Feet, carts and machinery — all conspire to inflict wear on your turfgrass, affecting both the leaf surface and the underlying soil. Silicon (Si) has long been touted as a tool for potentially increasing the rigidity of turfgrass swards, with applications of silicon possibly providing a tougher and more upright leaf that can withstand abrasive wear.
To test this theory, researchers at the University of Georgia (L. Trenholm, Ph.D., is now at the University of Florida) examined the effects of silicon on the wear tolerance and quality of seashore paspalum.
Two seashore paspalum ecotypes (an experimental and SeaIsle 2000) were maintained at a 1.25-inch (3.2-cm) mowing height. From May to July in year 1 and July to August in year 2, foliar and drench applications of potassium silicate (20.8% SiO2 and 8.3% K2O) were made every other week. Foliar silicon was applied at rates of 1 or 2 pounds silicon/acre (1.1 or 2.2 kilograms/hectare), and the drench treatment was applied at 20 pounds silicon/acre (22.4 kilograms/hectare) in a water solution of 960 gallons/acre (0.9 liter/square meter).
Because the silicon source was potassium silicate, the trial was balanced to uniformity for the supplied potassium using potassium chloride. There was also a potassium-only (potassium chloride) treatment, applied at 14 pounds potassium/acre (15.6 kilograms/hectare), which was also the rate of potassium applied with the highest potassium silicate treatment.
Artificial traffic was used to simulate wear using rubber-covered rollers designed to provide wear to the leaf surface with minimal pressure to the soil, reducing underlying compaction. Collected data included leaf tensile strength (the point at which leaf tissue broke); leaf load-bearing capacity (shoot tissue displacement when covered with a weight); shoot growth; silicon and potassium content in shoot tissue; normalized difference vegetation index (NDVI) spectral reflectance; and turfgrass quality, color, density and injury.
The low rates of silicon, applied as foliar treatments, did not improve wear tolerance or quality of the seashore paspalum. Shoot growth and leaf strength were also not improved.
In the first experiment, seashore paspalum sprayed with foliar potassium never had more silicon in the plant tissue than untreated grass in the control plots did. In the second experiment, there was more silicon in the plant tissue that received the high silicon rate as a foliar spray (as compared with the control plots). This increase in tissue silicon did not translate to improvements in wear tolerance, however. Basically, foliar application of silicon did not enhance wear tolerance or reduce injury of seashore paspalum.
However, when potassium silicate was applied as a drench at a high rate, wear tolerance was enhanced. But here’s the rub: These improvements in wear tolerance and quality were a function of the potassium supplied with the silicate, and not the silicon alone. Because of the inclusion of the potassium-only check, the authors were able to state that the wear tolerance increased because of the application of either potassium alone or the combination of silicon and potassium.
When only potassium was applied, wear injury was reduced from 35% to 14%, and when potassium + silicon was applied, wear injury was reduced from 35% to 20% compared with plots that did not receive potassium or silicon, or plots that received foliar applications.
The authors hypothesized that potassium was working because it increased cell turgor pressure and cell elasticity. And a last point: Only wear, injury and quality were examined, and no data were collected on disease (the effects of silicon on disease have been studied elsewhere).
Source: Trenholm, L.E., R.R. Duncan, R.N. Carrow and G.H. Snyder. 2001. Influence of silica on growth, quality, and wear tolerance of seashore paspalum. Journal of Plant Nutrition 24:245-259.
Beth Guertal, Ph.D., is a professor in the Department of Crop, Soil and Environmental Sciences at Auburn University in Auburn, Ala., and president-elect of the Crop Science Society of America. She is a 20-year member of GCSAA.