SYNTHETIC MACRONET HYDROPHILIC POLYMERS AS SOIL CONDITIONERS .2. THE EFFECT OF THE FINAL ION FORM OF CROSS-LINKED SULFONATED POLYSTYRENE ON SEEDLING GROWTH

Hydrophilic polymers were obtained via modification of linear polystyrene and were applied to various plant-soil systems. Sandy-loam soil and quartz sand were used as substrates for tomato and lettuce cultivation. Three different ion species were studied as the final form of the sulfonic group attached to the polystyrene backbone. The sodium (Na+), ferrous-iron (Fe2+), and hydrogen (H+) forms were employed in order to determine the influence of the ion-exchange processes in which the conditioner is involved. The results showed slightly improved growth in the presence of Fe2+ form, while there was significant growth response of seedlings to the acid form of the sulfonated polystyrene resins. The ion-exchange behaviour of the polymers in the acid form was studied by pH measurements employing water suspensions. Finally, the influence of the new polymers on the growth of seedlings was compared to that of a known commercial product based on polyacrylamide.