Looking for a Good Organic
Nitrogen Fertilizer?

A good organic nitrogen fertilizer should be added to the soil whenever you plant heavy-feeding vegetables like tomatoes, peppers, chiles, eggplants, cucumbers, squash, melons, or cruciferous vegetables like broccoli, cabbage, and cauliflower. Leafy vegetables like lettuce and spinach also benefit from high levels of nitrogen in the soil.

Nitrogen fuels green, leafy growth, which in turn supplies your plants with the nutrients they need to produce tomatoes, peppers, and other fruit.




Organic Nitrogen Fertilizers

An organic nitrogen fertilizer can be animal-based, plant-based, or manure-based.


Plant-Based Organic Nitrogen Sources

Plant-based organic soil amendments like alfalfa meal, soy meal, and cottonseed meal are light-weight and won’t attract animals if mixed into the soil or potting mix. They’re usually balanced organic fertilizers, in that they supply small amounts of phosphorous and potassium, in addition to nitrogen.


Plant-based organic nitrogen sources tend to be less concentrated, and have a lower percent of nitrogen than animal-based organic nitrogen sources, so they need to be applied at higher rates.


They also only work well when the soil is warm, because they rely on an active soil food web for the release of their nutrients. They’re summertime soil amendments. For best results, soil temperatures should be in the 50’s (10-15° C) or higher when using a plant-based organic nitrogen fertilizer.


Manure-Based Organic Nitrogen Sources

Composted animal manures, especially poultry manure, are a great nitrogen source for organic gardens. It’s important that manure is aged or composted prior to use in organic vegetable gardens, especially where food is in contact with the soil.

Composting kills or degrades disease-causing organisms like e. coli or salmonella.




Animal-Based Organic Nitrogen Sources

If you’re looking for a high nitrogen organic fertilizer, animal-based organic nitrogen fertilizers are your best choice. They include bi-products of the cattle industry (blood meal), poultry industry (feather meal), and fisheries (fish meal, crab meal, shrimp meal).

I include worm castings, which are technically a manure, in this group, as well as “boutique” soil amendments like high-nitrogen bat guano.

Animal-based fertilizers release more quickly than plant-based and most manure-based organic fertilizers, and work better in the cool seasons of spring and fall. They’re useful when soils are lean or depleted, and for growing vegetables in containers, where the limited soil volume often requires a concentrated organic nitrogen fertilizer to maintain leafy growth.

An animal-based organic nitrogen fertilizer like blood meal may “burn” delicate vegetable roots if applied without mixing into the soil, or too close to established plants. They should be worked into the soil a few days before planting to avoid this.

If you don’t have time to wait, mix them thoroughly into a 5-gallon bucket of compost, topdress around the plants, and cultivate lightly with a garden claw into the top inch or two (2-5 cm) of soil. Avoid cultivating within 6” (15 cm) of plant stems. Water thoroughly with a water wand or overhead sprinkler after cultivating.

In addition to burning roots, animal-based fertilizers may also attract rats, raccoons, oppossums, and other unwelcome nocturnal visitors.

For heavy feeding vegetables, I like the combination of alfalfa meal for early-season nitrogen, and feather meal as an organic slow release nitrogen source that starts releasing nutrients late in the season, for end-of-summer growth.



We have a long growing season in California—where I live, tomatoes peak in September. Most of our summer heat comes in August and September, when the marine layer subsides and the coastal fog burns back to the ocean.

The feather meal kicks in 2-3 months after you mix it into the soil, and fuels leafy growth while the plants are fruiting, producing sweeter tomatoes and shading the fruit to prevent sunscald at the same time.



Animal-Based Organic Nitrogen Fertilizer for Use in All Seasons—Links Go to Offsite Suppliers to Purchase Organic Soil Amendments
 Soil Amendment  N-P-K  Description  Lasts  Application Rate
Worm Castings 1-0-0  Excellent quick-release source of N, with a long-term, slow-release component. Inoculates soil with beneficial fungi & microbes from the worm gut.  3-6 Months  (10-15 lbs/100 sq ft)
Use up to 1/3 volume in container mixes.
Feather Meal 12-0-0  A slow-release source of N made from ground-up chicken feathers, for late-season growth. Excellent for growing tomatoes, peppers, and chiles organically.  3-6 Months  4-8lbs/100 sq ft, 1/3 cup for 5gal pot, ½ cup for 7gal
Fish Meal 9-4-1  Ground-up fish carcasses. One of the best cool-season N sources for early spring plantings. May attract raccoons.  3-4 Months  Up to 5lbs/100 sq ft, 1/3 cup for 5gal pot, ½ cup for 7gal
Bat Guano (High-Nitrogen) 10-6-2  From insect-eating bats. Excellent source of N and P. One of the best soil amendments for container gardens. Provides spectacular, sustained foliar growth. Encourages microbial diversity in soil or container mix.  2-8 Months  1-2lbs/100 sq ft, 1Tbs/8” pot
Blood Meal 13-0-0  Made from dried cattle blood. Good cool-season N source for early spring or fall plantings. May attract raccoons.  3-4 Months  4-8lbs/100 sq ft
Seabird Guano 10-10-0  Powerful all-around organic npk fertilizer--a little goes a long way! Use as a side-dressing or foliar tea the first half of the season. Stimulates microbial growth in the soil.  1-3 Months  1-2lbs/100 sq ft
Crab Meal 5-2-0, Ca, chitin  Chitin-containing soil amendments fuel growth of chitin-eating microbes. When the crabshells are gone, they turn to nematodes, which contain high levels of chitin. Nematode-limiting effect develops in 4-8 months—sooner in warm soils with high N. Good for Southern gardens with nematode problems.  3-12 Months   1-2lbs/100 sq ft
Shrimp Shell Meal 6-6-0, Ca, Chitin  Ground up shrimp shells. Chitin-containing soil amendments fuel growth of chitin-eating microbes. When the shrimp shells are gone, they turn to nematodes, which contain high levels of chitin. Nematode-limiting effect develops in 4-8 months—sooner in warm soils with high N. Good for Southern gardens with nematode problems.  3-12 Months  1-2lbs/100 sq ft


Top of Organic Nitrogen Fertilizer Page


Organic Nitrogen Sources for
Cool-Season Vegetables

Most organic soil amendments require soil microorganisms to convert their nutrients into plant-available form. These organisms work slowly in the cool soil temperatures of early spring and fall, so choose an organic nitrogen fertilizer with more labile nitrogen, like one of the following, when growing cool-season vegetables.


Animal-Based Organic Nitrogen (N) Sources for Use in All Seasons—Links Go to Offsite Suppliers to Purchase Organic Soil Amendments
 Soil Amendment  N-P-K  Description  Lasts  Application Rate
Worm Castings 1-0-0  Excellent quick-release source of N, with a long-term, slow-release component. Inoculates soil with beneficial fungi & microbes from the worm gut.  3-6 Months  1” layer

(10 5-gal buckets/100 sq ft)
Use up to 1/3 volume in container mixes.
Fish Meal 9-4-1  Ground-up fish bones and carcasses. A good cool-season N source for early spring plantings. May attract raccoons.  3-4 Months  Up to 5lbs/100 sq ft
Chicken Manure 1.1-0.8-0.5  Excellent quick-release source of N. Poultry manure releases up to 75% of its N the first year in the soil, compared with 33% for most other manures.  3-12 Months  1/2-1” layer

(5-10 5-gal buckets/100 sq ft)
Bat Guano (High-Nitrogen) 10-6-2  Excellent source of N and P. One of the best soil amendments for container gardens. Provides spectacular, sustained foliar growth. Encourages microbial diversity in soil.  2-8 Months  1-2lbs/100 sq ft, 1Tbs/8” pot
Blood Meal 13-0-0  Made from dried cattle blood. Good cool-season N source for early spring plantings. May attract raccoons.  3-4 Months  4-8lbs/100 sq ft
Seabird Guano 10-10-0  Powerful all-around organic fertilizer--a little goes a long way! Use as a side-dressing or foliar tea the first half of the season. Stimulates microbial growth in the soil.  1-3 Months  1-2lbs/100 sq ft




Organic NPK Fertilizer
(N)itrogen  |   (P)hosphorus  |   (K) Potassium
(Ca) Calcium



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