Organic Fertilizer Secrets

September 7th, 2012  |  Published in Jim Verner

While more and more cities, landscapers, nurseries, urban farmers, and home owners are turning to organics, many do not understand all the benefits of organics, how they work, and when they should be applied. Those who come from a synthetic fertilizer background often attempt to use organics in ways similar to the chemical fertilizers. When they do, they are missing much of the benefit organics offer. The goal of this brief paper is to mention some of the “secrets” that will not only give better agronomic results with organics… but also save you money.

Effective use of fertilizers is as much art as science. Your plants will tell you a great deal when you “listen.” And how do you listen to your plant? By keeping a close eye on how it grows. If it is not looking like the picture in the seed catalog, something is wrong. Often this is due to stress that causes the plant to lose its genetic potential. And that is an area where good organic fertilizers can work wonders since saving genetic potential is a key to healthy plants.

1. Not all organic and “natural” fertilizers are the same!

Read labels carefully. Ingredients should be listed, although many labels show this in small print. Unfortunately, many landscape and garden fertilizers that call themselves “organic” or “natural” are simply a mix of some organic material with synthetic fertilizers. These products will not build a healthy soil the way a true organic fertilizer does. Certified Organic Farmers are required to use only true organic inputs per the rules of the USDA National Organic Program. Look for the OMRI or Washington State Organic seal on the label to know you are getting a true organic.

2. Plants can use, and benefit from, the organic form of nitrogen!

This will lead some to shake their heads in disbelieve. For years, soil scientists taught us that plants could only use the inorganic forms of nitrogen – ammonium (NH4+) and nitrate (NO3-). We learned that organic matter and proteins had to be broken down in the soil to these forms of nitrogen. They said the benefits of organics were improved soil structure and micronutrients, not a special form of nitrogen. Now, research and practical experience have shown that plants do use the organic protein form of nitrogen (NH2) and that it has very significant benefits – stronger root systems and greater stress resistance. Of course the organic proteins also supply the ammonium and nitrate that plants need. With synthetic fertilizers, the plant only gets the inorganic forms and has to use its energy – energy that could be used for better growth, flowering and fruiting – to metabolize them into the organic NH2 that is a precursor to the proteins and carbohydrates that provide the energy to the plant.

3. Relying on compost to supply all the nitrogen needed by the plant has a downside!

Compost is a wonderful soil amendment, especially when it is a fine, finished grade compost. It supplies a full range of nutrients the plant needs plus the microbes that are essential for a healthy soil. But, it is important to understand that even the best compost has about the same amount of the major nutrients – nitrogen (N), phosphorous (P), and potassium (K). Plants need considerably more N (the only nutrient that makes growth) than P and K so when you only use compost, the levels of P and K increase to excessive levels and these two nutrients reduce the availability of calcium (Ca). Since Ca is needed for strong tissue, if the plant doesn’t get it in sufficient amounts the tissue is weak. If you supply an organic protein fertilizer that has higher N, it makes an excellent complement to compost.

4. Organic fertilizers containing animal proteins and manures smell – plant proteins don’t!

Organic materials like blood meal, feather meal, guano, fish, etc. definitely smell. The odor makes them difficult to store and they can draw flies if not mixed well into the soil. Plant proteins have a clean, cereal smell, and their nutrients are quick acting and long lasting.

5. Organic fertilizers can be applied at any time! Even with the seed!

Because organic nitrogen does not leach or volatilize like synthetic nitrogen, it can be applied any time. In fact, there are real benefits when the organic protein fertilizer is applied with the seed or earlier in the season than is recommended for synthetic fertilizers. Applying synthetic fertilizers with the seed can burn roots and cause damping-off, but organics won’t burn. This is because the organic NH2 form of nitrogen is similar to the seed’s own protein that produces growth immediately before the plant has any leaves, so it enhances germination and establishment. It is important to use good quality compost in potting mixes since the microbes improve the availability and effectiveness of the organic protein.

6. Not all composts are the same!

Look for good, fine particle size compost that has a clean earth smell. If it contains bits of wood and leaves, the microbes will use the nitrogen to breakdown these woody bits rather, stealing the nitrogen your plant should be getting. Your compost supplier should be able to give you a carbon-nitrogen ration (C:N). The best composts are in the 15:1 range. Composts with woody material can be 100:1 or higher and this robs your plants of the nitrogen they need for optimum growth. If you make your own compost, remember that food scraps, while they contain many good nutrients, can be high in sodium. If your compost has a manure or ammonium smell, it is not finished – and this can burn roots just like synthetic fertilizers.

7. For turf, leave the cuttings, and use a mulch mower if possible!

When grass cuttings are hauled off, all the good nutrients and organic matter in them are lost. By leaving cuttings, you will help increase the soil’s organic matter and recycle the nutrients. This improves water holding capacity of the soil and reduces the need for fertilizer applications.

8. If you use recycled water or if your soil has high sodium levels you need extra care!

Sodium (Na) can be toxic to plants if levels are high, and since it is very soluble in the soil solution a soil test can be misleading. Recycled water tends to have high sodium as well as other “salts” (but some of those salts are good nutrients and will be beneficial, even reducing the amounts of fertilizer needed). The best way to overcome high sodium is to periodically, maybe once a year, a) increase organic matter by applying a good quality compost, and b) add a fine ground calcium sulfate (gypsum) to the compost or spread it on its own.

There are many more “secrets” that will help you get the most from your organic inputs. If you have questions or comments, just give me a call: Jim Verner,, 559-286-5646.

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