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AGRONOMY SERIES
TIMELY INFORMATION
Agriculture & Natural Resources
DEPARTMENT OF CROP, SOIL & ENVIRONMENTAL SCIENCES, AUBURN
UNIVERSITY, AL 36849-5633
S-01-14
October, 2014
IT’S SO EASY. . .
to fertilize everything in your garden
Charles C. Mitchell, Extension Agronomist-Soils & Professor
COMMENT FROM AN ALABAMA GARDENER I got my soil test report back for my backyard garden. My county extension agent said it was important to “take a soil test.” I looked down at the numbers and comments and was totally confused. I think I know what “HIGH” and “VERY HIGH” mean. But then there was a whole bunch of “see comments”. These comments made absolutely no sense to me. For example, this comment was on my report: “Comment 2 -­‐ Per 1,000 square feet broadcast 2.3 pounds m uriate of potash (1 quart 0-­‐0-­‐60). Per 100 feet of row apply 0.4 pound N (1 pint 34-­‐0-­‐0 or equivalent) at planting and sidedress with 0.4 pound N.” First, I cannot weigh out 2.3 p ounds of anything. My bathroom scale isn’t this accurate. What in the world is “muriate of potash”? I’ve never seen this at Wal-­‐mart. All they have is 13-­‐13-­‐13 or 10-­‐10-­‐10 or a whole bunch of boxed fertilizers for everything from tomatoes to African violets. I couldn’t find any 34-­‐0-­‐0 but I did find some 32-­‐0-­‐0. Can I u se this instead? Actually, I’d much rather use all organic fertilizers but these were not mentioned. My county agent was wrong. Soil testing didn’t help me. It only confused me. I have no idea what to do so I’ll just probably keep putting on some 13-­‐13-­‐13 or cow manure As an Extension soil fertility specialist, I’ve heard these types of complaints over and over again
but really didn’t have a simple answer for our gardening friends who really want to do the best
job they can. We have tried to make recommendations that fit the soil test results just like we do
for farmers. We failed to realize that home gardeners don’t have access to all the fertilizer
materials that farmers can get. Trying to go from pounds per acre to pounds per 1,000 square
feet or per 100 feet of row, resulted in a lot of small numbers with decimal places that only added
to the gardener’s confusion. A confused and frustrated gardener certainly isn’t likely to follow a
soil test recommendation.
ALABAMA A&M AND AUBURN UNIVERSITY, AND TUSKEGEE UNIVERSITY, COUNTY GOVERNING BODIES AND USDA
COOPERATING
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1 I’ve tried to come up with a simple formula that all gardeners can use to fertilize all their plants.
They do it anyway whether we recommend it or not. It is usually just a few handfuls of 13-13-13
around everything or maybe just pile on the organic fertilizer. After almost 40 years of dealing
with this home gardening dilemma, I think I have an answer. It has been there all along in our
turf grass recommendations but I just realized we can use this for all plants.
1 pound N per 1,000 sq. feet per application.
This rule will work with just about any plant or crop you are growing. ( For those agronomists
who think in terms of acres, this is equivalent to about 43 pounds N per acre.) Full-season
annuals and lawn grasses may need as many as 3 applications during the growing season (Table
1). Shrubs, woody plants, and fruit trees may need only one application. Multiple applications
will stimulate green, leafy growth. That’s what nitrogen fertilizers do. Note that I’m not
purposely recommending any phosphorus (P) or potassium (K). That’s because if you use the
first number on the fertilizer bag or box (nitrogen, N) as a guide, you will usually apply adequate
P and K fertilizer (the second and third number on the bag or box), especially if you use a
balanced fertilizer such as 10-10-10 or 13-13-13. Also, most soils from gardens, lawns and
shrubs test high or very high in P and K.
Another important point is:
1 pint of dry fertilizer is about a pound.
Examples:
Lawn. 2,500 sq. ft. bermudagrass lawn fertilized with Scott’s Turfbuilder 27-3-4. Because the
fertilizer contains 27% N, you’ll need to apply about 4 pounds of fertilizer per 1,000 sq. feet
(1.0/0.27 = 3.7). This would be about 4 pints per 1,000 sq. ft. But you have 2,500 sq. feet so
you’ll need to apply 2.5 times this much or about 10 pints on the entire lawn. Repeat this
application 2 more times during the growing season if you want more growth.
Blueberries. 6 established blueberry plants spaced 6 feet apart with ammonium sulfate 21-0-0.
The bed is about 10 feet wide. First, calculate the approximate area of the entire bed, e.g., 6
plants x 6 feet apart x 10 feet wide = 360 sq. feet. This is much less than 1,000 sq. feet. If you
had 1,000 sq. feet, you’d have to apply ~5 pounds (~5 pints) of ammonium sulfate (1.0 pound N/
0.21 N = 4.76). Therefore 0.36 x 4.76 pints = 1.71 pints or about 1 ¾ pints of ammonium sulfate
on the entire blueberry bed. This should be applied in early spring and again after harvest (twice
during the season.).
Vegetable Garden. A mixed vegetable garden with 20-foot rows spaced 3 feet apart. You’d like
to use 13-13-13 because you can get it. Each row is 60 square feet (20’ x 3’ = 60 sq. ft.). If you
had 1,000 sq. ft., you’d have to apply 1.0/0.13 = 7.69 pounds or about 7.7 pints of 13-13-13.
Since you only have 60 sq. ft. in each row, you’ll need to apply 60/1000 x 7.69 = 0.46 pounds
per row or about ½ pint or about 1 cup per row. (Note: Since you are putting out so much P and
K in the 13-13-13 at planting, consider using only a nitrogen fertilizer at side dressing such as
34-0-0. You’d need slightly less than ½ cup per row of 34-0-0 for your sidedress application.
2 Vegetable Garden fertilized with 15-0-15. We’ll use the same garden as above but you had the
soil tested and discovered it was “EH” (extremely high) in phosphorus (P). No more P was
recommended. You chose to use 15-0-15 fertilizer because it does not contain any P. You’d
have to apply about 6.6 pounds 15-0-15 per 1,000 sq. ft. (1.0/0.15 = 6.6). Per row above, you’d
apply 6.6 x 60/1000 = 0.4 pounds 15-0-15 per row per application. That’s about a half pint or
about a cup of 15-0-15.
Organic vegetable garden. An organic vegetable garden fertilized only with backyard compost
(~0.5-0.5-0.5). 1 pound N per 1,000 sq. ft. would be about 200 pounds compost per 1,000 sq. ft.
(1.0/0.005 = 200). If your rows are spaced the same as those in the above example, this would
be about 12 pounds compost per row. You would still need to sidedress your vegetables with
more N later. I’d suggest fish emulsion which is 5-1-1. You’d have to sidedress with 20 pounds
(~20 pints) per 1,000 sq. ft. or about 1 ¼ pints per row.
Organic blackberries. Bed is 5 feet wide by 20 feet long. This is exactly 100 square feet or 1/10
of 1,000 sq. feet. I’d suggest perhaps using cottonseed meal (6-1-1) because it is available at
most feed and seed stores in Alabama. You’d need 1.0/0.06 = 16.6 pounds per 1,000 sq. feet or
about 1.66 pounds or pints in your bed. Apply this twice during the growing season.
Even in the garden, you cannot get away from some simple calculations but much of these
calculations can be done without a calculator, computer or even a pencil. Just think about it.
3 Table 1. Number of N applications during growing season. Additional applications may be
applied to stimulate green, leafy growth.
Apply once in early spring or
Apply twice during growing
Apply three times during
after planting.
season.
growing season.
woody shrubs
tomatoes
corn
perennial vines
peppers
sorghum
figs
eggplant
Bermuda/zoysia/St. Augustine
lawns
pears
broccoli
Collard greens
grapes
cabbage
persimmons
cauliflower
apples
onions
young ornamental trees
ornamental grasses
cover crops
fescue/bluegrass lawns
flowering perennials
blueberries
established bulbs
blackberries
squash
peaches
carrots
plums
lettuce
sunflowers
spinach
sugarcane
centipede lawn
strawberries
roses
melons
cucumbers
squash
okra
annual flowers
turnip greens
4 Table 2. Pounds of some common fertilizers that will contain approximately 1 pound N per
1,000 sq. ft. Most dry, granular fertilizers will weigh about 1 pound per pint. Organic fertilizers
will not be as dense and should be weighed.
Fertilizer grade
Per 1,000 sq. ft.
Per 100 sq. ft.
Per plant or per 10 sq.
N-P2O5-K2O
(20’ X 50’ bed)
(10 x 10’ bed)
feet (3.2’ x 3.2’ area)
Dry, granular fertilizers
20-20-20
5
0.5
2 Tablespoon
17-17-17
5.9
0.59
2 Tablespoon
13-13-13
7.7
0.77
2.5 Tablespoon
10-10-10
10
1.0
3.2 Tablespoon
8-8-8
12.5
1.25
4 Tablespoon
15-0-15
6.7
0.67
2 Tablespoon
27-3-4 (Scott’s Turf
3.7
0.37
1.2 Tablespoon
Builder®)
21-0-0 (ammonim sulfate)
34-0-0 (ammonium nitrate
or a urea/ammonium
sulfate blend)
45-0-0 (urea)
18-46-0 (diammonim
phosphate)
16-0-0 (sodium nitrate)
18-6-12 StaGreen®
19-6-12 Osmocote®
14-14-14 Osmocote®
Blood meal (~12-0-0)
Feather meal (~14-0-0)
Cottonseed meal (6-1-1)
Fish emulsion (5-1-1)
Composted cow manure
(1-1-1)
Chicken litter (3-3-4)
Legume hay (3-1-2)
Horse manure (0.4-0.20.3)
Backyard compost (0.50.5-0.5)
4.8
2.9
0.48
0.29
1.5 Tablespoon
1 Tablespoon
2.2
5.5
0.22
0.55
2 teaspoons
1 ¾ Tablespoons
6.25
5.55
5.26
7.14
8.3
7.1
16.7
20
100
0.62
0.55
0.53
0.71
Organic fertilizers (pounds)
0.83
0.71
1.61
2.0
10.0
------
33.3
33.3
250
3.33
3.33
25.0
----
200
20
--
5 2 Tablespoons
1 ¾ Tablespoons
1 ¾ Tablespoons
2.3 Tablespoons