WWW.CLEMSON.EDU/PSAMEDIA

DATE:     4/19/01        
WRITER:   Chris Ray, Clemson Fertilizer and Seed Certification,
           (864)-646-2145
EDITOR:   Giles Singleton, (864) 656-3876

When more can be too much:
Avoiding over fertilization

     CLEMSON -- Spring is here and everyone is eager to get busy 
in their gardens. Gardeners have visions of lush ornamentals laden 
with blooms of all shapes and colors, tremendous vegetables, delectable
fruits and well-manicured lawns.
     These visions are great motivators to the home gardener; they 
show the rewards for all those hours of hard work. Unfortunately, 
at times this same motivation leads to practices that can be harmful
to the environment and to our beloved plants like over fertilizing.
     The old saying "if a pound is good then two pounds is twice as
good" does not apply to fertilizing our gardens today.
     All plants have certain requirements like water, nutrients and
light. These needs must be satisfied so plants can grow and develop
properly. However, if we exceed these plants' requirements there is 
a good chance that we will do more harm than good, especially where
fertilizer is concerned. 
     Excessive fertilization can cause unused fertilizer to leach
through the soil and contaminate groundwater, and to run off the 
soil surface after heavy rainfall and contaminate surface water.
     Too much fertilizer -- particularly nitrates -- in groundwater 
can lead to a reduction of oxygen in young children's blood. Excess
fertilizer in surface water can increase algae growth in streams 
and lakes. When the excess algae die, the oxygen level in the water 
is lowered, which in turn kills fish and other aquatic animals.
     Too much fertilizer can also lead to nutrient toxicity in plants,
which can have a variety of negative effects on a plant's growth 
and development. An example is excessive nitrogen content, which, 
in flowers and fruits, leads to excessive growth of leaves and 
stems, as well as reduced root and reproductive growth. Other 
nutrient elements present in soils at toxic levels can cause a
decline in plant growth or death of the plants.
     Over-fertilization can also cause an unwanted decline in your 
bank account. If you apply more fertilizer than your plants can 
use, the excess fertilizer will likely be lost as it leaches from
rainfall and irrigation; this translates to lost money.
     Because different plant species and different soil types have
different fertilization requirements, the simplest and best way
to determine how much fertilizer you should apply is by taking a 
soil sample to your county's Clemson University Cooperative 
Extension office. It is a good idea to call first for instructions 
on how to take the sample, or go to 
http://hubcap.clemson.edu/~blpprt/bobweb/bobweb.html, maintained
by Bob Lippert, Clemson Extension soil fertility specialist. In
addition to the phone book, you can locate your county's Extension
office at: www.clemson.edu/extension.
     If you are going to be applying fertilizer, then it is important
to understand how to interpret the information provided on the label 
of a fertilizer container. 
     For example, with a complete fertilizer, one that contains
nitrogen, phosphorus, and potassium, the three numbers on a bag
represent the percentage of nitrogen (N), phosphorus (P), and 
potassium (K) contained in the bag. So if a bag of fertilizer has 
an analysis of 10-10-10 it would contain 10% nitrogen, 10% phosphorus,
and 10% potassium. If the same bag of fertilizer has a net weight 
of 50 pounds, it would contain five pounds of nitrogen, five pounds 
of phosphorus, and five pounds of potassium.
     For detailed information on fertilization and other cultural
practices relating to specific crops, contact your county's Clemson
Extension office. They can provide advice and literature that will
guide you through the growing process from planting to harvesting.
     With spring in the air and planting time rapidly approaching,
remember to accurately apply the appropriate amounts of fertilizer 
to the plants you are growing. If you are good to your plants and 
give them what they need, you will be rewarded with healthy plants 
and abundant harvests.
     For more information on fertilizers, check out:
http://fscs.clemson.edu .
                 *****************************
     If you have gardening questions, write to PSA Media Relations,
A-101 Poole Agricultural Center, Clemson University, Clemson, S.C.
29634-0129. You might also want to search our website at:
www.clemson.edu/psamedia.
                              END