Abstract
Little information is available concerning the beneficial effects of polyacrylamide (PAM) polymer on plant nutrient availability. To obtain a better understanding on this subject, a laboratory column leaching study was conducted to investigate the effect of water-soluble synthetic polymers on the availability and mobility of fertilizer P added to the surface of two agricultural soils collected from the central and southern regions of Saudi Arabia. Air-dried soil samples were uniformly treated with three PAM polymers (one nonionic and two anionic) at rates of 0 and 200 mg kg
−1
, and packed into 50 cm columns. The top 5 cm of soil from each column was removed, mixed thoroughly with fertilizer P (KH
2
PO
4
) at rate of 400 mg kg
−1
, and then replaced in the column. All columns were subjected to an intermittent leaching and incubation for 63 days. Extraction and analysis of each 5 cm layer of the soil columns at the end of the experiment showed that extractability and movement of added P in soils were drastically reduced in the presence of synthetic polymers compared to fertilizer P only. The extractability and movement of P decreased with increasing anionic charge of the polymer. Thus the reactivity of P fertilizer with the polymers was the dominant and overriding determinate of the extraction and movement of surface-applied P. The transformation of added P showed a decrease in NH
4
Cl-P, Al-P, and Ca-P fractions in all samples amended with polymers, whereas the Fe-P fraction increased with polymer addition. In general, evidence is provided for synthetic polymers playing a major role in reducing downward movement, and available inorganic fractions of added P in both calcareous and noncalcareous soils. The actual mechanisms involving fertilizer P reactions with polymers merit further investigation.