Tree Fruit Soils and Nutrition



Soil Nutrient Cycling

  • Materials are broken down by macro and meso-fauna
  • Nutrients are taken up and converted by lower life forms in the soil
  • They convert these nutrients to organic forms within the cell or to inorganic forms released to soil
  • These organisms die and are decomposed by other organisms
  • This also releases inorganic ions for plant or other microbe uptake and…
  • The cycle starts all over

Nitrogen Cycle: Nitrogen is the nutrient needed in largest amounts by plants and is the most commonly applied fertilizer. Excess N can have negative affects on plant growth and crop quality as well as harming the environment, especially water quality.

Nitrogen is present in one of five forms in soil:

  1. Organic N: 90% of N is in organic form. It must be mineralized to become available.
  2. Ammonium N (NH4+): Inorganic, soluble form
  3. Nitrate (NO3-): Inorganic, soluble form
  4. Atmospheric N (N2): 80% of atmosphere but unavailable to most plants except N-fixers
  5. Nitrite (NO2-): only under anaerobic conditions. This form is toxic to plants and normally will not be present in significant amounts in soil.

Mineralization vs Immobilization

Mineralization - the release of organically bound nutrients in an inorganic form usable to organisms and/or plants

Immobilization - the conversion of an element from the inorganic to the organic form unavailable to plants

C:N (carbon to nitrogen) ratios

  • Low C:N ratios (<25:1) are indicative of mineralization and rapid rates of decomposition
  • High C:N ratios (>25:1) indicate immobilization and slower decomposition rates
  • Low C:N materials (high N values)
    – Undiluted manure and blood meal, grass clippings (can get high), vegetable wastes
  • Intermediate C:N materials
    – Most composts, leaf mulches, cover crop residues
  • High C:N materials
    – Straw, bark, wood chips, sawdust, paper, cornstalks, foliage

Composting and your garden

  • Excellent source of organic matter
  • Turn kitchen scraps into soil amendments
  • Key is to balance air, water, and energy materials and bulking agents.
  • Four main systems:
    – hot (fast), cold (slow), worm bins, or soil trenches.
  • Excellent source: Backyard Composting in the 1990s,

Using Compost

  • Add 1-2 inches of compost each year
  • Compost “teas” are very beneficial in gardens and house plants.
  • One cubic yard of compost covers about 300 square feet 1 inch deep
  • Be cautious of C:N materials and watch for N deficiencies.


Next page: 13 essential nutrients & fertilizers



Updated July 15, 2004


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