Python codes were used to i) calculate intrinsic stability constant of PDMA-metal complexes using Davies equation The stability constants determined by using potentiometric titrations were used to develop a novel and specific database to model and predict for the first time i) the behavior and the distribution of [Zn(PDMA)] -complexes at different soil pH (from 3 to 9), ionic strength (I= 0.02, 0.1 and 0.7 M) and redox conditions (Eh = -300 and +350 mV), ii) the behavior and the distribution of PDMA with relevant elements in soil; and iii) the selectivity of [Zn(PDMA)] - complex in presence of other soil elements (pH from 3 to 10). The ionic strengths applied to the model correspond to the low (0.02 M), moderate (0.1 M) and very high (0.7 M) salinity conditions for soil according to USDA classification . These conditions were tested to include the great part of possible soil salinity conditions. In general, the ionic strength of soil ranges from 0.01 to 1 M 30 . According with Araujo et al. , the ionic strength of 0.01 represents the soil solution of weathered soils, while the higher ionic strengths were chosen to simulate the change after the application of soil amendments and fertilizers (I = 0.1 M), and to study the behavior of metal:PDMA complexes in more extreme conditions (I = 0.7). The redox values used in the model considered two extreme redox conditions of paddy soil.