Abstract

Potassium release was studied in a field in Clay loam soil in one of by the wheat fields of Ba'wiza site,
Mosul city (Nineveh Governorate) in the north of Iraq , dominate Ilite mineral, Batch equilibrium method was used
of an artificial root of calcium-saturated resin that was field-placed to a depth of 10 centimeters, for a period of 35
days . The potassium release towards the resin reservoir was described using the parabolic diffusion equation, in
which it was clear that the release capacity decreased with the increase in the contact time of the resin with the soil,
and that the release process went through two phases (the first rapid expressed the alternating phase with a release
capacity of (29.87) mg.kg-1. With a coefficient of releasing rate of (5.21) mg.kg.min 0.5, it increased to a releasing
capacity of (5.21) mg.kg-1, and with a coefficient of releasing velocity (16.82) mg.kg.min 0.5 after biochar addtion
As for the second stage of the release path, which expressed the non-exchangeable phase responsible for the
process of release and food processing in long periods, it was characterized by a release capacity of (216.77) mg.kg-
1 and a rate coefficient of (16.91) mg.kg. minutes 0.5 before addtion. It increased to a release capacity of (1030.50)
mg.kg-1. With a coefficient of release rate (73.80) mg.kg. min 0.5 after biochar addtion . The fertility calendar based
on the capacity and rate of releasing potassium from the mica mineral showed that the soil under study was
characterized by a low storage of (246.64) and (1135.9) mg kg-1 in the control and addtion soils, respectively, and
a low release rate of (9.555) And (45,309) mg .kg, min 0.5 in control and addtion soils, respectively, and thus these
soils are considered to be of low avalibility of potassium release, and this conclusion is of great practical importance
to address the problem of potassium in calcareous soils.