slowly over later years.
Why the nitrogen figure isn't the whole story
- Most manure nitrogen is organic, and soil microbes release it slowly. Poultry manure is the exception. It contains a lot of ammonium, which is available at once but escapes as ammonia gas if the manure is left on the surface. Dig it in the day you spread it, especially in warm, dry, breezy weather.
- Composting slows the release. In PNW 533's tables, fresh beef manure releases 15–30 % of its nitrogen in the first season, but beef manure compost only 0–10 %. Bags labelled "composted poultry litter" are often only partly composted and behave like fresh litter, with a strong ammonia smell.
- Low-nitrogen manures can starve plants at first. PNW 533 expects at least a short-term tie-up from anything under about 1.5 % nitrogen on a dry-weight basis, such as horse manure with lots of bedding.
- Manure is also a soil builder. Its organic matter improves soil structure over time, whatever it adds in nutrients.
How much to spread
Work in grams of nitrogen that plants can actually use:
rate needed (g/m²) = usable N wanted ÷ ( N % ÷ 100 × share released )
A 100 g/m² dose of 3.5 % pellets carries 3.5 g of nitrogen. At 40–60 % released, that is 1.4–2.1 g the plants can use this season. Fresh beef cattle manure at 0.7 % and 15–30 % released gives 1.05–2.1 g per kilogram. So it takes about 1–2 kg of cow manure per square metre to match 100 g of pellets for first-season nitrogen. The manure adds far more organic matter.
To see the grams of N, P and K any label rate puts on your bed, use the fertiliser calculator. It includes chicken manure pellets and blood-and-bone mixes.
Mushroom compost
Spent mushroom compost is the growing mix left over from mushroom farms. Penn State Extension describes the typical ingredients: horse-bedded straw, hay, poultry manure, corn cobs, cottonseed hulls and gypsum. Its figures:
- 1.5–3 % nitrogen, on a dry-weight basis
- 40–60 % organic matter
- pH mostly 6.0–8.0
- soluble salts that can be higher than in other composts
That makes it a good bulk soil improver. It is a poor choice around acid-loving plants such as blueberries, and around salt-sensitive plants. Use the compost calculator for volumes.
Handling and safety
- Heat and dry soil: the chicken manure pellet label says not to spread when the day's top is forecast above 30 °C, or when the soil is dry and plants are stressed.
- Weeds and pathogens: PNW 533 notes that raw manure is more likely than compost to carry weed seeds and pathogens such as Salmonella and E. coli. Compost is less likely to carry them. On vegetable beds, prefer composted or pelleted products, and wear gloves.
- Water quality: manure has more potential than compost to wash nutrients into waterways. Keep heaps covered and away from drains.
Questions
Is blood and bone or chicken manure better?
Compare the labels rather than the names. Many blood-and-bone products are poultry manure with blood and bone added. One such label reads 4.8-3.0-1.3, against 3.5-1.1-1.6 for plain chicken manure pellets. So the blood-and-bone mix carries a little more nitrogen and nearly three times the phosphorus at the same rate.
How much blood and bone per square metre?
The label quoted here gives 100 g/m² every six weeks for vegetables and flowers and 70 g/m² for lawns. For fruit trees it gives 500 g per year of the tree's age, up to 2.5 kg. Always follow your own product's label.
Is cow manure a good fertiliser?
It is a better soil improver than fertiliser. Fresh beef manure has about 0.7 % nitrogen as it comes, and only 15–30 % of that is released in the first season. It takes 1–2 kg per square metre to match 100 g of chicken manure pellets. Composted cow manure releases even less at first.
Can I put fresh horse manure on the garden?
It won't feed plants much. With bedding it can tie up soil nitrogen for a while, because microbes use nitrogen to break down the wood shavings or straw. Compost it first.
Sources
- Yates Hort & Ag, AgriBoost Plus Blood & Bone Granules and Dynamic Lifter Pellets. Covers label analyses, ingredients, application rates and the heat and dry-soil warning.
- Bary A., Cogger C. and Sullivan D., Fertilizing with manure and other organic amendments, PNW 533 (Washington State University, Oregon State University and University of Idaho, 2016). Tables 2, 3 and 5 give nutrient content, dry matter and first-season nitrogen availability, converted here from lb per ton as-is (÷ 20 = %). The text covers ammonia loss, composting, immobilisation and the compost versus manure comparison.
- Penn State Extension, Spent mushroom substrate as a soil amendment. Covers ingredients, nutrients, pH, organic matter and salts.
Last reviewed 24 September 2026 · Report an error