Dan West Garden Center

August 2006 Newsletter

As promised, this month's lecture is on fertilizer.  First, lets look at the numbers.  On a container of fertilizer (liquid or granular), you will see three numbers like 8-8-8.  The numbers represent the percentage of fertilizer by weight.  In this case, if you had 100 lbs. of 8-8-8, you would have 8% or 8 lbs. of nitrogen (the first number), 8% or 8 lbs of phosphorous (the second number) and 8% or 8 lbs. of potassium (yep, you guessed it, the third number).   If you run the numbers, you find there's 24 lbs of the three nutrients that plants require in significant amounts.  The other 76 lbs. may have some other nutrients that plants require such as iron and sulfur, but the bulk of the 76 lbs. is filler or carrier.  Too many people focus on the weight of a bag of fertilizer, when the important thing to consider is the ratio of the nutrients to each other and the type of nitrogen. Let's look at each number and it's importance to your plants.

N - Nitrogen (remember...the first number) encourages growth.  If you want to grow leaves to look at (foliage plants), to eat (cabbage, greens, etc) or to mow you need a higher ratio of nitrogen (12-6-6), but there is a world of difference in the types of nitrogen.  Nitrate nitrogen is rapidly available to plants in cold or warm soils.  Ammoniac nitrogen it rapidly available only in warm soils, rather useless in cold soils.  These are what you find in most agricultural grade fertilizers like 8-8-8 or 13-13-13.  They feed quickly but the nitrogen is gone in just a few days.  Better quality fertilizers contain a little quick release nitrogen, but mostly slower types so you get micro doses of fertilizer over an extended period.  This is a much healthier way to grow plants, particularly lawns.  The application rate for almost all plants is about 1 lb. per 1000 sq. ft. but the frequency depends on what you are growing.  Bermuda lawns - every 30 - 60 days, Zoysia lawns - every 60 - 90 days, Fescue lawns - twice a year, most shrubs are once or twice a year.

P - Phosphorous encourages flowers.  If you want to see it flower or eat it's fruit, then the middle number should be higher (9-15-13).  Phosphorous helps plants develop new roots, seeds and aids in resistance to heat, drought and disease.

K - Potassium (potash) helps regulate many of the biochemical processes including photosynthesis.  It improves vigor, root and stem strength and improves resistance to drought and disease also.

These are just three of the sixteen elements that plants need.  The others are needed in much smaller quantities but are just as important, so look for and use the most complete fertilizer(s). 

Question time ... you sir, in front of the computer.

I've been using 13-13-13 all my life, why shouldn't I use it? And I've got some, so what spreader setting should I use?

You can live off peanut butter and jelly sandwiches, it's just not the healthiest thing to do.  As I mentioned earlier, field grade fertilizers usually have only ammoniac nitrogen.  When you apply this to your lawn, it gets a quick boost and grows so fast you practically have to cut your way back to the house.  Have you ever noticed the brown cast to your lawn the morning after you mowed?  You've cut back to the stems, now the grass has to burn carbohydrates stored in the root system, to replace the leaves, to produce the carbohydrates, to store back in the root system.  Feeding with a controlled release quality fertilizer gives you a slower, time released feed plus some iron and sulfur for good green color, but less green is removed at mowing which makes for a healthier turf. What spreader setting?  It's difficult to say.  Every field grade fertilizer manufacturer uses a different carrier or particle size which would effect you setting.  However, there is an easy way to figure the bag coverage.  Remember I said 1 lb. of nitrogen per 1000 sq. ft.? Here's the formula for coverage:

Multiply the first number on the bag (the nitrogen) times the weight of the bag and add a zero on the right to equal the square foot coverage.

Here's an example:  6-12-12  40 lb. bag   6 x 40 = 240 + 0 = 2400 sq. ft.  It work's every time!

Here's another one:  28-3-3   20 lb. bag   28 x 20 = 560 + 0 = 5600 sq.  Cool, ain't it!

Let's do one more - ammonia nitrate - 33.5-0-0   40 lb. bag   33.5 x 40 - 1340 + 0 = 13,400 sq. ft.  Apply it heavier and some plants will burn.  Apply it heavier to your lawn and you can hear it grow!

Since you know the coverage, set your spreader setting low, mark off that much area and criss cross until you run out.

Next question...the lady in blue.

Which is better for plants, organic or synthetic fertilizer?

This may start a ruckus, but let's look at the science.  Plants can only absorb very small molecules.  Nitrogen can be absorbed as nitrate NO3 or ammonia NH4.  Organic nitrogen molecules are much too large to be absorbed and have to be broken down by microbes into inorganic forms - nitrate molecules - NO3 - the exact same molecule that is readily available in some synthetic fertilizers. There is no difference! Usually the decision to use organic or synthetic is based on what a person perceives the process of making it or using it has on the environment.  You could say that using fish or seaweed is organic, natural and uses renewable resources or you could say using synthetic fertilizer protects the indiscriminate loss of marine life while harvesting fish and kelp.  Is the cup half full or half empty?  It's a perception thing for you, not the plants.

Next month...MULCHES! 

DAN WEST GARDEN CENTERS

4763 POPLAR             12061 HWY 64

MEMPHIS, TN 38117    EADS, TN 38028

901-767-6743            901-867-2283

KENNETH MABRY - MANAGER                JIM CROWDER - MANAGER