Writing the Soil Rx - The Ideal Soil 2014 - page 80

It is generally safe to add 2200 kg/ha or 2200 lbs/ac (22 kg/100m 2 or
50lbs/1000ft 2 ) of any phosphate rock to any soil in a single application . Up to
twice that much may safely be added at once if the phosphate rock is a
non-reactive type like Calphos. If one needs to add a large amount of reactive rock
phosphate it should be split into two or more applications a few months apart, and
the soil's pH and Ca levels monitored, as reactive rock phosphates frequently have
a net acid reaction in soils.

Calcium Content of Phosphate Rock
The question arises: Should the amount of Calcium in the phosphate be counted
as contributing to Exchangeable Calcium? If it is a reactive phosphate, all of the
Ca will be chemically bonded with P or other anions. Ca will be released only
when the chemical bond is broken and the P is made available; it is not
available in the soil solution , not a free cation, and not available to fill a negative
exchange site. The same applies to phosphate sources like fish bones or crab
shells: the P and Ca are chemically bonded and the Ca is not readily available.

Phosphorus P ppm 100 Add 1733# Calphossoftrockphosphate

Non-reactive phosphates like Calphos may have some free Calcium but generally
not enough to remedy a Calcium deficiency. As a rule, do not count the
Calcium in any phosphate source when calculating the amount of Ca being
added to a soil.

We will add 1733 kg/ha (or 1733 lbs/acre) of Calphos soft rock phosphate

So far we have determined the amendments needed to bring us to the Ideal Soil
balance for the minerals P, Ca, Mg, K, and Na. We have provided part of the S, but
still need another 63 kg/ha or lbs/acre of Sulfur to reach our ideal level where S =
½ of Ideal K. The extra S needed will come from the sulfate forms of Iron,
Manganese, and Copper we will be adding.

Next we need to calculate the secondary elements Boron, Iron, Manganese,
Copper, and Zinc.

Boron B
There are several Boron compounds produced especially for agriculture, ranging
up to 20% B by weight. The easiest form of Boron to find in the USA, however, is
regular borax powder (sodium borate, 20 Mule Team Borax ) sold in the soap and
detergent section of grocery stores in the USA. It averages about 9% B by weight.

The worksheet calls for adding 1.34 ppm, which is 2.68 kg/ha or lbs/acre. Using
regular mined borax, Sodium borate 9%B, we will need 2.68 / 0.09 = 29.77# borax
(round up to 30#). We need to add 30# borax 9% B.