Nitrogen in Lawn Soil

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How to increase nitrogen in lawn soil is easy without having to rely on chemical fertilizers. Organic fertilizers raise nitrogen in your lawn but the grass plant can only absorb inorganic forms of it.

Nitrogen (n) in lawn soil is what makes grass-green.  It’s the most important of the lawn nutrients and can be added easily by applying fertilizer. It represents the first letter of N-P-K which indicates amounts located on the fertilizer bag.

Nitrogen in lawn soil is essential in building proteins such as chlorophyll.  Grass lacking in it will turn yellow, in part because the chloroplasts are not functioning properly.

Grass can only use nitrogen in lawn soil in its inorganic form, which is what synthetic fertilizers offer.

Organic matter such as compost, is food for microbes in the soil.  Microbes being bacteria, fungi, protozoa etc. break the organic matter down and turn Nitrogen into its inorganic form and thus feed the grass plant.

Both synthetic nitrogen fertilizer and organic nitrogen fertilizer form produce the same results. Synthetic is harmful to the environment as it leaches through the soil.  Organic is healthy, slowly increases nitrogen in lawn soillevels and it’s sustaining.  A steady slow supply fertilizing your lawn.

Two forms of nitrogen in lawn soil are available, ammonium and nitrates. Grass plants prefer their lawn nitrogen in nitrate form. A good portion of the soil food web releases N in ammonium form but it is quickly converted “fixed” to nitrate through bacteria. Grass likes its soil slightly acidic and acidic soil is more bacterial than basic soil, which is fungal.


A side note on soil nitrogen:

  • Lawns, annuals and vegetables like bacterial soil.
  • Trees, shrubs and perennials like fungal soil.

Having over 5% organic matter will generally result in adequate amounts of nitrogen for lawn soil.

free nitrogen in lawn soilNot bagging your clippings while your mowing supplies your lawn with an additional free 1 pound of nitrogen.

Grass clippings feed the bacteria in the soil. The clippings break down quickly, feed the bacteria which hang around the rhyzosphere. The bacteria turn the broken down clippings into inorganic nitrogen raising your levels.

Depending on the size of your lawn, a bag of fertilizer can cost you $20-$100 per application. By leaving the grass clippings down you just saved the cost of at least one bag of fertilizer not to mention helping the environment.


Nitrogen in Lawn Soil Cycle

Nitrogen is the most abundant element by far in the atmosphere comprising 79% percent of it. In its available gaseous form it is of no use to organisms. The N must be “fixed” it can be of any use. The high energy of lightning strikes can convert the gas into its usable form and we already talked about how bacteria converts ammonium into nitrate but nitrogen in lawn soil can also be fixed by certain plants most people would consider to be weeds.

Legumes such as white clover and vetch are considered “nitrogen-fixing” plants where they take N out of the air and make it available in the soil.

Sure when clover flowers it’s not the most attractive thing on a lawn but the benefits outweigh any slight inconvenience. Besides clover leaves are a nice dark green and fills any bare spots in your lawn nicely. Considering how clover can raise nitrogen in lawn soil, it’s much more attractive than that of thistle or plantain who offer nothing.

soil nitrogen for lawnsEarthworm castings will also provide this free organic nitrogen fertilizer. So, as you can see there are plenty to increase the levels of nitrogen in your grass without doing anything. Just leave or mulch your grass clippings when you’re mowing and stop using chemicals lawn fertilizers and pesticides.

Are you thinking you no longer have to apply fertilizer?


Did you have your soil tested yet?

If your results come back and your organic matter is a minimum of 5% and your having problem then you should be concentrating on applying more biology either through more compost or compost teas.

Your soil test does come with Nitrogen levels but it’s not a clear indication of its availability to the plant. Fluctuation in soil temperatures throughout the year, make it difficult to test accurately. The best way to determine if your lawn is in need of N is simply by observing the color, density and vigor.

Organic lawn fertilizers that raise levels of soil nitrogen are:

  • Alfalfa meal
  • Blood meal
  • Fish hydrolysate
  • Chicken manure
  • Corn Gluten
  • Cotton seed meal
  • Soybean meal
  • Compost

Here you can find more information on organic fertilizers.

Besides compost, the above products are available as stand alone or mixed together. I prefer a blend where different microbes have different appetites. If there is something involving your lawn you want to keep happy, it’s your microbes! They are the ones responsible for increasing levels of nitrogen in lawn soil.

nitrogen in grass soilMost grass types do well with around 3 pounds of lawn nitrogen applied per 1000 sq. feet per year. It should only be applied at 1 lb. per 1000 sq. feet at a time.

Grass loves soil nitrogen, some varieties more than others. New seed varieties are always being developed that naturally have a darker green color. The appearance will appease us while it requires less fertilizer applications to raise levels of n.

Nitrogen in Lawn Soil Can Be Free of Charge

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