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Organic Gardening: Challenges and Opportunities Carl E. Motsenbocker School of Plant, Environmental and Soil Sciences LSU AgCenter Sustainable agriculture refers to farm practices that : provide a more profitable farm,

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organic gardening challenges and opportunities
Organic Gardening: Challenges and Opportunities

Carl E. Motsenbocker

School of Plant, Environmental and Soil Sciences

LSU AgCenter

sustainable agriculture refers to farm practices that
Sustainable agriculture refers to farm practices that:
  • provide a more profitable farm,
  • promote environmental stewardship by protecting and improving soil quality,
  • reduce dependence on non-renewable resources,
  • minimize adverse impacts on safety, wildlife, water quality and other environmental resources,
  • while promoting stable, prosperous farm families and communities

(Sustainable Agriculture Research and Education Program, 2007). 


US Organic Standard

  • In October of 2002, the US Congress mandated National Organic Standards.
  • All products labeled as “organic” meet stringent standards established by the US Department of Agriculture (USDA).
  • US consumers have the force of law behind all organic labeling claims, providing peace of mind that when something says it is “organic”, it will meet the strict standards set by the USDA.
us organic standards
US Organic Standards
  • Land on which organic food or fibers are grown must not have had prohibited substances applied
    • (such chemical pesticides and fertilizers) for three years prior to certification.
  • Farmers and processors must keep detailed records of methods and materials used in growing or processing organic products.
us organic standards5
US Organic Standards
  • A third party certifier approved by the USDA must inspect methods and materials annually.
  • All handlers and farmers are required to maintain an Organic Handling Plan detailing their management practices.
  • Under the USDA regulations, In order for a product to be labeled as “organic” it must contain a minimum of 95% organic ingredients.
categories of organic products
Categories of organic products

The USDA three categories of organic products:

100% Organic

Made with 100% organic ingredients


Made with at least 95% organic ingredients, with strict restrictions on the remaining 5% including no GMOs

Made With Organic Ingredients

Made with a minimum of 70% organic ingredients with strict restrictions on the remaining 30% including no GMOs

Products with less than 70 percent organic ingredients may list specific organically produced ingredients on the side panel of the package, but may not make any organic claims on the front of the package.

us government organic standards
US Government Organic Standards
  • The National Organic Program (NOP)
  • List of allowed and disallowed practices and materials
  • 3 Major disallowed practices:
    • GMOs
    • Radiation
    • Slewage sludge
  • Periodic review of materials and review
growth in organic product sales us
Growth in organic product sales (US)

Year Sale ($ )

1980 178 million

1989 631 million

1990 1.0 billion

1992 1.2 billion

1994 2.3 billion

1996 3.5 billion

1998 5.5 billion

2001 9.3 billion

2005 20.0 billion

(compounded growth rates for the past ten years > 20 % per year)

why organic gardening is increasing
Why organic gardening is increasing
  • Public acceptance
  • Consumer demand
  • Environmental and health concerns
  • Sustainable agriculture movement etc.
  • Local/fresh produce
  • “Organic” represents the approach of working with nature to improve soil health and using the most environmentally sensitive products available.
  • Identifying and understanding nature’s systems and work within those systems.

Nitrogen Cycle


N fixation


Residues, manures and wastes

Fertilizer and rain

Gaseous loss

Air N2





Soil Microorganisms



Clay minerals






Healthy soils lead to healthy plants;

healthy plants produce healthy animals and humans”

JI and Robert Rodale “started” the organic movement in the US > 60 years years ago.

The idea of adding organic matter and minerals through natural products to improve the health and nutrition of food crops.

soil management
Soil Management
  • Basis of farm and garden productivity and therefore the cornerstone of any ecologically sound approach to farming/gardening.


understanding the soil system
Understanding the soil system
  • Soil fertility - soil capacity to nurture healthy plants. Organic / sustainable agriculture aims to protect the soil’s ability to regenerate nutrients lost when crops are harvested.
  • Regeneration depends on diversity, health, and vitality of the organisms that live, grow, reproduce and die in the soil.
  • Activities of soil microbes makes available the basic raw materials needed by plants at the right time and in the right form and amount.
life in the soil
Life in the soil
  • The soil community, and its living organisms, assists in the cycles that permits nutrients to “flow” from the soil to the plant.
  • Soil microorganisms are the essential link between mineral reserves and plant growth.
  • The organisms involved: bacteria, fungi, actinomycetes, algae, protozoans, nematodes, mites, earthworms.
  • The goal of ecological/organic soil management is to assist these microorganisms.
The basic aim of ecological soil management is to provide hospitable conditions for the life within the soil.
  • Your garden/farm is both the product and producer of soil … and is a “living organism” that achieves its greatest long-term productivity when its natural cycles and processes are enhanced.
  • Soil type
    • the best is a sandy loam
    • soil proportion (clay : silt : sand)
    • Texture will influence nutrient status, workability, aeration and drainage.
      • Clay soils - hold water & nutrients, often difficult to work and are poorly drained.
      • Sandy soils - easy to work & well drained, poor nutrient and water holding capability
soil depth
Soil depth
  • Depth to bedrock
  • Depth to water table
  • Depth of topsoil (usually 4 to 12” deep)
soil fertility
Soil Fertility
  • Overall goal: build and maintain proper levels of and balances of soil nutrients
  • Goal 1: adding fertilizers to the soil to build nutrients up to their proper levels and balances for your type of soil, climate, rainfall, sun exposure, altitude, and cation exchange capacity.
  • Goal 2: keep those nutrients in the garden area by composting properly and recycling wastes.
  • Goal 3: use enough nutrients, water, and compost.
feeding the soil
Feeding the soil
  • Adding minerals and organic matter can turn an infertile soil into a fertile soil in a cumulative process.
  • Two sources of nutrients for the soil –
    • organic matter (remains of previously living organisms)
    • finely ground rock particles that is the mineral fraction of the soil.
  • Nutrients are made available through biological and chemical processes.
building the soil
Building the soil
  • Nutrient availability is a result of biological and chemical soil processes that are stimulated by: crop rotations, green manures, and animal manures.

Five amendments need to be supplied as raw materials. Especially on POOR soils (Coleman):

  • Organic matter: compost or manure applied at the rate of 20 tons/acre every other year.
Table 1. Average biomass yields and nitrogen yields of several legumes (4).
  • ________________________________________
  • Cover Crop Biomass Nitrogen

Tons/acre lbs./acre

  • Sweet clover 1.75 120
  • Berseem clover 1.1 70
  • Crimson clover 1.4 100
  • Hairy vetch 1.75 110
Best: soil testing- pH, nutrients. (Send a sample to a university or university extension service)
  • LSU Ag Center Cooperative Extension Service
fertilizer analysis n p k
Fertilizer Analysis (N-P-K)
  • Percentage of total Nitrogen (N), which is the sum of all forms of nitrogen present.
  • Available Phosphoric acid (P).
  • Soluble Potash (K).
  • A statement of each secondary plant nutrient in the mixture.
  • Chlorine content stated as a maximum percentage in the mixture.
organic matter
Organic matter
  • Vegetables require the richest soils of all farm crops for best quality and growth.
  • Organic matter is key to the soil - foundation for the microbiological life of the soil.
organic matter29
Organic matter
  • Source of plant food and physical stability
  • Opens heavy soils up so they are more easily workable and binds sandy soil so that it holds water better.
  • The quantity and quality of organic matter is essential for microbial life in the soil. Microbes grow and decay, solubilize minerals and liberate carbon dioxide.
  • Organic matter in heavy soils allows them to be more easily worked, is a source of plant food, stabilizes the soil physically.
  • Well made compost has been shown to have plant growing benefits such as nutrients as well as “suppression of plant diseases and increasing plant resistance to stress”.
  • Making compost:
    • straw bale enclosure 2 - 3 bales high
    • 2 to 3” layers of straw
    • 1 to 6”layers of green ingredients
    • layer of topsoil over the green layer
    • compost ready in a year and ½, ~ 3 to 6 months in La.
soil fertility compost
Soil fertility - Compost
  • Composting is a form of aerobic digestion where original raw substances are transformed into stable humus.
    • Composted organic matter is used as a long-term soil builder.
    • Composted manure - long a staple for soil improvement for vegetable growing.
green manure crops
Green manure crops
  • Crop grown due to their benefits to the soil.
    • Soil organic matter
    • Help protect against erosion
    • Retain nutrients
    • Suppress germination and growth of weeds
    • Cycle nutrients from the lower soil layers to the upper layer
    • Legumes - provide N to the following crop
what makes a successful organic garden
What makes a successful organic garden?
  • Crop selection:
    • mix of crops /rotation; cool season/warm season crops

Average last spring freeze

what makes a successful organic garden40
What makes a successful organic garden?
  • Stand establishment
    • Seed quality (organic seed)
    • Transplant vs. direct seeding
transplant mix
Transplant Mix
  • Classic soil-based mix
  • 1/3 mature compost or leaf mold, screened
  • 1/3 garden topsoil
  • 1/3 sharp sand
  • Organic substitute for Cornell Mix
  • ½ cu. yd. sphagnum peat½ cu. yd. vermiculite10 lbs. bonemeal5 lbs. ground limestone5 lbs. bloodmeal
  • PVFS 1.5 Cu Ft Organic Potting Soil –Peaceful Valley Gardening

Coco fiber (see Coco peat), beneficial mycorrhizae fungi, ms. worm castings, bat guano, bone meal, soybean meal, soft rock phosphate, greensand, fish meal, blood meal, langbenite (K-mag) and kelp meal.

OMRI Listed." OMRI — the Organic Materials Review Institute

what makes a successful organic garden42
Eating quality


Pest & disease restce

Days to maturity





Ease of harvest

Time of harvest

Frost restce & hardiness

Day length

Ease of cleaning


Ease of preparation




What makes a successful organic garden?

Variety selection -cultivars (cultivated varieties)

biointensive gardening
Biointensive Gardening

• Double-Dug, Raised Beds

• Composting

• Intensive Planting

• Companion Planting

• Carbon Farming

• Calorie Farming

• The Use of Open-Pollinated Seeds

• A Whole Gardening Method

  • The Biointensive gardening method is a whole system and all the components of the method must be used together for the optimum effect.

John Jeavons, 1995, How to Grow More Vegetables/

organic pest management
Organic Pest Management
  • Crop pests, weeds, and diseases will be controlled primarily through management practices including physical, mechanical, and biological controls.
  • When these practices are not sufficient, a biological, botanical, or synthetic substance approved for use on the National List may be used.
    • The National List of Allowed and Prohibited Substances
insect management
Insect management
  • Proactive Strategies (Cultural Controls)
  • Biological Controls
  • Mechanical Controls
  • Pest Identification
  • Monitoring
  • Economic Injury & Action Levels
proactive strategies cultural controls
Proactive Strategies (Cultural Controls)
  • Healthy, biologically active soils (increasing below ground diversity)
  • Habitat for beneficial organisms (increasing above ground diversity)
  • Appropriate plant cultivars (and season)
  • Cultural controls are manipulations of the agroecosystem that make the cropping system less friendly to the establishment and proliferation of pest populations.
biological control
Biological Control
  • Biological control is the use of living organisms —parasites, predators, or pathogens—to maintain pest populations below economically damaging levels, and may be either natural or applied.
  • Beneficial organisms should be viewed as mini-livestock, with specific habitat and food needs to be included in farm planning.
beneficial aspects of insects
Pollinators – bees for cucurbits

Food sources – part of the food chain

Biological control agents for weeds and other insects

Enhance soil properties

Aesthetic value

Beneficial Aspects of Insects
insects as vectors of plant diseases
Insects as vectors of plant diseases
  • Thrips- tomato spotted wilt virus
  • Aphids- watermelon, squash, cucumber mosaic viruses
  • Cucumber beetles- bacterial wilt of cucumbers
  • Grasshoppers- tobacco mosaic virus
insect pest mgt cultural practices
Insect Pest Mgt: Cultural Practices
  • Companion planting/intercropping
  • Soil tillage- bury insects or expose them to adverse weather
  • Physical control - hand picking insects
  • Clean - insect-free transplants
  • Reflective mulches
  • Row covers

Tomato and marigolds

insect pest mgt cultural practices51
Insect Pest Mgt: Cultural Practices
  • Crop rotation
  • Time of planting – early, season etc.
  • Tolerant/resistant cultivars
  • Trap cropping
  • Traps and lures
biological natural pest controls
Biological /Natural Pest Controls
  • Green lacewings- aphids and other soft bodied insects, mites and eggs
  • Lady beetles- aphids and other soft bodied insects, mites and eggs
  • Trichogamma wasps- moth larva
biological natural pest controls53
Biological /Natural Pest Controls
  • Preying mantid- general feeder
  • Minute pirate bug- soft bodied insects
  • Parasitic nematodes – parasitic nematodes
biological insecticides and repellents
Biological insecticides and repellents
  • Bt (Bacillus thuringiensis v. kurstaki) Dipel DF, - moth larvae
  • Bt v. israelensis – fungus gnat
  • Bt v. san diego tenebrionis – Colorado potato beetle
  • Milky spore disease- Japanese grubs and beetles
  • Garlic, hot pepper or mixtures of these
  • Pyrethrins
  • Rotenone
  • Sabadilla
  • Tobacco – not allowed
mineral soaps and oils
Mineral soaps and oils
  • Insecticidal soap
  • Oils
  • Diatomaceous earth
disease management

Disease Management

Causal Organisms





Others (mycoplasmas, viroids, spiroplasms)

cultural practices that reduce diseases
Cultural Practices that Reduce Diseases
  • Crop rotation
  • Scouting
  • Soil sterilization
  • Sanitation and rouging of diseased plants
  • Tolerant / Resistant varieties
  • Solarization – plastic mulch
  • Plastic mulch - reflective materials (silver)
  • Compost teas
chemical control within organics
Chemical Control Within Organics
  • Some copper and sulfur products are allowed
  • Excessive use of copper can lead to toxicities
  • Be careful with “inert” ingredients
  • Curcubits are sensitive to sulfur compounds
  • Really no effective chemical control for viral diseases and few for bacteria.
weed problems associated with weeds
Weed - Problems Associated With Weeds
  • Weed competition for light, water, nutrients etc. can reduce yields
  • Harbor pests and disease
  • Can reduce crop quality
  • Interfere with harvest
benefits of weeds
Benefits of “Weeds”
  • Prevent erosion
  • Take up nutrients normally lost due to leaching
  • Reduce insect damage to crops
  • Harbor beneficial insects
  • Improve soil quality
  • Aesthetic value
  • Medicinal value
  • Food value
weed survival mechanisms
Weed Survival Mechanisms
  • Seed longevity
  • Large number of seeds produced
  • Dormancy
  • Vegetative structures – tubers, nutlets
  • Sometimes difficult to detect in crop
  • Survive adverse conditions
cultural weed mgt strategies
Cultural Weed Mgt Strategies
  • Mulch – organic/plastic
  • Mechanical – hoeing/cultivation
  • Crop rotation
  • Flame weeding
  • Cover crops
  • Soil solarization
cultural weed mgt strategies cont
Cultural Weed Mgt. Strategies (cont.)
  • Use of transplants
  • Clean equipment
  • Avoid weeds in transplants, mulch, manure
  • Prevent weeds from flowering
  • Weed early
  • Crop canopy development
wheel hoe
Wheel hoe
  • Oscillating stirrup hoes (6 to 14”)
  • Can be fitted with 2 wheels and straddle the crop and cultivate 2 rows at once.
  • Plow attachments to turn a single furrow - bury the edge of plastic mulch or floating row covers.
Hoe cultivation:
  • Not want to move excess soil (bury seedlings/throw soil on plants) - therefore the blade should be narrow and thin.
  • Action with the hoe should be accurate so as to not damage the plants. Work should be shallow and not cut crop roots - skim not chop the soil.
cultivating hoe
Cultivating hoe
  • Hand and body position:
    • Both thumbs up
    • Stand comfortably upright
  • Razor edge - increase the efficiency of cultivation
  • Tool weight - the lighter the implement, the less expenditure of energy
flame weeding
Flame weeding
  • Flame or heat to kill weeds
  • Weed scorcher - 1839, heat to kill weeds
  • Flame weeders using liquid fuel patented in the US in 1852.
  • Since the 1940’ - liquid propane used - clean burning and leaves no residue.
biological control of weeds
Biological Control of Weeds
  • Animals (fish, goats, geese, chickens)
  • Insects (klamath beetle)
  • Pathogens (strangle weed in citrus)
  • Corn gluten
lsu organic garden plots
LSU Organic Garden Plots
  • Raised beds: 5 to 6 feet wide, semi-permanent, friable, weed free (?)
  • 3 years - organic production methods, not certified
  • Fertility:
    • green manure cover crops in winter
    • compost (manure) application in spring
    • weekly applications during fall semester class: fish emulsion and/or seaweed extract
  • Irrigation
    • manual watering, overhead sprinklers (trickle?)
lsu organic garden student plots
LSU Organic Garden Student Plots
  • Vegetables, herbs, flowers -
    • use healthy transplants where possible to “get an instant garden”
    • plant in “proper” season
    • direct seeding - viable seed, follow directions on spacing
  • Companion plantings/trap crops
  • Biointensive / square foot gardening
    • 5 by 10 foot raised bed
pests at organic teaching plots
Pests at Organic Teaching Plots
  • Insects:
      • Physical removal
      • garlic/pepper sprays, Bt, rotenone?
      • Companion plantings, trap crops, crop diversity
      • Beneficials (Lady Beetles, Lacewings)
pests at organic teaching plots72
Pests at Organic Teaching Plots
  • Weeds:
      • transplants
      • physical control early (pull, hoe)
      • mulch- straw, plastic
      • Flame weeding
  • Diseases:
      • Resistant cultivars
      • Healthy plants
      • Growing in the “correct” season?
      • Rotations, cover crops
lsu organic garden student plots73
LSU Organic Garden Student Plots
  • Fall 2002 - biointensive / square foot gardening
    • 1999 - 5 by 20 foot raised bed
    • 2000 - 5 by 15 foot raised bed
    • 2001 - 2005 - 5 by 10 foot raised bed
book references
Book References
  • Eliot Coleman, 1995, the New Organic Grower: a Master’s Manual of Tools and Techniques for the Home and the Market Gardener.
  • John Jeavons, 1995, How to Grow More Vegetables (than you ever thought possible on less land than you can imagine)
  • Rodale’s References
  • G. Gershuny and J. Smillie, 1995, the Soul of Soil: a Guide to Ecological Soil Management.
slide75 Appropriate Technology Transfer to Rural Areas (USDA funded site) Rodale Institute Rural Advancement Foundation International USA Organic Farming Research Foundation Organic Materials Review Institute Howard Garrett's Basic Organic Program The Soil Foodweb International Federation of Organic Agriculture Movements