Various anionic polyacrylamide polymers (PAMs) are frequently used to improve soil properties and reduce erosion. However, the effects of their application on plant growth remain unclear. Aggregate-free loess with high water holding capacity was used as growing substrate to test the effects of two rates (10 and 40 kg ha−1) of a linear PAM on the growth of maize (Zea maize L.) for a period up to one month. The PAM effects were evaluated at three levels of soil water content (SWC) and three plant ages, based on water consumption, shoot and root biomass, as well as allocation of recently assimilated C in plants and soil using 14C labeling. Both SWC and maize age significantly affected water consumption, biomass accumulation, and 14C allocation in plant parts and soil. Even though consistent increases in plant biomass and total assimilated 14C were observed, the effects of PAM application were insignificant on either of these variables. The effects of PAM application were directly connected to soil rather than to maize, and could be masked by the non-structural loess. The effects tended to be age and soil-moisture specific, and were modulated by the rhizodeposition processes. The possible mechanisms of PAM application on plant growth were also discussed.
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