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Assessing and Supplying Fertilizer Needs Under Organic Systems

Assessing and Supplying Fertilizer Needs Under Organic Systems. M. Elena Garcia, Professor Horticulture Dept. University of Arkansas . Conventional vs. Organic Plant Nutrition . Fundamental principles the same, whatever the production system used: Conventional systems:

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Assessing and Supplying Fertilizer Needs Under Organic Systems

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  1. Assessing and Supplying Fertilizer Needs Under Organic Systems M. Elena Garcia, Professor Horticulture Dept. University of Arkansas

  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. 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. 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. Advantages and Disadvantages of Organic Fertilizers Advantages 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 • 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

  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. Organic Regulations • Organic regulations require growers to rely on the use of manures, cover crops, crop rotations, and the use of untreated products

  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. 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. 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. Soil Health • Overlapping of the physical, chemical, and biological properties • General picture of soil’s capacity to support plant growth without degradation… sustainability Physical Chemical Biological

  12. Ability of Soils to Supply Nutrients • Soil texture • Soil chemistry • Soil moisture • Soil tilth • Soil aeration

  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. 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. 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. 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+

  17. 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.

  18. 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

  19. 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

  20. 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

  21. 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

  22. Effect of pH and Element Availability in Mineral Soils organicgarden.org.uk/?page_id=2387

  23. 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.

  24. Plant needs Soil The Nutrition Equation Balancing Act

  25. 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

  26. 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

  27. 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.

  28. Essential Elements • From air • Carbon: CO2 • Hydrogen: H2O • Oxygen: H2O and O2

  29. Plant Needs for Growth and Development • Macronutrients • Nitrogen: NH4+,NO3- • Phosphorus: H2PO4-, HPO42- • Potassium: K+ • Calcium: Ca++ • Magnesium: Mg++ • Sulfur: SO42-

  30. Plant Needs • Micronutrients: • Iron, Zinc, Manganese, Copper, Boron, Molybdenum, Chlorine, Silicon, • Sodium, Cobalt, Vanadium essential to some plants

  31. 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

  32. xylem Phloem Roots 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

  33. Nutrient Movement from Soil to Plant • Mobile vs. immobile elements

  34. 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

  35. Nutrient Status Limitations • Crop • Rootstock • Variety • Soil depth • Root distribution • Soil water status • Temperature • Crop load • Soil pests • Soil Chemistry / nutrient availability

  36. Nitrogen Utilization Tagliavini, et al. 2000

  37. Phosphorous Utilization Tagliavini, et al. 2000

  38. 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

  39. 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

  40. 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!

  41. 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.

  42. 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/

  43. 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 CESHeather Friedrich, University of ArkansasObadiah Njue, University of Arkansas at Pine BluffJeanine Davis, North Carolina State UniversityGeoff Zehnder, Clemson UniversityCharles Mitchell, Auburn UniversityRufina Ward, Alabama A&M UniversityKen Ward, Alabama A&M UniversityKaren Wynne, Alabama Sustainable Agriculture Network

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