Effect of polyacrylamide on seedling emergence of three grass species

We performed two greenhouse trials to determine the effects of 0, 0.2, 2.0, 20.0, and 200.0 kg ha of polyacrylamide (PAM), a soil conditioner, on seedling emergence of sideoats grama (Bouteloua curtipendula [Michx.] Torr.), alkali sacaton (Sporobolous airoides [Torr.] Torr.), and Boer lovegrass (Erogrostis chloromelas Steud.). The pots of the first experiment were irrigated every 5 d, and pots in the second experiment were irrigated every 8 d. A soil with unfavorable physical conditions and with a history of crusting was used as a support medium. Shear strength and water infiltration were also evaluated.Emergence of 100% within 22 d of planting for sideoats grama was obtained in experiment 1 with 200 kg ha PAM application. As expected, the real effect of PAM was more noticeable in the second experiment, where emergence of 100% was noted for both 20− and 200-kg-ha PAM applications, though only 50% emergence occurred in control pots. No significant differences in seedling emergence were found for alkali sacaton in experiment 1. In experiment 2, however, significantly more seedlings were obtained in PAM treatments than in the control pots. Plants of alkali sacaton became desiccated 1 month after emergence. Boer lovegrass emergence was not improved with PAM applications in experiment 1, but in experiment 2, more seedlings were obtained with PAM applications. Like plants of alkali sacaton, Boer lovegrass began desiccating 1 mo after emergence.Values of shear strength showed that PAM worked well as an anticrustant amendment. In general, as PAM rates increased, shear strength values decreased. Infiltration rates did not show a clear trend; infiltration was improved in experiment 1, but no effect was noted for experiment 2. It seems reasonable to conclude that application of PAM may be a viable method of assuring good stand development of seeded grasses on crusting range soils.