2012 Organic Cabbage Trial

This is a demonstration project:  A single field without controls or replications for statistical analysis.  The purpose of this trial is to explore possibilities before launching a full-scale research program.

Experimental Location:  Homestead, Florida, United States of America.  25.47 degrees North Latitude, 80.52 degrees West Longitude.

Climate:  Homestead has a semi-tropical monsoon climate with a hot, humid summer and a cooler, drier winter.  Average annual temperature = 74.8 degrees Fahrenheit = 23.75 degrees Centigrade.  Average annual rainfall = 58.23 inches = 147.90 centimeters.  Average January low temperature = 56 degrees Fahrenheit = 13.2 degrees Centigrade.  Average January high temperature = 77 degrees Fahrenheit = 24.8 degrees Centigrade.  Frost Free Growing Season = approximately 355 days.  Homestead gets about 5 to 10 frosts (36 degrees Fahrenheit) and freezes (32 degrees Fahrenheit) each winter.

Experimental Plot Size:  1 acre = 208 feet x 208 feet (approximately).

Soil Type:  Everglades Peat = Muck

Crop Rotation:  Sunn Hemp (Crotalaria juncea) was planted in spring 2012 to suppress weeds and control root knot nematodes.  Hemp cover crop was shredded with a forage chopper then Crimson Clover (Trifolium incarnatum) was broadcast seeded over hemp mulched field.  Cabbage seedlings were transplanted into rotary mowed crimson clover in November 2012.

Tillage:  Field was mulched using a common silage chopper.  Crimson clover was cut with a rotary mower.  Cabbage seedlings were planted using a no-till transplanter with a fluted coulter.

Plants Per Acre:  Cabbage transplants were set 18 inches apart in rows 30 inches apart = approximately 11,000 plants per acre.  (138 plants per row x 83 rows per acre = 11,454 plants per acre exactly).  80% field survival is common so final plant density = approximately 9,000 plants per acre.

Crop Variety:  Brassica oleracea cultivated variety “Golden Acre”.  This is an early season (58 day) round cabbage with small heads averaging 3 to 4 pounds each.

Common Weed Varieties:  Bull Thistle (Cirsium vulgare), Coffee Senna (Senna occidentalis), Hemp Sesbania (Sesbania exaltata), Morning Glory (Ipomoea species), Lambs Quarters (Chenopodium album), and Pigweed (Amaranthus blitum).

Weed Management:  Sunn hemp cover crop and crimson clover living mulch eliminated most weeds.  Field was better than 95% weed free so no herbicides were used for this trial.

Weed Spacing:  Approximately 2,200 weeds grew above the crimson clover living mulch = approximately 1 weed per 19.8 square feet.  Clumps of weeds were hand thinned to single weeds spaced about 4 to 5 feet apart.

Irrigation:  Overhead sprinkler irrigation, 1 to 2 inches applied each week as needed.

Organic Fertilizers:  Greensand and colloidal phosphate rock were broadcast with sunn hemp seed according to soil test recommendations.  Hemp seed was covered with 20 tons = 40,000 pounds of composted stable bedding.  Fish emulsion and liquid seaweed (Kelp) were used as starter fertilizers for cabbage transplants.

Insect Control:  Cabbage plants were sprayed with a harmless biological insecticide “BT” = Bacillus thuringiensis subspecies kurstaki strain SA-12 every 7 to 10 days throughout the growing season.  BT is a naturally occurring bacterial disease that kills caterpillars = juvenile forms of moths and butterflies.

Cabbage Yield:  Approximately 9,000 marketable heads were harvested.  Average head weight = approximately 3.375 pounds = 3 pounds 6 ounces (normal range is 3 to 4 pounds).  Yield per acre = approximately 30,000 pounds = 15 tons.

Production Costs:  $5,924 per acre (mostly for amortized irrigation system and farm machinery).

Cabbage Income:  30,000 pounds cabbage (9,000 marketable heads) x $0.35 per pound organic produce premium wholesale price = $10,500 gross income.

Net Income:  $10,500 gross income – $5,924 production costs = $4,576 net income from 1 acre of organic cabbage sold wholesale.  ($4,576 net income / $10,500 gross income) x 100 = 43.58% before tax profit.  ($4,576 net income / $5,924 production cost) x 100 = 77.2451 = 77% gross return on investment.

Agronomy Notes:

>>>  Most south Florida soils are coarse sands with very low humus content (often less than 2%).  Large amounts of organic matter must be added to these soils to keep them productive.  Cash crops must be rotated with soil building cover crops in order to maintain humus levels at 3% or above.

>>>  Muck soils also require large amounts of organic matter to replace humus lost to accelerated decomposition when swamps are drained.  Drainage and cultivation expose peat soils to large amounts of oxygen.  Rapid oxidation causes soil subsidence if organic matter is not replaced.

>>>  Root knot nematodes are serious agricultural pests in south Florida.  The most economical control method is to rotate cash crops with highly nematode-resistant cover crops like Sunn Hemp (Crotalaria juncea), Velvet Bean (Mucuna deeringiana), Cowpea (Vigna unguiculata), or Hairy Indigo (Indigofera hirsuta).

>>>  Sunn hemp, forage maize, and silage corn produce enormous amounts of organic matter for soil improvement (surface mulch or green manure).  Few farmers use hemp or maize as green manure or mulch crops because the plants must first be shredded in order to decompose quickly.  (If long-lasting mulch is desired, knock down cover crops with a roller-crimper then plant through dead mulch with a no-till seeder or transplanter).

>>>  Widely spaced weeds did not appear to have any negative effects on cabbage yield or quality.  Many cabbages growing near weeds were larger than those without any weed competition.  Light shade may be beneficial for cabbage growth.

>>>  Crimson Clover (Trifolium incarnatum) is often sown along Florida highways because it has large flowers.  Crimson clover makes good living mulch because it normally grows only 6 to 12 inches high.  Ideal living mulches grow short so they do not compete with crop plants for light.

Would You Like To Know More?  Please contact the Author directly if you have any questions or need additional information about using living mulches for weed control.

Please visit:  http://www.worldagriculturesolutions.com  — or —  send your questions to:  Agriculture Solutions, 413 Cedar Drive, Moon Township, Pennsylvania, 15108 United States of America  — or —  send an e-mail to:  Eric Koperek = worldagriculturesolutions@gmail.com

About the Author:  Mr. Koperek is a plant breeder who farms in Pennsylvania during the summer and Florida during the winter.  (Growing 2 generations each year greatly speeds development of new crop varieties).

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