Mark Judson and Dr. Val Jo Anderson, Plant and Animal Science
The Uncompahgre Plateau Project involves a series of studies to help with the production of native seeds for large-scale restoration of this Colorado Plateau Region. Studies are being conducted at various research centers throughout the United States. The present study at Brigham Young University sought to identify optimum row spacing and evaluate irrigation regimes for maximum seed production and harvest efficiency.
The reestablishment of native plant communities following severe disturbance is vital to restoring the land to its original capacity for habitat wildlife species and production of a grazing resource. Exotic grasses have historically been used to stabilize sites and produce forage; however, this approach has severely limited habitat improvement for species such as the mule deer, neo-tropical migrant birds, and sage grouse. Even with the recognition and desire to correct this approach, the use of native species for habitat restoration has been hampered by low seed availability.
A primary objective of this study was to develop cultural practices that would allow wildland species to be grown in cultivation for mass production of seed; specifically, the study attempted to determine the row spacing and irrigation regimes that would maximize seed yields and harvest efficiency with the hope that native forbs could be harvested economically.
Sites that could be easily accessed and contained irrigation systems were needed for the experiment. Two sites were chosen for this study: The Division of Wildlife Resources in Fountain Green, Utah, and Brigham Young University’s Native Plant Materials Research Facility in Spanish Fork, Utah.
Four native species of forbs, identified as having high habitat value, were selected for this study: Erigeron pumilus, Erigeron speciosus, Heterotheca villosa, and Tetraneuris acaulis. Tetraneuris acaulis was only planted at the Spanish Fork site due to the inability to secure plants for both sites. Because of high mortality of Tetraneuris acaulis at the Spanish Fork site, and the lack of replacement plants, data was not collected and analyzed for this species.
Each forb species was planted at three different row spacings and replicated three times in each of two irrigation treatment blocks. Plants were spaced at a constant within-row spacing of 12 inch centers. Spacing between rows was 24, 36, and 48 inches, respectively. The irrigation treatments included a single watering in spring and season-long watering, which were chosen to examine if seed production could be synchronized with spring watering or maximized with season-long watering.
Researchers tracked the native forbs’ phenology throughout the growing season to predict when the heaviest crop of seed would occur. Flower counts were conducted once a week from May until the end of August. This procedure was performed during the first year of data collection only. In addition, seed collection was conducted once each week beginning with the first production of seed and ending in late August. Gas powered vacuums (shred vacs) were originally used to harvest seeds, but the filters protecting the motors did not protect against fine particles and consequently malfunctioned. Electric powered shop vacs then replaced shred vacs for seed harvesting. Seeds were stored and later separated from the debris. This weekly sampling procedure was performed to determine when the peak seed production times occurred for each species.
Once the seeds from each species were isolated, data was compiled and analyzed. Results showed no significant difference in phenology between the Spanish Fork and the Fountain Green sites. Results from data collection during the first year indicated that Erigeron pumilus peaked on June 8th and then tapered off through the rest of the summer. Once flowering started around the end of May, Heterotheca villosa remained relatively consistent throughout the rest of the summer. Erigeron speciosus peaked on June 14th and was harvested a couple of weeks later. The harvesting method used to collect seed from Erigeron speciosus prevented any further flowering from this species, and consequently, any further tracking of its phenology, as the seeds were harvested by manually clipping the seed heads from the plant. When flower counts were concluded at the end of August, Heterotheca villosa was still flowering heavily. These results found during the first year’s data collection guided researchers in predicting the peak times to collect seed during the second year of data collection.
Having approximated when the peak seed production would occur, procedures for the second year of data collection were altered slightly. Flower counts were no longer performed, and seed collection was limited to three collection times. These collection times were performed one week before peak seed production time, one week during the peak production time, and one week after the peak production time. Shop vacs were used again to collect the seeds, and samples were labeled and stored for analysis.
For analysis, samples needed to be cleaned to eliminate the dirt and other debris accumulated with the seeds during collection. Machines such as vibrating decks and blowers were used to clean the samples. After as much foreign material as possible was eliminated from the sample, individual samples were combined into one sample for each of the three between row spacing treatments for each species. Sub-samples were taken from each of the combined samples, and seeds were separated from the remaining debris to determine pure live seed (PLS), or the amount of seed to debris material in each combined sample.
The results of this study assisted researchers in determining which between row spacing was best suitable for maximizing the production of seed for three native forb species. Researchers found that the 36 inch between row spacing was best suited for Heterotheca villosa, and the 48 inch between row spacing was best suited for Erigeron speciosus. Spacing had no effect for Erigeron pumilus. Irrigation regimes were found to have no effect in influencing production of Erigeron speciosus and Erigeron pumilus. The irrigation regimes did have an effect on Heterotheca villosa at the Spanish Fork site, but that effect was do to the seed sticking to the ground and being unable to be harvested. Conversely, at the Fountain Green site, the irrigation treatment had a positive influence on seed production for Heterotheca villosa. Researchers believed the difference was caused by drip lines being used as the water delivery system at Fountain Green which prevented seed from sticking to the ground.
Seed collection of native forbs in the wild is often difficult and not cost effective for some reclamation purposes. If native forbs are to be utilized in large scale reclamation projects a more economical approach is necessary. The information gained in this study is important to guide production of native forb seed in a more cost effective manner. This study, and other similar studies, provides information to guide conservationists in determining which row spacing and irrigation treatment should be used to maximize seed production to place more seed on the market, thus hopefully lowering the cost of essential seed needed for rangeland seed mixes in rangeland reclamation projects.