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Conversion Tables, Formulas and Suggested Guidelines for Horticultural Use (B 931)

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Bodie V. Pennisi, Gary L. Wade, Melvin P. Garber, Paul A. Thomas and James T. Midcap, Horticulture Department
Originally prepared by S.C. Myers and A.J. Lewis, Extension Horticulturists

Formulas for calculating greenhouse volume

  • Uneven-span greenhouses
  • Quonset structures
  • Even-span greenhouses

Pesticide and fertilizer recommendations are often made on a pounds per acre and tons per acre basis. While these may be applicable to field production of many crops, orchardists, nurserymen and greenhouse operators often must convert these recommendations to smaller areas, such as row feet, square feet, or even per tree or per pot. Thus pints, cups, ounces, tablespoons and teaspoons are the common units of measure. The conversion is frequently complicated by metric units of measure. This publication is designed to aid growers in making these calculations and conversions, and also provides other data useful in the management, planning and operation of horticultural enterprises.

Table 1. Equivalents for liquid measure (volume)
Units of Measure
Gallons (gal) Quarts (qt) Pints (pt) Fluid Ounces
(fl oz)
Cups Table-spoons (tbs) Tea-spoons (tsp) Milli-liters (ml) Cubic Centi-meters (cc) Liters
(l)
1 4 8 128 16
1 2 32 4
1 16 2 32
1 1/8 2 6 30
1 16 48 240
1 3 15
1 5
1 1
1000 1000 1

Table 2. Metric system conversion table
Liquid capacity
1 fluid ounce (fl oz)
1 pint (pt) = 16 fl oz
1 quart (qt)
1 gal (gal)
1 liter (l)
1 milliliter (ml)
=
=
=
=
=
=
30 milliliters (ml)
473 ml
946 ml
3,785 ml
1,000 ml
1 cubic centimeter (cc)
Dry material weight
1 ounce (avoirdupois)
1 pound (lb)
1 kilogram (kg)
=
=
=
28.4 grams (g)
453.6 g
1,000 g = 2.2 lb
Volume
1 cubic inch (in3)
1 cubic foot (ft3)
1 bushel (bu)
1 cubic yard (yd3)
=
=
=
=
16.4 milliliters (ml)
7.48 gal = 28.3 liters (l)
1.24 ft3 = 35.2 liters
21.7 bu = 765 liters
Linear
1 inch (in)
1 foot (ft)
1 yard (yd)
1 meter (m)
=
=
=
=
2.54 centimeters (cm)
30.48 cm
91.44 cm
100 cm
Area
1 square inch (in2)
1 square foot (ft2)
1 square yard (yd2)
1 acre (a)
1 square mile (M2)
=
=
=
=
=
6.45 square centimeters (cm2)
0.09 square meter (m2)
0.84 square meter (m2)
0.40 hectare (ha)
2.59 square kilometer (km2)

Table 3. Dilution of liquid pesticides at various concentrations
Dilution
Amount Desired
1 Gal 3 Gal 5 Gal 15 Gal
1-100 2 tbs + 2 tsp ½ cup ¾ cup + 5 tsp 1 cup + 3 tbs
1-200 4 tsp ¼ cup 6½ tbs ½ cup + 2 tbs
1-400 2 tsp 2 tbs 3 tbs 4 tbs + 2½ tsp
1-800 1 tsp 1 tbs 1 tbs + 2 tsp 3 tbs + 2½ tsp
1-1000 ¾ tsp 2¼ tsp 1 tbs + 1 tsp 1 pt +½ cup

Example: Directions call for a 1:200 dilution. To prepare 3 gal of finished product, you would need to add ¼ cup.

Table 4. Equivalent quantities of dry materials (wettable powders) for various quantities of water based on recommended pounds per 100 gallons
Water Recommended Rate
100 gal 1 lb 2 lb 3 lb 4 lb 5 lb 6 lb
50 gal ½ lb 1 lb 1½ lb 2 lb 2½ lb 3 lb
25 gal 4 oz 8 oz 12 oz 1 lb 1¼ lb 1½ lb
12.5 gal 2 oz 4 oz 6 oz 8 oz 10 oz ¾ lb
5 gal 3 tbs 1½ oz 2½ oz 3¼ oz 4 oz 5 oz
1 gal 1 tsp 2 tsp 1 tbs 4 tsp 5 tsp 2 tbs

Example: Directions for use specify a rate of 4 lb per 100 gal. water. To prepare 1 gal of solution would require 4 tsp of material

Table 5. Equivalent quantities of liquid materials (emulsion concentrates, etc.) for various quantities of water based on pints per 100 gallons
Water Recommended Rates
100 gal ½ pt 1 pt 2 pt 3 pt 4 pt 5 Spt
50 gal 4 fl oz 8 fl oz 1 pt 1½ pt 2 pt 2½ pt
25 gal 2 fl oz 4 fl oz 8 fl oz 12 fl oz 1 pt 1¼ pt
12.5 gal 1 fl oz 2 fl oz 4 fl oz 6 fl oz 8 fl oz 10 fl oz
5 gal 1 tbs 1 fl oz 2 fl oz 2½ fl oz 3 fl oz 4 fl oz
1 gal ½ tsp 1 tsp 2 tsp 3 tsp 4 tsp 5 tsp

Example: Directions for use specify a rate of 4 pt per 100 gal water. To prepare 5 gal of solution would require 3 fl oz material.

Table 6. Rate of application equivalent table
Rate Per Acre Rate Per 1000 sq ft Rate per 100 sq ft
Liquid Materials
1 pt ¾ tbs ¼ tsp
1 qt 1½ tbs ½ tsp
1 gal 6 tbs 2 tsp
25 gal 42/3 pt ½ pt
50 gal 42/3 qt 1 pt
100 gal 21/3 gal 1 qt
200 gal 42/3 gal 2 qt
300 gal 7 gal 3 qt
400 gal 9¼ gal 1 gal
500 gal 11½ gal 1¼ gal
Dry Materials
1 lb 2½ tsp ¼ tsp
3 lb 2¼ tbs ¾ tsp
4 lb 3 tbs 1 tsp
5 lb 4 tbs 1¼ tsp
10 lb ½ cup 2 tsp
100 lb 21/3 lb ¼ lb
200 lb 42/3 lb ½ lb
300 lb 7 lb ¾ lb
400 lb 9¼ lb 1 lb
500 lb 11½ lb 1¼ lb

Examples: For liquid materials, 100 gal per acre is equivalent to 21/3 gal per 1000 ft2 or 1 qt per 100 ft2. For dry materials, 4 lb per acre is equivalent to 3 tbs per 1000 ft2 or 1 tsp per 100 ft2.

Table 7. Fertilizer conversions for specified square feet and row area
Material grouped by approximate weight per pint
Recommended rate per acre Fertilizer Rate for Specific Areas
100
sq ft
1000 sq ft 10
sq ft
100
sq ft
Per 10 feet of row spaced*
1 ft 2 ft 3 ft
lb lb lb tbs pt tbs tbs cup
10 oz per pint
Sulfur 100 0.2 2.3 1.2 0.4 1.2 2.4 0.2
Dried Blood 500 1.2 11.5 6.0 1.9 6.0 12.0 1.1
1000 2.3 23.0 12.0 3.7
13 oz per pint
Urea 100 0.2 2.3 0.9 0.3 0.9 1.8 0.2
Ammonium Nitrate 500 1.2 11.5 4.5 1.4 4.5 9.0 0.8
Ammonium Chloride 1000 2.3 23.0 9.0 2.8
16 oz per pint
Ammonium Phosphate 100 0.2 2.3 0.7 0.2 0.7 1.4 0.1
Potassium Chloride 500 1.2 11.5 3.5 1.2 3.5 7.0 0.7
Gypsum 1000 2.3 23.0 7.0 2.3
Mixed Fertilizers
19 oz per pint
Calcium Nitrate 100 0.2 2.3 0.6 0.2 0.6 1.2 0.1
Ammonium Sulfate 500 1.2 11.5 3.0 1.0 3.0 6.0 0.6
Superphosphate 1000 2.3 23.0 6.0 2.0
23 oz per pint
Ground limestone 100 0.2 2.3 0.5 0.2 0.5 1.0 0.1
Potassium sulfate 500 1.2 11.5 2.5 0.8 2.5 5.0 0.5
1000 2.3 23.0 5.0 1.6
2000 4.6 46.0 10.0 3.2
*High Rates, not desirable in row fertilization, are omitted in the table.

Example: You wish to apply calcium nitrate at the rate of 500 lbs per acre. It weighs approximately 19 oz per pt. for applications to 100 ft2, you need 1.2 lb or 1.0 pt.

Table 8. Fertilizer weight as measured by standard pot size
Fertilizer Pot Size
2¼" 3" 3½" 4" 5" 6"
Ammonium nitrate 2 oz 5½ oz 9 oz 15 oz 1 lb 12 oz 2 lb 15 oz
Urea, 45-0-0 2½ oz 6 oz 9 oz 1 lb 1 lb 13 oz 3 lb
Superphosphate 2½ oz 6 oz 9½ oz 1 lb 1 lb 14 oz 3 lb 2 oz
Dusting sulfur 2½ oz 6 oz 10 oz 1 lb 1 lb 14 oz 3 lb 3 oz
Peters, 20-5-30 2½ oz 6 oz 10 oz 1 lb 1 oz 1 lb 15 oz 3 lb 3 oz
Ammonium sulfate 3 oz 7 oz 11 oz 1 lb 3 oz 2 lb 3 oz 3 lb 11 oz
Osmocote, 14-14-14 3 oz 7½ oz 12 oz 1 lb 4 oz 2 lb 5 oz 3 lb 13 oz
MagAmp, 12-62-0 3 oz 7½ oz 12 oz 1 lb 4 oz 2 lb 5 oz 3 lb 14 oz
Gypsum, CaSO4 3 oz 8 oz 12½ oz 1 lb 5 oz 2 lb 7 oz 4 lb 1 oz
Calcium nitrate 3 oz 8 oz 12½ oz 1 lb 6 oz 2 lb 8 oz 4 lb 2 oz
Peters, 15-0-15 3½ oz 8 oz 13 oz 1 lb 6 oz 2 lb 9 oz 4 lb 5 oz
Potassium chloride 3½ oz 9 oz 14 oz 1 lb 8 oz 1 lb 12 oz 4 lb 9 oz
Sodium nitrate 4 oz 9 oz 15 oz 1 lb 9 oz 2 lb 14 oz 4 lb 13 oz
Dolomitic limestone 5½ oz 13 oz 1 lb 5 oz 2 lb 4 oz 4 lb 2 oz 6 lb 14 oz

Clay flower pots are frequently used for fertilizer measurement by greenhouse operators. The above shows average weights of several representative fertilizers as measured by standard clay pots when level full. The 3-inch standard is considered to contain 8 fl oz, or one cup. Since the actual pot size varies with the manufacturer and the volume of a given weight of fertilizer varies with moisture and compaction, deviations of 10 percent may be expected but up to 40 percent may occur.

Table 9. Element concentrations for pounds soluble fertilizer in 1000 gal (U.S.) water
Pounds of Fertilizer Needed
Desired PPM % Nitrogen (N) % Phosphate (P2O5) % Potash (K2O)
30 25 20 15 10 20 15 10 5 25 20 15 10
300 8.3 10.0 12.5 16.7 23.0 12.0 15.0 20.0 30.0
275 7.8 9.2 11.4 15.3 23.0 11.0 13.7 18.2 27.5
250 7.3 8.4 10.2 13.9 21.8 10.0 12.5 16.7 26.2
225 6.2 7.5 9.3 12.5 18.7 9.0 11.3 15.0 22.5
200 5.6 6.7 8.4 11.1 16.7 19.2 8.0 10.0 13.3 20.0
175 4.9 5.8 7.3 9.7 14.6 16.8 22.4 7.0 8.8 10.7 17.5
150 4.2 5.0 6.3 8.3 12.5 14.4 19.2 28.8 6.0 7.6 10.0 15.0
125 3.5 4.2 5.3 7.0 10.2 12.0 16.0 24.0 48.0 5.0 6.2 8.4 12.5
100 2.8 3.4 4.2 5.6 8.3 9.6 12.6 19.2 38.4 4.0 5.0 6.7 10.0
75 2.1 2.5 3.1 4.2 6.2 7.2 9.6 14.4 28.8 3.0 3.8 5.0 7.5
50 1.4 1.7 2.1 2.8 4.2 4.8 6.4 9.6 19.2 2.0 2.5 3.4 5.0
25 0.7 0.9 1.1 1.4 2.1 2.4 3.2 4.8 9.6 1.0 1.3 1.7 2.5

Example: You wish to apply 200 ppm N using a 20-10-20 soluble fertilizer. Reading across from 200 ppm under the 20 percent N column, you find 8.4 lb are needed for 1000 gal water.

NOTES: 1 oz/2 gal is about 30 lb/1000 gal; 1 oz/3 gal is about 20 lb/1000 gal; 1 oz/5 gal is about 12 lb/1000 gal. 1 oz/gal = 7490 ppm; 1 oz/100 gal = 75 ppm.

To determine Parts Per Million (ppm) of an element in a fertilizer, simply multiply the percent of that element by 75. The answer will be the ppm of the element per oz of the fertilizer in 100 gal of water. As an example, Ammonium Sulfate contains approximately 20 percent Nitrogen. 20 percent multiplied by 75 is 15, which is the ppm of Nitrogen in 1 oz of Ammonium Sulfate per 100 gal of water.

Table 10. Number of pots per bushel and per cubic yard of soil mix
Size of Pot No./bu No./cu yd
2¼ in. standard 316 6,952
2½ in. standard 220 4,840
3 in. standard 134 2,948
4 in. standard 58 1,276
5 in. standard 32 704
6 in. standard 18 396
7 in. standard 11 242
8 in. standard 8 176
12 in. standard 2 44
4 in. azalea 70 1,540
5 in. azalea 35 770
6 in. azalea 20 440
5 in. low pan 50 1,100
6 in. low pan 39 858
7 in. low pan 17 374
NOTE: Based on volume of pots when filled level to rim with loose, unpacked soil mix.

Table 11. Coverage estimates for perlite, peat, topsoil and straw
Thickness 4 cu ft
Perlite
6 cu ft
Canadian peat (compressed)
1 cu yd*
Peat mulches

Topsoil, etc.

1 Bale
Pinestraw Wheatstraw
2 in 28 sq ft 72 sq ft 162 sq ft 90 sq ft 180 sq ft
1 in 48 sq ft 144 sq ft 324 sq ft 180 sq ft 360 sq ft
½ in 96 sq ft 288 sq ft 648 sq ft 360 sq ft 720 sq ft
¼ in 192 sq ft 576 sq ft 1296 sq ft 720 sq ft 1440 sq ft
*1 cubic yard (yd3) = 27 cubic feet (ft3)

Table 12. Plant spacing guide (greenhouse)
Spacing Plants/sq ft Plants/A of production area Plants/A of ground covered*
8" x 9" 2.0 87,000 58,000
8" x 8" 2.3 98,000 65,000
8" x 7" 2.6 114,000 76,000
8" x 6" 3.0 130,000 87,000
6" x 7" 3.4 147,000 98,000
6" x 6" 4.0 174,000 116,000
6" x 5" 4.8 208,000 139,000
5" x 5" 5.8 252,000 168,000
5" x 4" 7.2 313,000 209,000
5" x 3" 9.6 418,000 279,000
4" x 3" 12.0 522,000 348,000
*Assuming 1/3 of production area devoted to aisles, etc.

Table 13. Plant spacing guide (field/orchard)*
Spacing Between Plants Within the Row
Spacing Between Rows of Plants Feet 6 8 10 12 14 16 18 20 22 24 26
4 1815 1361 1089 907 777 680 605 544 495 453 418
6 1218 907 726 605 518 453 403 363 330 302 279
8 907 680 544 453 388 339 302 272 247 226 209
10 726 544 435 362 311 272 242 218 207 181 167
12 605 453 362 302 259 226 201 181 165 151 139
14 518 388 311 259 222 194 172 155 141 129 119
16 453 339 272 226 194 169 151 136 123 113 104
18 403 302 242 201 172 151 134 121 110 100 93
20 363 272 218 181 155 136 121 108 99 90 83
22 330 247 207 165 141 123 110 99 90 82 76
24 302 226 181 151 129 113 100 90 82 75 69
26 279 209 167 139 119 104 93 83 76 69 64
Number of Plants Per Acre
*To determine the number of plants per acre for spacings not given in the table, multiply the distance in the row by the distance between rows and divide that number into 43,560.

Formulas for calculating greenhouse volume

For the following formulas:

L = length
W = width
W1 = width of short span
W2 = width of long span
He = height from floor to eave
Hr = height from eave to top

Uneven-span greenhousesUneven-span greenhouses

Greenhouse volume in cubic feet = [(W x He) + ([W1 x Hr] ÷ 2) + ([W2 x Hr] ÷ 2)] x L

Quonset structuresQuonset structures

Greenhouse volume in cubic feet = [(W x He) + ([3.14 x Hr²] ÷ 2)] x L

Even-span greenhousesEven-span greenhouses

Greenhouse volume in cubic feet = [(W x He) + ([W x Hr] ÷ 2)] x L

Acknowledgements

The authors wish to acknowledge the following sources, certain tables from which were adapted to use in this publication.

  • Cornell Recommendations for Commercial Floricultural Crops, Part 1. Cultural Practices and Production Programs.
  • Nutrition of Greenhouse Crops. Cooperative Extension Services of the Northeast States.
  • Tons to Teaspoons, L2285. University of California Cooperative Extension Service.

Reviewed on Apr 25, 2012