Let’s continue our discussion from yesterday and see exactly what is in our bag of fertilizer.
NITROGEN
Of course nitrogen is still an important nutrient. It makes the grass blades grow and green up. On the plus side, nitrogen makes a sturdy rapidly maturing, quick spreading grass, which in itself fights weeds. On the negative side, excessive nitrogen causes shoots to grow too fast, making the succulent and tender, which reduces the ability of the roots to support them. Over extended grass is susceptible to diseases such as brown patch, fusarium patch pithier and powdery mildew.
GRASS TYPES NITROGEN NEEDS (lbs. / 1,000 SQ.FT/year)
Kentucky Bluegrass 2 3 lbs
Fine fescue 1 2 lbs
Tall Fescue 1 2 lbs
Perennial Ryegrass 2 3 lbs
Synthetic fertilizers are here today, gone tomorrow. There are two forms of nitrogen; water-soluble and water-insoluble. The solubility determines how fast the nitrogen becomes available. Water-soluble start breaking down as soon as they hit the dirt, while water-insoluble takes time to break down with the help of soil microorganisms. It may sound great that the nitrogen is readily available, but remember that it is also leached through the soil just as readily. Chances are that there is more water-soluble than water-insoluble in the bags of fertilizer. The three types of water-soluble nitrogens are urea, which contains 45% nitrogen and is sometimes combined with formaldehyde (a suspected carcinogen)to create ureaform, and there is also Ammonium Nitrate, a very strong and very soluble fertilizer that quickly leaches from your soil.
Organic fertilizers are the best type to use because the are slow-acting. This type of fertilizer will help green-up your lawn without the excessive growth. Less growth also means less watering and less fertilizer in the long run. They are moderate in nitrogen content, neutral pH and water-insoluble - just like the lawn likes it. They are usually lower in nitrogen than synthetic fertilizers and may be more expensive, pound per pound in the short run. The idea is that since 1/2 the synthetic nitrogen is loss to leaching, you are closer to being price competitive than you think. There are many organic fertilizers on the market today, so take your time and look at the back panel of the fertilizer bags to make sure.
CALCULATING THE POUNDS/1,000 SQ.FT.
The numbers on the fertilizer bag explains it all. Lets take for example a 50 LB. bag of a 5-10-5 fertilizer. The numbers are the actual pounds per 100 pounds of fertilizer. Also lets say that the 50 LB bag covers 5,000 square feet. There is 2.5 lbs. of nitrogen in the 50 lb. bag. Divide the 2.5 by the SQ.FT. and times by 1000(2.5/5000=.0005x1000=.5 pounds) If your grass type needs 2 lbs. per 1000sq.ft., you would need to apply this 4 times a year, or buy a 10-10-10, etc
THE FORGOTTEN FIVE
The other five macronutrients - phosphorous, potassium, calcium, magnesium and sulfur - don’t get as much attention as nitrogen, but they are just as important. If you have used a high-nitrogen fertilizer in the past, there may be an imbalance in the soil. The best thing you can do is have your soil tested for pH and nutrients. This will not only tell you if you have a deficiency, but will also tell you how much of each nutrient to add to you soil. Phosphorous Phosphorous works behind the scenes and in the soil. It helps seed to germinate and to establish itself quickly and strongly. For established turf it aids in root growth. Phosphorous is present in every plant cell, where it is used to transform other elements into energy. To maintain adequate supplies of phosphorous in the soil, you need to add only 1/2 pound per 1,000 square feet per year. That can be provided with 5 pounds of bone meal, or you can use fish emulsion, cottonseed meal, or milorganite. Potassium Potassium doesn’t show up in color, growth or density, but has been shown to “toughen” the turf. It makes grass more resistant to heat, cold, drought, disease and traffic. The normal rate per year is 1 to 2 pounds per 1,00 square feet. A good source of potassium is wood ash, but that is not something you can put on your lawn, considering you would need 10 to 20 pounds per 1,000 square feet. Calcium, Magnesium and Sulfur Calcium helps by improving the uptake of nitrogen and increasing the growth of root hairs. It is also necessary for cell division within the plant. You can provide calcium by applying dolomitic limestone, which will also supply Magnesium. Magnesium is a component of chlorophyll that plays an important part in photosynthesis and helps absorb phosphorous. Sulfur is a nutrient you shouldn’t have to worry about unless you have been using the high-nitrogen fertilizer. Sulfur improves the grass color, increases carbohydrate reserves, contribute to cold tolerance, protein synthesis and new growth. Powdery mildew is more prevalent when sulfur is low.
Micronutrients
Iron improves fall and winter color, enhances root development, reduces the effects of stress, and is essential for the formation of chlorophyll. Excessive phosphorous creates an iron deficiency. Milorganite is a good source of iron. Manganese Manganese activates the photosynthesis process. Soils that have a high pH (7.5 or above) are usually deficient in this. Zinc, Copper, Boron and Molybdenum These are needed in minute quantities and if not applied properly, can cause the lawn more harm than being deficient. Check the fertilizer bag to see if these are included.
Tomorrow we will look at lime and why we need it.
For more information on organic lawn car, check out my Manual at http://www.thegardeningguru.com/index-11.html
Good Luck and Good Gardening!
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