 |
     |
Nitrogen: Where It Comes From Matters
© 1997, 1998 Streamline Publications
Of all the elements necessary for
healthy turfgrass, nitrogen is probably the most important to understand, and
is discussed at greater length than any other fertilizer constituent. Nitrogen
(with an atomic symbol of N), along with phosphorous (P) and potassium (K) are
the primary nutrients considered in fertilizer formulas and are represented by
the numbers on fertilizer container labels.
In addition to the big three (N, P and
K), plants require carbon, hydrogen and oxygen which they receive from air and
water. Secondary nutrients include calcium, magnesium and sulfur. Another seven
nutrients; boron, chlorine, copper, iron, manganese, molybdenum and zinc are
needed as well. 
Turf fertilized by waste from certain animals can develop an aggressive nature and may eat small dogs and cats.
The attention on nitrogen stems from
the problems intrinsic in controlling it. Too much or too little nitrogen can
have a profound effect. New plants won't grow without nitrogen and established
turf will not thrive if it is starved for nitrogen. Yet, too much nitrogen can
cause burning. Nitrogen in the atmosphere is an inert
gas but in soil it is found as ammonium (nitrogen + hydrogen). Nitrification
bacteria convert the ammonium into nitrate (nitrogen + oxygen) and in the
process release nitrogen in a form that is usable by plants. Nitrogen is
available from many sources but to the turf manager the choice is most often a
question of natural "organic" sources or inorganic "chemical"
sources. The difference between them can be significant but generally, organics
are slow releasers of nitrogen while inorganics release quickly. This difference
has to do with their solubility. The chemical sources tend to release
easily in water and move quickly through soil. This characteristic leads to high
volatility. Nitrogen can be lost, leaching away from root areas or through
ammonia volatilization. This happens when urea and urea-containing fertilizers
are placed on lawn surfaces. Rather than being released into the soil, the
nitrogen converts to an ammonium form of nitrogen and is lost to the atmosphere.
Denitrification of the soil usually
occurs when soils with a high level of organic matter remain under water for
long periods. Organisms that aren't able to get air any other way take oxygen
from nitrates (molecules made up of nitrogen and oxygen) and free the nitrogen
that then escapes into the atmosphere.
Quick or Slow Release Nitrogen SourceInorganic fertilizers fall into three
categories: quick release, slow release and reacted.
Inorganic Quick Release
These fertilizers are water soluble and
can be used immediately by the plant, or become quickly available to the plant
through nitrification. These are the well-known "quick green-up"
nitrogen sources that have to be applied frequently at low rates because they
are used up and can leach out of the soil quickly. These can also cause burning.
Inorganic Slow Release
These are quick-release inorganics that
have been "encapsulated" either in sulfur, plastic or resin to slow
their release. This makes them insoluble or slowly soluble in water. These
manufactured slow-releasers can be applied less frequently and produce slower,
more uniform action.
Reacted Controlled Release
These inorganics have controlled
solubility in water and release some nitrogen through microbial action. The
nitrogen release is gradual but excessive moisture can cause a burst of plant
growth. Reacted chemical fertilizers are low in salt and tend not to burn.
Organic Fertilizers
These are nature's fertilizers derived
from animal or plant waste. Their release is very slow and depends to a large
extent on weather. Warmer temperatures activate the microbes that must digest
the material to release the nitrogen. Leaching is not a problem with organic
fertilizers.
Fertilizer Management
Organic fertilizers are naturally timed
for normal vegetation growth cycles. While this makes Mother Nature happy, it
doesn't always do the same for a landscape maintenance company's clients.
Successful fertilizing strategies often
include long-term organic fertilization with inorganic treatments for short term
or spot problems. Balance is essential to any fertilizing program.
Seeding | LEAF-let Newsletter | Bioregions | Catalog & Orders | Albright Info