WHAT IS IT? Weed seeds = Elevator Screenings are what is left when grain is run through a seed cleaner. Clean grain goes into a bin and residues = screenings are disposed. Most grain elevators give weed seeds away free to any farmer willing to haul them. Some elevators charge nominal sums for screenings because they can be fed to animals. For example, 10% to 15% weed seeds can be mixed into chicken feed.
HOW TO MAKE WEED SEED MEAL: Seeds of most plants make good fertilizer. The trick is to mill = grind seeds into a coarse meal or flour so they do not sprout. Most farmers use roller mills, hammer mills, or gristmills to grind weed seeds. If milling equipment is not available weed seeds can be baked in shallow (2 inch ~ 5 centimeter deep) pans at 350 degrees Fahrenheit ~ 176 degrees Centigrade for 1 hour to kill seeds. Baked weed seeds make very slow release organic fertilizer ideal for plants (like roses) sensitive to excess nitrogen.
If weed seeds are not available, substitute any type of waste or spoiled grain, for example, wet or dry brewer’s grains. There is no standard analysis for weed seed meal; nutrient content varies depending on species and proportion which change by locality and season. It is good practice to test weed seed samples yearly so fertilizer application rates can be adjusted as needed.
Below are some average nitrogen (N), phosphorous (P), and potassium (K) values for rough calculations. Note: lb = pound. 1 pound = 0.454 kilogram. 1 American ton = 2,000 pounds = 908 kilograms = 0.908 metric ton. 1 metric ton = 1 megagram = 1,000,000 grams = 1,000 kilograms = 2,200 pounds = 1.1 American tons.
WEED SEED MEAL & SIMILAR AGRICULTURAL WASTES. FERTILIZER ANALYSIS IN PERCENT BY WEIGHT (Nitrogen : Phosphorous: Potassium):
BARLEY (spoiled, dry): 1.75% N : 0.75% P : 0.50% K = 35 lb N + 15 lb P + 10 lb K per ton (Manitoba 2011)
BEANS, SOUP (broken, dry): 4.0% N : 1.20% P : 1.30% K = 80 lb N + 24 lb P + 26 lb K per ton (New York 1988)
BREWER’S GRAINS (dry): 4.53% N : 0.47% P : 0.24% K = 90 lb N + 9 lb P + 4 lb K per ton (Pennsylvania 2012)
BREWER’S GRAINS (wet): 0.90% N : 0.50% P : 0.05% K = 18 lb N + 10 lb P + 1 lb K per ton (Pennsylvania 2012)
CANOLA SEED MEAL: 6% N : 2% P : 1% K = 120 lb N + 40 lb P + 20 lb K per ton (Saskatchewan 2014)
CASTOR BEANS (pressed): 5.5% N : 2.25 % P : 1.125% K = 110 lb N + 45 lb P + 22 lb K per ton (Egypt 2012)
COFFEE GROUNDS (dry): 2.0% N : 0.35% P : 0.52% K = 40 lb N + 7 lb P + 10 lb K per ton (Uganda 2015)
CORN, DENT (spoiled, dry): 1.65% N : 0.65% P : 0.40% K = 33 lb N + 13 lb P + 8 lb K per ton (Maryland 2014)
COTTON SEED (whole): 3.15% N : 1.25% P : 1.15% K = 63 lb N + 25 lb P + 23 lb K per ton (USDA 2015)
COTTON SEED (pressed): 4.51% N : 0.64% P : 1.25% K = 90 lb N + 12 lb P + 25 lb K per ton (USDA 2015)
COTTON SEED MEAL: 6.6% N: 1.67% P : 1.55% K = 132 lb N + 33 lb P + 31 lb K per ton (Egypt 2012)
COWPEAS (broken, dry): 3.10% N : 1.00% P : 1.20% K = 62 lb N + 20 lb P + 24 lb K per ton (California 2014)
FLAXSEED = LINSEED MEAL: 5.66% N : 0.87% P : 1.24% K = 113 lb N + 17 lb P + 24 lb K per ton (Manitoba 2008)
OATS (broken, dry): 2.00% N : 0.80% P : 0.60% K = 40 lb N + 16 lb P + 12 lb K per ton (New York 2010)
RICE BRAN: 4.00% N : 3.00% P : 1.00% K = 80 lb N + 60 lb P : 20 lb K per ton (India 2015)
RICE, BROWN (spoiled, dry): 1.0% N : 0.48% P : 0.32% K = 20 lb N + 9 lb P + 6 lb K per ton (California 2016)
RICE HULLS = HUSKS: 1.9% N : 0.48% P : 0.81% K = 38 lb N + 9 lb P + 16 lb K per ton (Philippines 2014)
RICE, WHITE (broken): 1% N : 0.21% P : 0.27% K = 20 lb N + 4 lb P + 5 lb K per ton (California 2016)
SOYBEAN MEAL: 7.0% N : 2.0% P : 0.0% K = 140 lb N + 40 lb P + 0 lb K per ton (Brazil 2011)
WEED SEED MEAL: 2.7% N : 0.90 % P : 0.90% K = 54 lb N + 18 lb P + 18 lb K per ton (Hungary 2013)
WEED SEED MEAL: 3.02% N : 0.56% P : 0.77% K = 60 lb N + 11 lb P + 15 lb K per ton (Saskatchewan 2015)
WHEAT, HARD RED WINTER (broken): 2.00% N : 0.85% P :0.50% K = 40 lb N + 17 lb P + 10 lb K per ton (Kansas 2011)
For comparison, fresh dairy cow manure (86% water) contains 0.60% Nitrogen : 0.15% Phosphorous : 0.45% Potassium = 12 lb N + 3 lb P + 9 lb K per ton. Cow manure is the traditional standard against which all other organic fertilizers are measured.
For slow release fertilizer mill weed seeds into coarse flakes or meal. Grind weed seeds into powder for fast acting fertilizer.
WEED SEED MEAL APPLICATION RATES: Calculate application rates according to soil test recommendation for desired crop. Minimum application rate is 1 ton = 2,000 pounds per acre ~ 5 pounds or 1 gallon per 100 square feet ~ 2 Tablespoons or 2/3 ounce per square foot. Apply 1 pound of weed seed meal for every 25 feet of row or trench. Mix 1/2 to 1 cup of weed seed meal in each bushel (8 gallons) of potting soil.
Average density of weed seed meal = 0.3125 to 0.40 ounce per Tablespoon ~ 5 to 6.5 ounces per cup ~ 20 to 25.6 ounces per quart ~ 80 to 102.4 ounces per gallon ~ 5 pounds to 6 pounds 6.4 ounces per gallon ~ 40 to 51 pounds per bushel (8 gallons). 1 ton = 2,000 pounds weed seed meal = 40 to 50 bushels.
For example: 200 bushel per acre corn crop requires 200 pounds of nitrogen per acre. 200 pounds N divided by 54 pounds of nitrogen per ton of weed seed meal = 3.70 ~ 4 tons of weed seed meal needed per acre of corn. Weed seed meal can be tilled into the earth by conventional plowing, broadcast on soil surface, side banded down rows, or drilled into furrows or trenches.
For feeding earthworms broadcast weed seed meal (1 ton per acre or 2 Tablespoons per square foot) on soil surface. Reapply throughout the growing season when meal is no longer visible.
–> Weed seed meal is a natural = biological = organic fertilizer that requires decomposition before nutrients are available to plants. Bacteria, fungi and many other soil organisms eat weed seed meal then excrete nutrients in plant available forms. As soil organisms live and die, nutrients are constantly recycled = most fertilizer is tied up in the bodies of soil “critters” and is only available to plant roots in small amounts over extended time periods. Thus, weed seed meal is a slow release fertilizer that will not burn plant roots or leach from the soil.
–> Cold, wet soils delay weed seed meal decomposition. Warm, moist soils speed fertilizer availability. Early season crops may show signs of nitrogen deficiency (light green leaves) if soils are especially cold or poorly aerated = oxygen deficient. This is a temporary condition that will ordinarily correct itself in 2 or 3 weeks. Every 5 degree Fahrenheit temperature increase doubles microbial activity. As soils warm, nutrient cycling speeds up and more fertilizer is released for absorption by plant roots.
–> If crops must be seeded in cold soils, apply weed seed meal 2 to 3 weeks before planting so soil organisms have more time to decompose fertilizer and make nutrients available to plants.
–> Weed seed meal is an indirect fertilizer — it feeds soil organisms rather than plant roots. Large amounts of weed seed meal can be applied without crop damage or nutrient loss because the fertilizer is held by soil biology rather than soil chemistry. Thus, nutrients can be banked = stored for use by following crops. Weed seed meal has a “half-life” of several years. Nutrients are continually released in small amounts long after fertilizer is applied.
–> Weed seed meal works best on soils managed biologically. Chemically managed soils typically have smaller populations of soil organisms. Fewer “critters” slows nutrient cycling and restricts fertilizer absorption by plant roots.
–> To use LIVE weed seeds as fertilizer broadcast seeds into a standing cover crop like Red Clover (Trifolium pratense). Earthworms, ants, beetles and other critters eat the weed seeds. Clover kills any weeds that germinate. Caution: Do not try this unless you have a tall, aggressive cover crop that blankets the soil with dense shade.
RELATED PUBLICATIONS: Managing Weeds as Cover Crops; Trash Farming; No-Till Hungarian Stock Squash; Planting Maize with Living Mulches; Living Mulches for Weed Control; Organic Herbicides; Pelleted Seed Primer; Crops Among the Weeds; Forage Maize for Soil Improvement; Forage Radish Primer; and Rototiller Primer.
WOULD YOU LIKE TO KNOW MORE? Contact the Author directly if you have any questions or need additional information on fertilizing soils with weed seed meal.
Please visit: http://www.worldagriculturesolutions.com — or — send your questions to: Eric Koperek, Editor, World Agriculture Solutions, 413 Cedar Drive, Moon Township, Pennsylvania, 15108 United States of America — or — send an e-mail to: Eric Koperek = firstname.lastname@example.org
ABOUT THE AUTHOR: Mr. Koperek is a plant breeder who farms in Pennsylvania during summer and Florida over winter. (Growing 2 generations yearly speeds development of new crop varieties).