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FACTORS AFFECTING FERTILIZER UPTAKE
FACTORS AFFECTING FERTILIZER UPTAKE
Factors Affecting Fertilizer Uptake
Contact: Diane Relf, Extension Specialist, Environmental Horticulture
Posted April 1997
There are numerous factors that affect how easily and well trees and
shrubs will take up fertilizers. The most important of these is fertilizer
form. Generally, inorganic, fast-release, or liquid forms are faster-acting
than organic, slow-release, or dry forms. Compared to synthetic fertilizer
formulations, most organic fertilizers contain relatively low concentrations
of actual nutrients.
- Soil composition-- Soils high in clay particles will absorb
(bind to their surface) more nutrients, while fertilizer will leach (wash
through) faster through sandy soil. Organic matter in the soil increases
its nutrient-holding capacity and contributes nutrients upon its breakdown.
- Soil microorganisms-- Some fungi and bacteria may "tie
up" nutrients while others convert the fertilizer to a form that the
plant can take up. Some microorganisms are involved in mutually beneficial
(symbiotic) relationships with plants. Rhizobium bacteria grow within the
roots of some plants. They convert nitrogen from the air into a usable
form for the plant while obtaining nutrition from the host plant.
- Soil pH-- Extremes in pH affect availability of plant nutrients
and the concentration of plant-toxic minerals. At low pH levels, calcium,
phosphorus, and magnesium become unavailable and manganese can concentrate
at toxic levels. At high pH values, phosphorus, iron, copper, zinc, boron,
and manganese become less available.
- Nutrient availability-- Nutrients may be present but may first
require conversion to an "available" form that the plant is capable
of taking up and utilizing. Conversion to an available form is affected
by soil microorganisms, pH, soil moisture and chemical reactions.
- Soil moisture content-- Most nutrients are taken up via the
soil solution, so soil water is needed to dissolve them.
- Soil aeration-- Oxygen is needed in the soil to help roots with
uptake processes. Where there is no oxygen, such as in flooded sites, sugar
cannot be utilized by the plants to produce energy for nutrient uptake.
Decomposed organic matter helps develop good air-water relationships in
the soil.
- Soil temperature-- Nutrient uptake is faster in warmer soils
than in cold soils.
- Plant condition-- Plants under stress will be less able to take
up nutrients, generally due to a reduced or damaged root system.
- Competition-- If the roots of many plants occupy an area, a
reduced amount of nutrients will be available for each. When using close
spacing for vegetable plants, more fertilizer will be needed in a bed than
in a conventionally spaced row garden. Weeds where present will take up
nutrients intended for landscape or crop plants. Reduction of weeds will
reduce fertilizer needs.
(Prepared by Virginia Nathan, Extension Technician, Consumer Horticulture, Virginia Tech, Blacksburg, VA 24061-0327, and approved by Bonnie Appleton, Extension Specialist, Nursery Crops.)
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