Medicine Food Water Music Doctors

Tweet

Page Updated: April-26-2012

View All
Healthy Soil
Articles

Global increase in fertilizer use enlarge

Manufactured Synthetic Fertilizers or Natural Organic Fertilizers?

By Kevin Schoessow 1,University of WiscousinExtention, Agricultural and Natural Resources.

Recent interest in sustainable or organic gardening has stimulated questions about the use of organic or naturalfertilizers for home garden use. This interest has spurred the debate on the qualities of natural vs. manufacturedmaterials. Unfortunately, misconceptions confuse the issues for people selecting fertilizers.

Keep Things in Perspective

In order to make the best decision on which fertilizer to apply, there are some basic plant nutritional concepts thatneed to be understood. Through photosynthesis and other plant metabolic processes, plants manufacture thecomplex structures they need to grow and reproduce. They do not require vitamins, minerals, or other complexcompounds; they only need four basic requirements to grow. They need water, air, sunlight and thirteen essentialelements. How they obtain these basic requirements is dependant on the environment and the growth media in whichthey live. For most home gardeners, this growth media is soil.Soil is a living entity teeming with life. In ideal situations the soil and its associated microbial communities provideall the essential nutrients needed for healthy plant growth. Often times a soil is natural fertility is not sustainableunder intensive gardening practices and additions must be made to the soil. The basic objective of soil fertilitymanagement is to feed the soil, not necessarily the plant.

Avoid the Quick-Fix mentality

Too often we search for a quick fix to our plant nutritional needs. There are literally hundreds of fertilizers we canadd to the soil that claim they will improve our soil and make our plants more healthy, vibrant, and productive.Advertising and sales techniques readily exploit this trait in many of the promotional materials used to sell theirnatural products. It should be remembered, however, that natural processes have their own rhythm, one usuallymuch slower than we might like.Ultimately, the effectiveness of any soil fertilizer depends far more on the soil and the gardening system than itdepends on the fertilizer itself. Put another way, if a soil is excessively acid and poorly drained, then it doesn't matterhow much fertilizer (manufactured or natural/organic) is applied; yields will be disappointing at best.Primary considerations in selecting a garden fertilizer should include release rate and cost. Fertilizers with fastrelease rates will stimulate quick growth, particularly in cool soils, and are also more prone to leaching of thenitrates into the groundwater and burning when over applied.There are many kinds of fertilizers available for homeowners. For comparison purposes, the products will begrouped according to their source. There are natural organic fertilizers, manufactured organic fertilizers, andmanufactured inorganic fertilizers.

Natural Organic Fertilizers

Natural organic fertilizers are commonly made form waste products of various sources ranging from chickenfeathers and manures to treated sewage sludge. These materials have very slow release rates, requiring soilbacterial action to convert the organic matter into forms usable by plants. Nutrients released will be excessivelyslow when cool soil temperatures reduce bacterial activity. Higher application rates may be applied and thefertilizer will last over a longer period of time.Natural organic fertilizers, being comparatively low in nutrient content and light weight per volume, will requiresignificantly larger volumes in application. Problems associated with their use include slow response, particularlyin cool soils, and homeowners misjudge application rates due to the larger volume of material needed. Cost arecomparatively high. Natural fertilizers may also contain other nonessential elements not required by the plant.Some examples are cottonseed meal, soybean meal, blood meal, bone meal, fish meal, seaweed, and compostedmanures.

Manufactured Organic Fertilizers

In the manufacturing of organic fertilizers, carbon is the building blocks that contain other plant nutrients.Manufactured organic fertilizers vary in release rate depending on the product. Urea is the most commonmanufactured organic fertilizer and is moderately fast in release, while sulfur coated urea is relatively slow release.Costs range from inexpensive to moderate.

Manufactured Inorganic Fertilizers

Manufactured inorganic fertilizer are chemically simply compared to organic fertilizers. Nitrogen fertilizers arenormally made from petroleum or natural gas. Being relatively high in nutrient content, small volumes are required,and the fertilizer can burn if over applied. Phosphorus, potassium and other trace element fertilizers are often minedfrom the earth. Manufactured inorganic fertilizers include common products like ammonium nitrate, ammoniumsulfate, triple superphosphate, potassium chloride (potash) and magnesium sulfate (Epsom salt). Since they do notrequire microbial action to make them available to plants, these products are quick acting even in cool soils and theyare inexpensive. Being prone to leaching, application rates on sandy soil must be very light and more frequent, thusthey have a disadvantage on sandy soil.

Nutrient composition of various fertilizer materials

Material	Composition	N	P2O5	K2O
Urea	(NH2) 2CO	45	0	0
Ammonium nitrate	NH4NO3	33	0	0
Potassium nitrate (salt peter)	KNO3	11	0	44
Triple superphosphate	Ca(H2PO4)2	0	46	0
Muriate of potash	KCl	0	0	60
Potassium sulfate	K2SO4	0	0	50
Epsom salt	MgSO4-H2O			9, 13
Gypsum	Ca SO4-2H2O			21
Activated sludge		5	3	0
Blood Meal		15	1.3	0.7
Cow manure		0.3	0.1	0.4
Horse manure		0.6	0.3	0.5
Chicken manure		1	.5	0.5
Coffee grounds		0.9	0.3	0.6
Granite dust		0	0	5
Seaweed		1.6	.7	5
Wood ashes		0	1.5	7
Compost nutrient content varies		0.5-3.5	0.5-1.0	1-2

Reference

1. Kevin Schoessow, Instructor, University of Wisconsin Cooperative Extension, Burnett, Washburn, and Sawyer Counties; Spooner Ag Research Station, W6646 Hwy. 70, Spooner Wisconsin. 54801

Where organic sources are used for fertilizer, bacterial and fungal activity increases in the soil.

Compared to synthetic fertilizer formulations, organic fertilizers contain relatively low concentrations of actual nutrients, but they perform important functions which the synthetic formulations do not. They increase the organic content and consequently the water-holding capacity of the soil. They improve the physical structure of the soil which allows more air to get to plant roots. Where organic sources are used for fertilizer, bacterial and fungal activity increases in the soil. Mycorrhizal fungi which make other nutrients more available to plants thrive in soil where the organic matter content is high. Organically derived plant nutrients are slow to leach from the soil making them less likely to contribute to water pollution than synthetic fertilizers.- Diane Relf, Extension Specialist, Environmental Horticulture, Virgina State University, excerptfrom Organic Fertilizers.