Karen Campbell and Dr. Bryan Hopkins, Plant and Wildlife Sciences
Introduction
The governments of the United States spend millions of dollars every year to reseed native species after a wildfire. However, less than 1% of all the seeds they lay actually germinate. By coating seeds in various fertilizers, we hope to increase the rate of germination of these grassland species. By increasing the germination percentage, it will be easier to maintain the natural habitat of arid grasslands as well as prevent the onset of invasive grasses, which are known to cause more frequent and intense wildfires. Before testing seed coatings on native grass seeds, coatings must should be tested on commercial grass seeds as to be more cost effective and also because these species are well known and so their behavior can be compared to the standard in the industry.
Methodology
The study was performed in the BYU Greenhouse. Kentucky Blue Grass seed (Poa pratensis L.) was used due to its wide usage and relatively quick germination time. There were 9 different treatments of fertilizer seed coatings, including a control. The type of fertilizer remained constant, but different concentrations were used along with the presence of a base and/or finish coating1. Forty seeds were hand placed in a 9 cm2 pot filled with 11cm of silica sand and then covered with ¼ cup of the same sand.2 Eight replications of each treatment were made to minimize error. All pots were placed in a large tub and watered from below. Until initial germinal, the water level in the tube was kept at a contestant depth of one inch, once germination had occurred, the tub was allowed to dry completely before being filled again. Germination counts were taken every day for the first two weeks, after that germination counts were taken every 4 days until there were no longer changes in germination counts. After germination counts were completed, the grass was allowed to dry out and die so that bio mass could be taken.
Results
– 2L fert/kg with a finish coating but without a base coating had significantly higher biomass than all other treatments (figure 1).
– Treatments without a base coating had significantly higher biomass than those with a base coating (figure 1)
– All treatments besides the control showed a delay in germination by about 8 days, with treatments with both a base and finish coating being delayed about 15 days.
1 Base and finish coatings contained no fertilizer, but are simply adhesives used to better seal the fertilizer to the seed (finish coating) or to protect the seed itself (base coating).
2 Silica sand was chosen due to its low nutrient content. The lack of supplemental nutrients for the seeds allows the effect of the fertilizer to be more pronounced. The low water and nutrient retention of silica sand also mimics that of desert soils.
– Treatments with both a base and finish coating had the lowest total percentage of germination, with 4L fert/kg with a base and finish coating having the lowest percentage of 22.8% (figure 4).
– The control, 2L fert/kg with finish coating without base coating, 2L fert/kg without finish coating with base coating, and 2L fert/kg without finish coating without base coating had no significant difference in germination percentage by day 25 (figure 2).
Discussion
The addition of coatings to the seed, in every situation, significantly increased the time it took to germinate when compared to the control. This is probably due to the coatings blocking air from the seed surface. It is for this same reason that the treatments with both finish and base coatings had significantly lower germination overall.
The purpose of the base coating is to prevent fertilizer burn from killing the grass seed. However, it appears that it rather kept the seed from accessing the fertilizer, with most of the fertilizer coating eroded away before the base coating was penetrated.
It appears that 2L fert/kg was the closest to the optimum concentration of fertilizer for the grass seed since its treatments had the healthiest results overall.
It is proposed that the reason that treatments that had a finish coating but no base coating tended to have higher biomass levels than the control was because the finish coating worked as a ‘cup’ for the fertilizer, keeping it close to the seed for a longer period by preventing it from being leeched out. The lack of a base coating helped because then the seed could freely access the fertilizer.
Conclusion
Overall, the addition of fertilizer resulted in a significantly higher amount of biomass, peaking with treatments that contained no base coating. However, seed coating has not shown to be successful in encouraging the rapid establishment of Kentucky Bluegrass, rather, more fertilizer and coating increased the time between seeding and establishment and decreased the total germination percentage. The amount of coating applied was also found to be a more influential factor than the percentage of fertilizer, though 2 L fert/kg was found to have a better germination percentage on average. Higher applications of fertilizer appear to be more detrimental to total germination percentage than lower application rates.
Overall, seed coatings have not been shown to discourage rather than encourage rapid establishment in Kentucky Bluegrass. Therefore it would not be recommended for the use of quickly establishing ground cover. However, further testing with seed coating needs to be done on native grass species (such as Pseudoroegneria spicata, or Bluebunch Wheatgrass) to see its potential for wildfire remediation.