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 firstname.lastname@example.org.