Issue 02 · What Feeds the Rows

What Are Fertilizers?

By Clark J. Madsen · From KB Garden

Organic vs inorganic, urea chemistry, phosphate choices, and potash from ancient brine.

What are fertilizers By Clark J. Madsen

TOC \o \z \u \hIntroduction What Are Fertilizers? Inorganic Fertilizers Organic Fertilizers Nitrogen Phosphorus Potassium Potassium Chloride Potassium Sulfate Potassium Magnesium Sulfate Potassium Nitrate Why Do We Need Fertilizers

Introduction In this article, we will discuss the different types of common fertilizers and the methods for their proper use. We will also look at the synthetic verses the organic debate and see if we cannot find the truth.

To start with, all fertilizers can be divided up into two distinct categories: organic fertilizers and inorganic fertilizers. The major difference between the two categories of fertilizer is not the nutritional content of the fertilizer, but rather in what is used to create the fertilizer.

What Are Fertilizers? Fertilizers are natural and chemical additives that are applied to the soil to promote plant growth. All fertilizers are made up primarily of three basic nutrients: nitrogen (N), phosphorus (P), and potassium (K) also known as potash. Fertilizers also have smaller quantities of three secondary nutrients: calcium (CA), sulfur (S), magnesium (MG). In addition to these six macronutrients, fertilizers hold trace amounts of the following minerals: boron (BO), chlorine (CL), manganese (MN), iron (FE), zinc (ZN), copper (CU), molybdenum (MO), selenium (SE).

All these nutrients are essential for proper plant growth. As plants grow, they deplete the soil of these nutrients. Fertilizers are used to replace depleted nutrients and keep the soil's nutrient content at the optimal level to support plant growth. The three main macronutrients are consumed from the soil by the plants in large quantities; therefore, they must be replaced into the soil in equally large quantities. The secondary macronutrients and the micronutrients likewise are consumed by plants, but in smaller quantities. While they too must be replenished, many of them are replaced naturally as they are absorbed from the atmosphere by the soil. Additionally, insects and organic organisms that live within the soil also help to replace these nutrients.

If your soil has the proper amounts of N-P-K it will remain in a proper state for growing healthy and hearty plants. If any of these nutrients are low or missing, plant grown, and plant quality will suffer. On the other hand, if soil has too much of any of these nutrients plant growth will be adversely affected. Soil nutrient balance must be achieved for best plant growth to accrue. Proper fertilizer knowledge and usage is essential to support a healthy garden.

Inorganic Fertilizers Inorganic fertilizers, or chemical fertilizers, are chemical based synthetic soil additives. These synthetic fertilizers were developed during the industrial revolution in the late 19th century. Inorganic fertilizers do not have all, or sometimes any, of the micronutrients needed for plant growth. Therefore, inorganic fertilizers are also known as “Macronutrient Fertilizers.”

Since they only have the three main macronutrients, they are labeled as N-P-K (Nitrogen – Phosphate - Potassium) fertilizers. They are listed by the percentage of total weight of each of these nutrients in the order of N-P-K. For example, a 25 lbs. bag of 16-16-0 fertilizer would consist of 4 lbs. nitrogen, 4 lbs. phosphate, and 0 lbs. potassium. The remaining 17 lbs. (68%) is filler material: sawdust, sand, dirt, etc. Now you may ask, ‘Why am I paying for something that is 68% filler?”

The N-P-K is distributed throughout the filler to reduce the chance of “Fertilizer Burn.” Since chemical fertilizers are usually 100% water soluble, all the nitrogen in the fertilizer is released instantly. If too much nitrogen is added to your garden too quickly, the nitrogen will “burn” the plants, causing the roots to dry out. This will affect the plant's ability to absorb water and other nutrients from the soil. As a result, the plant growth will be stunted, or the plant may even die. The fillers in chemical fertilizers are needed so that the nutrients are not so concentrated that they will damage or burn your plants, your skin, and anything else they touch.

Organic Fertilizers Organic fertilizers are naturally occurring and are derived from animal manure, compost, and other organic materials. Organic fertilizers have been used for thousands of years. We can even read in the bible about the dunging of vineyards. Organic fertilizers do not necessarily have fillers, as they are made up of a variety of natural components that in one way or another will help your plants

Let us take a few moments to look at some of the most common sources of N-P-K found in organic and inorganic fertilizers, and exactly what N-P-K does for plant life. As we go through this process notice how the plant being fertilized determines the source of the N-P-K that should be used. So not only do you need to know the amount of N-P-K you are using on a given plant, but you also need to know of the type of N-P-K that is being used.

Nitrogen Nitrogen promotes the overall strong foliage growth in plants. Crops like potatoes and tomatoes need consistent levels of nitrogen to produce bountiful crops.

The most common source of nitrogen is “Urea.” Urea is listed by weight as 46% nitrogen. Over 79% of all dry nitrogen fertilizers are urea based.

Urea is a natural substance found in the urine of mammals. In 1828, urea, also known as carbamide, became the first naturally occurring compound to be synthetically created.

When urea is applied to soil it reacts with the water and bacteria of the soil and is converted to ammonia gas, then to ammonium, and finally to nitrate, the plant usable form of nitrogen. This conversion process takes about two or three days. Some volatilization (loss of the ammonia gas into the atmosphere) may occur as the ammonia changes into ammonium.

This volatilization is increased if the urea is applied to the surface of the soil; this fertilization method is known as "top dressing" or “side dressing.” The volatilization of ammonium increases with temperature, so topdressing with urea in summer months is not recommended.

Since urea is highly water soluble, the nitrogen becomes completely available to plants within two to three days. In contrast, it also means that the soil will not maintain a nitrogen reserve from the urea for long. Likewise, if the urea is derived from animal urine or fresh manure, ammonia volatilization will quickly reduce the available nitrogen content by more than 50% of the original urea nitrogen capacity. As such, new urea will need to be applied about every three weeks to insure proper nitrogen levels.

Organic farmers have raised concerns over the use of urea and synthetic compounds used as nitrogen fertilizers. Their concern is centered on the water solubility of the resulting nitrogen. Since the release of the nitrogen from its primary form is so rapid, the fear is that plants are not given enough time to absorb the available nitrate, therefore unnecessary nitrogen is being leached into the ground water. This is why organic farmers prefer to use dried bovine manure. The nitrogen compound in bovine manure is eventually converted to the usable nitrate form. The release of nitrogen from organic fertilizers occurs as part of a decomposition process. This gradual release of nitrate into the soil extends nitrogen availability, reduces overall leaching, and makes it almost impossible to fertilize burn your plants. Gradual nitrogen release can be expected from bovine manure, with only 35% of the total nitrogen being released in the first year. As such, when preparing a new plot of land to become a garden, enough manure may be applied at the start of the season, for the entire year's nitrogen needs. Since the decomposition process occurs over time, there will still be some remaining organic nitrogen left over in the soil after the first year. Thus, a smaller amount of manure will be required next year. If the same rate of manure is applied each year as the first, the soil will accumulate unnecessarily elevated levels of nitrogen, and plant growth may suffer. Another source of nitrogen is Ammonium Nitrate. Ammonium Nitrate is an inorganic nitrogen source that is listed by weight as 33% nitrogen. It is decreasing in popularity due to storage problems and its connection to terrorism, as it can be highly explosive. Over ½ of its weight is in soluble nitrate form, which makes it immediately susceptible to leaching; therefore, it should never be used in the fall since winter precipitation will cause leaching.

Ammonium sulfate is an inorganic nitrogen source mostly produced as a waste product by some industrial processes. Ammonium sulfate is listed by weight as 21% nitrogen. All the nitrogen in Ammonium Sulfate comes in the form of ammonium. As such, volatilization is less of an issue. It is an excellent fertilizer for use in soils with a high pH and is an excellent choice especially when the soil is low in sulfur. It is the most acidifying form of nitrogen and requires lime to offset the acid.

In addition to ammonium nitrate and ammonium sulfate, there are three other main inorganic nitrogen fertilizer sources: Calcium Nitrate 16%, Potassium Nitrate 13%, and Sodium Nitrate - 16%. All the nitrogen in these fertilizers comes in the form of nitrate, so leaching can be a problem since no transformation process is needed. In addition to nitrogen, these fertilizers are an excellent source of calcium, potassium, and sodium respectfully.

Phosphorus Most phosphate fertilizers are highly water soluble. Phosphate is one of the elements essential for plant growth and seed production. Phosphate is crucial for the stimulation of early plant growth. Phosphorus also stimulates plants to grow even when it is cold and wet, like during the early spring months. Therefore, it is important to properly prepare your soil by adding fertilizer high in phosphorus before your spring till. Due to the water solubility of the phosphorus, planting should follow quickly before leaching occurs.

When applied to the soil phosphorus is converted into orthophosphate by hydrolysis (adding water). Orthophosphates is the form of phosphorus that can be used by plants. In as little as two weeks 50% of the applied phosphorus can be converted into the usable orthophosphate form.

When it comes to the different types of phosphates, there are only two major characteristics to be concerned with, how much phosphate a fertilizer contains and does the phosphate source also contain nitrogen.

There are only a couple of phosphates that do not contain nitrogen: normal superphosphate (20%), concentrated superphosphate (46%) also known as triple superphosphate. Notice that the level of phosphate in concentrated superphosphate is over double that of normal phosphate. Since phosphate is highly water soluble, all this phosphate is released into the soil at once. It is so concentrated that some studies show it bonds with trace minerals in the soil, like manganese and magnesium, locking them up so they are not made available for plant absorption.

Since we know that ammonium is converted to nitrate once applied to the soil, just by looking at the names we should be able to discern that phosphate sources like diammonium phosphate (18-46-0) and monoammonium phosphate (11-46-0) contain ammonium. As such, the ammonium in these fertilizers will add additional nitrate to the soil. Care must be taken when fertilizing before and during seed times; the ammonia content of the soil may become too high and cause seed germination injury if it comes in direct contact with the seeds. For this reason, I prefer to use fertilizer containing normal superphosphate in my garden. This way my seeds and seedlings have the needed phosphorus to promote proper germination and early growth, without causing the soil’s nitrogen levels to become too high and damaging the seeds.

Potassium Potassium is the seventh most abundant element found in the earth's sediment. Upwards of 93% of the world's potassium consumption is utilized in fertilizers. Potassium fertilizer, more commonly known as Potash, is highly water soluble and unlike nitrogen and phosphorus, potash requires no additional conversion process. As such, the potash is ready to be absorbed by the plants in its natural form the moment it is applied to the soil. After the potash is dissolved by water, it is stored in the soil by the clay until it can be absorbed by the plants. As such, leaching of potassium is only an issue in sandy soils where clay levels are low. Potassium helps protect plants against disease and pests, allows them to adjust to rapid changes more easily in weather, and encourages plants to absorb nutrients.

The term potash comes from the old method of making salts; when it comes right down to it, all fertilizing nutrients are in salt from when applied to the soil. Centuries ago, leftover tree branches and roots were burned, after which their ashes were soaked in hot water and then filtered into a lye compound. This lye material was then placed into large pots and baked in a kiln to evaporate the remaining water. The remaining ash in the pots, or potash, was a form of potassium carbonate that was perfectly formed for use as a potassium fertilizer. Farmers could make more money selling this potash than they could from selling wood or the crops from their fields.

Now days, 99% of worlds potash comes from mines located in western Canada, New Mexico, and Utah. In fact, one of the best sources of potash can be found right here in the Great Salt Lake area. Over an extended period, the ancient brine from the Great Salt Lake has turned into an excellent source potassium sulfate. Most sources of potassium naturally occur from ancient brine deposits. Industrial mining processes are used to collect and refine potash into a usable format. Because of these mining and refining processes organic farmers consider these sources of potash to be inorganic.

As such, the only true organic source of potassium comes from compost or from burning your own potash. Wood ashes contain around 6% of their total weight in potassium and a considerable amount of lime. Corn cobs can also be burned, which ash contains as much as 35% of its total weight in potassium. In fact, the ash from burning anything fibrous and organic will result in potash. Let us look at some of the different forms of commercially available potash.

Potassium Chloride Potassium Chloride, also know as Murite of Potash, is about 60% pure potassium. Murite is Latin for brine, so as could be expected it comes from petrified brine deposits from ancient inland seas. These deposits are mined at depths of over 3,000 feet. Potassium Chloride is the most commonly used source for potassium fertilizers. Organic growers claim this to be the worst potassium fertilizer; asserting that it is too harsh on the soil and that the chlorine content leaches rapidly when applied to soil, so it is harmful to plant roots and certain beneficial soil bacteria.

Potassium Sulfate Potassium Sulfate, also known as Sulfate of Potash, is about 50% pure potassium. This form of potassium is ideal for crops like tobacco, potatoes, and vegetables, where the chloride from potassium chloride can hurt these plants. Potassium sulfate has been shown to dramatically increase the size of potato tubers. Also, it is a reliable source of sulfur when soil is found to be deficient. Organic growers say this is the best source of potassium fertilizer since it does not contain chlorine. This is the type of potassium that comes from the Great Salt Lake in Utah.

Potassium Magnesium Sulfate Potassium Magnesium Sulfate, also known as Sulfate of Potash Magnesia, is about 22% pure potassium. Like sulfate of potash, it is a reliable source of sulfur and magnesium when soils are found to be deficient of either.

Potassium Nitrate Potassium Nitrate, also known as Nitrate of Potash, is about 44% pure potassium. This source of potassium is excellent for celery corps, tomato plants, potatoes, and most leafy vegetables and fruit crops. Because of its nitrate compound, it has a very low salt index and can be a good choice to help regulate the acidity of the soil.

Table 1 - Primary and Secondary Nutrient Composition of Some Selected Fertilizer Materials From MSUE Agricultural Extension Fertilizer Materials PercentWaterSolubility Nutrient composition   N           P2O5          K2O         Ca          Mg           S

____________________%_______________________ Nitrogen N

Ammonia, anhydrous 100 82 -- -- -- -- -- Ammonia, aqua 100 16-25 -- -- -- -- -- Ammonium nitrate 100 33.5 -- -- -- -- -- Ammonium nitrate-limestone 100 20.5 -- -- 7.3 4.4 -- Ammonium sulfate 100 21 -- -- -- -- 23.7 Ammonium sulfate-nitrate 100 26 -- -- -- -- 15.1 Calcium cyanamide 100 21 -- -- 38.5 -- -- Calcium nitrate 100 15 -- -- 19.4 1.5 -- Nitrogen solutions 100 21-49 -- -- -- -- -- Sodium nitrate 100 16 -- -- -- -- -- Sulfur-coated urea Variable 35 -- -- -- -- 21 Urea 100 46 -- -- -- -- -- Ureaform Variable 38 -- -- -- -- --

Phosphate P

Ammoniated super-phosphate 35 3-6 18-20 -- 17.2 -- 12 Ammoniated phosphate nitrate 100 27 15 -- -- -- -- Ammonium phosphate sulfate 90+ 13-16 20-39 -- -- -- 15.4 Ammonium polyphosphate 100 10-15 34-62 -- -- -- -- Bone meal -- 2-4.5 22-28 -- 20-25 -- -- Diammonium polyphosphate 95+ 16-21 48-53 -- -- -- -- Monoammonium phosphate 90+ 11 48 -- 1.1 -- 2.2 Nitric phosphates 40 14-22 10-22 -- 8-10 -- 1-3.6 Phosphoric acid 100 -- 52-60 -- -- -- -- Rock phosphate <1 -- 30-36* -- -- -- -- Superphosphate, normal 85 -- 18-20 -- 20.4 -- 11.9 Superphosphate, concentrated 87 -- 42-50 -- 13.6 -- 1.4 Superphosphoric acid 100 -- 69-75 -- -- -- --

Potash K

Nitrate of soda-potash 100 15 -- 14 -- -- -- Potassium chloride (muriate) 100 -- -- 60-62 -- -- -- Potassium magnesium sulfate 100 -- -- 22 -- 11.2 22.7 Potassium nitrate 100 13 -- 44 -- -- -- Potassium sulfate 100 -- -- 50 -- 1.2 17.6 * Relatively unavailable to plants in most soils

Why Do We Need Fertilizers If nutrients are not present in the soil, there is now way these nutrients can be found in the plant yields from the soil. In other words, healthy fruits and vegetables are derived directly from healthy soil. Like the old adage says, “You are what you eat”, and plants can’t have in them what they don’t absorb from the soil.

United States Food and Drug Administration (FDA) studies show a dramatic decline between the nutrient content of fruits and vegetables grown before 1960's, when primarily organic fertilizers were used, and after the 1960's when our nations farmers switched to the convince of inorganic fertilizers. These studies show that modern soil nutrient depletion has caused up to a 75% decline in the nutrient level of fruit and vegetables when compared to crops prior to 1960's. (The Journal of Alternative and Complementary Medicine. April 7th, 2001)

Nutrient deficiency in the average American diet has been liked to many of our nation’s modern day health issues. " "

Nutrient deficiency in the average American diet has been liked to many of our nation’s modern day health issues. Since most people decide to grow home gardens for two main reasons, economic savings and healthier foods, it then seems quite impractical to use inorganic fertilizers in home gardens.

No matter what decision you make, as to the use of organic or commercial fertilizers, just know that you need to be using fertilizers in your garden to achieve any level of success. Until next time, keep those thumbs green.

“Fillers in chemical fertilizers are needed so nutrients are not so concentrated that they burn your plants.”

What Are Fertilizers?