Agriculture Reference
In-Depth Information
Because of its tendency to become immobilized in the soil, you may find
it beneficial to band phosphorus materials along your tree rows, rather than
broadcasting them throughout the orchard. Do not band materials that con-
tain boron, nitrogen, or potassium.
To make phosphorus available more quickly to your fruit trees, add the
phosphate materials to the soil 1 to 2 years before planting your trees and
then grow one or more green manure crops of buckwheat. Cornell University
reports that buckwheat is very effective at using these sources of phosphor-
us. When the buckwheat is tilled into the soil, the phosphorus in its tissues
becomes available to other plants. Be sure to till under the buckwheat before
it sets seeds because it can become a weed problem.
Potassium
Potassium is abundant in many North American soils and often does not
need to be added before planting an orchard. Check your soil analysis results
to see if potassium is deficient before adding this nutrient to your planting
site.
Ways to Add Potassium
Granite dust contains about 5 percent potassium, but little of it is available
for plant growth, and this material has little value for organic fruit growers.
If used, the potassium is most rapidly available on acidic soils. Granite dust
can contain silica, known to cause lung cancer. If you choose to apply granite
dust, use respiratory protection during all handling and application activities.
Greensand is a naturally occurring sandstone found worldwide, often in as-
sociation with other marine deposits of chalk and clay. It contains glaucon-
ite, a greenish-colored iron potassium silicate compound. Greensand typic-
ally contains about 6 percent K O and 1 to 2 percent P O . Both are very
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slowly available to plants, and greensand is best applied to an orchard dur-
ing preplant preparation. Greensand is more effective on sandy soils than on
heavier-textured soils.
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