Archive for March, 2011

Healthy Soil Part 1

Synthetic vs. Organic Fertilizers

What are the effects on plants, soil and the environment of synthetic versus organic fertilizers?  Fillers, water solubility, nutrient availability, reduced disease resistance, environmental damage, reduced soil carbon levels and reduced nutritional value of food crops are all factors related to the use of synthetic fertilizers.

A standard synthetic fertilizer like 15-5-10 has 15% nitrogen, 5% phosphorus and 10% potassium.  This adds up to only 30%, so what is the other 70%?  Filler!  This filler can be most anything and in some cases, toxic substances that can be harmful to the environment and once applied to food crops these materials can enter our food.  An EPA study on the accumulation of heavy metals in soils treated with synthetic fertilizer found increased levels of cadmium, lead, arsenic, mercury, copper and zinc.1 Without this filler the soluble nitrogen rate would be so high that it would burn both plants and soil biology.   With organic fertilizer all of the material in the bag is organic and will furnish many of the other elements that plants need and will help the process of building organic material in your soil to support beneficial soil biology.

The N-P-K in synthetic fertilizer is very water-soluble so it can act very rapidly for plant growth. This sudden increase in growth is not desirable because it causes plants to grow with weak cell walls making the plants susceptible to insects and reduces disease resistance.2 This works out nicely for the chemical manufacturers because they sell more insecticide, fungicides and other chemical poisons in an effort to battle the weakened plants.  Studies have shown that up to 36% of the synthetic derived nitrogen applied to the soil will become environmental pollutants in the ground water.3 While organic fertilizers reduce the amount of nitrogen that is leached through the soil and ends up in the ground water.4 Synthetic fertilizer also have excessive amounts of salt that reduce the water holding capacity of the soil, reduces the plant roots ability to absorb water and will kill many types of beneficial soil biology.  With organic fertilizer the N-P-K are in a more stable form and will not burn plants or harm the beneficial soil biology.

Most synthetic fertilizers use triple super phosphate, which is made by treating rock phosphate with phosphoric acid.  It is not in a form plants can use so if not converted by soil biology, it leaches out and becomes an environmental pollutant.  Phosphate also locks up many of the trace elements plants need reducing the overall nutrient availability. The phosphate in organic fertilizers is in a plant available form that binds to other organic matter and does not readily wash through and become a pollutant.

The potassium in most synthetic fertilizers is muriate of potash or potassium chloride. They are both highly water-soluble and tend to pass through the plant root zone very rapidly.  The continued use of synthetic fertilizers slowly reduces  the soil of organic carbon and lowers crop yields, so the more fertilizer applied the smaller the reaction in plants.5 This also results in the vegetables being grown having between 5%-40% less nutritional value when compared to vegetables grown 50 years ago before the introduction and use of synthetic fertilizers.6

When looking at the cost of fertilizer you need to consider what you are getting for your money. If a 40 pound bag of 10-10-10 synthetic fertilizer cost you $10.00 you are paying that money for 12 pounds of active useful ingredients or $0.83 per pound. For a 40 pound bag of organic fertilizer you pay $20.00 you are getting 40 pounds of active useful ingredients or $0.50 per pound. What is not used of the organic fertilizer in the first year stays in the soil and helps build the total organic matter in the soil.7

“Every pound of excess Nitrogen applied to the soil by artificial fertilizers destroys 100 pounds of humus… ” The Carbon Connection, L. Ridzon and C. Walters

Our 100% organic Turfpro USA and AgriPro products add organic carbon to the soil as well as many types of beneficial soil biology and most needed trace elements. They help build the water holding capacity of the soil while opening the soil up to allow air to plant roots and soil biology.


2 E. N. Yardim and C. A. Edwards, “Effects of Organic and Synthetic Fertilizer Source on Pest and Predatory Insects Associated with Tomatoes”,  Phytoparasitica, (2003).

3 Dale Weston and Bruce Seelig, Managing Nitrogen Fertilizer to Prevent Groundwater Contamination, North Dakota State University, Extension Bulletin No. 64, April, 1994.

4 Martha Turner, P.E Austin Area Fertilizer Impacts.  City of Austin Watershed Protection and Development Review Department, Environmental Resource Management Division, Water Resources Evaluation Section, 2003.

5 R.L. Mulvaney, S.A. Khan, T.R. Ellsworth Synthetic Nitrogen Fertilizers Deplete Soil Nitrogen , Univeristy of Illinois, 2009.

6 Donald R. Davis, “Declining Fruit and Vegetable Nutrient Compostion”, Journal of HortScience, Febuaray 2009.

7 M.S. Clark, W.R. Horwath, C. Shennan, and K.M. Scow. 1998. “Changes In Soil Chemical Properties Resulting From Organic And Low-Input Farming Practices”. Agronomy Journal.

3/9/2011                                                                                                                                                                                                           B0002