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Assessing and Supplying Fertilizer
Needs Under Organic Systems
M. Elena Garcia, Professor
Horticulture Dept.
University of...
Conventional vs. Organic Plant
Nutrition
Fundamental principles the same, whatever the
production system used:
Conventiona...
Plant Nutrition in Organic
Systems
Organic systems: Long-term solutions
and ecological approach
Preventive not reactive
Wo...
Organic Fertilizers
Naturally occurring materials of
biological or mineral origin and are low
in nutrient concentration or...
Advantages and Disadvantages
of Organic Fertilizers
Advantages
Mild, non-caustic
materials
Slow release makes them
availab...
Conventional vs. Organic Plant
Fertilizers
Difference between organic and
synthetic fertilizers:
Not in the kind of nutrie...
Organic Regulations
Organic regulations require growers to
rely on the use of manures, cover crops,
crop rotations, and th...
Organic Horticulture Systems
Intensive
High dependency on imported nutrients
Crops have high demand for major and
minor nu...
The Fertility Equation: Soil
The ability of the soil to supply nutrients
needed for plant growth.
Recognize:
physical,
bio...
Soil Quality
Capacity of a soil to function within
ecosystem boundaries to:
Sustain biological activity
Maintain environme...
Soil Health
Physical Chemical
Biological
Overlapping of the
physical, chemical,
and biological
properties
•General picture...
Ability of Soils to Supply Nutrients
Soil texture
Soil chemistry
Soil moisture
Soil tilth
Soil aeration
Soil Organic Matter (SOM)
Organic matter will prevent deterioration
of the physical properties of the soil by
serving as a...
Using Organic Amendments to
Improve Fertility
 Organic amendments
increase OM content in
soil
 OM increases CEC,
increas...
Plant Available N
Knowing total amounts of N-P-K does not
tell how much is available
Manure: total N is ~ 25-40%
Available...
Plant Available Nitrogen (PAN) from Amendments ( Gale et al)
PAN (%)
Amendment C:N NH4-N (g kg-1 Field Lab
Dry broiler lit...
SOM, pH and Buffering Capacity
SOM has ability to moderate major
changes in pH
Soil pH is determined by amount of
positive...
Pre-Plant Preparations
Soil analysis must!!
Adjust pH prior to planting.
Difficult to change pH after establishment.
Addit...
Cover Crops
• Grasses or legumes
grown in pure or mixed
stands
• Planted after harvest of
primary crop, as a fallow
crop, ...
Crop Residue
• Portion of plant
remaining after harvest
left on soil surface
• Widely used method of
maintaining OM
• May ...
Mulches
Helps keep soil cool in summer
Helps retain soil moisture
Adds organic matter, helps in nutrition
Improves soil st...
Tillage Effects on Fertility
• Purpose:
– Prepare seedbed
– Control weeds
– Break up traffic pans &
soil compaction
– Inco...
Effect of pH and Element
Availability in Mineral Soils
organicgarden.org.uk/?page_id=2387
Nutrient Budgets
Commonly used to evaluate the effects
of nutrient management on farm and
field sustainability
Are the out...
The Nutrition Equation
Balancing Act
Soil
Plant needs
The Fertility Equation: Plant Demand
Plant health
Ability of root system to absorb nutrients
Soil type
pH
Soil water conte...
Essential Elements
16 elements are classified as essential
for all crops
Two criteria are used to establish the
essentiali...
Law of the Minimum
Justus von Liebig, generally credited as the "father of
the fertilizer industry", formulated the law of...
Essential Elements
From air
Carbon: CO2
Hydrogen: H2O
Oxygen: H2O and O2
Plant Needs for Growth and
Development
Macronutrients
Nitrogen: NH4
+,NO3
-
Phosphorus: H2PO4
-, HPO4
2-
Potassium: K+
Cal...
Plant Needs
Micronutrients:
Iron, Zinc,
Manganese, Copper,
Boron, Molybdenum,
Chlorine, Silicon,
Sodium, Cobalt,
Vanadium ...
Role of Mineral Nutrients
Mineral nutrients affect crop quality and
yield
Direct
Indirect
N excess over stimulates growth:...
Flow of Nutrients into Plant
Simplistic view
Xylem transports
water and mineral
nutrients from roots to
the rest of the tr...
Nutrient Movement from Soil to Plant
Mobile vs. immobile elements
Ionic
Form
Soil Mobility Plant Mobility
N NH4+
NO3-
Immobile
Mobile
Immobile
Mobile
P H2PHO4- -Immobile Immobile
K K+ -Imm...
Monitoring Mineral Nutrition
Knowledge of:
Site/soil characteristics and chemistry
Plot design requirements
Plant physiolo...
Nutrient Status Limitations
Crop
Rootstock
Variety
Soil depth
Root distribution
Soil water status
Temperature
Crop load
So...
Nitrogen Utilization
Tagliavini, et al. 2000
Phosphorous Utilization
Tagliavini, et al. 2000
Interactions
N: Too much = Poor fruit quality
Too much N may create nutrition imbalances
N deficiencies common in organic ...
Diagnosing Nutritional Status
Soil analyses: Tell what is in the soil– pH, OM
Limitations:
Sampling
Time
Depth
Foliar anal...
Soil vs. Foliar Analyses
Many studies show poor correlation
between soil tests and leaf analyses in
orchards
Deep rooted
A...
Ground vs. Foliar Application
The most efficient way to apply nitrogen,
phosphorus, potassium, and magnesium is
by ground ...
Sources for Organic Fertilizers
Sources of Organic Fertilizers, and
amendments
http://attra.ncat.org/attra-pub/orgfert.php...
Acknowledgements
This presentation address general organic production practices. It is to be
to use in planning and conduc...
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Organic fertilizers

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Organic Fertilizers

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Organic fertilizers

  1. 1. Assessing and Supplying Fertilizer Needs Under Organic Systems M. Elena Garcia, Professor Horticulture Dept. University of Arkansas
  2. 2. Conventional vs. Organic Plant Nutrition Fundamental principles the same, whatever the production system used: Conventional systems: Relies on targeted short-term solutions Reactive Application of soluble fertilizers
  3. 3. Plant Nutrition in Organic Systems Organic systems: Long-term solutions and ecological approach Preventive not reactive Work within natural systems and cycles Maintain or increase long-term soil fertility Use renewable resources as much as possible Management of soil organic matter (OM) Rotation design for nutrient cycling
  4. 4. Organic Fertilizers Naturally occurring materials of biological or mineral origin and are low in nutrient concentration or solubility or have both properties May be altered physically in processing for agricultural use, but chemical processing does not usually occur (Baker, 2010)
  5. 5. Advantages and Disadvantages of Organic Fertilizers Advantages Mild, non-caustic materials Slow release makes them available for longer time If high OM content = improvements in soil physical properties Sources of many essential elements Recycling of materials Disadvantages Low concentration of nutrients = large application Slow release may not supply plant’s immediate needs Concentration may be too low to supply plant’s needs Expense
  6. 6. Conventional vs. Organic Plant Fertilizers Difference between organic and synthetic fertilizers: Not in the kind of nutrients supplied but, Rate of release Generally: Organic fertilizers release nutrients slowly and in response to environmental factors such as soil moisture and temperature
  7. 7. Organic Regulations Organic regulations require growers to rely on the use of manures, cover crops, crop rotations, and the use of untreated products
  8. 8. Organic Horticulture Systems Intensive High dependency on imported nutrients Crops have high demand for major and minor nutrients Usually several crops within one growing season Crop rotation difficult in perennial systems Soli fertility maintenance major concern
  9. 9. The Fertility Equation: Soil The ability of the soil to supply nutrients needed for plant growth. Recognize: physical, biological, and chemical components these are interrelated.
  10. 10. Soil Quality Capacity of a soil to function within ecosystem boundaries to: Sustain biological activity Maintain environmental quality Promote “plant health” It is not a soil property Soil health = soil quality
  11. 11. Soil Health Physical Chemical Biological Overlapping of the physical, chemical, and biological properties •General picture of soil’s capacity to support plant growth without degradation… sustainability
  12. 12. Ability of Soils to Supply Nutrients Soil texture Soil chemistry Soil moisture Soil tilth Soil aeration
  13. 13. Soil Organic Matter (SOM) Organic matter will prevent deterioration of the physical properties of the soil by serving as an energy source (i.e. food) for microorganisms which promote stable aggregation of the soil particles. Essential nutrients are obtained by plants as organic matter decomposes
  14. 14. Using Organic Amendments to Improve Fertility  Organic amendments increase OM content in soil  OM increases CEC, increasing nutrient storage capabilities  OM supplies plant nutrients  OM improves buffering capacity (stabilizes pH)  OM promotes/aides beneficial microbial populations  Types of Organic Amendments: – Animal Manure – Cover Crops – Crop residues – Yard debris – Biosolids
  15. 15. Plant Available N Knowing total amounts of N-P-K does not tell how much is available Manure: total N is ~ 25-40% Available N in compost is < 10% (stabilized from)
  16. 16. Plant Available Nitrogen (PAN) from Amendments ( Gale et al) PAN (%) Amendment C:N NH4-N (g kg-1 Field Lab Dry broiler litter 9 6.3 41 45 Composted dry broiler litter 9 7.3 38 45 Composted chicken litter 8 5.6 47 25 Yard-trimmings 13 3.0 19 25 Composted yard trimmings 17 0.7 3 5 Bio-Gro pelleted fish byproduct 5 1.1 77 57 Feather meal 4 2.0 99 74 On-farm compost 15 0.1 6 4 Composted rabbit manure 27 0.1 -6 -7
  17. 17. SOM, pH and Buffering Capacity SOM has ability to moderate major changes in pH Soil pH is determined by amount of positively charged H ions (H+) in the soil solution OM buffers the soil Making H+ more constant Taking and releasing H+
  18. 18. Pre-Plant Preparations Soil analysis must!! Adjust pH prior to planting. Difficult to change pH after establishment. Addition soil amendments prior to planting. Generally, fruits crops do not respond P applications after establishment.
  19. 19. Cover Crops • Grasses or legumes grown in pure or mixed stands • Planted after harvest of primary crop, as a fallow crop, or interplanted with primary crop • Can be incorporated into soil or left on surface as residue • Sometimes referred to as green manure, catch crop, or living mulch depending on purpose • Benefits: – Reduced soil erosion – Improve soil structure – Suppress of weeds, insects, and diseases – Enhance soil fertility • Increases OM content • Retention of nutrients • Prevention of leaching losses • Increases N content • Greater diversity of soil microbes
  20. 20. Crop Residue • Portion of plant remaining after harvest left on soil surface • Widely used method of maintaining OM • May be partially incorporating at planting time • Can harbor disease and insect pests – May be avoided by: crop rotation, removing residue to compost it, or proper timing of incorporation • Benefits: – Increases OM content – Increases soil aggregation – Prevents soil crusting and erosion – Improves water infiltration rates – Provides nutrients
  21. 21. Mulches Helps keep soil cool in summer Helps retain soil moisture Adds organic matter, helps in nutrition Improves soil structure Helps reduce weed pressure Increases soil water holding capacity
  22. 22. Tillage Effects on Fertility • Purpose: – Prepare seedbed – Control weeds – Break up traffic pans & soil compaction – Incorporate crop residue • Tillage and cultivation practices should be implemented that maintain or improve soil health and minimize soil erosion. • Negative effects of conventional tillage on fertility: – Destroys soil organic matter – Decreases diversity and populations of soil microbes and earthworms – Decreases water infiltration rates – Increases compaction
  23. 23. Effect of pH and Element Availability in Mineral Soils organicgarden.org.uk/?page_id=2387
  24. 24. Nutrient Budgets Commonly used to evaluate the effects of nutrient management on farm and field sustainability Are the outcome of a simple accounting process that tracks inputs and outputs to a given, defined system over a fixed period of time Useful when accounting for renewable resources in production and processing as a way to avoid pollution and waste.
  25. 25. The Nutrition Equation Balancing Act Soil Plant needs
  26. 26. The Fertility Equation: Plant Demand Plant health Ability of root system to absorb nutrients Soil type pH Soil water content Ability of plant to utilize nutrients Physiological stage Crop load Weed control
  27. 27. Essential Elements 16 elements are classified as essential for all crops Two criteria are used to establish the essentiality If the plant fails to grow and complete its life cycle without this element Constituent of a necessary metabolite b
  28. 28. Law of the Minimum Justus von Liebig, generally credited as the "father of the fertilizer industry", formulated the law of the minimum: if one crop nutrient is missing or deficient, plant growth will be poor, even if the other elements are abundant.
  29. 29. Essential Elements From air Carbon: CO2 Hydrogen: H2O Oxygen: H2O and O2
  30. 30. Plant Needs for Growth and Development Macronutrients Nitrogen: NH4 +,NO3 - Phosphorus: H2PO4 -, HPO4 2- Potassium: K+ Calcium: Ca++ Magnesium: Mg++ Sulfur: SO4 2-
  31. 31. Plant Needs Micronutrients: Iron, Zinc, Manganese, Copper, Boron, Molybdenum, Chlorine, Silicon, Sodium, Cobalt, Vanadium essential to some plants
  32. 32. Role of Mineral Nutrients Mineral nutrients affect crop quality and yield Direct Indirect N excess over stimulates growth: Fruit often softer, does not store as well Shading causes loss of color in fruit
  33. 33. Flow of Nutrients into Plant Simplistic view Xylem transports water and mineral nutrients from roots to the rest of the tree Phloem transports leaf-assimilated compounds through the stems to roots Mature leaf Fruit Roots xylem Phloem
  34. 34. Nutrient Movement from Soil to Plant Mobile vs. immobile elements
  35. 35. Ionic Form Soil Mobility Plant Mobility N NH4+ NO3- Immobile Mobile Immobile Mobile P H2PHO4- -Immobile Immobile K K+ -Immobile Mobile S SO4- Mobile Mobile Ca Ca+ Immobile -- Immobile Mg Mg++ Immobile Mobile B H3BO3 Mobile --Immobile Zn Zn++ --Immobile Immobile Cu Cu++ --Immobile Immobile Mn Mn++ --Immobile Immobile Mo MoO4- Immobile Immobile
  36. 36. Monitoring Mineral Nutrition Knowledge of: Site/soil characteristics and chemistry Plot design requirements Plant physiological stages Fertilizer inputs Cultural practices Tissue analysis Observation and judgment
  37. 37. Nutrient Status Limitations Crop Rootstock Variety Soil depth Root distribution Soil water status Temperature Crop load Soil pests Soil Chemistry / nutrient availability
  38. 38. Nitrogen Utilization Tagliavini, et al. 2000
  39. 39. Phosphorous Utilization Tagliavini, et al. 2000
  40. 40. Interactions N: Too much = Poor fruit quality Too much N may create nutrition imbalances N deficiencies common in organic orchards during establishment years K: Pre-planting applications Depletion common Adding K without Mg can create Mg deficiencies P: Pre-plant application very important Too much P can create Zn and Cu deficiencies
  41. 41. Diagnosing Nutritional Status Soil analyses: Tell what is in the soil– pH, OM Limitations: Sampling Time Depth Foliar analyses: Tell what is actually in the plant Limitations: Sampling Time Condition of sample
  42. 42. Soil vs. Foliar Analyses Many studies show poor correlation between soil tests and leaf analyses in orchards Deep rooted Accumulation of nutrients through out the year IMPORTANT TO DO BOTH ON A REGULAR BASIS!
  43. 43. Ground vs. Foliar Application The most efficient way to apply nitrogen, phosphorus, potassium, and magnesium is by ground application. Foliar applications of these elements should be viewed as temporary or emergency solutions only. Boron, zinc, copper, and manganese can be added by either foliar or ground application. The foliar method is usually preferred because very small amounts are applied per acre.
  44. 44. Sources for Organic Fertilizers Sources of Organic Fertilizers, and amendments http://attra.ncat.org/attra-pub/orgfert.php How to convert an inorganic fertilizer recommendation into an organic one http://pubs.caes.uga.edu/caespubs/pubs/PDF/C 853.pdf crops_generic.pdf http://www.omri.org/
  45. 45. Acknowledgements This presentation address general organic production practices. It is to be to use in planning and conducting organic horticulture trainings. The presentation is part of project funded by a Southern SARE PDP titled “Building Organic Agriculture Extension Training Capacity in the Southeast” Project Collaborators • Elena Garcia, University of Arkansas CES Heather Friedrich, University of Arkansas Obadiah Njue, University of Arkansas at Pine Bluff Jeanine Davis, North Carolina State University Geoff Zehnder, Clemson University Charles Mitchell, Auburn University Rufina Ward, Alabama A&M University Ken Ward, Alabama A&M University Karen Wynne, Alabama Sustainable Agriculture Network

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