Agriculture Reference
In-Depth Information
8.2 ppm - 1.07 ppm = 7.13 ppm Copper needed
We need to add 7.13 ppm of Copper to this soil.
Zinc Zn
The Ideal Soil chart says Zinc should equal 1/10 of Phosphorus. In the last chapter
we determined our ideal Phosphorus level for this soil to be 178 ppm (100 ppm in
the soil, plus 78 ppm to be added).
178 ppm x 0.10 =
17.8 ppm
total is our desired level of Zn.
The soil report reading for Zinc is 16.4ppm
17.8 ppm - 16.4 ppm = 1.4 ppm. This is less than 10% of the ideal total, and well
within the margin of error for soil sampling and lab testing. It is close enough.
We do not need to add any Zinc.
That's it. We are done calculating the amounts of the primary and secondary
minerals that need to be amended. Next we will take a brief look at the trace
minerals and micro-elements, and then we will be ready to write the soil
prescription.
The completed soil report with all of our work so far is on the page following the
comments about Copper and Zinc below
Notes on Fertilizing with Copper and Zinc:
The Ideal Soil guidelines are for elemental Zinc to be at 10% of elemental
Phosphorus by weight, and for Copper to be 1/2 of Zinc.
Caution is advised when amending the Copper levels in the soil because "free"
Copper can be toxic to soil organisms as well as fish and other aquatic life. Keep
Copper out of streams and ponds; don't apply close to the water or where the Cu
can wash into to the water before it soaks into the soil.
As a general rule, it is safe enough to add 3.5 to 5 ppm of elemental Copper to
most soils at any one time. Soils that are high in organic matter, high CEC clays
with a good amount of Calcium, and high Ca soils in general have a large
buffering capacity and can easily adjust to higher amounts of Copper in a single
application than low CEC soils.
The Copper example above calls for 14 kg/ha or 7ppm of Copper. This is a safe
amount to add to this soil in a single application as long as the other minerals on
the soil Rx are added as well.
