Abstract

Soil moisture deficits often hinder rangeland revegetation efforts. Due to sheer numbers and germination timing, invasive annual species can easily outcompete those of desired seeded species for resources, including water. One way to increase seedling establishment may be to increase the amount of water available to seeded species. Superabsorbent polymers (SAPs) can absorb and release hundreds of times their weight in water and slowly release it. Concentrated SAP bands at or near seedling rooting depth may act as a soil water reservoir for germinating seedlings and increase rangeland seedling establishment. The objective of these studies was to evaluate the effect of banded SAP on soil moisture and seedling establishment through a series of eight glasshouse and field trials with different combinations of: species, SAP band rate, SAP band placement depth, seeding rate, fertilizer application, and seedling distance from the SAP band. Two grasses, bottlebrush squirreltail (Elymus elymoides) or Siberian wheatgrass (Agropyron fragile) were used as test species in all studies but one. In that study six species commonly used in rangeland restoration [bottlebrush squirreltail, crested wheatgrass (Agropyron cristatum (L.)), Lewis flax (Linum lewisii Pursh), yellow sweet clover (Melilotus officinalis), Wyoming big sagebrush (Artemisia tridentata Nuttall ssp. wyomingensis Beetle Young), and forage kochia (Kochia prostrata (L.) Schrad.)] were used. Concentrated band of SAP at rates up to 6000 kg ha-1 were placed below the seeds at depths ranging from the soil surface to 15 cm deep or mixed into the top 8 or 15 cm of soil. Measurements varied with trial. Soil moisture measurements included gravimetric water content, volumetric water content, and/or soil matric potential. Seedling growth parameters included seedling time to emerge, number emerged, longevity, percent of seedlings alive, shoot length, blade count, root length, root biomass, shoot biomass, and/or root:shoot ratio. Banded SAP at high rates increased usable soil moisture up to 49 days in the glasshouse and in spring of the first year after installation in the field. Rates ? 1500 kg ha-1 increased seedling longevity up to 12 days in the glasshouse but resulted in raised and cracked soil. This negatively impacted seedling survival in the field but not the glasshouse and may also reduce the amount of available soil moisture over time. Banded SAP at rates < 1500 kg ha-1, intended to reduce soil cracking, had no impact on soil moisture or live seedlings in the field. Further work is needed to investigate alternative application methods, such as blending the SAP into the soil.

Degree

PhD

College and Department

Life Sciences; Plant and Wildlife Sciences

Rights

https://lib.byu.edu/about/copyright/