By Beth Deckert, Natural Choice Editor
Nitrogen influences the health and quality of turfgrass more than any
other nutrient. Nitrogen is the primary component of amino acids, the building
blocks of proteins found in all living organisms and the most abundant element
found within a turfgrass plant. Even more importantly, our atmosphere is almost
80% nitrogen. With nitrogen so abundant, why do turfgrass managers struggle to
keep this nutrient available to their turfgrass? Why is fertility value so
important when buying decisions are made? The answer lies with the reactions
nitrogen undergoes in the soil.
All compounds that have proteins present represent nitrogen in an
“organic” form. Microbial activity will degrade this type of
material. Some forms of “organic” nitrogen are broken down as far
as they can go, and in the soil, are referred to as humus.
“Inorganic” nitrogen is any nitrogen compound that releases through
microbial breakdown or chemical reactions. This includes nitrate, nitrite,
ammonium and ammonia. Nitrate and ammonium compounds are the forms plants will
readily take up nitrogen, while nitrite and ammonia are toxic to plants. How
ammonium and nitrate are formed and the characteristics of both compounds will
effect the amount of nitrogen available to a plant.
Ammonium (NH4+) Formation
When microbes break down an organic nitrogen product, ammonification will
take place, converting organic nitrogen ultimately to ammonium nitrogen. The
nitrogen will be broken down into smaller and smaller molecules until it is
finally ammonium. The microbes ingest the ammonium through mineralization. The
ammonium is immobilized, and as the microbes die off, release nitrogen to the
plant. This is the ideal form for the plant. Ammonium is immobile in the soil
and will not readily leach into the water table. Various factors can influence
the mineralization/immobilization process. Optimum temperatures (above 40°F, below 60°F), a good supply of water, soil pH
above 5.5, good aeration and a low Carbon:Nitrogen Ratio will keep microbial
activity at its peak allowing for the conversion of the material to ammonium.
An active, healthy microbial population will help maintain the available
ammonium concentrations for the plant.
Nitrate Nitrogen (NO3-)
With much higher temperatures and higher C:N Ratios, microbes have
problems decomposing the fertilizer material. This allows the process of
nitrification to occur. In nitrification, the ammonium is converted into
nitrate. A plant enlists the help of Nitrogen-fixing bacteria in this process.
The ammonium will be converted to nitrite by Nitrosomonas bacteria, and then
Nitrobacter bacteria will quickly convert this nitrite to nitrate without any
harm coming to the plant. These bacteria can also fix Nitrogen from the
atmosphere. Nitrate will make up the majority of the nitrogen used by a plant.
A plant can easily use the nitrate form, however, due to the movement of
nitrate through the root zone via water, it is more prone to leaching. Whatever
the plant does not readily use, will be leached out of the root zone.
It is important to remember that whenever nitrogen fertility, whether
organic or inorganic, is applied, both ammonification and nitrification will
occur. The soil conditions determine which will be the primary mode of nitrogen
breakdown. Last year, many areas of the country had plenty of rainfall and
comfortable temperatures. Many superintendents skipped applications of
fertilizers because of this. Because the conditions were favorable, more
microbial activity took place, allowing for ammonification and mineralization
to occur. In areas that were hot and dry, nitrate was the final product
requiring increased applications of nitrogen to maintain nitrogen availability.
According to Dr. James Cambretato in an article in SC Turfgrass Foundation
News, any research to date done on either turfgrass or agriculture products has
shown ammonium nitrogen outperforming nitrate nitrogen through denser root
systems, increased numbers of tillers and greater dry matter.
There are other bacteria and fungus in the soil that are beneficial to
plants. Azotobacter can fix Nitrogen directly from the atmosphere, Rhizobial
bacteria form nodes on roots of legumes that will fix nitrogen, and mycorrhizae
of fungus literally become part of the plant’s root system increasing
root surface area significantly. All of these are important to plants for
helping with nitrogen uptake. However, the most cost effective fertility
product for turf managers is one that stimulates microbial activity, promotes
ammonification and mineralization through these populations, ensures ammonium
formation through these processes so nitrogen leaching does not occur and
develops better and stronger root systems for increased uptake of nitrogen. That
fertility program can be found in Nature Safe. To further validate this check
out Dr. George Lazarovits’ research, “Influence of Nature Safe on
the Microbiology of Soil” and “Effect of Nature Safe and Synthetic
Fertilizer Application on Bacterial and Fungal Populations” along with
our research on “Leaching Rates” by Dr. Gary Janicke. These
research summaries will provide further insights into Nature Safe’s
importance in a fertility program. For questions or more information concerning
Nature Safe in a fertility program, contact Nature Safe at
sales@griffinind.com.