He wants P to me at 100 ppm on a soil test. Elemental not p202. 

What do you think about the below? Am I missing something when he says the deal soil level for P is 100 ppm? He defiantly isnt talking p202. Anyway would like some discussion on it !

Albrecht says below in which he is quoting a soil test he is analyzing-

P = Ideal K by weight (ppm) BUT: phosphate (P205) should be ~2X potash (K2O)

The equation above says that Potassium and Phosphorus should be equal by weight in the soil. If we are going to end up with 178 ppm of Potassium; we want to end up with 178 ppm of Phosphorus too. This gets a little tricky for a couple of reasons: • On a fertilizer label in the USA and some other countries, the letters N, P, and K do not stand for Nitrogen, Phosphorus, and Potassium. They stand for Nitrogen, phosphate, and potash. N is elemental Nitrogen, but phosphate is P2O5, 2 atoms of Phosphorus and 5 atoms of Oxygen. Potash is K2O, 2 atoms of Potassium and 1 atom of Oxygen. More on this below, but in effect the P on the fertilizer label is only 44% Phosphorus by weight, while the K on the fertilizer label is 83% Potassium by weight. There is almost twice as much Potassium by weight in potash as there is Phosphorus in phosphate. This is why the Ideal Soil chart says phosphate should be 2X potash.

The soil worksheet says that we need to add 78ppm or 156# elemental Phosphorus. In Chapter 4 on Phosphorus, Sulfur, and Chlorine we determined that phosphate, P2O5, is 44% Phosphorus by weight. Florida clay phosphate is 20% P2O5; 44% of 20% is: 0.20 x 0.44 = 0.088 or 9% actual P

The choice we make will depend on the type of soil we are working with, our proximity to the source, and the price at which it is available. As of 2013, the “rock” phosphate most commonly available in the US is Calphos brand colloidal clay phosphate from Florida, which we determined was 9% Phosphorus. 156 / 0.09 = 1733# of Calphos soft rock phosphate needed. 1733 lbs/ac or kg/ha is a lot of phosphate rock.. Is it too much to add all at once? No, because the readily available P2O5 is only 3%, so we are really applying only 60# of “available” P2O5.

It is generally safe to add 2200 kg/ha or 2200 lbs/ac (22 kg/100m2 or 50lbs/1000ft2 ) 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