GardenNotes #234
Organic Fertilizers
Outline: Terms
Plant by-products
Alfalfa meal or pellets
Corn gluten meal
Cottonseed meal
Soybean Meal
Animal by-products
Bat guano – high N
Bat guano – high P
Blood meal
Bone meal
Feather meal
Fish emulsion
Enzymatically digested hydrolyzed liquid fish
Fish meal
Fish powder
Compost, manure and biosolids based products
Rock powders
Colloidal phosphate
Seaweed
Kelp meal
Kelp powder
Liquid kelp
Additional information
Terms
By legal definition, the term fertilizer refers to a soil amendment that guarantees the minimum percentages of nutrients (at least the minimum percentage of nitrogen, phosphate, and potash).An organic fertilizer refers to a soil amendment derived from natural sources that guarantees, at least, the minimum percentages of nitrogen, phosphate, and potash. Examples include plant and animal by-products, rock powders, seaweed, inoculants, and conditioners. These are often available at garden centers and through horticultural supply companies.
These should not be confused with substances approved for use with the USDA National Organic Program (NOP). The USDA NOP, with its “USDA Organic” label, allows for the use of only certain substances. The Organic Materials Review Institute (OMRI www.omri.org) approves brand name products made with ingredients from the “National List” for use with the NOP (see www.ams.usda.gov/nop and click “NOP Regulations” and then “National List Information”). Many of the organic fertilizers listed here will meet NOP standards (based on the National List). Growers participating in the NOP should consult with their certifier to ensure compliance for organic certification.
The terms soil amendment refers to any material mixed into a soil. Mulch refers to a material placed on the soil surface. By legal definition, soil amendments make no legal claims about nutrient content or other helpful (or harmful) affects it will have on the soil and plant growth. In Colorado, the term compost is also unregulated, and could refer to any soil amendment regardless of active microorganism activity.
Many gardeners apply organic soil amendments, such as compost or manure, which most often do not meet the legal requirements as a “fertilizer” but add small amounts of nutrients.
Notes:
Release Time – Organic products require the activity of soil microorganisms before nutrients are available for plant uptake. Microorganism activity is dependant on soil temperatures greater than 50º F in the presence of sufficient soil moisture. Dry and/or cold soil conditions will delay the release of nutrients from these organic sources. This period refers to how long these products are available if applied to the soil. Use this information to time the application of the product.
Application – Different products may be applied in various ways. Some may be tilled in (worked into the soil with a machine or hand tool), others may be applied as a foliar spray (mixed with a surfactant and sprayed in a fine mist on the leaf surface while temperatures are below 80º F), and some may be injected into a drip or overhead irrigation system (fertigation with a siphon mixer). Application rates in this fact sheet are generalized and based on some manufacturers’ recommendations. Over or under fertilization may occur using these recommendations. See soil and fertility resources on this page for taking a soil sample, interpreting soil test results, guidelines for fertilizing vegetables, and best management practices for N and P fertilization: www.ext.colostate.edu/pubs/crops/pubcrop.html#soil
Plant by-products
Alfalfa meal or pellets are often used as animal feed. Primarily they are used to increase organic matter in the soil but do offer nutrients and a high availability of trace minerals. They contain trianconatol, a natural fatty-acid growth stimulant.
| Typical NPK analysis | 2-1-2 |
| Release time | 1-4 months |
| Pros | Available at feed stores |
| Cons | May contain seeds |
| Application | Till in 2-5 pounds per 100 square feet |
Corn gluten meal materials have a high percentage of nitrogen. It carries a warning to allow 1 to 4 months of decomposition in the soil prior to seeding. Allelopathic properties will inhibit the germination of seeds. However, there is no danger to established or transplanted plants. This product is also marketed as a pre-emergent weed control for annual grasses in bluegrass lawns.
| Typical NPK analysis | 9-0-0 |
| Release time | 1-4 months |
| Pros | Very high nitrogen |
| Cons | Germination inhibitor, some are GMOs |
| Application | Till in 20-40 pounds per 1000 square feet |
Cottonseed meal is a rich source of nitrogen. Buyers should be aware that many pesticides are applied to cotton crops and residues tend to remain in the seeds. Pesticide-free cottonseed meal is available.
| Typical NPK analysis | 6-0.4-1.5 |
| Release time | 1-4 months |
| Pros | High nitrogen |
| Cons | Pesticide residues, most are GMOs |
| Application | Till in 10 pounds per 100 square feet |
Used primarily as an animal feed product. Available bagged at many feed stores.
| Typical NPK analysis | 7-2-1 |
| Release time | 1-4 months |
| Pros | High nitrogen, available at feed stores |
| Cons | Almost half of the conventionally grown soy is GMO |
| Application | 8 pounds per 100 square feet |
Animal by-products
Bat guano (feces) harvested from caves is powdered. It can be applied directly to the soil or made into a tea and applied as a foliar spray or injected into an irrigation system.
| Typical NPK analysis | 10-3-1 |
| Release time | 4+ months |
| Pros | Stimulates soil microbes |
| Cons | Cost |
| Application | Till in 5 pounds per 100 square feet or as a tea at 3 teaspoons per gallon of water |
See the description above. Difference is that it is processed for high phosphorus content.
| Typical NPK analysis | 3-10-1 |
| Release time | 4+ months |
| Pros | Stimulates soil microbes |
| Cons | Cost |
| Application | Till in 5 pounds per 100 square feet or as tea at 3 teaspoons per gallon of water |
Blood meal, made from dried slaughterhouse waste, is one of the highest non-synthetic sources of nitrogen. If over-applied it can burn plants with excessive ammonia.
| Typical NPK analysis | 12-0-0 |
| Release time | 1-4 months |
| Pros | Available at feed stores |
| Cons | Can burn. Expensive at garden centers |
| Application | Till in 5–10 pounds per 100 square feet |
A well-known source of phosphorus, bone meal is steam processed and widely available at feed stores and in garden centers. If purchased at feed stores, P is expressed on the label as elemental phosphorus and is 2.3 times higher than numbers shown on garden center labels for phosphate (i.e. – 12% phosphate is the same as 27% phosphorus). However, recent CSU research has shown that P from bone meal is only available to plants in soils that have a pH below 7.0
| Typical NPK analysis | 3-15-0 |
| Release time | 1-4 months |
| Pros | Highly plant available form of phosphorus |
| Cons | Cost |
| Application | Till in 10 pounds per 100 square feet |
Sourced from poultry slaughter, feather meal has fairly high nitrogen levels but is slow to release the N.
| Typical NPK analysis | N varies 7 – 12% on process |
| Release time | 4+ months |
| Pros | Long term fertilizer |
| Cons | Cost versus speed of N release |
| Application | Till in 2.5-5 pounds per 100 square feet |
Infamous for its foul smell, emulsions are soluble, liquid fertilizers that have been heat and acid processed from fish waste.
| Typical NPK analysis | 5-2-2 |
| Release time | 1 – 4 months |
| Pros | Adds needed micronutrients |
| Cons | Some have foul smell |
| Application | Mix 6 tablespoons per gallon of water |
Enzymatically digested hydrolyzed liquid fish
Enzymatically digested hydrolyzed liquid fish may be using enzymes to digest the nutrients from fish wastes instead of using heat and acids. This retains more of the proteins, enzymes, vitamins and micronutrients than emulsions.
| Typical NPK analysis | 4-2-2 |
| Release time | 1 – 4 months |
| Pros | More nutrients than emulsions |
| Cons | More expensive than emulsions |
| Application | Mix 5 tablespoons per gallon of water |
Fish meal is ground and heat dried fish waste.
| Typical NPK analysis | 10-6-2 |
| Release time | 1 – 4 months |
| Pros | N and P source |
| Cons | Heat processed |
| Application | Till in 5-10 pounds per 100 square feet |
Fish power is dried with heat and turned into water-soluble powder. It is a high source of nitrogen. Many can be mixed into solution and injected into an irrigation system.
| Typical NPK analysis | 12-0.25-1 |
| Release time | Immediate to 1 month |
| Pros | Adds micro-nutrients |
| Cons | Heat processed |
| Application | Till in 1-2 oz. Per 100 square feet OR Mix at 1 tablespoon per gallon of water |
Compost, manure and biosolids based products
For information on biosolids, worm casting, manure, and compost, refer to the following CMG GardenNotes:
Rock powders
Those that are relevant for use in Colorado soils supply phosphorus. Those that serve as a potassium source (greensand, feldspar, potassium sulfate, biotite, etc.) are not necessary as Colorado soils are naturally high in potassium. Similarly, it is not necessary to add calcium (gypsum, lime, etc.) due to naturally high calcium levels in Colorado soils and arid conditions.If you are making annual applications of manure and/or compost to your garden to add nitrogen, you should have sufficient levels of phosphorus in your soil. If you are applying manure or compost to your garden based on P needs, you might have an excess N supply. Excess N can lead to poor flower/fruit development and increases water pollution potential from N leaching from the soil.
Generally, plant or animal sources are the best value for phosphorus in the home garden. Recent CSU research results concluded that no rock P (regardless of mesh size) is available for plant use unless the soil pH is below 7.0
Colloidal phosphate – a.k.a. soft rock phosphate
This product is made by surrounding clay particles with natural phosphate. Total phosphate is about 20% while available phosphate is about 2-3%. This is why you can apply large amounts of colloidal phosphate, as it will release slowly over the years (usually more available the second year than the first). For home gardeners the cost/return is adequate to apply colloidal phosphate at rates to supply phosphorus for this season’s crops. This product does add micronutrients to soil.Micronized (passing through 1000 mesh screen [1000 wires per square inch]) sources may be more available than regular soft rock grinds in soils with a pH below 7.0
Seaweed
Kelp is the most common form and is valued not for its macronutrient (N, P, and K) contributions but for micronutrients, trace minerals, amino acids and vitamins plus growth hormones that stimulate plant cell division.
Kelp is often mixed with fish products to enhance growth.
Three processes are available: extracts (as kelp meal or powder), cold-processed (usually liquid) and enzymatically digested (liquid). Ranked in quality of content and plant availability they are (highest to lowest)
- enzymatically digested
- cold-processed
- extracts.
Kelp meal, a product of the ocean, is used primarily as a trace mineral source. It is often combined with fish meal to add N-P-K value.
| Typical NPK analysis | negligible |
| Release time | 4+ months |
| Pros | Adds micro-nutrients |
| Cons | Insignificant NPK value |
| Application | Till in 1 pound per 100 square feet |
Kelp powder is similar to kelp meal but ground fine enough to put into solution and applied as a foliar spray or injected into an irrigation system.
| Typical NPK analysis | 1-0-4 |
| Release time | Immediate – 1 month |
| Pros | Adds micro-nutrients |
| Cons | Insignificant NPK value |
| Application | Mix ¼ to ½ teaspoon/gallon of water |
Usually cold processed, liquid kelp will have higher levels of growth hormones than extracts. Some may also be enzymatically digested, making the growth hormones even more available to the plants.
| Typical NPK analysis | negligible |
| Release time | Immediate – 1 month |
| Pros | Adds micronutrients plus helps plant with stress |
| Cons | Insignificant NPK value |
| Application | Mix 1 – 2 TBS/gal of water for foliar or mix at ¼ - 1¼ tsp/gal/100 ft2 and inject |
Additional Information – CMG GardenNotes on Soils, Fertilizers and Soil Amendments:
#211 The Living Soil
#212 Earthworms
#213 Managing Soil Tilth
#214 Estimating Soil Texture
#215 Soil Compaction
#216 Mulching with Wood/Bark Chips, Grass Clippings and Rock
#217 Soil Drainage
#221 Soil Tests
#222 Soil pH
#223 Iron Chlorosis
#224 Saline Soils
#231 Plant Nutrition
#232 Understanding Fertilizers
#233 Calculating Fertilizer Rates
#234 Organic Fertilizers
#241 Soil Amendments
#242 Using Manure
#243 Using Compost
#244 Cover Crops and Green Manure Crops
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Authors: David Whiting, Adrian Card and Carl Wilson: Colorado State University Extension.
o Colorado Master Gardener GardenNotes are available on-line at www.cmg.colostate.edu.
o Colorado Master Gardener training is made possible, in part, by a grant from the Colorado Garden Show, Inc.
o Colorado State University, U.S. Department of Agriculture and Colorado counties cooperating.
o Extension programs are available to all without discrimination.
o No endorsement of products mentioned is intended nor is criticism implied of products not mentioned.
o Copyright © 2002-2006. Colorado State University Extension. All Rights Reserved. CMG GardenNotes may be reproduced, without change or additions, for non-profit educational use. Revised December 2006