Individual study: Responses of prickly saltwort Salsola kali and switchgrass Panicum virgatum to mycorrhizal fungi, phosphorus and soil organic matter on taconite mine tailings at the Jackson County Iron Mine, Wisconsin, USA
Johnson N.C. (1998) Responses of Salsola kali and Panicum virgatum to mycorrhizal fungi, phosphorus and soil organic matter: implications for reclamation. Journal of Applied Ecology, 35, 86-94
This study utilized unreclaimed taconite mine tailings as a mycorrhiza-free ecosystem to gain insights about the influence of arbuscular mycorrhizas and soil organic matter on the growth of prickly saltwort Salsola kali (an early successional colonist of taconite tailings) and switchgrass Panicum virgatum (a late successional grass often planted during reclamation).
To assess relative mycorrhizal responsiveness, both plant species were grown in taconite mine tailings along an experimental phosphorus gradient with and without mycorrhizal fungal inoculum isolated from reclaimed taconite tailings.
Study site: The experiment investigating responses of prickly saltwort Salsola kali and switchgrass Panicum virgatum to mycorrhizal fungi, phosphorus and soil organic matter on taconite (low grade iron ore) mine tailings was undertaken at the Jackson County Iron Mine, Wisconsin, USA.
Experimental design: An experimental phosphorus gradient on taconite tailings with and without mycorrhizal fungal inoculum (see original paper for innoculation procedure) was established to assess responses of Salsola kali and Panicum virgatum to mycorrhizal fungi. Seven levels of P were established by adding NaH2PO4 such that bicarbonate extractable P levels were: 1.45, 2.14, 2.84, 4.22, 6.90, 12.40 and 29.19 mg/kg.
Sixteen 1 m² plots were delineated in an area of unreclaimed tailings in May 1995. These were treated with or without inoculum and with or without organic matter (15 kg/plot composted papermill sludge) in a 4-times replicated factorial experiment. Plots with organic matter added were tiled to 15 cm depth,
Amended and amended samples were analysed for N (nitrogen), P (phosphorus), K (potassium), pH, bulk density and organic content.
Plots were then roto-tilled to 18 cm depth, and 7 kg soil and chopped roots from mycorrhizal or non-mycorrhizal millet Sorghum tilled in. Plots were then fertilized and Salsola and Panicum seed was sown in each half of a plot. Plots were covered with a thin oat straw mulch and 10 l water added at sowing, and after 1 and 3 weeks.
In October 1985, at the end of the growing season in 25 x 25 cm quadrats, plant height and above ground biomass was determined.
At low phosphorus concentrations, mycorrhizal inoculum enhanced the growth (height and dry mass) of Panicum, but growth was decreased at the two highest phosphorous concentrations (12.40 and 29.19 mg/kg). At no phosphorus level did mycorrhizal inoculum enhance the growth of Salsola but it decreased growth at the highest phosphorus concentrations.
In the field plots, mycorrhizal inoculum and organic soil amendment (composted papermill sludge) enhanced the growth of Panicum but decreased the growth of Salsola.
Conclusions: In this experiment, mycorrhizal inoculum enhanced the growth of the late successional grass, switchgrass Panicum virgatum, but, during reclamation operations, manipulating edaphic conditions to favour mycotrophy may be more cost-effective than large-scale inoculation. The study results suggest that mycotrophy is favoured by increasing soil organic matter and avoiding heavy fertilization.
Note: If using or referring to this published study, please read and quote the original paper. The original paper can be viewed at: http://www.blackwell-synergy.com/doi/abs/10.1046/j.1365-2664.1998.00277.x