1 College of Agriculture University of Baghdad.

2 college of Agriculture University of Wasit.


A field experiment has been conducted at Suwera Researches Station in Wasit Governorate in spring season 2015 in clay loam in order to study the effect of sulfur sources R1 agriculture sulfur (90% sulfur) R2-foam sulfur (75% sulfur) at the levels of 0, 2500, 5000 kg,s,ha-1. represented the levels of S0, S1, S2 and time of addition T (30 days before sowing T0), 15 days before sowing (T1) and during sawing (T2) on the availability and release of sulfur in soil extracted by (5*10-4 M) citric acid during the period of plant growth (30, 60, 90, 120 days after sowing) by using kinetics concepts to determine the best kinetics equation that describes well the mechanic of sulfur release in soil which represents the amounts of sulfur availability for the plant.
Results show significant effect on sources, levels and addition time of sulfur availability and release abstracted by citric acid (5*104 M) during plant growth periods. Agriculture sulfur source is the highest level at the addition level S2 (5000 kg S. H-1) at addition time T2. The highest values are achieved at 30 days after sawing, at 376, 382 and 375 mg soil respectively. Also, the triple interaction treatment R1S2T2 has achieves the highest values of released sulfur abstracted by citric acid at the same time, at 520 mg
Results show that all kinetics equations of sulfur which is abstracted by citric acids (5*104 M) in soil growth plant periods. Also, all the kinetic are equations clarifying well the mechanism of releasing sulfur from soil and fertilizers and the first order equation is the highest amongst all equations. The values of coefficient of sulfur release speed (ks) between 0.001 – 0.004 Cmolc. Kg-1 day-1. 0.001-0.004 .