Blood meal is a powdered plant food made from dried animal blood. While it’s not ideal for vegetarian gardeners, it is an excellent organic source of nitrogen and iron without having to turn to synthetic plant foods.
While blood meal might seem like a magic bullet for the garden, fixing low nitrogen, it’s important to use it at the right growth stage, particularly with tomatoes. In this article, we’ll look at when, why, and how to use blood meal for tomatoes, and what it is good for.
Using blood meal for tomatoes
Blood meal contains all the nutrients that tomatoes need at their early growth stage, and works similarly for potatoes, peppers, and aubergines too. All of which are members of the solanum family and require high nitrogen in their soils to develop after the seedling stage.
While blood meal is great for young tomato plants, it’s important to use it sparingly, and not use it during germination, or after the first trusses have formed as it is an unbalanced fertilizer that can lead to tomatoes not flowering.
What is blood meal?
Blood meal is the dried blood of animals and a by-product of the meat industry, so usually from beef abattoirs. Once drained, the blood is dried into a powdered form and packaged with no extra processes, making it completely organic, but distinctly gruesome.
Strictly speaking, blood meal is a soil amendment, rather than a fertilizer as it changes the nutrient content of the soil, rather than directly targeting plants. Once watered, plants are able to take up the nutrients.
What nutrients are in blood meal?
Blood meal NPK
NPK is the guidance given on the packaging of most fertilizers but is often missing from organic fertilizers due to differences between batches and nutrient levels in the source material. NPK presents the constituent parts of the three ‘macro-nutrients’ in any fertilizer; Nitrogen (N), Phosphorous (P), and Potassium (K).
Blood meal has an NPK of 13-1-0, meaning it is 13% Nitrogen, 1% Phosphorous, and less than 1% Potassium. Some Blood meals can have Nitrogen as high as 20%, and others, as low as 10%.
Micronutrients & minerals in blood meal
As well as macronutrients known as NPK, the micronutrients in blood meal include significant percentages of calcium, iron, and zinc. Although each makes up less than 0.5% of the overall composition, small amounts can help tomato plants in their own way.
Iron helps tomatoes manage nitrates and sulfates, allowing roots to take up nutrients more efficiently as well as being crucial in small amounts for photosynthesis.
Zinc supports the function of auxin, a growth-regulating hormone that helps manage the distance between nodes (in other words, more zinc=more tomatoes, as short nodes on trusses mean more fruit). Auxins are also the main hormone in most rooting gels which help plant cells recover and regrow when damaged.
Calcium is essential for beefsteak and salad tomatoes in particular as they are very susceptible to a disease called blossom end rot which turns the base of the tomato crispy and brown. Calcium helps prevent this, even in tiny quantities like in blood meal.
How does blood meal benefit tomatoes?
So, we know blood meal is a great way to amend your soil, but is blood meal a good fertilizer for tomatoes?
Blood meal adds high amounts of nitrogen to the soil which is available to tomato plants throughout the year, so a single application across your raised bed is all you need when you plant your tomatoes out in late spring.
The high nitrogen content of blood meal speeds up top growth, encourages foliage production, and trusses during the early stages of tomato growth. As your tomato plants develop they will need potassium and phosphorous added into their water to boost flower and fruit production though, so blood meal should never be used by itself as your only tomato fertilizer.
Blood meal pros and cons
Blood meal has a few undeniable pros, but they are matched by the cons of blood meal so deciding to use blood meal as an early-season tomato fertilizer should be given careful consideration:
|Nutrients||Blood meal is perfect for young tomato plants to promote foliage and truss production. Calcium supports healthy flowering later in the season and reduces the chances of blossom end rot.||Blood meal can shock seedlings if used too early because of its high concentration of nitrogen. |
Later in the season, blood meal can override other feeds and limit flowering.
|Ethics||Blood meal is organic and beneficial for your soil. It is one of the safest fertilizers you can use in the garden without risking harm to wildlife.||Vegetarians and vegans cannot use blood meal as it is a direct animal product and a by-product of the meat industry.|
|Pests||Nitrogen supports healthy foliage which reduces the chance of pests on tomato foliage.||Blood meal is an animal product so has an odor that attracts rats, raccoons, and other vermin into the garden.|
|Diseases||Blood meal gives roots easy access to nitrogen which helps create stronger root systems early in the season. Roots will be less likely to rot with overwatering.||Pruning will be required to manage excess foliage as a result of high nitrogen. Without pruning, bushy top growth can harbor fungal spores and lead to blight.|
|Environmental impact||Using blood from slaughterhouses removes potential diseases from the environment, and keeps it out of landfills and water systems, creating a cleaner meat industry.||The energy used to dry blood meal is still non-renewable so there is a high carbon footprint in the production of blood meal.|
How to fertilize tomato plants with blood meal
Blood meal is best used just before planting tomato plants out into their final position. If you grow tomatoes in raised beds or grow bags, mixing a handful of blood meal into the area directly around your tomato will give it all the nitrogen it needs until it begins flowering.
Only apply blood meal once per season unless you have very free-draining soil where it may wash out before its nutrients have been used up.
To apply blood meal, simply shake a small handful of powered fertilizer onto the soil surface and rake it into the top layer of soil. Then dig a hole and plant your tomato plants directly into their final position.
Can you mix blood meal with water?
You can buy soluble blood meal, but most blood meal is not water-soluble and should be applied as a powder directly to the soil.
Water-soluble blood meal is used as a foliar spray which can help plants recover from damage or if their leaves are significantly drooped. Blood meal foliar sprays are not beneficial to tomatoes though as they require washing off, and wetting tomato leaves is never advised.
Blood meal vs bone meal – which is better?
Bone meal is different from blood meal as it is far higher in calcium and phosphorous which are useful for tomatoes later in the season. Adding bone meal to the soil when trusses begin to form can encourage more flowering, particularly on cordon tomatoes.
For a middle ground between bone meal and blood meal, consider fish, blood and bone, which has more balanced nutrients and can be used twice through the growing season – once when you plant tomatoes out, and again when flowers begin to form.
|NPK:||Blood meal||Bone meal||Fish, blood and bone|
What are the alternatives to blood meal?
For vegetarian gardeners, it can be difficult to find a true and effective alternative to blood meal, as it is uniquely high in nitrogen for organic fertilizer. The good news though, is that there are vegetarian and vegan alternatives to blood meal:
- Alfalfa meal (vegan)
- Grass clippings (vegan)
- Chicken manure/rabbit pellets (vegetarian)
Alfalfa meal is a great vegan alternative to blood meal, with high nitrogen content that works in exactly the same way despite subtler nutrient levels. Alfalfa meal has an NPK of 3-1-1, but does tend to vary depending on the time of year it’s produced as a seasonal legume crop.
You can either use more alfalfa meal to produce the same nitrogen output or use it sparsely for a gentle soil amendment.
Grass clippings have an NPK of 4-0-2 and a lot of other minerals in the mix. As a natural material, they are slow to break down, so should be used as a mulch rather than mixed into the soil. Use grass clippings before planting tomatoes so they have 2-3 months to break down slightly and release their nutrients into the soil.
Grass clippings are a great way to garden completely organically and use garden waste before it has fully composted.
Chicken manure/rabbit manure
Chicken manure and rabbit manure are animal products but are generally seen as vegetarian (particularly if you have your own rabbits or chickens). Both have good nitrogen content and are full of other minerals that support healthy soil, though neither is a true replacement for blood meal as they are at least 10x less potent.
Most commercial tomato foods are not truly organic as they are made through chemical processes and can actively damage beneficial soil bacteria and deter the insects that churn up and aerate the soil.
As fertilizers go, blood meal is good for tomatoes and is a great organic option for gardeners looking to change how they feed tomatoes but does require a more considered approach to feeding through the growing season.