Agriculture Reference
In-Depth Information
crease for several years after each application. Unlike a conventional orch-
ard where soil nutrient concentrations can be changed quickly, we want to
change organic soils gradually, nudging them into the desired condition and
not overshooting the mark.
Phosphorus
Phosphorus is rather a puzzle when it comes to orchard crops. Although it
is required by plants and soils can be deficient in available phosphorus, we
seldom see shoot growth or fruit yield increases following phosphorus fertil-
ization of fruit trees.
Ways to Add Phosphorus
Rock phosphate,
also called hard rock phosphate, is mined from ancient
ocean deposits and contains only 1 to 2 percent available phosphate in a
form that is available very slowly to most plants, particularly in alkaline
soils. It typically becomes available over a period of years to centuries. From
economic and horticultural perspectives, this is an inefficient and expensive
form of phosphorus.
Colloidal phosphate,
also known as soft rock phosphate, consists of clay
particles surrounded by naturally derived phosphorus. Although it contains
around 20 percent phosphorus, only about 2 to 3 percent is available phos-
phate. Its phosphorus is also available to plants slowly, but it is more readily
available than the phosphorus from hard rock phosphate.
Bonemeal
is a rich source of phosphorus that is readily available to plants.
Use steamed bonemeal to reduce the risk of pathogens that can infect hu-
mans. Other organic sources of phosphorus are available, although most
have low concentrations of phosphorus.
Wood ashes
can be added to supply phosphorus if potassium is low and the
